Somatosensory evoked potentials and magnitude of perception.

With step indentations of the index finger tip in randomized order, via a mechanostimulator, the tactile receptors of human skin were adequately stimulated. Recording the EEG over the contralateral and ipsilateral cortex, the evoked potentials and their 95% confidence limits were analysed. Simultaneously the psychophysical magnitude estimations were analysed. 1. The perceptual estimations were linearly related to step amplitude. 2. The early components of the E.P. show no obvious correlation to stimulus amplitude. 3. The later components (with peak latencies of 120 msec or more) show a monotone, non-linear rising function with respect to stimulus amplitude. 4. The early waves of the evoked potentials up to about 120 msec are well localized over the contralateral postcentral hand area while the late components resemble the alpha rhythm in wave length and distribution over both hemispheres. The possible role of alpha-synchronisation in the later components is discussed.

RCT Entities:   Population Interventions Outcomes