Johan Frederik Storm

• Halder, Sebastian; Juel, Bjørn Erik; Pope, Kenneth J.; Hardy, Andrew; Willoughby, John O. & Storm, Johan Frederik (2026). An experimental study of the effect of neuromuscular blockade on EEG-based measures of awareness. Scientific Reports. doi: 10.1038/s41598-026-50911-6. Fulltekst i vitenarkiv Vis sammendrag

  Both basic and clinical consciousness research aims to find objective measures that reliably distinguish conscious from unconscious brain states. Electroencephalogram (EEG) measures are widely used, although they may be affected by interference from electrical signals such as those generated by muscles. To assess this source of error, we investigated the impact of neuromuscular blockade (NMB) on proposed measures of awareness (spectral slope, Lempel–Ziv complexity (LZc), connectivity, alpha peak frequency, power in canonical EEG frequency bands) computed from spontaneous high-density EEG recorded from six healthy volunteers in three different conditions: (1) awake-unparalysed (normal wakefulness), (2) awake-paralysed (complete paralysis caused by neuromuscular blocking agent (NMBA)), and (3) sedated-paralysed (deep sedation with propofol, with paralysis by NMBA). The measures we investigated distinguished awake-unparalysed states from sedated-paralysed with close to perfect accuracy in accordance with past findings. However, our analysis revealed a serious failure of most measures to recognise the awake-paralysed condition as an aware state. Errors ranged from 7% of awake-paralysed time segments predicted as unaware (using alpha power) to 100% (using LZc). Using a unique high-density EEG data set, this study clearly demonstrates that many EEG-based measures fail to recognise awareness in awake subjects under the influence of muscle relaxants. These results highlight critical limitations of current EEG-based measures at detecting awareness.

• Sanchez-Vives, Maria V; Manasanch, Arnau; Pigorini, Andrea; Arena, Alessandro; Camassa, Alessandra & Juel, Bjørn Erik [Vis alle 20 forfattere av denne artikkelen] (2026). Multiscale dynamical characterization of cortical brain states: from synchrony to asynchrony. eLIFE. doi: 10.7554/elife.108613.1. Fulltekst i vitenarkiv Vis sammendrag

  The cerebral cortex spontaneously displays different patterns of activity that evolve over time according to the brain state. Sleep, wakefulness, resting states, and attention are examples of a wide spectrum of physiological states that can be sustained by the same structural network. Furthermore, additional states are generated by drugs (e.g., different levels of anesthesia) or by pathological conditions (e.g., brain lesions, disorders of consciousness). While the significance of understanding brain states in relation to brain dynamics and behavior has become increasingly evident over the past two decades, a unified definition of brain states remains elusive. In this review, we focus on two extremes of this spectrum: synchronous versus asynchronous states. These functional states predominantly underlie unconsciousness and consciousness, respectively, although exceptions exist. Our aim is to integrate data from different levels into a multiscale understanding, ranging from local circuits to whole-brain dynamics, including properties such as cortical complexity, functional connectivity, synchronization, wave propagation, and excitatory-inhibitory balance that vary across states and characterize them. Experimental and clinical data, as well as computational models (at micro-, meso-, and macrocortical levels) associated with the discussed brain states, are made available to readers.

• Pastorelli, Elena; Yegenoglu, Alper; Kolodziej, Nicole; Wybo, Willem; Simula, Francesco & Diaz-Pier, Sandra [Vis alle 8 forfattere av denne artikkelen] (2025). Simplified two-compartment neuron with calcium dynamics capturing brain-state specific apical-amplification, -isolation and -drive. Frontiers in Computational Neuroscience. 19. doi: 10.3389/fncom.2025.1566196. Fulltekst i vitenarkiv
• Destexhe, Alain; Goldman, Jennifer S; Tort-Colet, Nuria; Roques, Axel; Fousek, Jan & Petkoski, Spase [Vis alle 35 forfattere av denne artikkelen] (2025). State-dependent brain responsiveness, from local circuits to the whole brain. eLIFE. 14, s. 1–36. doi: 10.7554/elife.108768.1. Fulltekst i vitenarkiv Vis sammendrag

  The objective of this paper is to review physiological and computational aspects of the responsiveness of the cerebral cortex to stimulation, and how responsiveness depends on the state of the system. This correspondence between brain state and brain responsiveness (statedependent responses) is outlined at different scales from the cellular and circuit level, to the mesoscale and macroscale level. At each scale, we review how quantitative methods can be used to characterize network states based on brain responses, such as the Perturbational Complexity Index (PCI). This description will compare data and models, systematically and at multiple scales, with a focus on the mechanisms that explain how brain responses depend on brain states.

• Bajwa, Imad Javaid; Nilsen, Andre Sevenius; Skukies, René Sebastian; Aamodt, Arnfinn; Ernst, Gernot Walter & Storm, Johan Frederik [Vis alle 7 forfattere av denne artikkelen] (2025). A repeated awakening study exploring the capacity of complexity measures to capture dreaming during propofol sedation | Scientific Reports. Scientific Reports. 15, s. 1–12. doi: 10.1038/s41598-025-12695-z. Fulltekst i vitenarkiv Vis sammendrag

  Patients undergoing general anesthesia are often assumed to be unconscious. However, it is known that conscious experiences in the form of dreams occur even in unresponsive states induced by anesthetics. Here, we recorded resting state electroencephalography (EEG) as well as EEG combined with TMS perturbations in 20 healthy participants during propofol sedation. Participants were repeatedly awoken from deep sedation and asked immediately whether they had experiences just before waking up and what they experienced. Out of the 52 attempted awakenings in this study, 24 produced reports of having had an experience, while there were 5 reports of no experience. In the remaining 23 attempts, the subject was either unarousable or the report too incoherent to provide information about their experience prior to awakening. We then tested whether two different consciousness measures based on EEG complexity—the state transitions perturbational complexity index (PCIst) and single-channel Lempel-Ziv complexity (LZc)—differed between awakenings with and without experience. While our study confirms earlier findings that the EEG complexity measures significantly decrease from the awake state to the sedated state, we find no evidence that these measures differ between periods associated with reports of dreaming and non-dreaming, within the sedated state. A few interpretations and limitations are discussed.

• Bajwa, Imad Javaid; Nilsen, Andre Sevenius; Skukies, René Sebastian; Aamodt, Arnfinn; Ernst, Gernot Walter & Storm, Johan Frederik [Vis alle 7 forfattere av denne artikkelen] (2025). A repeated awakening study exploring the capacity of complexity measures to capture dreaming during propofol sedation. Scientific Reports. 15. doi: 10.1038/s41598-025-12695-z. Fulltekst i vitenarkiv Vis sammendrag

  Patients undergoing general anesthesia are often assumed to be unconscious. However, it is known that conscious experiences in the form of dreams occur even in unresponsive states induced by anesthetics. Here, we recorded resting state electroencephalography (EEG) as well as EEG combined with TMS perturbations in 20 healthy participants during propofol sedation. Participants were repeatedly awoken from deep sedation and asked immediately whether they had experiences just before waking up and what they experienced. Out of the 52 attempted awakenings in this study, 24 produced reports of having had an experience, while there were 5 reports of no experience. In the remaining 23 attempts, the subject was either unarousable or the report too incoherent to provide information about their experience prior to awakening. We then tested whether two different consciousness measures based on EEG complexity—the state transitions perturbational complexity index (PCIst) and single-channel Lempel-Ziv complexity (LZc)—differed between awakenings with and without experience. While our study confirms earlier findings that the EEG complexity measures significantly decrease from the awake state to the sedated state, we find no evidence that these measures differ between periods associated with reports of dreaming and non-dreaming, within the sedated state. A few interpretations and limitations are discussed.

• Fleiner, Anne Sjøbakken; Kolnier, Daniel; Hagger-Vaughan, Nicholas James; Ræder, Johan & Storm, Johan Frederik (2025). Effects of ketamine and propofol on muscarinic plateau potentials in rat neocortical pyramidal cells. PLOS ONE. 20(1). doi: 10.1371/journal.pone.0316262. Fulltekst i vitenarkiv Vis sammendrag

  Propofol and ketamine are widely used general anaesthetics, but have different effects on consciousness: propofol gives a deeply unconscious state, with little or no dream reports, whereas vivid dreams are often reported after ketamine anaesthesia. Ketamine is an N-methyl-D-aspartate (NMDA) receptor antagonist, while propofol is a γ-aminobutyric-acid (GABAA) receptor positive allosteric modulator, but these mechanisms do not fully explain how these drugs alter consciousness. Most previous in vitro studies of cellular mechanisms of anaesthetics have used brain slices or neurons in a nearly “comatose” state, because no “arousing” neuromodulators were added. Here we tested mechanisms of anaesthetics in rat medial prefrontal cortex (mPFC) slices after bath-applying the cholinergic agonist muscarine to partly mimic an “aroused-like” state, using whole-cell patch-clamp recordings from layer 2/3 pyramidal cells (L2/3PCs). According to leading theories of access consciousness and working memory, L2/3PCs are particularly important for these cognitive functions. We found that muscarine induced long-lasting depolarising plateau potentials (PPs) and spiking following brief depolarising current injections in the L2/3PCs. After 2 hours of pre-incubation with ketamine or propofol, the muscarine-induced PPs were altered in seemingly different ways: 3 μM propofol reduced the PPs and (significantly) spiking, whereas 20 μM ketamine seemed to enhance PPs and spiking (non-significantly). Brief wash-in of these drug concentrations failed to induce such effects, probably due to insufficient equilibration by diffusion in the slices. In contrast, pre-incubation with a high dose (100 μM) of ketamine suppressed the PPs and spiking. We discuss whether the apparently different effects on PPs may possibly be related to contrasting clinical effects: ketamine causing atypical anaesthesia with vivid, “psychedelic” dreaming while propofol causes less dreaming.

