Speaker: Philippe Isope
Subject: Short term plasticity and E/I balance combine to control Purkinje cell discharge in the cerebellum
Location: Erasmus MC
Author: Renée van der Winden
Philippe Isope came to talk to us about his work on some of the workings of the cerebellum. He started with giving us a very brief overview of how the cerebellum works, namely, that it is for motor coordination. He mentioned two mechanisms that were important for the rest of his talk. Those were the fact that the cerebellum can predict the sensory input caused by a voluntary movement and that it adapts its feedback systems through plasticity. One of the questions Isope was concerned with was: ‘Do different tasks of the cerebellum rely on the same processing mechanism?
He then went on to talk about Purkinje cells, which provide the sole output of the cerebellar cortex. The firing of these cells can precede movement, which is linked to the predictive function of the cerebellum. The next topic was the different modules in the cerebellum. It turns out the cerebellum is physiologically heterogeneous and is divided into different modules. The parallel processing this makes possible ensures precision in the cerebellum. Moreover, the communication between the different modules did not seem to be important. This led to a working hypothesis, which said that the individual modules can be coordinated by parallel fibers. However, this raises the question of how they can be precise if the information is spread between them.
Figure 1: A brief overview of the different ways a Purkinje cell is regulated
In order to test this, Isope and his group first identified the modules they wanted to work with. After that, they mapped granule cell inputs in the Purkinje cells. They found out that activity can quite easily tune these maps, so they are apparently not genetically determined. This shows the cerebellum is capable of plasticity. The conclusion was that the E/I (excitation/inhibition) balance is spatially organized and that that leads to precision. In the end, these two things were put together to show that both short term plasticity and the E/I balance working together to control the discharge of the Purkinje cells.
I thought this talk was quite difficult to follow, in part because of the very thick accent of the speaker. This made it less enjoyable to listen to. However, I am still curious about neuroscience so the topic in itself interested me. However, I am sorry to say that I just did not understand quite enough of it to find it truly interesting.