Multisensory Integration Causes Non-Informative Auditory Stimuli to Facilitate Visual Search: An event-related potential investigation of the Ă˘â‚¬Ĺ“Pip and PopĂ˘â‚¬? phenomenon
Durk Talsma, Erik Van der Burg, Christiaan Olivers, Jan Theeuwes
Last modified: 2008-05-13
It has recently been demonstrated that non-informative auditory stimuli can facilitate visual search (Van der Burg, Olivers, Bronkhorst, and Theeuwes, in press, JEP:HPP). This effect, labeled the Ă˘â‚¬Ĺ“pip and popĂ˘â‚¬? phenomenon has been attributed to multisensory integration. Here we present an event-related potential study that elucidates the neural mechanisms behind this effect. Diagonally oriented line segments were presented in two confined regions in visual space; one region in the left visual field, and one region in the right. All elements could change orientation at random moments. A target stimulus was defined by one line element that changed to a horizontal or vertical orientation. Participants were required to report the orientation of the target item at the end of the trial. On one-third of the trials, a tone was presented that was synchronized with the orientation change of the target stimulus (AV trials). On one third of the trials, a tone was presented that was not synchronized with any visual stimulus (auditory-only trials). On the remaining trials no sound was presented (i.e. visual-only trials). We expected to find increased accuracy on the AV trials, and an early multisensory integration related modulation of the ERP wave. Furthermore, we expected that a shift of attention to the target location in the AV condition would be reflected in an N2pc component. Both behavioral and ERP result largely adhere to our expectations. We therefore conclude that multisensory integration can cause a bottom-up driven spread of attention from the auditory to the visual modality.