P300 Amplitudes In Response Research Articles

Left lateralized P300 amplitude deficit in schizophrenic patients depends on pitch disparity

The general reduction of P300 amplitude in response to auditory oddball stimuli is one of the most consistently replicated biological observations in schizophrenic patients. Several groups have reported a P300 asymmetry in schizophrenic patients, others have not been able to replicate this finding. In order to clarify this issue, we examined the effect of stimulus discriminability on P300 amplitude distribution in schizophrenic patients and in age-matched normal control subjects, using two different auditory oddball paradigms. The detection of the target tone was either simple or difficult, due to manipulation of pitch disparity. The P300 amplitude was comparatively smaller in the schizophrenic patient group compared to the healthy controls and in the difficult task compared to the simple. The schizophrenic patients showed a specific P300 amplitude reduction over left temporal electrode sites when the simple paradigm was used. The difficult paradigm did not elicit asymmetrical P300 amplitudes in schizophrenic patients.

Effects of Hypnotic Instructions on P300Event-Related-Potential Amplitudes: Research and Clinical Implications

Abstract Apparently conflicting findings in two recent studies of the effects of hypnotic hallucination on the P300 component of cortical event-related potentials are examined. In one study, Barabasz and Lonsdale (1983) found an increase in P300 amplitude in response to hypnotic anosmia instructions. However, Spiegel, Cutcomb, Ren, and Pribram (1985) obtained a decrease in P300 amplitude after instructing high hypnotizables that an imaginary cardboard box blocked their view of the stimulus generator. These differences are reconciled on the basis of differences in the hypnotic instructions given. The former study employed language which emphasized negation (“You will not smell anything at all”), while the latter had subjects focus on a competing obstructive hallucination. The anosmia subjects were surprised when they smelled anything at all, leading to an enhanced P300 response, while the subjects in the visual study were so absorbed in the hallucinated obstruction that perception of the stimulus was reduc...