Before the defence, Charlotte Christensen presented her trial lecture "The role of inhibition in neurodevelopmental disorders."
The PhD defence and trial lecture were fully digital.
Summary
Our brain is constantly challenged to learn new skills and form new memories, while at the same time having to retain stable memories of previous experiences.
In this thesis, I have investigated the role of peri-neuronal nets (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 Lastly, a long-standing hypothesis suggest that grid cell activity is dependent on brainwaves of a particular frequency. By using optogenetics to disrupt the source of thetawaves 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.