Spatiotemporal properties modulate intermodal influences on early somatosensory processing during sensory-guided movement.
OBJECTIVE
Somatosensory evoked potentials (SEPs) were used to (1) investigate intermodal influences upon somatosensory processing in primary somatosensory cortex (S1), (2) determine the influence of spatiotemporal relationships between bimodal stimuli in S1 and (3) observe behavioral changes associated with intermodal modulation.


METHODS
Median nerve SEPs were elicited from electrical stimulation and recorded from scalp electrodes during continuous tracking of one of two simultaneously presented stimuli (vibrotactile/visual). In Experiment 1, spatial relationship was manipulated by placing the visual stimulus in the same/opposite hemi-field as the vibrotactile stimulus. In Experiment 2, temporal synchrony was manipulated by altering the pattern of intensity changes such that they followed identical/different patterns.


RESULTS
For Experiment 1, greater spatial relationship reduced the amplitude of the P27 SEP component whereas in Experiment 2 greater temporal synchrony increased the amplitude of the P27 SEP component. Temporal synchrony increased P50 amplitude only during vibrotactile tracking. Tracking performance mirrored early SEP amplitude changes. In Experiment 2, task-relevance was associated with increased N140 amplitude.


CONCLUSIONS
The changes in P27 amplitude observed in Experiments 1 and 2 reflect an intermodal mechanism of somatosensory gating dependent upon spatiotemporal properties of bimodal stimulation whereas the P50 reflects multisensory aspects of somatosensory processing. Changes in behavior may reflect the importance of these early influences to sensorimotor transformations.


CONCLUSIONS
Modulation of the P27 component reflects an intermodal sensory gating in somatosensory processing.
Meehan
Sean K
SK
Department of Kinesiology, University of Waterloo, 200 University Ave. West, Waterloo, Ont., Canada N2L 3G1.
Legon
Wynn
W
Staines
W Richard
WR
D000328:Adult; D004558:Electric Stimulation; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D007699:Kinesthesis / Q000502:physiology*; D008297:Male; D008475:Median Nerve / Q000502:physiology; D009068:Movement / Q000502:physiology*; D010775:Photic Stimulation; D055139:Sensory Gating / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*; D013037:Spatial Behavior / Q000502:physiology*; D013647:Task Performance and Analysis; D013998:Time Perception / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology