Abstract
Previous studies indicated that empty time intervals are better discriminated in the auditory than in the visual modality, and when delimited by signals delivered from the same (intramodal intervals) rather than from different sensory modalities (intermodal intervals). The present electrophysiological study was conducted to determine the mechanisms which modulated the performances in inter- and intramodal conditions. Participants were asked to categorise as short or long empty intervals marked by auditory (A) and/or visual (V) signals (intramodal intervals: AA, VV; intermodal intervals: AV, VA). Behavioural data revealed that the performances were higher for the AA intervals than for the three other intervals and lower for inter- compared to intramodal intervals. Electrophysiological results indicated that the CNV amplitude recorded at fronto-central electrodes increased significantly until the end of the presentation of the long intervals in the AA conditions, while no significant change in the time course of this component was observed for the other three modalities of presentation. They also indicated that the N1 and P2 amplitudes recorded after the presentation of the signals which delimited the beginning of the intervals were higher for the inter- (AV/VA) compared to the intramodal intervals (AA/VV). The time course of the CNV revealed that the high performances observed with AA intervals would be related to the effectiveness of the neural mechanisms underlying the processing of the ongoing interval. The greater amplitude of the N1 and P2 components during the intermodal intervals suggests that the weak performances observed in these conditions would be caused by an attentional bias induced by the cognitive load and the necessity to switch between modalities.
Highlights
Understanding the neural and cognitive mechanisms underlying time perception is a fine challenge
We are able to perform a comparison between the duration of visual and auditory stimuli [2] or to reproduce by touch on a keyboard the duration of stimuli presented in the visual modality [3]
These early waves were followed by a negative component, the Contingent Negative Variation (CNV), which developed mainly at fronto-central and parietal electrodes
Summary
Understanding the neural and cognitive mechanisms underlying time perception is a fine challenge. Different data have revealed that sensitivity to time is better (lower discrimination threshold, less variability) in the auditory rather than visual modality, a finding that applies to both filled and empty intervals [5,6,7]. This auditory dominance for temporal processing has been observed with sequences of flashes or tones and with auditory and visual rhythms [2,8]
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