SIGNIFICANCE OF THE 2ND SOMATOSENSORY CORTEX IN SENSORIMOTOR INTEGRATION - ENHANCEMENT OF SENSORY RESPONSES DURING FINGER MOVEMENTS

THE functional significance of the second somatosensory cortex (SII) i s poorly understood. However, lesion and cortical stimulation studies indicate that SII may be involved in sensory aspects of tactile learni ng and in movement control. In the present study, we explored a possib le role of SII in sensorimotor integration in humans using a multichan nel magnetometer. Somatosensory evoked fields (SEFs) from SII to elect rical stimulation of left and right median nerves were recorded in six healthy volunteers during rest and in different test conditions. Cont inuous cutaneous stimulation of the right hand or face reduced the SEF s to both left and right median nerve stimulation. Right-sided finger movements increased the SEFs to right, but not left, median nerve stim ulation. The responses were simple finger flexion movement sequence. T he suppression of SEFs by competing cutaneous inputs from different ar eas of the body indicates that the neurones underlying the responses r eceive inputs from large, bilateral receptive fields. The enhancement of sensory reactions to signals from the actively moving limb but not to those from the opposite limb indicates a spatial tuning of the SII neurones to behaviourally relevant input channels, also suggesting tha t SII is important for the integration of sensory information to motor programmes.