Intramodal and crossmodal refracory effects: Evidence from oscillatory brain activity
Davide Bottari, Sophie Rohlf, Marlene Hense, Boukje Habets, Brigitte Roeder

Date: 2012-06-21 01:30 PM – 03:00 PM
Last modified: 2012-04-27

Abstract


Event-related potentials (ERP) to the second stimulus of a pair are known to be reduced in amplitude. The magnitude of this “refractoriness” is modulated by both the interstimulus interval and the similarity between the two stimuli. Intramodal refractoriness is interpreted as an index of a temporary decrement in neural responsiveness. So, cross-modal refractoriness might be an indicator of shared neural generators between modalities. We analysed oscillatory neuronal activity while participants were engaged in an oddball paradigm with auditory (4000Hz, 50ms-long, 90db, bilateral) and tactile stimuli (50ms-long, 125Hz-vibrations, index fingers) presented in a random order with an ISI of either 1000ms or 2000ms. Participants were required to detect rare tactile (middle fingers) and auditory deviants (600Hz). A time-frequency analysis of the brain response to the second stimulus of each pair (T-T, A-A, T-A and A-T) contrasting Short and Long ISIs revealed a reduced refractory effect after Long ISI with respect to Short ISI, in all pairs (both intramodal and cross-modal). This emerged as a broadly distributed increase of evoked theta activity (3-7 Hz, 100-500ms). Only in intramodal tactile pairs and cross-modal tactile-auditory pairs we also observed that Long ISI with respect to Short ISI determined a decrease of induced alpha (8-12 Hz, 200-700ms), a typical sign of enhanced neural excitability and thus decreased refractoriness. These data suggest that somatosensory and auditory cortices display different neural markers of refractoriness and that the auditory cortex might have a stronger low level degree of influence on the tactile cortex than vice-versa.

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