Thesis Defense of Shrabasti Jana 12/12/24

Thursday 12th December 2024, at 14:00, Henri Gastaut meeting room

Shrabasti Jana (CoMCo team)

Motor Control Principles of  Trajectory Selection in Rhesus Macaques

Jury
Gabriella CERRI – Rapporteure
Department of Medical Biotechnology and Translational Medicine, University of Milan
Cécile GALLEA – Rapporteure
Movement Investigation and Therapeutics Team, Paris Brain Institute, Sorbonne University, Inserm U1127, CNRS UMR7225, Paris, France
David THURA – Examinateur
Lyon Neuroscience Research Center (CRNL) – CNRS / Inserm / Claude Bernard University / Jean Monnet University
Fabrice SARLEGNA – Examinateur
CNRS, Institute of Movement Sciences / Aix-Marseille University & CNRS, France
Jozina DE GRAAF – Présidente
CNRS, Institute of Movement Sciences, UMR 7287, Marseille
Thomas BROCHIER – Directeur de thèse
CNRS, Institute of Neurosciences of Timone, UMS 2018 MPRC & UMR 7289 INT

Abstract: Reaching movements, though seemingly simple, involve complex motor control processes that select a specific trajectory from an infinite range of possible trajectories. Despite the inherent variability in voluntary movements, both humans and non-human primates often display stereotyped trajectories. My PhD research investigates how such stereotyped trajectories are selected and how they change with practice in two-dimensional visually guided reaching tasks performed by two rhesus monkeys.

Through behavioral analysis, my work challenges conventional perspectives suggesting that trajectory selection primarily maximizes straightness or minimizes kinetic energy (KE). Instead, the findings reveal that the motor system prioritizes maintaining a “safe KE range,” where minor trajectory deviations have negligible effects on energy expenditure. Additionally, I found that movements in our experimental setup can be broadly categorized into two classes based on their trajectory shapes. These movement classes also show striking differences in their KE constraints. I found that the trajectory shapes are more constrained in the high KE movement class than the other one suggesting distinct motor control strategies for the two classes: flexibility and exploration in low energy movements and precision and exploitation of the best solution for the high energy ones.

To validate these findings and uncover their neural basis, I analyzed the electrophysiological data recorded from the motor and premotor cortices during task performance. The results from this analysis reveal clear differences in how variability in preparatory neural activity correlates with different movement features for the two movement classes. Also, a larger proportion of the recorded neurons were found to be tuned to the movement class that have a higher KE. These differences in the preparatory neural activity for the two movement classes align with the notion that distinct motor strategies of trajectory selection are employed for the movements based on their biomechanical constraints.