Sound-Driven Synaptic Inhibition in Primary Visual Cortex

Summary

Multimodal objects and events activate many sensory cortical areas simultaneously. This is possibly reflected in reciprocal modulations of neuronal activity, even at the level of primary cortical areas. However, the synaptic character of these interareal interactions, and their impact on synaptic and behavioral sensory responses are unclear. Here, we found that activation of auditory cortex by a noise burst drove local GABAergic inhibition on supragranular pyramids of the mouse primary visual cortex, via cortico-cortical connections. This inhibition was generated by sound-driven excitation of a limited number of cells in infragranular visual cortical neurons. Consequently, visually driven synaptic and spike responses were reduced upon bimodal stimulation. Also, acoustic stimulation suppressed conditioned behavioral responses to a dim flash, an effect that was prevented by acute blockade of GABAergic transmission in visual cortex. Thus, auditory cortex activation by salient stimuli degrades potentially distracting sensory processing in visual cortex by recruiting local, translaminar, inhibitory circuits.

Highlights

► Activation of a sensory cortex causes hyperpolarizing responses in neighboring ones ► Sound activates GABAergic synapses onto layer 2/3 pyramids of the visual cortex ► Sound-driven inhibition is due to activation of few cells in layer 5 of visual cortex ► Sound-driven inhibition reduces neuronal and behavioral responses to visual stimuli

Abstract

Iurilli et al. examined the interplay between sensory modalities and discovered that auditory cortex activation can inhibit visual cortical neurons via cortico-cortical inputs that activate inhibitory subcircuits originating in the deep layers of the visual cortex.