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The effect of dorsal column stimulation (DCS) on single cell activity of the thalamus was analyzed in a patient who underwent stereotaxic thalamotomy following implantation of a dorsal column stimulator. Nine thalamic units were monitored long enough for an adequate evaluation of the effect of repeated DCS upon spontaneous thalamic activity. The units’ firing frequency decreased significantly during DCS and decreased even further following cessation of the stimulation. These data, even if obtained from a small cell population, extend to the cellular level in the human thalamus the previous observations that DCS exerts marked effects on supraspinal structures.

8 Ss were exposed to vibrotactile stimulation of 250 Hz, applied to the tip of the left index finger. Seven stimulus intensities, ranging from 26 to 48 db, were each combined with three stimulus durations, 50, 250, and 1200 msec. A magnitude-estimation technique with fixed standard was employed to obtain scale values of the apparent duration of each stimulus. The results indicate that apparent duration can be described as a logarithmic function of stimulus intensity. This conclusion is in line with our previous findings concerning apparent duration of electrical stimulation.

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