Psychophysiological inhibition theories of hysterical anesthesia were not supported in a study of habituation of scalp somatosensory average-evoked responses. Facilitation, rather than habituation, was found in responses contralateral to the affected side with strong tactile stimuli in patients with hysterical hemianesthesia or hemihypoesthesia, regional pain, and weakness.
We suggest that the increase in response amplitude is related to the unusual cognitive set in these patients. Corticifugal influences on tactile sensory input might be mediated through increasing excitation in a spinal-gating system.
Moldofsky H, England RS. Facilitation of Somatosensory Average-Evoked Potentials in Hysterical Anesthesia and Pain. Arch Gen Psychiatry. 1975;32(2):193-197. doi:10.1001/archpsyc.1975.01760200057005