Abstract
Previous studies show that the spinal cord and subcortical components of the somatosensory evoked potentials are not attenuated during movement in man. The objective of the present study was to investigate the effect of simultaneous fractionated finger movement on cortically generated somatosensory evoked potentials. Left median nerve somatosensory evoked potentials were recorded from a scalp array of 21 electrodes over the right scalp in 9 normal subjects aged 18-31 years. They reclined, eyes closed as recordings were made at rest and during fractionated finger movements of the left hand. Latency and peak-to-peak amplitude of the parietal N20 and frontal P20 waves did not show statistically significant difference between rest and movement conditions. This represents activity in the tangentially arranged pyramidal neurons in area 3b. Amplitude of the parietal P25 wave, representing activity in radially arranged area 1 pyramidal neurons was attenuated during finger movement by 70% (P<,0.01; Wilcoxon's test). Fractionated finger movements utilise the corticospinal pathway from the motor cortex. In animal studies it has been shown that there is evidence for an inhibitory cortico-cortical pathway from area 4 (motor) to area 1 (sensory) cortex but not to area 3b. We propose that activity in this pathway is responsible for our findings. This can be considered as a physiological evidence for the function of a cortico-cortical pathway in man. [J Physiol Sci. 2006;56 Suppl:S89]
