Psychophysiological differences in identical twins discordant for schizophrenia: a critical index for the onset of schizophrenia.

It has been hypothesized that not only genetic but also environmental factors contribute to the onset of schizophrenia. We therefore conducted psychophysiological studies on a pair of identical twins discordant for schizophrenia, to differentiate non-genetic from genetic indexes possibly associated with this disease. The affected and unaffected twins were 28 year-old females.

Reduced word-repetition effect in the event-related potentials of thought-disordered patients with schizophrenia.

Repetition effect in event-related potentials (ERPs) was studied in 10 non-thought-disordered (non-TD) patients with schizophrenia, 8 thought-disordered (TD) patients with schizophrenia, and 10 normal control subjects while they performed a semantic categorization task with incidental word repetitions. All patients were in a stable or partially remitted stage. Although both healthy control and non-TD groups produced more positive ERPs to the repeated words than to the new words (ERP repetition effect) for 250-500 ms, the TD group did not show the ERP repetition effect.