An Electroencephalographic Investigation of the Effects of Attention on Crossmodal Temporal Acuity

Science Center, Bent Corridor

Our perception of the world hinges on our ability to accurately combine the many stimuli in our environment. This multisensory integration is highly dependent on the time differences between unisensory events of the different sensory modalities (senses) and our brain’s ability to discern these small time differences (crossmodal temporal acuity). Our previous research investigated whether attention alters crossmodal temporal acuity using a crossmodal temporal order judgment (CTOJ) task in which participants were asked to report if a flash or beep occurring at different time intervals appeared first while concurrently completing a visual distractor task. We found that increasing the perceptual load of the distractor task led to sharp declines in participants’ crossmodal temporal acuity. The current study uses electroencephalography (EEG) to understand the neural mechanisms that lead to decreased crossmodal temporal acuity. Participants completed a CTOJ task as described above while EEG activity was recorded from 64 scalp electrodes. EEG activity was averaged based on the onset of the first stimulus for each participant, producing an event-related potential (ERP) waveform for each perceptual load level and stimulus onset asynchrony (time differences between the flash and beep) combination. We replicated our previous finding of decreases in crossmodal temporal acuity with increasing perceptual load. We found that increasing perceptual load most strongly influenced the amplitude of the N1/P2 ERP waveform across parietal electrodes in response to the flash. However, we did not find differences in ERP activity across perceptual load in response to the beep. EEG activity attributable to primary and secondary visual cortices differed across perceptual load for all but the longest time intervals between the flash and beep. This suggests that decreases in crossmodal temporal acuity with increasing visual perceptual load may be mediated by alterations to visual processing. This line of research could ultimately help our understanding of the disruptions in temporal acuity often found in attentional disorders.