Simulation of optogenetic stimulation in a computational model of Basal Ganglia
CBN (Computational Biology and Neurocomputing) seminars
Friday 20 September 2013
to 11:00 at
Pierre Berthet (CB, KTH and SU)
Optogenetic stimulation of specific types of medium spiny neurons (MSNs) in the striatum has been shown to bias the selection of mice in a two choices task. This shift is dependent on the localisation and on the intensity of the stimulation and on the recent reward history. We have implemented a way to simulate the increased activity produced by the optical flash in a computational model of the basal ganglia (BG). This abstract model features the direct and indirect pathways commonly described in biology, and a reward prediction pathway (RP), in a framework similar to Actor-Critic and to the ventral/dorsal distinction in the striatum. We thus investigated the impact on the selection caused by an added stimulation in each of the three pathways and were able to reproduce in our model the bias in action selection observed in mice with optogenetic stimulation. We studied the shift in action selection profile that stimulation of RP could cause. Biasing RP did affect the results only when the ratio of trials with stimulations over the total number of trials was increased. We found that increasing only the reward prediction had a different effect if the stimulation in RP was action dependent (only for a specific action) or not. We then looked at the evolution of the change in the weights depending on the relative position within a block of a trial. A bias in RP impacts the plasticity differently depending on that position and on the delivery of a reward. It remains to experimentally test how the dopaminergic neurons are affected by specific stimulations of neurons in the striatum and to relate data to predictions of our model.