Fifteen healthy subjects with obsessive character (OC) and 15 control
subjects were tested for endogenous event-related potentials using the
auditory odd ball paradigm. A difference was found in the peak amplit
ude of the P200 component in response to both stimuli; the subjects wi
th OC had smaller amplitudes than the controls, and the mean amplitude
for the 120 to 200 ms latency range was smaller (negative shift) for
the OC subjects. In the OC subjects, NA appears to be markedly induced
to both rare and frequent stimuli; moreover, the OC subjects may show
excessive reactions to selective attention as well as to the process
of pattern recognition.