• Wong, William; Herzog, Ruben; Andrade, Kátia Cristine; Andrillon, Thomas; Araujo, Draulio Barros de & Arnulf, Isabelle [Vis alle 53 forfattere av denne artikkelen] (2025). A dream EEG and mentation database. Nature Communications. 16. doi: 10.1038/s41467-025-61945-1. Fulltekst i vitenarkiv Vis sammendrag

  Magneto/electroencephalography (M/EEG) studies of dreaming are an essential paradigm in the investigation of neurocognitive processes of human consciousness during sleep, but they are limited by the number of observations that can be collected per study. Dream research also involves substantial methodological and conceptual variability, which poses problems for the integration of results. To address these issues, here we present the DREAM database—an expanding collection of standardized datasets on human sleep M/EEG combined with dream report data—with an initial release comprising 20 datasets, 505 participants, and 2643 awakenings. Each awakening consists, at minimum, of sleep M/EEG ( ≥ 20 s, ≥100 Hz, ≥2 electrodes) up to the time of waking and a standardized dream report classification of the subject’s experience during sleep. We observed that reports of conscious experiences can be predicted with objective features extracted from EEG recordings in both Rapid Eye Movement (REM) and non-REM (NREM) sleep. We also provide several examples of analyses, showcasing the database’s high potential in paving the way for new research questions at a scale beyond the capacity of any single research group.

• Murphy, Ricardo; Alle, Henrik; Geiger, Jörg R. P. & Storm, Johan Frederik (2024). Estimation of persistent sodium-current density in rat hippocampal mossy fibre boutons: Correction of space-clamp errors. Journal of Physiology. ISSN 0022-3751. s. 1–30. doi: 10.1113/JP284657. Fulltekst i vitenarkiv Vis sammendrag

  We used whole-cell patch clamp to estimate the stationary voltage dependence of persistent sodium-current density (iNaP) in rat hippocampal mossy fibre boutons. Cox's method for correcting space-clamp errors was extended to the case of an isopotential compartment with attached neurites. The method was applied to voltage-ramp experiments, in which iNaP is assumed to gate instantaneously. The raw estimates of iNaP led to predicted clamp currents that were at variance with observation, hence an algorithm was devised to improve these estimates. Optionally, the method also allows an estimate of the membrane specific capacitance, although values of the axial resistivity and seal resistance must be provided. Assuming that membrane specific capacitance and axial resistivity were constant, we conclude that seal resistance continued to fall after adding TTX to the bath. This might have been attributable to a further deterioration of the seal after baseline rather than an unlikely effect of TTX. There was an increase in the membrane specific resistance in TTX. The reason for this is unknown, but it meant that iNaP could not be determined by simple subtraction. Attempts to account for iNaP with a Hodgkin–Huxley model of the transient sodium conductance met with mixed results. One thing to emerge was the importance of voltage shifts. Also, a large variability in previously reported values of transient sodium conductance in mossy fibre boutons made comparisons with our results difficult. Various other possible sources of error are discussed. Simulations suggest a role for iNaP in modulating the axonal attenuation of EPSPs.

• Storm, Johan Frederik; Klink, P. Christiaan; Aru, Jaan; Senn, Walter; Goebel, Rainer & Pigorini, Andrea [Vis alle 12 forfattere av denne artikkelen] (2024). An integrative, multiscale view on neural theories of consciousness. Neuron. ISSN 0896-6273. 112(10), s. 1531–1552. doi: 10.1016/j.neuron.2024.02.004. Fulltekst i vitenarkiv Vis sammendrag

  How is conscious experience related to material brain processes? A variety of theories aiming to answer this age-old question have emerged from the recent surge in consciousness research, and some are now hotly debated. Although most researchers have so far focused on the development and validation of their preferred theory in relative isolation, this article, written by a group of scientists representing different theories, takes an alternative approach. Noting that various theories often try to explain different aspects or mechanistic levels of consciousness, we argue that the theories do not necessarily contradict each other. Instead, several of them may converge on fundamental neuronal mechanisms and be partly compatible and complementary, so that multiple theories can simultaneously contribute to our understanding. Here, we consider unifying, integration-oriented approaches that have so far been largely neglected, seeking to combine valuable elements from various theories.

• Nilsen, Andre Sevenius; Storm, Johan Frederik & Juel, Bjørn Erik (2024). Does Cognitive Load Affect Measures of Consciousness? Brain Sciences. 14(9). doi: 10.3390/brainsci14090919. Fulltekst i vitenarkiv Vis sammendrag

  Background: Developing and testing methods for reliably measuring the state of consciousness of individuals is important for both basic research and clinical purposes. In recent years, several promising measures of consciousness, grounded in theoretical developments, have been proposed. However, the degrees to which these measures are affected by changes in brain activity that are not related to changes in the degree of consciousness has not been well tested. In this study, we examined whether several of these measures are modulated by the loading of cognitive resources. Methods: We recorded electroencephalography (EEG) from 12 participants in two conditions: (1) while passively attending to sensory stimuli related to the measures and (2) during increased cognitive load consisting of a demanding working memory task. We investigated whether a set of proposed objective EEG-based measures of consciousness differed between the passive and the cognitively demanding conditions. Results: The P300b event-related potential (sensitive to conscious awareness of deviance from an expected pattern in auditory stimuli) was significantly affected by concurrent performance on a working memory task, whereas various measures based on signal diversity of spontaneous and perturbed EEG were not. Conclusion: Because signal diversity-based measures of spontaneous or perturbed EEG are not sensitive to the degree of cognitive load, we suggest that these measures may be used in clinical situations where attention, sensory processing, or command following might be impaired.

• Nilsen, Andre Sevenius; Arena, Alessandro & Storm, Johan Frederik (2024). Exploring effects of anesthesia on complexity, differentiation, and integrated information in rat EEG. Neuroscience of Consciousness. 2024(1). doi: 10.1093/nc/niae021. Fulltekst i vitenarkiv Vis sammendrag

  To investigate mechanisms underlying loss of consciousness, it is important to extend methods established in humans to rodents as well. Perturbational complexity index (PCI) is a promising metric of “capacity for consciousness” and is based on a perturbational approach that allows inferring a system’s capacity for causal integration and differentiation of information. These properties have been proposed as necessary for conscious systems. Measures based on spontaneous electroencephalography recordings, however, may be more practical for certain clinical purposes and may better reflect ongoing dynamics. Here, we compare PCI (using electrical stimulation for perturbing cortical activity) to several spontaneous electroencephalography-based measures of signal diversity and integrated information in rats undergoing propofol, sevoflurane, and ketamine anesthesia. We find that, along with PCI, the spontaneous electroencephalography-based measures, Lempel–Ziv complexity (LZ) and geometric integrated information (ΦG), were best able to distinguish between awake and propofol and sevoflurane anesthesia. However, PCI was anti-correlated with spontaneous measures of integrated information, which generally increased during propofol and sevoflurane anesthesia, contrary to expectations. Together with an observed divergence in network properties estimated from directed functional connectivity (current results) and effective connectivity (earlier results), the perturbation-based results seem to suggest that anesthesia disrupts global cortico-cortical information transfer, whereas spontaneous activity suggests the opposite. We speculate that these seemingly diverging results may be because of suppressed encoding specificity of information or driving subcortical projections from, e.g., the thalamus. We conclude that certain perturbation-based measures (PCI) and spontaneous measures (LZ and ΦG) may be complementary and mutually informative when studying altered states of consciousness.

• Hagger-Vaughan, Nicholas James; Kolnier, Daniel & Storm, Johan Frederik (2024). Non-apical plateau potentials and persistent firing induced by metabotropic cholinergic modulation in layer 2/3 pyramidal cells in the rat prefrontal cortex. PLOS ONE. 19(12). doi: 10.1371/journal.pone.0314652. Fulltekst i vitenarkiv Vis sammendrag

  Here we describe a type of depolarising plateau potentials (PPs; sustained depolarisations outlasting the stimuli) in layer 2/3 pyramidal cells (L2/3PC) in rat prefrontal cortex (PFC) slices, using whole-cell somatic recordings. To our knowledge, this PP type has not been described before. In particular, unlike previously described plateau potentials that originate in the large apical dendrite of L5 cortical pyramidal neurons, these L2/3PC PPs are generated independently of the apical dendrite. Thus, surprisingly, these PPs persisted when the apical dendrite was cut off (~50 μm from the soma), and were sustained by local calcium application only to the somatic and basal dendritic compartments. The prefrontal L2/3PCs have been postulated to have a key role in consciousness, according to the Global Neuronal Workspace Theory: their long-range cortico-cortical connections provide the architecture required for the “global work-space", “ignition”, amplification, and sustained, reverberant activity, considered essential for conscious access. The PPs in L2/3PCs caused sustained spiking that profoundly altered the input-output relationships of these neurons, resembling the sustained activity suggested to underlie working memory and the mechanism underlying “behavioural time scale synaptic plasticity” in hippocampal pyramidal cells. The non-apical L2/3 PPs depended on metabotropic cholinergic (mAChR) or glutamatergic (mGluR) modulation, which is probably essential also for conscious brain states and experience, in both wakefulness and dreaming. Pharmacological tests indicated that the non-apical L2/3 PPs depend on transient receptor potential (TRP) cation channels, both TRPC4 and TRPC5, and require external calcium (Ca2+) and internal Ca2+ stores, but not voltage-gated Ca2+ channels, unlike Ca2+-dependent PPs in other cortical pyramidal neurons. These L2/3 non-apical plateau potentials may be involved in prefrontal functions, such as access consciousness, working memory, and executive functions such as planning, decision-making, and outcome prediction.

