Responses of neurons in somatosensory cortex to direct electrical stimulation

Abstract

1. The response of neurons in the somatosensory cortex to its direct electrical stimulation consists of three successive processes: the initial response, the inhibitory period, and the after-phenomena. 2. The initial response is inconstant. It depends on the strength of stimulation, the character of the background fixing, and, if stimulation of medium strength is used, it appears in about 3% of the neurons. The inhibitory period is a universal reaction, recorded in all neurons. The mean duration of inhibition is 200–500 msec. 3. The after-phenomens probably depend on the morphological and functional properties distinguishing the neurons, and they occur in one of three types: gradual restoration of the background activity, low-frequency and high-frequency after-responses, and after-discharges. The neurons generating the high-frequency after-responses are possibly concerned with the maintenance of traces of signals reaching the cortex. It is postulated that the after-responses and the after-discharges arise through the same connections between the cortical neurons. 4. The functional variations between the responses of cortical neurons to direct electrical stimulation are best revealed in the period of the after-phenomens.