Constructing Perception, Memory and Decision Making across Cortex

A fundamental problem in neurobiology is to understand how brain circuits represent sensory information and how such representations give rise to perception, memory and decision-making. I will show how a sensory stimulus engages multiple areas of the cerebral cortex, including primary sensory, prefrontal, premotor and motor cortices. As information transverses the cortical circuits it shows progressively more relation to perceptual, memory and decision reports. In particular, I will show how somatosensory areas of the parietal lobe generate a parameterized representation of a tactile stimulus. This representation is maintained in working memory by prefrontal and premotor areas of the frontal lobe. The arrival of a second stimulus, that monkeys are trained to compare with the first, generates decision-related activity reflecting which stimulus had the higher frequency. Importantly, I observed decision activity across several cortical circuits including prefrontal, premotor and parietal cortices. Sensory information is encoded by neuronal populations with opposite tuning, and suggests that a simple subtraction operation could be the underlying mechanism by which past and present sensory information is combined to generate perceptual decisions.

Ranulfo Romo is invited by the Collège de France Assembly, at the suggestion of Professor Alain Prochiantz, holder of the Morphogenetic Processes Chair.