The effect of cognitive training on evoked potentials in schizophrenia

Electrophysiological indices are sensitive to cognitive dysfunction in schizophrenia but have rarely been used to assess benefits of cognitive remediation. Our aim was to evaluate the effect of specific cognitive training approaches on event-related potentials. Forty-six patients with schizophrenia underwent either auditory (AUD) or visuo-spatial (VIS) cognitive training or treatment-as-usual (TAU). Cognitive training was computer-assisted and administered for 10 sessions within two weeks. Event-related potentials during an active odd-ball paradigm together with clinical and neuropsychological variables were assessed before and after training and again at a two-month follow-up. Compared to the TAU group both the AUD and VIS training groups showed decreased P2 latency following training. At follow-up, the P2-latency reduction was stable in the VIS group but the AUD group experienced a relapse. Training resulted in improved digit-span backward among neuropsychological variables. Increased P2 amplitude was related to more positive symptoms and lower social-occupational functioning and longer P2 latency was associated with greater severity of stereotyped thinking. The more general visuo-spatial training appears to have a longer-lasting effect on P2 latency than the specific auditory training. Alternatively, there may be specific auditory discrimination deficits in schizophrenia requiring more extensive training for a stable change

Mismatch negativity latency and cognitive function in schizophrenia.

BACKGROUND: The Mismatch Negativity (MMN) is an event-related potential (ERP) sensitive to early auditory deviance detection and has been shown to be reduced in schizophrenia patients. Moreover, MMN amplitude reduction to duration deviant tones was found to be related to functional outcomes particularly, to neuropsychological (working memory and verbal domains) and psychosocial measures. While MMN amplitude is thought to be correlated with deficits of early sensory processing, the functional significance of MMN latency remains unclear so far. The present study focused on the investigation of MMN in relation to neuropsychological function in schizophrenia. METHOD: Forty schizophrenia patients and 16 healthy controls underwent a passive oddball paradigm (2400 binaural tones; 88% standards [1 kHz, 80 db, 80 ms], 11% frequency deviants [1.2 kHz], 11% duration deviants [40 ms]) and a neuropsychological test-battery. Patients were assessed with regard to clinical symptoms. RESULTS: Compared to healthy controls schizophrenia patients showed diminished MMN amplitude and shorter MMN latency to both deviants as well as an impaired neuropsychological test performance. Severity of positive symptoms was related to decreased MMN amplitude to duration deviants. Furthermore, enhanced verbal memory performance was associated with prolonged MMN latency to frequency deviants in patients. CONCLUSION: The present study corroborates previous results of a diminished MMN amplitude and its association with positive symptoms in schizophrenia patients. Both, the findings of a shorter latency to duration and frequency deviants and the relationship of the latter with verbal memory in patients, emphasize the relevance of the temporal aspect of early auditory discrimination processing in schizophrenia

28 channel EEG amplitude distributions and comparison of the between-group MMN waveforms.

<p>Scalp electrode maps of MMN to frequency deviant (A, B) and duration deviant tones (D, E) in controls (A, D) and patients (B, E). MMN waveforms of patients and controls to frequency (C) and duration deviant tones (F), both at Fz are shown on the right.</p

Demographic, clinical and neuropsychological characteristics of schizophrenia patients and healthy controls.

<p>Demographic, clinical and neuropsychological characteristics of schizophrenia patients and healthy controls.</p

Positive symptom scores and MMN amplitude.

<p>Scatterplot of PANSS positive symptoms against MMN amplitude to duration deviants at FCz.</p

Linear associations between MMN latency and patient's verbal memory performance.

<p>Scatterplots of immediate (A) and delayed (B) verbal memory performance score against MMN amplitude to frequency deviants at Fz and FCz, respectively.</p

Grand averages of responses to standard and deviant tones and the resulting difference waveforms.

<p>Top: Frequency deviants in controls (A) and patients (B); bottom: Duration deviants in controls (C) and patients (D).</p

Mean (SD) amplitudes and latencies to duration and frequency deviants for schizophrenia patients and healthy controls.

<p>Between-group t-statistics (p-values) are reported for amplitude (µV) and latency (ms) separately for each electrode. Adjusted t-statistics (Welch-test) are reported (*), in the case of unequal variances.</p

Diagrams of group means and standard errors.

<p>MMN amplitudes to frequency (A) and duration deviants (B) are presented for both groups at midline electrode sites.</p