Auditory Event-Related Response in Visual Cortex Modulates Subsequent Visual Responses in Humans

Abstract

Growing evidence from electrophysiological data in animal and human studies suggests that multisensory interaction is not exclusively a higher-order process, but also takes place in primary sensory cortices. Such early multisensory interaction is thought to be mediated by means of phase resetting. The presentation of a stimulus to one sensory modality resets the phase of ongoing oscillations in another modality such that processing in the latter modality is modulated. In humans, evidence for such a mechanism is still sparse. In the current study, the influence of an auditory stimulus on visual processing was investigated by measuring the electroencephalogram (EEG) and behavioral responses of humans to visual, auditory, and audiovisual stimulation with varying stimulus-onset asynchrony (SOA). We observed three distinct oscillatory EEG responses in our data. An initial gamma-band response around 50 Hz was followed by a beta-band response around 25 Hz, and a theta response around 6 Hz. The latter was enhanced in response to cross-modal stimuli as compared to either unimodal stimuli. Interestingly, the beta response to unimodal auditory stimuli was dominant in electrodes over visual areas. The SOA between auditory and visual stimuli-albeit not consciously perceived-had a modulatory impact on the multisensory evoked beta-band responses; i.e., the amplitude depended on SOA in a sinusoidal fashion, suggesting a phase reset. These findings further support the notion that parameters of brain oscillations such as amplitude and phase are essential predictors of subsequent brain responses and might be one of the mechanisms underlying multisensory integration.

Pre-stimulus alpha oscillations over somatosensory cortex predict tactile misperceptions

“…Stimuli in one sensory modality have been shown to influence ongoing activity cross-modally, e.g., phase resets in visual cortex following an auditory stimulus (e.g. Naue et al, 2011;Romei, Gross, & Thut, 2012). Figure 3A shows that this may be possible here, given that changes in somatosensory alpha occurred after the light, even when no touch was present.…”

Effects of stimulus duration on audio-visual synchrony perception

“…However, without cortical involvement, multisensory enhancement does not occur (Sanford et al 2005), and cortical cross-modal interactions in humans do not occur until about 165 ms after stimulus onset in the occipitotemporal ventral stream, and not until about 220 ms in the peri-sylvian cortex (Teder-Sälejärvi et al 2002). More recently, Naue et al (2011) found evidence of auditory effects in frontocentral and occipital cortices about 50-200 ms after the auditory component of audio-visual pairs was presented. These delays in processing multimodal components of simple stimuli support the idea that stimulus onsets are processed before multimodal integration, and unimodal timing phenomena should be rendered intact in multimodal synchrony judgments.…”

Selection of events in time enhances activity throughout early visual cortex

“…Indeed, the literature on multimodal processing questions the degree to which early sensory areas are unisensory in nature (Brosch et al 2005;Driver and Noesselt 2008;Ghazanfar and Schroeder 2006). Auditory stimuli appear to facilitate the processing of lowthreshold visual stimuli (Noesselt et al 2010) and enhance early visual cortical responses to visual stimuli (Molholm et al 2002;Naue et al 2011), particularly when auditory and visual stimuli are predictably associated (Baier et al 2006).…”