Abstract
[Introduction] Effect of the audiovisual cross-modal attention, e.g., facilitation of auditory processing at the location attended visually, has been reported. To understand the underlying mechanism of such audiovisual attention, we estimated the spatial distribution of attentional modulation for visual and auditory processing around the focus of either visual or auditory attentions. [Methods] We measured attentional modulation in visual/auditory processing at 11 stimulus locations along a horizontal line, using a technique with Steady State Responses (SSRs) of electroencephalogram signals. At each of the 11 locations, a letter on a flickering disc was displayed and a loudspeaker was installed for sounds with amplitude modulations for the purpose of SSR measurements. Different temporal frequencies were assigned to the luminance flicker and amplitude modulation at different locations. The SSRs were extracted based on the temporal frequency tagged to each location, based on which we estimated distribution of attentional modulation around the focus of either visual or auditory attentions. Participants paid attention to a location indicated for detecting the target (i.e., A) in sequences of simultaneously presentations of vowel letters and vowel sounds (rapid serial bimodal presentations of A, E, I, O, U) at the location. The letters and sounds were presented also at the other locations to check false responses. [Results] The results showed that visual attention influences auditory responses. Contrary to the prediction, the influence of visual attention on the auditory response was suppression, rather than facilitation, and the influence was found in the area that visual attention covered. The auditory attention, instead, did not show statistically significantly effect on the visual responses, while the SSR amplitude for visual stimuli were larger around the focus of auditory attention than the other locations. [Conclusion] We conclude that there is common attention process with a spatial representation that integrates visual and auditory signals.