5th Congress of the Federation of European Psychophysiology Societies, Bordeaux
Octobre 2002

Influence of sensory modality on electromagnetic brain activity engaged in duration perception

N’Diaye K, Garnero L, Pouthas V

CNRS-UPR640 LENA, Paris, France

Although widely explored through psychophysics, the role of sensory modality on time perception has rarely been studied using brain imaging techniques. Our study involved 13 young male subjects performing a “temporal generalization” task in either visual or auditory modality. Subjects were asked to discriminate a previously memorized “standard” 700ms duration from randomly presented “test-stimuli” (ranging from 490 to 910ms). Signals used were either a continuous 440Hz tone or a LED light. Simultaneous EEG and MEG recordings were acquired using co-registration fiducials. Scalp electric potentials showed a sustained activity during stimulus presentation which developed over fronto-central or occipito-parietal regions according to the modality (respectively auditory or visual). Corresponding magnetic activity was observed, yet, more focal located on temporal and occipito-parietal sensors. By comparing the distribution of activity due to primary evoked response (auditory N100 or visual N170) with the one of the sustained potential in the same modality, we could observe large similarities between both. However, we identified specific signals due to on-going processing of the stimulus to be timed by subtracting these distributions at various latencies. Further analyses may help us to conclude whether these signals relate to duration perception per se.