Role of human SII cortices in sensorimotor integration

Objectives: To elucidate the functional properties of neurons in the human primary (SI) and ipsilateral and contralateral secondary (iSII or cSII) cortices in response to stimuli during finger movement. Methods: We measured somatosensory evoked fields (SEFs) produced by electric stimuli delivered to the median nerve at 0.2 Hz in 6 healthy subjects. Results: The amplitudes of evoked fields from both iSII and cSII were gradually attenuated with time. Consecutive blocks of trials were obtained to assess the habituation of each evoked field. Complex finger movements with attention (gating session) increased the amplitude of evoked fields from the iSII cortices but reduced the amplitudes of evoked fields from the cSII cortices (P<0.01). In contrast, the amplitude of P30m from the SI did not show habituation effects but decreased significantly in the gating session (P<0.01). Conclusions: The enhanced iSII as well as suppressed cSII cortices during complex finger movements with attention are not only considered to be result of gating effect but also attention. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.