Salient Sounds Activate Human Visual Cortex Automatically

Abstract

Sudden changes in the acoustic environment enhance perceptual processing of subsequent visual stimuli that appear in close spatial proximity. Little is known, however, about the neural mechanisms by which salient sounds affect visual processing. In particular, it is unclear whether such sounds automatically activate visual cortex. To shed light on this issue, the present study examined event-related brain potentials (ERPs) that were triggered either by peripheral sounds that preceded task-relevant visual targets (Experiment 1) or were presented during purely auditory tasks (Experiments 2, 3, and 4). In all experiments the sounds elicited a contralateral ERP over the occipital scalp that was localized to neural generators in extrastriate visual cortex of the ventral occipital lobe. The amplitude of this cross-modal ERP was predictive of perceptual judgments about the contrast of co-localized visual targets. These findings demonstrate that sudden, intrusive sounds reflexively activate human visual cortex in a spatially specific manner, even during purely auditory tasks when the sounds are not relevant to the ongoing task.

Sounds Activate Visual Cortex and Improve Visual Discrimination

“…The ACOP preceding correct discriminations was localized to the ventrolateral extrastriate visual cortex (Brodmann's area 19), as reported previously . The present results extend the previous finding of McDonald et al (2013) that larger ACOP amplitudes were associated with enhancement of the simple sensory feature of luminance contrast. The present trial-by-trial analysis demonstrates that the ACOP reflects an automatic cross-modal priming of the visual cortex that facilitates the perceptual processing of a subsequent visual event at the cued location and enables more effective discrimination of its detailed pattern characteristics.…”

“…4). The congruence between the results of these two very different source estimation techniques (LAURA and BESA) and the congruence with the ACOP sources previously estimated by McDonald et al (2013) increases our confidence in the ventrolateral occipital localization for the ACOP generators. However, it must be cautioned that inverse source estimations such as these can only serve as approximations of the true neural generator configuration because of the inherently ill-posed nature of the inverse problem (Nunez and Srinivasan 2006).…”

“…McDonald et al (2013) found that individuals with larger ACOP amplitudes to a lateralized sound tended to report colocalized visual targets as having higher luminance contrast, but it is unclear whether the ACOP signifies a more general improvement of visual processing that would lead, for example, to more accurate pattern discriminations. The present study examined this question by recording ERPs in a task in which a lateralized sound was followed after 400 ms by a visual target consisting of a masked letter "T" or "L," which was presented unpredictably at either the same location (valid trial) or on the opposite side (invalid trial) as the preceding sound.…”

Peripheral sounds rapidly activate visual cortex: evidence from electrocorticography

“…Although eye movements were not rigorously monitored in these patients, in the study of McDonald et al (2013), which presented lateralized sounds very similar to those used here, the sounds did not elicit any eye deviations as measured by the electrooculogram. In addition, the early onset of the auditory-evoked visual cortical responses (Ͻ50 ms) precludes the possibility that eye movements contaminated our ECoG-ERP results because saccade-induced neural responses in primary visual cortex occur 50 -100 ms postsaccade onset (e.g., Kagan et al 2008).…”

Cross-modal orienting of visual attention

“…cortex or mediated through multisensory convergence zones (Driver and Noesselt, 2008). To investigate whether spatially nonpredictive sounds would elicit activity in the visual cortex, McDonald et al (2013b) recorded ERPs to lateralized sounds under several different task conditions, including conditions where the sounds were irrelevant and where no visual stimuli were presented at all. The specific experimental conditions tested were the following: (1) the lateralized sound preceded a bilateral pair of Gabor patches-the paradigm of (2) the lateralized sound preceded a pair of target tone bursts; (3) the lateralized sounds were completely irrelevant and were presented in a randomized sequence with paired bilateral target tones; and (4) the lateralized sounds were completely irrelevant and were presented in a randomized sequence with central target tones.…”