• Hönigsperger, Christoph; Storm, Johan Frederik & Arena, Alessandro (2023). Laminar evoked responses in mouse somatosensory cortex suggest a special role for deep layers in cortical complexity. European Journal of Neuroscience. ISSN 0953-816X. s. 1–19. doi: 10.1111/ejn.16108. Fulltekst i vitenarkiv Vis sammendrag

  Abstract It has been suggested that consciousness is closely related to the complexity of the brain. The perturbational complexity index (PCI) has been used in humans and rodents to distinguish conscious from unconscious states based on the global cortical responses (recorded by electroencephalography, EEG) to local cortical stimulation (CS). However, it is unclear how different cortical layers respond to CS and contribute to the resulting intra‐ and inter‐areal cortical connectivity and PCI. A detailed investigation of the local dynamics is needed to understand the basis for PCI. We hypothesized that the complexity level of global cortical responses (PCI) correlates with layer‐specific activity and connectivity. We tested this idea by measuring global cortical dynamics and layer‐specific activity in the somatosensory cortex (S1) of mice, combining cortical electrical stimulation in deep motor cortex, global electrocorticography (ECoG) and local laminar recordings from layers 1–6 in S1, during wakefulness and general anaesthesia (sevoflurane). We found that the transition from wake to sevoflurane anaesthesia correlated with a drop in both the global and local PCI (PCI st ) values (complexity). This was accompanied by a local decrease in neural firing rate, spike‐field coherence and long‐range functional connectivity specific to deep layers (L5, L6). Our results suggest that deep cortical layers are mechanistically important for changes in PCI and thereby for changes in the state of consciousness.

• Aamodt, Arnfinn; Nilsen, Andre Sevenius; Markhus, Rune; Kusztor, Aniko; Hasanzadehmoghadam, Fatemeh & Kauppi, Nils [Vis alle 9 forfattere av denne artikkelen] (2023). EEG Lempel-Ziv complexity varies with sleep stage, but does not seem to track dream experience. Frontiers in Human Neuroscience. 16, s. 1–19. doi: 10.3389/fnhum.2022.987714. Fulltekst i vitenarkiv Vis sammendrag

  In a recent electroencephalography (EEG) sleep study inspired by complexity theories of consciousness, we found that multi-channel signal diversity progressively decreased from wakefulness to slow wave sleep, but failed to find any significant difference between dreaming and non-dreaming awakenings within the same sleep stage (NREM2). However, we did find that multi-channel Lempel-Ziv complexity (LZC) measured over the posterior cortex increased with more perceptual ratings of NREM2 dream experience along a thought-perceptual axis. In this follow-up study, we re-tested our previous findings, using a slightly different approach. Partial sleep-deprivation was followed by evening sleep experiments, with repeated awakenings and immediate dream reports. Participants reported whether they had been dreaming, and were asked to rate how diverse, vivid, perceptual, and thought-like the contents of their dreams were. High density (64 channel) EEG was recorded throughout the experiment, and mean single-channel LZC was calculated for each 30 s sleep epoch. LZC progressively decreased with depth of non-REM sleep. Surprisingly, estimated marginal mean LZC was slightly higher for NREM1 than for wakefulness, but the difference did not remain significant after adjusting for multiple comparisons. We found no significant difference in LZC between dream and non-dream awakenings, nor any significant relationship between LZC and subjective ratings of dream experience, within the same sleep stage (NREM2). The failure to reproduce our own previous finding of a positive correlation between posterior LZC and more perceptual dream experiences, or to find any other correlation between brain signal complexity and subjective experience within NREM2 sleep, raises the question of whether EEG LZC is really a reliable correlate of richness of experience as such, within the same sleep stage.

• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Thürer, Benjamin; Aamodt, Arnfinn & Storm, Johan Frederik (2022). Are we really unconscious in “unconscious” states? Common assumptions revisited. Frontiers in Human Neuroscience. 16. doi: 10.3389/fnhum.2022.987051. Fulltekst i vitenarkiv Vis sammendrag

  In the field of consciousness science, there is a tradition to categorize certain states such as slow-wave non-REM sleep and deep general anesthesia as “unconscious”. While this categorization seems reasonable at first glance, careful investigations have revealed that it is not so simple. Given that (1) behavioral signs of (un-)consciousness can be unreliable, (2) subjective reports of (un-)consciousness can be unreliable, and, (3) states presumed to be unconscious are not always devoid of reported experience, there are reasons to reexamine our traditional assumptions about “states of unconsciousness”. While these issues are not novel, and may be partly semantic, they have implications both for scientific progress and clinical practice. We suggest that focusing on approaches that provide a more pragmatic and nuanced characterization of different experimental conditions may promote clarity in the field going forward, and help us build stronger foundations for future studies.

• Arena, Alessandro; Juel, Bjørn Erik; Comolatti, Renzo; Thon, Sarah & Storm, Johan Frederik (2021). Capacity for consciousness under ketamine anaesthesia is selectively associated with activity in posteromedial cortex in rats. Neuroscience of Consciousness. 2022(1), s. 1–15. doi: 10.1093/nc/niac004. Fulltekst i vitenarkiv Vis sammendrag

  It remains unclear how specific cortical regions contribute to the brain’s overall capacity for consciousness. Clarifying this could help distinguish between theories of consciousness. Here, we investigate the association between markers of regionally specific (de)activation and the brain’s overall capacity for consciousness. We recorded electroencephalographic responses to cortical electrical stimulation in six rats and computed Perturbational Complexity Index state-transition (PCIST), which has been extensively validated as an index of the capacity for consciousness in humans. We also estimated the balance between activation and inhibition of specific cortical areas with the ratio between high and low frequency power from spontaneous electroencephalographic activity at each electrode. We repeated these measurements during wakefulness, and during two levels of ketamine anaesthesia: with the minimal dose needed to induce behavioural unresponsiveness and twice this dose. We found that PCIST was only slightly reduced from wakefulness to light ketamine anaesthesia, but dropped significantly with deeper anaesthesia. The high-dose effect was selectively associated with reduced high frequency/low frequency ratio in the posteromedial cortex, which strongly correlated with PCIST. Conversely, behavioural unresponsiveness induced by light ketamine anaesthesia was associated with similar spectral changes in frontal, but not posterior cortical regions. Thus, activity in the posteromedial cortex correlates with the capacity for consciousness, as assessed by PCIST, during different depths of ketamine anaesthesia, in rats, independently of behaviour. These results are discussed in relation to different theories of consciousness.

• Arena, Alessandro; Comolatti, Renzo; Thon, Sarah Kriebel; Casali, Adenauer G. & Storm, Johan Frederik (2021). General Anesthesia Disrupts Complex Cortical Dynamics in Response to Intracranial Electrical Stimulation in Rats. eNeuro. 8(4). doi: 10.1523/ENEURO.0343-20.2021. Fulltekst i vitenarkiv Vis sammendrag

  The capacity of human brain to sustain complex cortical dynamics appears to be strongly associated with conscious experience and consistently drops when consciousness fades. For example, several recent studies in humans found a remarkable reduction of the spatiotemporal complexity of cortical responses to local stimulation during dreamless sleep, general anesthesia, and coma. However, this perturbational complexity has never been directly estimated in non-human animals in vivo previously, and the mechanisms that prevent neocortical neurons to engage in complex interactions are still unclear. Here, we quantify the complexity of electroencephalographic (EEG) responses to intracranial electrical stimulation in rats, comparing wakefulness to propofol, sevoflurane, and ketamine anesthesia. The evoked activity changed from highly complex in wakefulness to far simpler with propofol and sevoflurane. The reduced complexity was associated with a suppression of high frequencies that preceded a reduced phase-locking, and disruption of functional connectivity and pattern diversity. We then showed how these parameters dissociate with ketamine and depend on intensity and site of stimulation. Our results support the idea that brief periods of activity-dependent neuronal silence can interrupt complex interactions in neocortical circuits, and open the way for further mechanistic investigations of the neuronal basis for consciousness and loss of consciousness across species.

• Aamodt, Arnfinn; Nilsen, Andre Sevenius; Thürer, Benjamin; Moghadam, Fatemeh Hasanzadeh; Kauppi, Nils & Juel, Bjørn Erik [Vis alle 7 forfattere av denne artikkelen] (2021). EEG Signal Diversity Varies With Sleep Stage and Aspects of Dream Experience. Frontiers in Psychology. 12. doi: 10.3389/fpsyg.2021.655884. Fulltekst i vitenarkiv Vis sammendrag

  Several theories link consciousness to complex cortical dynamics, as suggested by comparison of brain signal diversity between conscious states and states where consciousness is lost or reduced. In particular, Lempel-Ziv complexity, amplitude coalition entropy and synchrony coalition entropy distinguish wakefulness and REM sleep from deep sleep and anesthesia, and are elevated in psychedelic states, reported to increase the range and vividness of conscious contents. Some studies have even found correlations between complexity measures and facets of self-reported experience. As suggested by integrated information theory and the entropic brain hypothesis, measures of differentiation and signal diversity may therefore be measurable correlates of consciousness and phenomenological richness. Inspired by these ideas, we tested three hypotheses about EEG signal diversity related to sleep and dreaming. First, diversity should decrease with successively deeper stages of non-REM sleep. Second, signal diversity within the same sleep stage should be higher for periods of dreaming vs. non-dreaming. Third, specific aspects of dream contents should correlate with signal diversity in corresponding cortical regions. We employed a repeated awakening paradigm in sleep deprived healthy volunteers, with immediate dream report and rating of dream content along a thought-perceptual axis, from exclusively thought-like to exclusively perceptual. Generalized linear mixed models were used to assess how signal diversity varied with sleep stage, dreaming and thought-perceptual rating. Signal diversity decreased with sleep depth, but was not significantly different between dreaming and non-dreaming, even though there was a significant positive correlation between Lempel-Ziv complexity of EEG recorded over the posterior cortex and thought-perceptual ratings of dream contents.

• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Farnes, Nadine; Romundstad, Luis Georg & Storm, Johan Frederik (2020). Behavioral effects of sub-anesthetic ketamine in a go/no-go task. Journal of Psychedelic Studies. 4(3), s. 156–162. doi: 10.1556/2054.2020.00126. Fulltekst i vitenarkiv Vis sammendrag

  Background and aims While psychedelic agents are known to have powerful, but largely unexplained, effects on contents of consciousness, there is an increasing interest in the potential clinical usefulness of such drugs for therapy, and legalization is discussed in some countries. Thus, it is relevant to study the effects of psychedelic compounds not only on experience, but also on behavioral performance. Methods Seven healthy participants performed a motor response inhibition task before, during, and after sub-anesthetic doses of intravenously administered ketamine. The infusion rate was individually adjusted to produce noticeable subjective psychedelic effects. Results We observed no statistically significant impact of sub-anesthetic ketamine on reaction times, omission errors, or post error slowing, relative to the preceding drug-free condition. However, we did observe significant correlations between performance impairment and self-reported, subjective altered states of consciousness, specifically experience of “anxiety” and “complex imagery.” Conclusions Considering the limited number of participants and large variation in strength of self-reported experiences, further studies with wider ranges of ketamine doses and behavioral tasks are needed to determine the presence and strength of potential behavioral effects.

• Farnes, Nadine; Juel, Bjørn Erik; Nilsen, Andre Sevenius; Romundstad, Luis Georg & Storm, Johan Frederik (2020). Increased signal diversity/complexity of spontaneous EEG, but not evoked EEG responses, in ketamine-induced psychedelic state in humans. PLOS ONE. 15:e024056(11), s. 1–21. doi: 10.1371/journal.pone.0242056. Fulltekst i vitenarkiv Vis sammendrag

  Objective How and to what extent electrical brain activity is affected in pharmacologically altered states of consciousness, where it is mainly the phenomenological content rather than the level of consciousness that is altered, is not well understood. An example is the moderately psychedelic state caused by low doses of ketamine. Therefore, we investigated whether and how measures of evoked and spontaneous electroencephalographic (EEG) signal diversity are altered by sub-anaesthetic levels of ketamine compared to normal wakefulness, and how these measures relate to subjective assessments of consciousness. Methods High-density electroencephalography (EEG, 62 channels) was used to record spontaneous brain activity and responses evoked by transcranial magnetic stimulation (TMS) in 10 healthy volunteers before and after administration of sub-anaesthetic doses of ketamine in an open-label within-subject design. Evoked signal diversity was assessed using the perturbational complexity index (PCI), calculated from the global EEG responses to local TMS perturbations. Signal diversity of spontaneous EEG, with eyes open and eyes closed, was assessed by Lempel Ziv complexity (LZc), amplitude coalition entropy (ACE), and synchrony coalition entropy (SCE). Results Although no significant difference was found in the index of TMS-evoked complexity (PCI) between the sub-anaesthetic ketamine condition and normal wakefulness, all the three measures of spontaneous EEG signal diversity showed significantly increased values in the sub-anaesthetic ketamine condition. This increase in signal diversity also correlated with subjective assessment of altered states of consciousness. Moreover, spontaneous signal diversity was significantly higher when participants had eyes open compared to eyes closed, both during normal wakefulness and during influence of sub-anaesthetic ketamine doses. Conclusion The results suggest that PCI and spontaneous signal diversity may be complementary and potentially measure different aspects of consciousness. Thus, our results seem compatible with PCI being indicative of the brain’s ability to sustain consciousness, as indicated by previous research, while it is possible that spontaneous EEG signal diversity may be indicative of the complexity of conscious content. The observed sensitivity of the latter measures to visual input seems to support such an interpretation. Thus, sub-anaesthetic ketamine may increase the complexity of both the conscious content (experience) and the brain activity underlying it, while the level, degree, or general capacity of consciousness remains largely unaffected.

• Arena, Alessandro; Thon, Sarah; Casali, Adenauer Girardi & Storm, Johan Frederik (2020). General anaesthesia disrupts complex cortical dynamics in response to intracranial electrical stimulation in rats. BioRxiv. ISSN 0362-4331. doi: 10.1101/2020.02.25.964056. Fulltekst i vitenarkiv
• Storm, Johan Frederik (2020). Why does the brain–mind (Consciousness) problem seem so hard?: Reflections on our mental limitations and dualistic intuitions: Neuroscepticism/neuro-complementarity. Journal of Consciousness Studies. ISSN 1355-8250. 27(5-6), s. 174–189. Fulltekst i vitenarkiv
• Halder, Sebastian; Juel, Bjørn Erik; Nilsen, Andre Sevenius; Raghavan, L Venkat & Storm, Johan Frederik (2020). Changes in measures of consciousness during anaesthesia of one hemisphere (Wada test). NeuroImage. ISSN 1053-8119. 226. doi: 10.1016/j.neuroimage.2020.117566. Fulltekst i vitenarkiv Vis sammendrag

  Background In the Wada test, one hemisphere is selectively anaesthetised by unilateral intracarotid injection of a fast-acting anaesthetic agent. This gives a unique opportunity to observe the functions and physiological activity of one hemisphere while anaesthetising the other, allowing direct comparisons between brain states and hemispheres that are not possible in any other setting. Aim To test whether potential measures of consciousness would be affected by selective anaesthesia of one hemisphere, and reliably distinguish the states of the anesthetised and non-anesthetised hemispheres. Methods We analysed EEG data from 7 patients undergoing Wada-tests in preparation for neurosurgery and computed several measures reported to correlate with the state of consciousness: power spectral density, functional connectivity, and measures of signal diversity. These measures were compared between conditions (normal rest vs. unilateral anaesthesia) and hemispheres (injected vs. non-injected), and used with a support vector machine to classify the state and site of injection objectively from individual patient's recordings. Results Although brain function, assessed behaviourally, appeared to be substantially altered only on the injected side, we found large bilateral changes in power spectral density for all frequency bands tested, and functional connectivity changed significantly both between and within both hemispheres. Surprisingly, we found no statistically significant differences in the measures of signal diversity between hemispheres or states, for the group of 7 patients, although 4 of the individual patients showed a significant decrease in signal diversity on the injected side. Nevertheless, including signal diversity measures improved the classification results, indicating that these measures carry at least some non-redundant information about the condition and injection site. We propose that several of these results may be explained by conduction of activity, via the corpus callosum, from the injected to the contralateral hemisphere and vice versa, without substantially affecting the function of the receiving hemisphere, thus reflecting what we call “cross-state unreceptiveness”.

• Aru, Jaan; Siclari, Francesca; Phillips, William A & Storm, Johan Frederik (2020). Apical drive - a cellular mechanism of dreaming? Neuroscience and Biobehavioral Reviews. ISSN 0149-7634. 119, s. 450–455. doi: 10.1016/j.neubiorev.2020.09.018. Fulltekst i vitenarkiv Vis sammendrag

  Dreams are internally generated experiences that occur independently of current sensory input. Here we argue, based on cortical anatomy and function, that dream experiences are tightly related to the workings of a specific part of cortical pyramidal neurons, the apical integration zone (AIZ). The AIZ receives and processes contextual information from diverse sources and could constitute a major switch point for transitioning from externally to internally generated experiences such as dreams. We propose that during dreams the output of certain pyramidal neurons is mainly driven by input into the AIZ. We call this mode of functioning “apical drive”. Our hypothesis is based on the evidence that the cholinergic and adrenergic arousal systems, which show different dynamics between waking, slow wave sleep, and rapid eye movement sleep, have specific effects on the AIZ. We suggest that apical drive may also contribute to waking experiences, such as mental imagery. Future studies, investigating the different modes of apical function and their regulation during sleep and wakefulness are likely to be richly rewarded.

• Juel, Bjørn Erik; Romundstad, Luis Georg; Storm, Johan Frederik & Larsson, Pål Gunnar (2020). Validation of a new approach for distinguishing anesthetized from awake state in patients using directed transfer function applied to raw EEG. Journal of clinical monitoring and computing. ISSN 1387-1307. s. 1–14. doi: 10.1007/s10877-020-00603-x. Fulltekst i vitenarkiv Vis sammendrag

  We test whether a measure based on the directed transfer function (DTF) calculated from short segments of electroencephalography (EEG) time-series can be used to monitor the state of the patients also during sevoflurane anesthesia as it can for patients undergoing propofol anesthesia. We collected and analyzed 25-channel EEG from 7 patients (3 females, ages 41–56 years) undergoing surgical anesthesia with sevoflurane, and quantified the sensor space directed connectivity for every 1-s epoch using DTF. The resulting connectivity parameters were compared to corresponding parameters from our previous study (n = 8, patients anesthetized with propofol and remifentanil, but otherwise using a similar protocol). Statistical comparisons between and within studies were done using permutation statistics, a data driven algorithm based on the DTF-parameters was employed to classify the epochs as coming from awake or anesthetized state. According to results of the permutation tests, DTF-parameter topographies were significantly different between the awake and anesthesia state at the group level. However, the topographies were not significantly different when comparing results computed from sevoflurane and propofol data, neither in the awake nor in anesthetized state. Optimizing the algorithm for simultaneously having high sensitivity and specificity in classification yielded an accuracy of 95.1% (SE = 0.96%), with sensitivity of 98.4% (SE = 0.80%) and specificity of 94.8% (SE = 0.10%). These findings indicate that the DTF changes in a similar manner when humans undergo general anesthesia caused by two distinct anesthetic agents with different molecular mechanisms of action.

• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Thürer, Benjamin & Storm, Johan Frederik (2020). Proposed EEG measures of consciousness: asystematic, comparative review. PsyArXiv. doi: 10.31234/osf.io/sjm4a. Fulltekst i vitenarkiv
• Kusztor, Aniko; Raud, Liisa; Juel, Bjørn Erik; Nilsen, Andre Sevenius; Storm, Johan Frederik & Huster, Rene (2019). Sleep deprivation differentially affects subcomponents of cognitive control. Sleep. ISSN 0161-8105. 42(4). doi: 10.1093/sleep/zsz016. Fulltekst i vitenarkiv
• Hagger-Vaughan, Nicholas & Storm, Johan Frederik (2019). Synergy of Glutamatergic and Cholinergic Modulation Induces Plateau Potentials in Hippocampal OLM Interneurons. Frontiers in Cellular Neuroscience. 13. doi: 10.3389/fncel.2019.00508. Fulltekst i vitenarkiv Vis sammendrag

  Oriens-lacunosum moleculare (OLM) cells are hippocampal inhibitory interneurons that are implicated in the regulation of information flow in the CA1 circuit, inhibiting cortical inputs to distal pyramidal cell dendrites, whilst disinhibiting CA3 inputs to pyramidal cells. OLM cells express metabotropic cholinergic (mAChR) and glutamatergic (mGluR) receptors, so modulation of these cells via these receptors may contribute to switching between functional modes of the hippocampus. Using a transgenic mouse line to identify OLM cells, we found that both mAChR and mGluR activation caused the cells to exhibit long-lasting depolarizing plateau potentials following evoked spike trains. Both mAChR- and mGluR-induced plateau potentials were eliminated by blocking transient receptor potential (TRP) channels, and were dependent on intracellular calcium concentration and calcium entry. Pharmacological tests indicated that Group I mGluRs are responsible for the glutamatergic induction of plateaus. There was also a pronounced synergy between the cholinergic and glutamatergic modulation, plateau potentials being generated by agonists applied together at concentrations too low to elicit any change when applied individually. This synergy could enable OLM cells to function as coincidence detectors of different neuromodulatory systems, leading to their enhanced and prolonged activation and a functional change in information flow within the hippocampus.

• Phillips, William A; Bachmann, Talis & Storm, Johan Frederik (2018). Apical Function in Neocortical Pyramidal Cells: A Common Pathway by Which General Anesthetics Can Affect Mental State. Frontiers in Neural Circuits. 12, s. 1–15. doi: 10.3389/fncir.2018.00050. Fulltekst i vitenarkiv Vis sammendrag

  It has been argued that general anesthetics suppress the level of consciousness, or the contents of consciousness, or both. The distinction between level and content is important because, in addition to clarifying the mechanisms of anesthesia, it may help clarify the neural bases of consciousness. We assess these arguments in the light of evidence that both the level and the content of consciousness depend upon the contribution of apical input to the information processing capabilities of neocortical pyramidal cells which selectively amplify relevant signals. We summarize research suggesting that what neocortical pyramidal cells transmit information about can be distinguished from levels of arousal controlled by sub-cortical nuclei and from levels of prioritization specified by interactions within the thalamocortical system. Put simply, on the basis of the observations reviewed, we hypothesize that when conscious we have particular, directly experienced, percepts, thoughts, feelings and intentions, and that general anesthetics affect consciousness by interfering with the subcellular processes by which particular activities are selectively amplified when relevant to the current context.

• Juel, Bjørn Erik; Romundstad, Luis Georg; Kolstad, Frode; Storm, Johan Frederik & Larsson, Pål Gunnar (2018). Distinguishing anesthetized from awake state in patients: A new approach using one second segments of raw EEG. Frontiers in Human Neuroscience. 12:40, s. 1–14. doi: 10.3389/fnhum.2018.00040. Fulltekst i vitenarkiv Vis sammendrag

  Objective: The objective of this study was to test whether properties of 1-s segments of spontaneous scalp EEG activity can be used to automatically distinguish the awake state from the anesthetized state in patients undergoing general propofol anesthesia. Methods: Twenty five channel EEG was recorded from 10 patients undergoing general intravenous propofol anesthesia with remifentanil during anterior cervical discectomy and fusion. From this, we extracted properties of the EEG by applying the Directed Transfer Function (DTF) directly to every 1-s segment of the raw EEG signal. The extracted properties were used to develop a data-driven classification algorithm to categorize patients as “anesthetized” or “awake” for every 1-s segment of raw EEG. Results: The properties of the EEG signal were significantly different in the awake and anesthetized states for at least 8 of the 25 channels (p < 0.05, Bonferroni corrected Wilcoxon rank-sum tests). Using these differences, our algorithms achieved classification accuracies of 95.9%. Conclusion: Properties of the DTF calculated from 1-s segments of raw EEG can be used to reliably classify whether the patients undergoing general anesthesia with propofol and remifentanil were awake or anesthetized. Significance: This method may be useful for developing automatic real-time monitors of anesthesia.

• Hönigsperger, Christoph; Nigro, Maximiliano José & Storm, Johan Frederik (2017). Physiological roles of Kv2 channels in entorhinal cortex layer II stellate cells revealed by Guangxitoxin-1E. Journal of Physiology. ISSN 0022-3751. 595(3), s. 739–757. doi: 10.1113/JP273024. Fulltekst i vitenarkiv Vis sammendrag

  The medial entorhinal cortex (mEC) is strongly involved in spatial navigation, memory, dementia and epilepsy. Although potassium channels shape neuronal activity, their roles in mEC are largely unknown. We used the new Kv2 blocker Guangxitoxin-1E (GTx; 10–100 nm) in rat brain slices to investigate Kv2 channel functions in mEC layer II stellate cells (SCs). These neurons project to the hippocampus and are considered to be grid cells representing space. Voltage clamp recordings from SCs nucleated patches showed that GTx inhibited a delayed rectifier K+ current activating beyond –30 mV but not transient A-type current. In current clamp, GTx (i) had almost no effect on the first action potential but markedly slowed repolarization of late spikes during repetitive firing; (ii) enhanced the after-depolarization (ADP); (iii) reduced fast and medium after-hyperpolarizations (AHPs); (iv) strongly enhanced burst firing and increased excitability at moderate spike rates but reduced spiking at high rates; and (v) reduced spike clustering and rebound potentials. The changes in bursting and excitability were related to the altered ADPs and AHPs. Kv2 channels strongly shape the activity of mEC SCs by affecting spike repolarization, after-potentials, excitability and spike patterns. GTx is a useful tool and may serve to further clarify Kv2 channel functions in neurons. We conclude that Kv2 channels in mEC SCs are important determinants of intrinsic properties that allow these neurons to produce spatial representation. The results of the present study may also be important for the accurate modelling of grid cells. This is the peer reviewed version of the article which has been published in final form at https://doi.org/10.1113/JP273024. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

• Storm, Johan Frederik; Boly, Melanie; Casali, Adenauer G.; Massimini, Marcello; Olcese, Umberto & Pennartz, Cyriel M.A. [Vis alle 7 forfattere av denne artikkelen] (2017). Consciousness regained: Disentangling mechanisms, brain systems, and behavioral responses. Journal of Neuroscience. ISSN 0270-6474. 37(45), s. 10882–10893. doi: 10.1523/JNEUROSCI.1838-17.2017. Fulltekst i vitenarkiv Vis sammendrag

  How consciousness (experience) arises from and relates to material brain processes (the “mind-body problem”) has been pondered by thinkers for centuries, and is regarded as among the deepest unsolved problems in science, with wide-ranging theoretical, clinical, and ethical implications. Until the last few decades, this was largely seen as a philosophical topic, but not widely accepted in mainstream neuroscience. Since the 1980s, however, novel methods and theoretical advances have yielded remarkable results, opening up the field for scientific and clinical progress. Since a seminal paper by Crick and Koch (1998) claimed that a science of consciousness should first search for its neural correlates (NCC), a variety of correlates have been suggested, including both content-specific NCCs, determining particular phenomenal components within an experience, and the full NCC, the neural substrates supporting entire conscious experiences. In this review, we present recent progress on theoretical, experimental, and clinical issues. Specifically, we (1) review methodological advances that are important for dissociating conscious experience from related enabling and executive functions, (2) suggest how critically reconsidering the role of the frontal cortex may further delineate NCCs, (3) advocate the need for general, objective, brain-based measures of the capacity for consciousness that are independent of sensory processing and executive functions, and (4) show how animal studies can reveal population and network phenomena of relevance for understanding mechanisms of consciousness.

• Wang, Kang; Mateos-Aparicio, Pedro; Hönigsperger, Christoph; Raghuram, Vijeta; Wu, Wendy W. & Ridder, Margreet C. [Vis alle 10 forfattere av denne artikkelen] (2015). IK1 Channels Do Not Contribute to the Slow Afterhyperpolarization in Pyramidal Neurons. eLIFE. doi: 10.1093/toxsci/kfv245. Fulltekst i vitenarkiv
• Hönigsperger, Christoph; Marosi, Mate Gabor; Murphy, Ricardo & Storm, Johan Frederik (2015). Dorsoventral differences in Kv7/M-current and its impact on resonance, temporal summation and excitability in rat hippocampal pyramidal cells. Journal of Physiology. ISSN 0022-3751. 593(7), s. 1551–1580. doi: 10.1113/jphysiol.2014.280826. Fulltekst i vitenarkiv
• Giglio, Anna Maria & Storm, Johan Frederik (2014). Postnatal development of temporal integration, spike timing and spike threshold regulation by a dendrotoxin-sensitive K+ current in rat CA1 hippocampal cells. European Journal of Neuroscience. ISSN 0953-816X. 39(1), s. 12–23. doi: 10.1111/ejn.12385. Fulltekst i vitenarkiv Vis sammendrag

  Spike timing and network synchronization are important for plasticity, development and maturation of brain circuits. Spike delays and timing can be strongly modulated by a low-threshold, slowly inactivating, voltage-gated potassium current called D-current (ID ). ID can delay the onset of spiking, cause temporal integration of multiple inputs, and regulate spike threshold and network synchrony. Recent data indicate that ID can also undergo activity-dependent, homeostatic regulation. Therefore, we have studied the postnatal development of ID -dependent mechanisms in CA1 pyramidal cells in hippocampal slices from young rats (P7-27), using somatic whole-cell recordings. At P21-27, these neurons showed long spike delays and pronounced temporal integration in response to a series of brief depolarizing current pulses or a single long pulse, whereas younger cells (P7-20) showed shorter discharge delays and weak temporal integration, although the spike threshold became increasingly negative with maturation. Application of α-dendrotoxin (α-DTX), which blocks ID , reduced the spiking latency and temporal integration most strongly in mature cells, while shifting the spike threshold most strongly in a depolarizing direction in these cells. Voltage-clamp analysis revealed an α-DTX-sensitive outward current (ID ) that increased in amplitude during development. In contrast to P21-23, ID in the youngest group (P7-9) showed smaller peri-threshold amplitude. This may explain why long discharge delays and robust temporal integration only appear later, 3 weeks postnatally. We conclude that ID properties and ID -dependent functions develop postnatally in rat CA1 pyramidal cells, and ID may modulate network activity and plasticity through its effects on synaptic integration, spike threshold, timing and synchrony

