Recovery functions of somatosensory peripheral nerve and cerebral evoked responses in man

Abstract

• 1. This study was conducted to obtain additional data concerning early recovery of human somatosensory and peripheral nerve responses and to determine the relation between recovery at these levels. In eleven subjects, using an averaging procedure for recording, recovery functions of median nerve and cerebral evoked responses were determined simultaneously. Equal intensity conditioning and test stimuli were suprathreshold for sensation and subthreshold for motor response. The numerous interstimulus intervals tested ranged from 1 to 100 msec.

• 2. Nerve recovery function results corresponded closely to those obtained by previous workers. Relative refractoriness lasted about 4 msec, was followed by a period of supernormality, and then by subnormality of variable duration (up to 100 msec).

• 3. Commencing with the initial peak negativity of the cerebral response (latency about 20 msec), six successive points of inflection were identified; the latencies of these points were determined and amplitudes were measured between them. During recovery there was a progressive reduction in latency of all points; latency recovery was usually complete at about 20 msec. Amplitude recovery was more variable. Most subjects showed one or more peaks of full amplitude recovery or facilitation before 20 msec, followed by a period of diminished responsiveness between 20 and 40 msec, and a subsequent return of responsiveness.

• 4. Intercorrelations between the nerve and cerebral response component recovery functions yielded no coefficient which could account for more than 3% common variance. The influence of peripheral factors on cerebral recovery functions thus appears negligible.

• 5. Intercorrelations between amplitude recovery functions of the cerebral response components were nearly all statistically significant, but slight in magnitude. This suggests that the various components reflect relatively independent processes.