Digital Public Defence: Ane Charlotte Christensen

MSc Ane Charlotte Christensen at Institute of Basic Medical Sciences will be defending the thesis “Balancing stability and plasticity-perturbations of extracellularmatrix and inhibitory activity in themature grid cell network” for the degree of PhD (Philosophiae Doctor).

The trial lecture will be held as a video conference over Zoom.

The digital trial lecture will follow regular procedure as far as possible, hence it will be open to the public and the audience can ask ex auditorio questions when invited to do so.

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Digital Trial Lecture – time and place

See Digital Trial Lecture.

Adjudication committee

  • First opponent: Professor Menno Witter, NTNU
  • Second opponent: Principal Investigator Elke C. Fuchs, University of Heidelberg
  • Third member and chair of the evaluation committee: Professor Lars Nilsson, University of Oslo

Chair of the Defence

Professor Emeritus Jon Storm-Mathisen, University of Oslo

Principal Supervisor

Associate Professor Torkel Hafting, University of Oslo

Summary

Our brain is constantly challenged to learn new skills and form new memories, while at the same time having to retain stabile memories of previous experiences. One component contributing to stability is a specialized form of protein structures named perineuronal nets (PNNs). Late in development, PNNs emerge around subpopulations of neurons, wrapping them like a fishnet with holes for synaptic contacts. The appearance of PNNs coincide with a drastic decrease in synaptic plasticity, thus diminishing the brains ability to rewire and change. However, it is unknown if this phenomenon is important for our sense of space.

In this thesis, I have investigated the role of PNNs for an area of the brain that is essential for navigation and spatial memory, the medial entorhinal cortex (MEC). Grid cells in MEC are active in highly specific triangular firing patterns, resembling coordinates on a map.

I show that MEC express high levels of PNNs in adult rodents, indicating that there is little plasticity in the MEC network. Furthermore, when recording from grid cells in rats with PNNs removed, I found that PNNs are important for stabilizing the activity pattern of grid cells, particularly when rats explored a new environment for the first time. It is likely that PNNs regulate the activity of neurons that directly inhibit grid cells and therefore help to maintain their timing and activity levels, thus also the specificity of their activity patterns.  Lastly, I went deeper into exploring the grid cell pattern. Grid cell activity is suggested to be dependent on brainwaves of a particular frequency. By using optogenetics to disrupt the source of rhythmic brainwaves in MEC while simultaneously recording grid cells, I falsified this hypothesis. This finding challenges several theoretical models used to explain grid cell activity and calls for alternative theories of how this remarkable pattern occurs.

 Overall, this work reveals new mechanisms at play for maintaining a stable sense of space.

Additional information

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Published Sep. 11, 2020 11:39 AM - Last modified Sep. 18, 2020 2:29 PM