Caroline Runyan
Department of Neuroscience
University of Pittsburgh

Distinct timescales of population coding across cortex

The cortex represents information across widely varying timescales. For instance, primary auditory cortex encodes stimuli that fluctuate over milliseconds, whereas in association cortex behavioral choices can require the maintenance of information over seconds I will discuss our recent findings that population codes are essential to achieve long and diverse coding timescales, and that codes differ fundamentally 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. Although both regions coded information by tiling in time neurons that were transiently informative for less than ~200 milliseconds, 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, extended over long time lags, and contributed to a long timescale population code characterized by consistent representations of choice lasting over two seconds. In contrast, coupling among AC neurons was weak, shorter-lived, and resulted in moment-to-moment fluctuations in stimulus and choice information. Our results suggest that population coupling is a variable property that affects the timescale of information coding. Finally, I will discuss plans for my future work, to study communication between auditory and other cortical networks, and the circuit mechanisms underlying its modulation by behavioral context and brain state.

A pizza lunch will be served.