INS/INT Keynote Seminar – Stefano Panzeri (Rovereto, Italy)
“The relationship between cross-cell coupling and the timescales of population coding across cortex”
The cortex needs to represents information across a wide range of timescales, from the millisecond-scale required to encode rapidly fluctuating sensory stimuli, to the maintenance of information over seconds that is required to implement certain behavioral choices. Do such diverse timescales result mostly from features intrinsic to individual neurons or from correlated activity in neuronal populations ? Here we report that population codes can be essential to achieve long coding timescales, and that the properties and time scales of population codes differ between sensory and association cortices. We compared coding for sensory stimuli and behavioral choices in auditory cortex (AC) and posterior parietal cortex (PPC) as mice performed a sound-localization task. Auditory stimulus information was strong in AC but weak in PPC, and both regions contained choice information. Although AC and PPC coded information by tiling in time neurons that were transiently informative, the areas had major differences in functional coupling between neurons, measured as activity correlations that could not be explained by task events. Coupling among PPC neurons was strong and extended over long time lags, whereas coupling among AC neurons was weak and short-lived. Stronger coupling in PPC led to a population code with long timescales and a representation of choice that remained consistent for approximately one second. In contrast, AC had a code with rapid fluctuations in stimulus and choice information over hundreds of milliseconds. Our results reveal that population codes differ across cortex and that cross-cell coupling affects the timescale of information coding.
This is joint work with Carolyne Runyan at Chris Harvey at Harvard Medical School and with Eugenio Piasini at IIT.
For any question, feel free to contact:
Benjamin Morillon (firstname.lastname@example.org) or Adam Williamson (adam.WILLIAMSON@univ-amu.fr)