3D Clustering of GABAergic Neurons Enhances Inhibitory Actions on Excitatory Neurons in the Mouse Visual Cortex

Abstract

Summary: Neocortical neurons with similar functional properties assemble into spatially coherent circuits, but it remains unclear how inhibitory interneurons are organized. We applied in vivo two-photon functional Ca2+ imaging and whole-cell recording of synaptic currents to record visual responses of cortical neurons and analyzed their spatial arrangements. GABAergic interneurons were clustered in the 3D space of the mouse visual cortex, and excitatory neurons located within the clusters (insiders) had a lower amplitude and sharper orientation tuning of visual responses than outsiders. Inhibitory synaptic currents recorded from the insiders were larger than those of the outsiders. Single, isolated interneurons did not show such a location-tuning/amplitude relationship. The two principal subtypes of interneurons, parvalbumin- and somatostatin-expressing neurons, also formed clusters with only slightly overlapping each other and exhibited a different location-tuning relationship. These findings suggest that GABAergic interneurons and their subgroups form clusters to make their inhibitory function more effective than isolated interneurons. : Ebina et al. find 3D clustering of GABAergic neurons and their principal subtypes, parvalbumin- and somatostatin-expressing neurons. They demonstrate that inhibitory actions on excitatory neurons inside these clusters are stronger than outside, suggesting that GABAergic neurons form clusters in order to make their inhibitory function more effective than in isolated neurons.