Several characteristics of somatosensory evoked responses (SER) were measured in a modified recovery function procedure in 22 bright young adults and 22 mongoloid and ten "idiopathic" retardates. The two retardate groups were of similar IQ to distinguish non-specific SER deviations associated with retardation from those related to the specific cause of mongolism.
Findings related to mongolism were: (1) For a given conduction pathway length, latency of the initial SER peak was longer in mongoloids. (2) The usually high correlation between conduction pathway length and initial latency was abnormally low in mongoloids (r = 0.35 vs 0.8 in normals and idiopathics). (3) There were significant sex differences in mongoloids and not in the other groups: women had larger amplitudes. Amplitude recovery was greater than normal in both retardate groups.