Abstract
In our environment, our senses are bombarded with a myriad of signals, only a subset of which is relevant for our goals. Using sub-millimeter-resolution fMRI at 7T, we resolved BOLD-response and activation patterns across cortical depth in early sensory cortices to auditory, visual and audiovisual stimuli under auditory or visual attention. In visual cortices, auditory stimulation induced widespread inhibition irrespective of attention, whereas auditory relative to visual attention suppressed mainly central visual field representations. In auditory cortices, visual stimulation suppressed activations, but amplified responses to concurrent auditory stimuli, in a patchy topography. Critically, multisensory interactions in auditory cortices were stronger in deeper laminae, while attentional influences were greatest at the surface. These distinct depth-dependent profiles suggest that multisensory and attentional mechanisms regulate sensory processing via partly distinct circuitries. Our findings are crucial for understanding how the brain regulates information flow across senses to interact with our complex multisensory world.
Highlights
In our natural environment, our senses are exposed to a constant influx of sensory signals that arise from many different sources
In this functional magnetic resonance imaging (fMRI) study, participants were presented with blocks of auditory (A), visual (V) and audiovisual (AV) looming stimuli interleaved with fixation (Figure 1A)
In A1 the linear shape parameter for [V-Fix] predicted the linear shape parameter of [AV-A]: vertices with less deactivations in deeper relative to superficial laminae in unisensory visual context showed a robust crossmodal enhancement that was most pronounced in deeper laminae (linear: t(10)=3.121, p=0.011, constant: t(10)=0.021, p=0.983, Figure 3Bii right). These results strongly suggest that visual stimuli generate a BOLD response in primary auditory cortex with a patchy topography similar for unisensory and audiovisual contexts
Summary
Our senses are exposed to a constant influx of sensory signals that arise from many different sources. Mounting evidence from neuroimaging (Beauchamp et al, 2004; Noesselt et al, 2007; Rohe and Noppeney, 2016), neurophysiology (Atilgan et al, 2018; Kayser et al, 2010; Kayser et al, 2008; Lakatos et al, 2007) and neuroanatomy (Falchier et al, 2002; Rockland and Ojima, 2003) suggests that interactions across the senses are pervasive in neocortex, arising even in primary cortices (Driver and Noesselt, 2008; Ghazanfar and Schroeder, 2006; Liang et al, 2013; Schroeder and Foxe, 2002). Visual stimuli can directly drive as well as modulate responses in cortices that are dedicated to other sensory modalities.
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