• Mateos-Aparicio, Pedro; Murphy, Ricardo & Storm, Johan Frederik (2014). Complementary functions of SK and Kv7/M potassium channels in excitability control and synaptic integration in rat hippocampal dentate granule cells. Journal of Physiology. ISSN 0022-3751. 592(4), s. 669–693. doi: 10.1113/jphysiol.2013.267872. Fulltekst i vitenarkiv
• Nigro, Maximiliano José; Mateos-Aparicio, Pedro & Storm, Johan Frederik (2014). Expression and functional roles of Kv7/KCNQ/M-channels in rat medial entorhinal cortex layer II stellate cells. Journal of Neuroscience. ISSN 0270-6474. 34(20), s. 6807–6812. doi: 10.1523/JNEUROSCI.4153-13.2014. Fulltekst i vitenarkiv Vis sammendrag

  The medial entorhinal cortex (MEC) is important for spatial navigation and memory. Stellate cells (SCs) of MEC layer II provide major input to the hippocampus, and are thought to be the neuronal correlate of the grid cells. Their electrophysiological properties have been used to explain grid field formation. However, little is known about the functional roles of potassium channels in SCs. M-current is a slowly activating potassium current, active at subthreshold potentials. Although some studies have suggested that Kv7/M-channels may affect subthreshold resonance in SCs, others have found no Kv7/M-current in these cells, so the expression and roles of Kv7/M-channels in SCs are still debated. Using whole-cell voltage-clamp, we have identified a typical M-current with pharmacological properties characteristic of Kv7/M-channels in rat MEC SCs. Current-clamp experiments showed that the specific Kv7/M-channel blocker XE991 increased SCs excitability, and reduced spike frequency adaptation. Our results demonstrate that Kv7/M-channels are expressed in SCs and contribute substantially to regulation of excitability in these cells.

• Molden, Sturla; Moldestad, Olve & Storm, Johan Frederik (2013). Estimating Extracellular Spike Waveforms from CA1 Pyramidal Cells with Multichannel Electrodes. PLOS ONE. 8(12). doi: 10.1371/journal.pone.0082141. Fulltekst i vitenarkiv
• Lauritzen, Knut Husø; Dalhus, Bjørn; Storm, Johan Frederik; Bjørås, Magnar & Klungland, Arne (2011). Modeling the impact of mitochondrial DNA damage in forebrain neurons and beyond. Mechanisms of Ageing and Development. ISSN 0047-6374. 132(8-9), s. 424–428. doi: 10.1016/j.mad.2011.02.006. Fulltekst i vitenarkiv
• Lauritzen, Knut Husø; Moldestad, Olve; Eide, Lars; Carlsen, Harald; Nesse, Gaute & Storm, Johan Frederik [Vis alle 9 forfattere av denne artikkelen] (2010). Mitochondrial DNA Toxicity in Forebrain Neurons Causes Apoptosis, Neurodegeneration, and Impaired Behavior. Molecular and Cellular Biology. ISSN 0270-7306. 30(6), s. 1357–1367. doi: 10.1128/MCB.01149-09. Fulltekst i vitenarkiv Vis sammendrag

  Mitochondrial dysfunction underlying changes in neurodegenerative diseases is often associated with apoptosis and a progressive loss of neurons, and damage to the mitochondrial genome is proposed to be involved in such pathologies. In the present study we designed a mouse model that allows us to specifically induce mitochondrial DNA toxicity in the forebrain neurons of adult mice. This is achieved by CaMKII-regulated inducible expression of a mutated version of the mitochondrial UNG DNA repair enzyme (mutUNG1). This enzyme is capable of removing thymine from the mitochondrial genome. We demonstrate that a continual generation of apyrimidinic sites causes apoptosis and neuronal death. These defects are associated with behavioral alterations characterized by increased locomotor activity, impaired cognitive abilities, and lack of anxietylike responses. In summary, whereas mitochondrial base substitution and deletions previously have been shown to correlate with premature and natural aging, respectively, we show that a high level of apyrimidinic sites lead to mitochondrial DNA cytotoxicity, which causes apoptosis, followed by neurodegeneration.

• Kaufmann, Walter A.; Kasugai, Y; Ferraguti, F & Storm, Johan Frederik (2010). TWO DISTINCT POOLS OF LARGE-CONDUCTANCE CALCIUM-ACTIVATED POTASSIUM CHANNELS IN THE SOMATIC PLASMA MEMBRANE OF CENTRAL PRINCIPAL NEURONS. Neuroscience. ISSN 0306-4522. 169(3), s. 974–986. doi: 10.1016/j.neuroscience.2010.05.070. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Aas, Kristina; Aass, Hanne Cecilia; Jemterud, Torkild; Juel, Bjørn Erik & Storm, Johan Frederik (2025). Hvorfor drømmer vi? [Radio]. NRK. doi: https:/radio.nrk.no/podkast/abels_taarn/l_8028544e-1ce4-4462-a854-4e1ce454629b. Fulltekst i vitenarkiv Vis sammendrag

  Hva er det som egentlig skjer i hjernen når vi drømmer? Hvordan kan drømmer føles så ekte, og hvorfor drømmer vi i det hele tatt? I denne miniserien tar vi et dypdykk i drømmenes verden.

• Storm, Johan Frederik (2022). MEASURES OF CONSCIOUSNESS. Varieties of measures and mechanisms accross species and conditions. Fulltekst i vitenarkiv
• Storm, Johan Frederik (2021). Hvordan oppstår bevisste opplevelser i hjernen? Innblikk i nyere naturvitenskapelig bevissthetsforskning. Fulltekst i vitenarkiv
• Storm, Johan Frederik (2020). Forskningsdagene 2020 - Hjernen og Bevisstheten. UiO web. Fulltekst i vitenarkiv Vis sammendrag

  https://www.med.uio.no/imb/forskning/grupper/hjernesignaler/i-media-nyheter/forskningsdagene-2020-hjernen-og-bevissthet.html

• Storm, Johan Frederik (2020). Forskergruppen "Hjernens signaler" deltar på Forskningsdagene 2020. UiO web. Fulltekst i vitenarkiv Vis sammendrag

  https://www.med.uio.no/imb/forskning/grupper/hjernesignaler/i-media-nyheter/forskningsdagene-2020.html

