2014-05-21 at 15:00
IDV, salle de conférences UCL
On the number of neurons and time scale of integration underlying the formation of percepts in the brain
All of our perceptual experiences arise from the activity of neural populations. Here we study the formation of such percepts under the assumption that they arise from a linear weighted sum of the neurons’ firing rates. We show that this assumption specifies the trial-to-trial covariance structure of neural activities and animal behavior. The predicted covariance structure depends on the readout parameters, and in particular on the temporal integration fire w and typical number of neurons K used in the formation of the percept. Using these predictions, we show how to infer the readout parameters from joint measurements of a subject’s behavior and neural activities. We consider three such scenarios: (1) recordings from the complete neural population, (2) recordings of neuronal subensembles whose average size exceeds K, and (3) recordings of neuronal subensembles that are typically smaller than K. Using theoretical arguments and artificially generated data, we show that the first two scenarios allow us to recover the typical spatial and temporal scales of the readout. In the third scenario, we show that the readout parameters can only be recovered by making additional assumptions about the structure of the full population activity. Our work provides the first thorough interpretation of (feed-forward) percept formation from a population of sensory neurons. It can readily be applied to experimental recordings in classic sensory decision-making tasks, and will hopefully provide new insights into the nature of perceptual integration.