[Responses of the neurons of the magnocellular portion of the medial geniculate body to acoustic and somatosensory stimulation].

The responses of 150 neurons of the magnocellular division of the medial geniculate body (MGB) to sound click and to contralateral forepaw electrical stimulation were studied in cats immobilized with myorelaxine. 68% of the studied neurons had bimodal responses, 16.6% of neurons responded only to click, and 15.4% - only to forepaw stimulation. The responses to click began with excitation more frequently, while initial inhibition was more often evoked by the forepaw stimulation. Latencies of the spike responses to click were between 5-27 ms (at an average 11.6 ms) and to forepaw stimulation between 6-33 ms (at an average 16.2 ms). A positive correlation was found in the same neurons between spike latencies to click and to forepaw stimulation as well as between the spike latencies to stimulation of the forepaw and of the spinal cord dorsal funiculus. A conclusion is made that the magnocellular division of the MGB is the transitional structure between VP and parvocellular division of the MGB and that is connected mainly with the auditory system. It is suggested that somatosensory input to the magnocellular division of the MGB is formed predominantly by the medial lemniscal fibres.