• Gjerstad, Leif; Jensen, Vidar; Langmoen, Iver Arne; Lømo, Terje; Moser, Edvard Ingjald & Moser, May-Britt [Vis alle 8 forfattere av denne artikkelen] (2020). Per Andersen. 9. doi: 10.4045/tidsskr.20.0353. Fulltekst i vitenarkiv
• Nicoll, Roger A; Storm, Johan Frederik & Storm-Mathisen, Jon (2020). Obituary. Per Andersen 1930–2020. 106, s. 366–368. doi: 10.1016/j.neuron.2020.04.016. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Marshall, William & Storm, Johan Frederik (2019). Estimating Integrated Information: How noise, sampling, and perturbations affect Phi. Fulltekst i vitenarkiv
• Murphy, Ricardo; Nilsen, Andre Sevenius; Juel, Bjørn Erik; Plesser, Hans Ekkehard; Hill, Sean & Nieus, Thierry [Vis alle 8 forfattere av denne artikkelen] (2019). A multiarea Hill-Tononi thalamocortical network model evaluated with proposed measures of consciousness. Fulltekst i vitenarkiv
• Roth, Fabian Christoph; Storm, Johan Frederik & Hu, Hua (2018). A unique subcellular distribution of HCN channels accelerates action potential propagation in GABAergic interneuron axons. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Nilsen, Andre Sevenius; Gosseries, Olivia; Sarasso, Simone; Larsson, Pål Gunnar & Boly, Malanie [Vis alle 9 forfattere av denne artikkelen] (2018). Measures of connectivity, complexity and signal diversity in EEG distinguish conscious from unconscious state during anesthesia. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Nilsen, Andre Sevenius; Murphy, Ricardo & Storm, Johan Frederik (2018). Thalamocortical model for studying the effects of neuromodulation on network properties. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius & Storm, Johan Frederik (2018). Tracking conscious states: the potential of spontaneous EEG signal complexity. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Romundstad, Luis Georg; Kolstad, Frode; Storm, Johan Frederik & Larsson, Pål Gunnar (2018). Changes in EEG captured by Directed Transfer Function is sufficient to accurately classify the state of wakefulness in patients undergoing sevoflurane anesthesia in accordance with the clinician’s judgement. Fulltekst i vitenarkiv
• Halder, Sebastian; Raghavan, L Venkat; Juel, Bjørn Erik; Nilsen, Andre Sevenius & Storm, Johan Frederik (2018). Effects of intracarotid sodium amobarbital procedure (ISAP) on cortical complexity. Fulltekst i vitenarkiv
• Murphy, Ricardo; Nilsen, Andre Sevenius; Juel, Björn E; Hill, Sean; Plesser, Hans Ekkehard & Nieus, Thierry [Vis alle 8 forfattere av denne artikkelen] (2018). Implementation of the Hill-Tononi thalamocortical network model in the neural simulator NEST. Fulltekst i vitenarkiv
• Murphy, Ricardo; Nilsen, Andre Sevenius; Juel, Bjørn Erik; Plesser, Hans Ekkehard; Hill, Sean & Nieus, Thierry [Vis alle 8 forfattere av denne artikkelen] (2018). Implementation of the Hill-Tononi thalamocortical network model in the neural simulator NEST. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Marshall, William & Storm, Johan Frederik (2018). Calculating conscious capacity: approximations, analogues, and correlates of PHI. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Juel, Bjørn Erik & Storm, Johan Frederik (2018). Attentional Modulation on Measures of Conscious States. Fulltekst i vitenarkiv
• Hagger-Vaughan, Nicholas; Klaus, Carolin & Storm, Johan Frederik (2017). Dual adrenergic modulation of HCN channels in hippocampal and neocortical pyramidal neurons. Fulltekst i vitenarkiv
• Hagger-Vaughan, Nicholas & Storm, Johan Frederik (2017). Differential basal properties and metabotropic modulation responses between OLM and Martinotti cells. Fulltekst i vitenarkiv
• Arena, Alessandro & Storm, Johan Frederik (2017). TOWARD THE EXPLORATION OF COMPLEXITY IN RATS. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Nilsen, Andre Sevenius; Farnes, Nadine & Storm, Johan Frederik (2017). Comparing electrophysiological markers of consciousness between physiologically distinct states of wakefulness. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Storm, Johan Frederik; Romundstad, Luis Georg & Larsson, Pål Gunnar (2017). Markers of consciousness before, during, and after anesthesia. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Kusztor, Aniko; Nilsen, Andre Sevenius; Farnes, Nadine; Larsson, Pål Gunnar & Romundstad, Luis Georg [Vis alle 7 forfattere av denne artikkelen] (2017). Changes in electrophysiological markers of consciousness in response to various anesthetics. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Storm, Johan Frederik; Murphy, Ricardo; Plesser, Hans Ekkehard & Hill, Sean [Vis alle 8 forfattere av denne artikkelen] (2017). Implementation of the Hill-Tononi thalamocortical network model in the neural simulator NEST. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Storm, Johan Frederik & Juel, Bjørn Erik (2017). Attentional Modulation on Measures of Conscious States. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Juel, Bjørn Erik & Storm, Johan Frederik (2017). Proxies for integrated information of microscale networks Is it possible to predict PHI? Fulltekst i vitenarkiv
• Bremnes, Thomas Rene; Juel, Bjørn Erik; Sarasso, Simone; Boly, Melanie; Casarotto, Silvia & Casali, Adenauer G. [Vis alle 12 forfattere av denne artikkelen] (2017). Unresponsive states with and without report of conscious experience show distinct patterns of EEG-based effective brain connectivity in humans. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Arena, Alessandro; Juel, Bjørn Erik; Storm, Johan Frederik; Murphy, Ricardo & Hu, Hua [Vis alle 7 forfattere av denne artikkelen] (2017). Forsknigstorget: Hvordan kan hjernen skape bevissthet. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Bremnes, Thomas Rene; Larsson, Pål Gunnar & Storm, Johan Frederik (2017). Classifying states of (un)consciousness based on one second of raw EEG. Fulltekst i vitenarkiv
• Farnes, Nadine; Juel, Bjørn Erik; Nilsen, Andre Sevenius; Romundstad, Luis Georg; Larsson, Pål Gunnar & Engstrøm, Morten [Vis alle 7 forfattere av denne artikkelen] (2017). Integrated information in sub-anaesthetic ketamine measured by TMS and EEG. Fulltekst i vitenarkiv
• Murphy, Ricardo; Nilsen, Andre Sevenius; Juel, Bjørn Erik; Plesser, Hans Ekkehard; Hill, Sean & Nieus, Thierry [Vis alle 8 forfattere av denne artikkelen] (2017). Implementation of the Hill-Tononi thalamocortical network model in the neural simulator NEST. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Murphy, Ricardo; Juel, Bjørn Erik; Plesser, Hans Ekkehard; Hill, Sean & Nieus, Thierry [Vis alle 8 forfattere av denne artikkelen] (2017). Simulating deep sleep and awake states in a mammalian thalamocortical model. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Romundstad, Luis Georg; Kolstad, Frode; Storm, Johan Frederik & Larsson, Pål Gunnar (2016). Differences in effective connectivity can be used to separate conscious from unconscious states in patients undergoing general anesthesia. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Bremnes, Thomas Rene; Larsson, Pål Gunnar & Storm, Johan Frederik (2016). Comparing Potential Objective Measures of Human Consciousness: the Perturbational Complexity Index and the Directed Transfer Function. Fulltekst i vitenarkiv
• Murphy, Ricardo; Hönigsperger, Christoph; Nigro, Maximiliano Jose & Storm, Johan Frederik (2016). Patch clamp and modeling suggest that Kv2 channels are an important determinant of firing patterns in layer II stellate cells of the medial entorhinal cortex. Fulltekst i vitenarkiv
• Hagger-Vaughan, Nicholas & Storm, Johan Frederik (2016). CA1 OLM cells exhibit plateau potentials in response to metabotropic glutamate receptor activation. Fulltekst i vitenarkiv
• Storm, Johan Frederik; Murphy, Ricardo & Mateos-Aparicio, Pedro (2016). Kv7/M-current function in axons: high-pass filtering of plateau potentials promotes full action potentials, also during cholinergic activation. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Romundstad, Luis Georg; Kolstad, Frode; Storm, Johan Frederik & Larsson, Pål Gunnar (2015). Monitoring Brain Connectivity to Predict Patients’ Level of Awareness. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Romundstad, Luis Georg; Kolstad, Frode; Storm, Johan Frederik & Larsson, Pål Gunnar (2015). Can We Monitor Consciousness in Real Time with EEG? Fulltekst i vitenarkiv
• Storm, Johan Frederik & Dehaene, Stanislas (2013). Signatures of conscious processing in the human brain. Fulltekst i vitenarkiv Vis sammendrag

  Sammen med Det Norske Videnskaps-Akademi, arrangerte forum for bevissthetsforskning et åpent møte med professor i kognitiv psykologi Stanislas Dehaene den 6. november. Mer en 150 deltakere møtte opp for å høre ham snakke om sin forskning på bevissthet. Dehaene holdt et foredrag om en serie eksperimenter han har gjort med sine samarbeidspartnere som forsøker å beskrive de endringene som skjer i hjernen når forsøkspersonene blir oppmerksom på ny informasjon. Forsøkene benytter små endringer i de eksperimentelle betingelsene som kan avgjøre om de samme stimuli blir registrert eller ikke. Det er, for eksempel, små endringer i hvor lenge et stimulus blir presentert for forsøkspersonene. Forskningen benytter EEG, fMRI og MEG for å studere endringer i hjernes aktivitet under disse eksperimentene. Resultatene fra Dehaenes forskning indikerer at bevissthet er forbundet med global økning i sen synkronisert aktivitet (en cortical «antenning») som er spredt over mange corticale områder. Sammen med sine medarbeidere har han utviklet en teori om et globalt nevronalt arbeidsminne eller -område i hjernen. I denne teorien er opplevelsen av bevissthet knyttet til tilgjengeligheten av informasjon i store nettverk i hjernen av pyramide-nevroner med langedistanse aksoner. Foredraget ble etterfulgt av en debatt ledet av Visepreses Nils Chr. Stenseth, og i panelet satt professor i nevrofysiologi Johan F. Storm, førsteamanuensis i psykologi Thomas Espeseth, post. doc. i filosofi Sebastian Watzl sammen med professor i kognitiv psykologi Stanislas Dehaene.

• Storm, Johan Frederik & Chalmers, David (2013). En samtale med David Chalmers om bevissthet og hjerne. Fulltekst i vitenarkiv Vis sammendrag

  På dette møtet fikk vi besøk av den berømte australske filosofen David Chalmers - en av vår tids mest markante bevissthetsfilosofer. Chalmers er en av de mest dyptpløyende deltakerne i dagens filosofiske diskusjon om bevissthetens natur. Han er kjent for sin formulering av "The hard problem of consciousness", som selve kjernespørsmålet: Hvorfor er vår hjernevirksomhet ledsaget at bevisste opplevelser, altså subjektive fornemmelser, følelser og tanker? "The easy problems of consciousness", derimot, definerer han som alle spørsmålene om hjernens målbare funksjoner som hjerneforskerne kan studere med sine metoder. Chalmers har markert seg som en skarp kritiker av den dominerende retningen i vår tids bevissthetsfilosofi: Fysikalismen – altså ideen at alt er noe fysisk, inkludert bevisstheten. Han mener fysikalismen er ute av stand til å besvare hvorfor vi har bevisste opplevelser. I motsetning til de aller fleste andre av dagens filosofer, fremmer Chalmers derfor et dualistisk syn på hjerne og bevissthet, naturalistic dualism, som imidlertid kan sies å ha fellestrekk med blant annet Bertrand Russells nøytrale monisme. Chalmers har også gitt viktige bidrag bl.a. til språkfilosofi og tolkning kvantemekanikkens paradokser. Chalmers besøker Oslo etter invitasjon av Centre for the Study of Mind in Nature, UiO (CSMN), og er invitert til vårt forum av professor Dagfinn Føllesdal. Møtet var lagt opp som en samtale med Chalmers om hjerne og bevissthet.

• Tuvnes, Frode Alexander; Storm, Johan Frederik; Larsson, Pål Gunnar; Mateos-Aparicio, Pedro; Murphy, Ricardo & Oksvold, Cecilie Petterson [Vis alle 8 forfattere av denne artikkelen] (2013). Hva skjer i hjernen din? Fulltekst i vitenarkiv Vis sammendrag

  Hva skjer i hjernen din? Hva er hukommelse? Hva er bevissthet? Hva skjer i hjernen din når du føler noe? Hvordan kan elektriske impulser kode tanker? Hos oss kan du: - Se hjernebølger. - Se levende hjernevev og hjerneceller. - Se og høre hjernecellene sende signaler til hverandre. - Se matematiske modeller av hjernecellenes signaler. Akkurat nå, mens du leser denne teksten, farer milliarder av elektriske signaler gjennom cellene i hjernen din. Men hva er egentlig disse gåtefulle hjerneprosessene? Vår forskergruppe prøver å finne svarene. Kom og få et innbilkk i hva som foregår i hjernen din!

