Average evoked responses and psychophysical performance in patients with pseudohypoparathyroidism.

Perceptual function in eight patients with pseudohypoparathyroidism (PHP) was studied with two neurophysiological measures, the average evoked response (AER) and nerve conduction velocity. A battery of psychophysical tasks including reaction time, size estimation, `hidden pictures,' and the rod and frame procedure was also used. Patients with PHP had significantly longer latency visual AER and slower reaction time than a group of normal volunteers, and they performed erratically and poorly on the other psychophysical tasks. Differentiating these patients with diffuse mental deficiency were two relatively specific perceptual response patterns: (1) AER amplitude decreased with increasing stimulus intensity, and (2) reaction time was abnormally influenced by the duration of the preparatory interval. Both of these patterns have previously been found in other patient groups.