Effects of anesthesia level and stimulus characteristic on the amplitude and latency of the somatosensory evoked response in monkeys.

The effect on the somatosensory evoked response (SER) of the level of anesthesia, and the effect of the site, intensity, duration, and frequency of the stimulus on the amplitude and latency of various components of the SER were studied in 8 Rhesus monkeys. Peroneal nerve stimulation produced similar patterns over both sides of the head, with a slightly larger amplitude over the contralateral cortex. With ulnar nerve stimulation, significantly different patterns were observed over the contralateral and ipsilateral cortex; however, the former still had a slightly larger amplitude. The latency of the various components in the SER's was not influenced by the level of anesthesia or by the intensity, duration, or frequency of the stimulus. As the level of anesthesia decreased, there was a general increase in amplitude of the SER's with peroneal nerve stimulation and no consistent change with ulnar nerve stimulation. The amplitudes of the SER increased with the increase in stimulus intensity or duration, and with a decrease in stimulus frequency.