Poster E117, Monday, March 27, 2:30 – 4:30 pm, Pacific Concourse
The Race May Be Over: Behavior and Neurophysiology Show Modality “Switch-Costs” Give Rise to Apparent Redundant Target Effect
Luke Shaw1, Eric Nicholas1, Matthew Braiman1, Kamy Wakim1, Ciara Molloy1, Sophie Molholm2, John Foxe1,2; 1University of Rochester, 2Albert Einstein College of Medicine
The facilitation of reaction times (RT) to a multisensory stimulus is a widely reported phenomenon in the field of multisensory integration. We show that a “modal switch cost” in RTs arises on the successive presentation of orthogonal unisensory stimuli, which greatly impacts standard experimental designs with blocks of randomly interleaved unisensory and multisensory stimuli. This switch cost accounts for much of the apparent RT facilitation to multisensory stimuli. Neurotypical adult (n=30) participants performed a simple reaction time task to audio and/or visual stimuli presented in a block-wise manner. Blocks were composed of sequential presentations of one of two unisensory stimuli (50 ms pure tone, or 50 ms circle on a monitor), a multisensory stimulus (the tone and circle simultaneously), or the two unisensory and multisensory stimuli intermixed. Behavioral data indicates increased RT latencies to unisensory stimuli immediately preceded by stimuli from the orthogonal modality. This effect is greatly reduced when unisensory stimuli are preceded by the multisensory stimulus or a stimulus of the same modality. RTs to the multisensory stimulus are not affected by this precedent effect, resulting in the comparative “speeding” of responses to multisensory stimuli in the mixed blocks. A complementary electrophysiological study (n=15) shows differences in evoked response potentials (ERPs) in line with behavioral findings. ERPs demonstrate unique physiology corresponding to the observed reaction time modality switch cost with differences in early sensory processing on presentation of orthogonal stimuli.
Topic Area: PERCEPTION & ACTION: Multisensory