An investigation of event-related potentials in adolescents with psychotic-like experiences

It is well established that patients with schizophrenia exhibit a wide range of deficits in sensory and cognitive processing. Neurophysiological mechanisms underlying these abnormalities are also impaired in patients with schizophrenia, as well as in first episode and prodromal patients and in unaffected family relatives. Recent evidence has documented the presence of psychotic-like experiences (PLEs) and other risk factors for psychosis in the general population (Kelleher and Cannon, 2011; Van Os et al, 2000). Adolescence is a critical time period that is marked by an increased vulnerability for the development of psychopathology, particularly psychosis (Poulton et al, 2000). Research has documented a relationship between the onset of psychotic symptoms in adolescence and the development of a psychotic disorder in adulthood (Poulton et al, 2000). Therefore, this group can be conceptualised as an at-risk group for psychosis.

This thesis examined neural correlates of sensory and cognitive processing in adolescents with PLEs from the general population. Using the event-related potential technique (ERP), we compared adolescents with PLEs to a group of age matched controls on tasks of auditory change detection, response inhibition, receptive language and semantic comprehension. The adolescents with PLEs were characterised by reductions in mismatch negativity (MMN) and P300 amplitude on tasks of auditory discrimination and language comprehension. In comparison to the controls, the adolescents with PLEs displayed delayed latency on the P300 component and prolonged latency on the N400 component on tasks of response inhibition and language comprehension, respectively. The abnormalities observed in these tasks were evident over frontal regions, which suggested possible evidence of early frontal dysfunction in this at-risk group. Evidence of impaired neurophysiological activity in adolescents with PLEs provides important information regarding risk for psychosis a t the level of the general population.