Lorenzo Fontolan Seminar

SPEAKER:
Lorenzo Fontolan, Ph.D.
Postdoctoral Researcher
Howard Hughes Medical Institute

TITLE:
Neural circuit dynamics underlying short-term memory in frontal cortex

ABSTRACT:
Short-term memories link events separated in time, such as past sensation and future actions. Short-term memories are correlated with slow neural dynamics, including selective persistent activity, which can be maintained over seconds. In a delayed response task that requires short-term memory, neurons in the mouse anterior lateral motor cortex (ALM) show persistent activity that instructs future actions. To determine the principles that underlie this persistent activity, we combined intracellular and extracellular electrophysiology with optogenetic perturbations and network modelling. We show that during the delay epoch, the activity of ALM neurons moved towards discrete end points that correspond to specific movement directions.

These end points were robust to transient shifts in ALM activity caused by optogenetic perturbations. Perturbations occasionally switched the population dynamics to the other end point, followed by incorrect actions. Our results show that: 1) discrete attractor dynamics underlie short-term memory related to motor planning; 2) preparatory activity in ALM becomes progressively more robust to stimuli, and this robustness increases with additional behavioral training. These results are consistent with recurrent network models in which the selected motor plan becomes robust to sensory information via discrete attractor dynamics.

BIO:
A physicist by training, my interest is to understand how the brain circuitry is able to generate the exceptional complexity of animal and human behaviour. I did my PhD at the ENS Paris and the University of Geneva under the supervision of Anne-Lise Giraud and Boris Gutkin, focusing on the role of neural oscillations during speech perception. I am currently a postdoctoral researcher at​ HHMI Janelia Research Campus in the group of Sandro Romani. In collaboration with the group of​ Karel Svoboda, I have investigated the dynamics of neural circuits during the preparation of movements in short-term memory tasks.