Visual P300 amplitude ‘a vulnerability marker for schizophrenia’
MedWire News: Results from a South Korean study show that patients with schizophrenia and those at ultra-high risk (UHR) for the disorder have reduced visual P300 amplitude, which may serve as a vulnerability marker for the condition.
"Event-related potentials (ERP) are neurobiological measures that are commonly used to examine information processing," explain Dong-Ho Song (Yonsei University College of Medicine, Seoul) and team.
"The P300 ERP, which is evoked by the detection of rare targets embedded in frequently occurring non-target stimuli (eg, oddball tasks), is thought to reflect working memory and/or attention."
They add that previous studies have suggested that P300 amplitude reduction, particularly in the auditory domain, is a potential neurobiological vulnerability marker of schizophrenia.
To investigate whether reduced visual P300 amplitude is a vulnerability marker for schizophrenia, the team studied 21 patients with a first episode of schizophrenia, 16 individuals considered to be at UHR for the condition due to the presence of one or more prodromal syndromes, and 16 mentally healthy controls.
All of the participants underwent electroencephalograms (EEG) while performing a visuospatial recognition task using the oddball paradigm, which involved pressing a button when targets were distinguished from non-targets on a screen. Eye blinks and movements were monitored by electrodes placed near the outer canthus and beneath the left eye.
The researchers found that, overall, first-episode schizophrenia and UHR patients displayed significantly smaller P300 amplitudes than controls. There was no difference in P300 amplitudes between first-episode and UHR patients.
Further analysis revealed that scores on the scale for the assessment of negative symptoms (SANS) were negatively associated with P300 amplitudes in both the UHR and first-episode schizophrenia patients.
However, there were no significant correlations between P300 amplitudes and scores on the scale for the assessment of positive symptoms (SAPS) in either of the patient groups.
The team also found that, among first-episode schizophrenia patients, antipsychotic medication equivalent doses were not correlated with P300 amplitudes.
Song and team conclude in the journal Neuroscience Letters: "These results suggest that the visual P300 may be a neurobiological vulnerability marker of schizophrenia, which is associated with enduring negative symptoms."
They add: "In the future, longitudinal studies with a larger sample following individuals with negative symptoms and reduced P300 amplitudes will be needed to clarify our findings and will aid in the identification of protective factors against schizophrenia."
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By Mark Cowen