Analysis of neural sources of p300 event-related potential in normal and schizophrenic participants

The P300 event-related potential (ERP) is associated with attention and memory operations of the brain. P300 is changed in many cognitive disorders such as dementia, Alzheimer, schizophrenia, and major depression disorder. Therefore, investigation on basis of this component can help to improve our understanding of pathophysiology of such disorders and fundamentals of memory and attention mechanism. In this study, electroencephalography (EEG) signals of 20 schizophrenic patients and 20 age-matched normal subjects are analyzed. The oddball paradigm has been used to record the P300, where two stimuli including target and standard are presented with different probabilities in a random order. Data analysis is carried out using conventional averaging techniques as well as P300 source localization with low-resolution brain electromagnetic tomography (LORETA). The results show that the P300 components stem from a wide cerebral cortex network and defining a small definite cortical zone as its generator is impossible. In normal group, cingulate gyrus, one of the essential components of working memory circuit that was reported by Papez, is found to be the most activated area and it can be in line with the hypothesis that at least a part of the P300 is elicited by working-memory circuit. In schizophrenic group, frontal lobe is the most activated area that was responsible for P300 sources. Our results show that the cingulate gyrus is not activated in comparison with normal group, which is in line with previous results that dysfunction of the anterior cingulate cortex plays a prominent role in the schizophrenia disorder.