Responses of neurons in somatosensory cortex to direct electrical stimulation

Conclusions

• 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.