Abstract
Recent studies in humans and monkeys have reported that acoustic stimulation influences visual responses in the primary visual cortex (V1). Such influences can be generated in V1, either by direct auditory projections or by feedback projections from extrastriate cortices. To test these hypotheses, cortical activities were recorded using optical imaging at a high spatiotemporal resolution from multiple areas of the guinea pig visual cortex, to visual and/or acoustic stimulations. Visuo-auditory interactions were evaluated according to differences between responses evoked by combined auditory and visual stimulation, and the sum of responses evoked by separate visual and auditory stimulations. Simultaneous presentation of visual and acoustic stimulations resulted in significant interactions in V1, which occurred earlier than in other visual areas. When acoustic stimulation preceded visual stimulation, significant visuo-auditory interactions were detected only in V1. These results suggest that V1 is a cortical origin of visuo-auditory interaction.
Highlights
According to the classical view of sensory cortices, sensory information from each modality is initially sent to a specific primary sensory area, while the convergence of different modalities occurs only in nonprimary areas [1]
For example, auditory stimulation that is simultaneously presented with visual stimulation modulates visual responses in the primary visual cortex (V1) [10]
All optical imaging was performed on the left hemisphere
Summary
According to the classical view of sensory cortices, sensory information from each modality is initially sent to a specific primary sensory area, while the convergence of different modalities occurs only in nonprimary areas [1]. Monkeys, and ferrets have reported that sensory responses at the early stage of hierarchical cortical processing, including those in the primary sensory cortices, are influenced by extramodal stimulation [2,3,4,5,6,7,8,9,10,11,12] Projections from auditory cortices to V1 have been demonstrated [18,19,20,21], these projections appear sparse
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