Human brain activity associated with audiovisual perception and attention

Coherent perception of objects in our environment often requires perceptual integration of auditory and visual information. Recent behavioral data suggest that audiovisual integration depends on attention. The current study investigated the neural basis of audiovisual integration using 3-Tesla functional magnetic resonance imaging (fMRI) in 12 healthy volunteers during attention to auditory or visual features, or audiovisual feature combinations of abstract stimuli (simultaneous harmonic sounds and colored circles). Audiovisual attention was found to modulate activity in the same frontal, temporal, parietal and occipital cortical regions as auditory and visual attention. In addition, attention to audiovisual feature combinations produced stronger activity in the superior temporal cortices than attention to only auditory or visual features. These modality-specific areas might be involved in attention-dependent perceptual binding of synchronous auditory and visual events into coherent audiovisual objects. Furthermore, the modality-specific temporal auditory and occipital visual cortical areas showed attention-related modulations during both auditory and visual attention tasks. This result supports the proposal that attention to stimuli in one modality can spread to encompass synchronously presented stimuli in another modality.