CAMBAM Applied Math Seminar (McGill University/U. Montreal)

Title:

Multiple roles of synaptic “inhibition” & how they arise in decision-making pathways in the basal ganglia

Abstract:

This talk concerns topics in mathematical neuroscience but will not assume any specific knowledge of neuroscience. It should be of interest to anyone who would like to learn more about general ideas of mathematical neuroscience or about certain specific topics: integration of multiple streams of inhibition in neural circuits, the role of the basal ganglia in decision-making and action selection, cortico-striatal plasticity, the impact of time-varying reversal potentials, and mechanisms of neural synchronization and oscillations.

The phrase “inhibition” suggests a holding back or suppression of activity. It has long been recognized that the roles of synaptic inhibition in neuronal circuits can be more diverse, however, and include promotion of activity through effects such as post-inhibitory rebound and disynaptic disinhibition. The basal ganglia (BG) is a hub for the reward signal dopamine and is believed to be involved in decision-making and action selection. Interestingly, most synaptic pathways within the BG involve neurotransmitters that are traditionally inhibitory. In the first section of my talk, I will introduce this circuitry and present modeling of how these pathways can collaborate to produce reward-driven action. I will also present joint work with Tim Verstynen, Cati Vich and our trainees, which (1) introduces a way to map between biologically detailed models and more abstract decision-making models and (2) suggests how different BG inhibitory neurons serve different roles in terms of evidence accumulation and decision thresholds. In the second section of my talk, I will present work with postdoc Ryan Phillips and our collaborator Aryn Gittis in which we model the integration of two inhibitory pathways by BG output neurons. Our modeling takes into account chloride dynamics and its impact on synaptic reversal potentials and shows how these pathways can actually induce excitatory effects, can contribute to synchronization and oscillations, and can affect action selection, which may be related to Parkinson’s disease.