• Hönigsperger, Christoph; Nigro, Maximiliano José & Storm, Johan Frederik (2013). Physiological roles of Kv2 channels in entorhinal cortex layer II cells revealed by Guangxitoxin-1E. Fulltekst i vitenarkiv Vis sammendrag

  The medial entorhinal cortex (mEC) plays a central role in memory formation and spatial navigation, and is often involved in epilepsy and dementia. In the mEC circuitry, stellate cells (SCs) of the layer II occupy a key position, as they receive inputs from association areas of the neocortex, and they are the main source of the perforant path input to the hippocampus. SCs are thought to be the neural correlate of mEC grid cells, which perform path integration and play a key role in spatial navigation. Distinctive electrophysiological properties of SCs are: prominent subthreshold resonance and membrane potential oscillations/fluctuations in the theta frequency range, spike clustering, and spike frequency adaptation. Although voltage-gated potassium (Kv) channels are known to be important for the electrophysiological characteristics of neurons, their physiological roles in mEC SCs largely remain to be determined. We focused on the roles of Kv2 channels, which are known to strongly regulate excitability and the action potential (AP) waveform in several other neuron types. The Kv2 channels are often located mainly in the soma and proximal dendrites of those neurons, and underlie the main delayed rectifier Kv current that activates and inactivates relatively slowly. Here we use a recently identified powerful blocker of Kv2 channels, Guangxitoxin-1E (GxTx) to unveil the physiological roles of Kv2 channels in mEC SCs. We found that 100 nM GxTx had no effect on the cell input resistance, as expected for a Kv2 blocker, but strongly increased the amplitude and area of the afterdepolarization (ADP) following a single AP. During steady, subthreshold depolarization that evoked oscillations and spontaneous firing in control conditions, GxTx induced bursting in 7 of the 8 cells tested. Using voltage clamp recordings in nucleated patches, we found that 100 nM GxTx blocked about 40% of the current at the end of a 400 ms voltage step from -84 mV to -14 mV, but had no significant effect on the peak current within the first 10 ms after the onset of the step. These results support the idea that GxTx acts mainly on Kv2 channels. Our results support the notion that GxTx is a potent and specific blocker of Kv2 channels in EC SCs, and indicate that Kv2 channels strongly modulate the excitability, spike afterpotentials, and discharge pattern of this cell type.

• Mateos-Aparicio, Pedro & Storm, Johan Frederik (2013). Dorsoventral differences in neuromodulation of dentate gyrus granule cells. Fulltekst i vitenarkiv
• Mateos-Aparicio, Pedro & Storm, Johan Frederik (2013). Dorsoventral differences in neuromodulation of dentate gyrus granule cells. Fulltekst i vitenarkiv
• Storm, Johan Frederik & Hu, Hua (2013). Robust propagation and initiation of dendritic action potentials in layer 2 stellate cells of the medial entorhinal cortex. Fulltekst i vitenarkiv Vis sammendrag

  Stellate cells (SCs) in layer 2 of the medial entorhinal cortex (mEC) display ‘grid’-like pattern of firing fields during spatial navigation, which is regarded as an essential neural mechanism for path integration. Computational models and experimental evidence have suggested that grid cell activity may depend on instrinsic biophysical processes within mEC stellate cells, including interference between dendritic and somatic subthreshold membrane potential oscillations. Therefore, examination of the biophysical properties of mEC stellate cell dendrites is fundamental for dissecting the mechanisms of grid formation. We performed simultaneous soma-dendritic or soma-axonal whole-cell recordings from rat mEC stellate cells (37 soma-dendritic and 13 soma-axonal recordings, respectively). We found that action potentials (APs) evoked by somatic depolarization were initiated in proximal axon (~ 25 µm from soma) and backpropagated into the dendrite (up to 151 µm) with little attenuation of their amplitude. In response to depolarizing input directly in the dendrite, APs could be initiated in both proximal (< 50 µm) and distal dendrites with high reliability. Tetrodotoxin (TTX) inhibited the initiation of dendritic APs, and strongly attenuated the amplitude of backpropagating APs. Spontaneous subthreshold membrane potential oscillations near theta frequency were measured in both the axon, dendrites and soma of mEC stellate cells. The membrane potential oscillations at these different subcellular compartments within the same stellate cell displayed identical oscillation frequency and were phase-locked to each other, with the proximal axon (~ 25 µm) displaying the strongest oscillation power. Thus, our results indicate that active dendritic properties support action potential backpropagation and initiation, and a putative axonal origin of subthreshold membrane potential oscillations in layer 2 mEC stellate cells.

• Storm, Johan Frederik (2013). Er bevissthetsproblemet et naturvitenskapelig forskbart problem? Fulltekst i vitenarkiv
• Larsson, Pål Gunnar; Stavrinou, ML; Kugiumtzis, Dimitris & Storm, Johan Frederik (2012). PERSISTENT CONNECTIVITY DURING AWAKE AND SLEEP OF BRAIN LOCATIONS GENERATING CONTINUOUS SPIKE AND WAVES DURING SLOW SLEEP (CSWS). Epilepsia. ISSN 0013-9580. 53, s. 237–237. Fulltekst i vitenarkiv
• Murphy, Ricardo; Alle, Henrik; Geiger, Jörg & Storm, Johan Frederik (2012). Estimation of persistent sodium and M current densities in poorly space-clamped dentate granule-cell mossy fibers. Fulltekst i vitenarkiv
• Hönigsperger, Christoph; Marosi, Mate Gabor & Storm, Johan Frederik (2012). Characteristics of subthreshold membrane dynamics in dorsal and ventral CA1 pyramidal neurons. Fulltekst i vitenarkiv Vis sammendrag

  The hippocampus shows differences in neuronal connectivity and expression of molecular markers along the dorso-ventral axis. Behavioral and other studies indicate that the dorsal part of the hippocampus performs mainly cognitive functions, whereas the ventral corresponds to emotion and stress. The goal of our study is to determine whether there are differences in the intrinsic electrophysiological properties of dorsal and ventral CA1 pyramidal neurons. Using somatic whole-cell patch-clamp recordings from CA1 pyramidal neurons (n=78), we examined their ability to generate membrane potential oscillations (MPO) at subthreshold range and to respond selectively to oscillating current injections at different frequencies. We also compared repetitive firing evoked by depolarizing current steps. To study resonance at subthreshold potentials, we applied a frequency-modulated sinusoidal current whose frequency increased linearly in time. Our results showed that the majority of dorsal CA1 pyramidal neurons (n=22/30) have a prominent resonance peak (frequency: 2.5±0.3Hz) compared to the ventral side where only few cells (n=7/30) showed detectable resonance, and the resonance frequency was lower (0.8±0.2Hz). We also observed a statistically significant difference in frequency of MPOs at subthreshold potentials (dorsal: 3.4±0.3Hz; ventral: 2.3±0.2Hz). MPOs in CA1 pyramidal neurons are probably generated by interplay of a persistent Na+ current and slowly deactivating K+ current, and it has been shown that subthreshold theta resonance in these cells is generated by persistent Na+ current and Kv7/M-type K+ channels. The Kv7 channels also regulate excitability, spike afterpotentials, and spike frequency adaptation. We hypothesized that Kv7 channels may also contribute to the generation of spontaneous oscillations (MPO) and tested the effect of XE991 (selective Kv7 channel blocker). Application of XE991 lowered the threshold and eliminated MPOs. Our findings indicate that the biophysical properties of CA1 pyramidal cells differ along the dorso-ventral axis, and that MPOs are Kv7-dependent in this cell type.

• Stavrinou, Maria; Larsson, Pål Gunnar & Storm, Johan Frederik (2012). Increased temporo-parietal connectivity in children with ADHD and CSWS. Fulltekst i vitenarkiv Vis sammendrag

  Attention-Deficit hyperactivity disorder (ADHD) is one of the most common neuropsychiatric conditions in childhood. It is characterized by inappropriate expression of impulsivity, inattention and hyperactivity. A per- centage of children with ADHD appear to have continuous spikes and waves during their sleep a condition most often called Continuous spike and waves during slow sleep (CSWS). One of the hypotheses used to explain the affected cognitive functioning of those children concerns changes in resting-state connectivity. In this framework, we studied the functional and effective brain connectivity in children with ADHD and CSWS, focusing on the resting state network with Electroencephalographic recordings. Twenty four-hour recordings including wakefulness and sleep, of children admitted to the National Centre for Epilepsy at Oslo University Hospital were analyzed and compared with controls of the same age group without ADHD. Di- rected transfer function (DTF) was used to measure the effective connectivity between brain areas, in the theta and gamma frequency bands. The analysis have shown an increased temporo-parietal connectivity of the ADHD children, when compared to the control group (p<0.035), most prominently in the left hemi- sphere. Parietal to frontal connections were also significantly different between patients and controls for both frequency bands. The time dynamics of these most active connections have shown increased values of connectivity during the day compared to sleep. This may be related to arousal impairment in children with ADHD.

• Mateos-Aparicio, Pedro & Storm, Johan Frederik (2012). Dorsoventral differences in the slow after-hyperpolarization of dentate gyrus granule cells. Fulltekst i vitenarkiv
• Murphy, Ricardo & Storm, Johan Frederik (2011). Correction of space-clamp errors in voltage-clamp experiments on neurons: Extension of Cox’s method. Fulltekst i vitenarkiv
• Giglio, Anna Maria & Storm, Johan Frederik (2010). Postnatal development of alpha-DTX sensitive D-current in rat CA1 hippocampal pyramidal cells. Fulltekst i vitenarkiv
• Moreno, Pedro Mateos Aparicio; Tuvnes, Frode Alexander & Storm, Johan Frederik (2010). SK channels underlying medium afterhyperpolarizations and excitability control in dentate gyrus granule cells. Fulltekst i vitenarkiv
• Moreno, Pedro Mateos Aparicio; Tuvnes, Frode Alexander & Storm, Johan Frederik (2010). SK channels underlying medium afterhyperpolarizations and excitability control in dentate gyrus granule cells. Fulltekst i vitenarkiv

Se alle arbeider i NVA