EXPERIENCE-DEPENDENT FEEDBACK PROCESSING IN MOUSE VISUAL CORTEX

Visual circuits in the brain are shaped by experience during development. Feedforward circuits convey direct information about the environment from the eye to the primary visual cortex, while feedback circuits from higher visual areas use this information to generate indirect, predictive signals based on the environment. Although the effects of experience on feedforward visual processing are well characterized, how experience differentially shapes feedforward and feedback processing remains elusive. Here, we characterize the effects of dark rearing until adulthood on feedforward and feedback processing in the primary visual cortex using in vivo two-photon calcium imaging and in vitro whole-cell recordings. On the first day of light exposure, neurons in primary visual cortex exhibited markedly reduced feedback-driven responses compared to those in age-matched normally-reared controls. Optogenetic feedback influence mapping from the higher visual area LM to neurons in primary visual cortex revealed an altered balance between depolarization and hyperpolarization in dark-reared animals. Over 20 days of passive visual experience, most response properties recovered to levels observed in age-matched normally reared controls. Together, these results demonstrate the necessity of visual experience for the development and normal function of cortical feedback circuits.