Abstract

Altered sensory input can change response properties in the visual cortex. How this is implemented at the level of individual synapses is not well understood. In this study we explore whether changes of neuronal response properties induced by monocular deprivation (MD) correlate with alterations of dendritic spines on pyramidal neurons in the visual cortex of adult mice. To address this question, we combined intrinsic signal imaging and two-photon microscopy in mice implanted with cranial windows. This approach allowed us to monitor functional changes of eye-representation in the binocular part of the visual cortex, as well as to image repeatedly the apical dendrites of GFP -labelled neurons before, during and after MD. We found that a brief period of MD robustly altered the balance of dendritic spine turnover in layer 5 neurons in binocular visual cortex. More spines were added during MD than under baseline conditions. In contrast, the rate of spine elimination did not change during MD, leading to an increased spine density. Restoring binocular vision returned spine dynamics to baseline levels, but absolute spine density remained persistently elevated. Importantly, spine addition did not increase again when the same eye was closed for a second time. This absence of structural plasticity after a second MD episode contrast with a robust and even faster change of eye-specific responses after repeated MD. Thus, dendritic spines added during the first monocular deprivation experience may provide a structural basis for subsequent functional shifts. These results provide a strong link between functional plasticity and specific synaptic rearrangements, revealing a mechanism of how prior experiences could be stored in cortical circuits.