Reduced auditory P300 amplitude, medial temporal volume reduction and psychopathology in schizophrenia.

Twenty-five schizophrenic patients diagnosed by DSM-III-R underwent event-related potentials and magnetic resonance imaging scans. Latency and amplitude of P300 waveform were measured using an auditory odd-ball paradigm. Anterior and posterior volumes of the superior temporal gyrus and medial temporal structure were measured from contiguous coronal images using the level of the mammillary body as an anatomical landmark. Principal component analysis of P300 latency and amplitude disclosed two orthogonal independent factors each: overall latency and residual, and amplitudes from posterior and anterior recordings, respectively. Structural volumes consisted of four orthogonally independent factors: left superior temporal volume, anterior medial temporal volume, right superior temporal volume, and posterior medial temporal volume. The factor score of the P300 amplitude from posterior recordings correlated with the factor score of volumetric changes in the anterior medial temporal structures. The present study failed to replicate a previously reported association between auditory P300 amplitude and superior temporal volume. Furthermore, the factor score of the P300 amplitude was correlated with the severity of clinical ratings of attentional impairments and positive thought disorder. These findings demonstrate that the information processing dysfunction of schizophrenia indicated by reduced P300 amplitude is associated with structural abnormality in the medial temporal lobe.