Adaptation maintains population homeostasis in primary visual cortex

Abstract

Sensory systems exhibit mechanisms of neural adaptation, which adjust neuronal activity based on recent stimulus history. In primary visual cortex (V1), in particular, adaptation controls the responsiveness of individual neurons and shifts their visual selectivity. What benefits does adaptation confer to a neuronal population? We measured adaptation in the responses of populations of cat V1 neurons to stimulus ensembles with markedly different statistics of stimulus orientation. We found that adaptation serves two homeostatic goals. First, it maintains equality in the time-averaged responses across the population. Second, it maintains independence in selectivity across the population. Adaptation scales and distorts population activity according to a simple multiplicative rule that depends on neuronal orientation preference and on stimulus orientation. We conclude that adaptation in V1 acts as a mechanism of homeostasis, enforcing a tendency towards equality and independence in neural activity across the population.