The production of “model psychoses” in animals and man by a variety of chemical substances is of great interest. While the relationship between disturbances so produced and schizophrenia are problematical, these investigations may eventually throw light upon the causes of this condition. More important, at present, is the fact that the investigation of the way these drugs modify various aspects of normal psychological functioning is of great value in suggesting the physiological and biochemical processes that underlie these functions.

This study was designed to replicate and extend earlier findings. Evoked potentials (EP) were recorded, using a task of varying complexity involving shape discrimination, with matched groups of obsessional and normal subjects. Results confirmed previous findings that obsessional patients are characterized by reduced amplitudes and decreased latencies of late EP components; divergences between the groups were more marked for tasks of increased complexity.

Averaged evoked potentials were recorded from a group of obsessional patients and matched normal controls for three types of visual stimulation: passive monitoring of a light flash, a pattern consisting of gratings and a cognitive task involving discrimination of two similar shapes. As the complexity of information processing required by the tasks increased, differences in the evoked potentials of obsessionals became more marked. The main finding was of faster latency and reduced amplitude of the N220 component in the cognitive task. The relevance of this finding to a theory of obsessional disorder is discussed.

No abstract