Functional organization of dendritic spines in mouse visual cortex layer 2/3 neurons

Cortical neurons receive heterogeneous excitatory synaptic inputs, yet the organizational principles underlying their distribution across the dendritic arbor remain poorly understood. Here, we examined how synaptic visual inputs to dendritic spines of mouse visual cortex layer 2/3 excitatory neurons are organized globally and locally using two-photon in vivo calcium imaging. In visually responsive neurons, sharply tuned proximal spines showed higher somatic tuning correlation than did distal spines. Responsive neurons had more responsive spines on their apical dendrites and higher pairwise tuning correlations between spines than did unresponsive neurons. While pairwise tuning correlations between spines did not vary significantly with their distance from the soma, spines on responsive neurons were locally clustered based on correlated tuning. Our findings reveal that visual input is not randomly distributed but organized globally and locally in relation to factors including correlation to and distance from the soma as well as correlation to neighboring spines.