Cognitive Deficits in Brain Disorders (PDF)

the neuropsychological evidence for these models and we also review the limited available literature that implicates ‘prefrontal–parietal’ circuitry. The main theme that emerges is that dysfunction of the prefrontal cortices is central to the disorder, and the involvement of other brain structures almost always relates to their connections with prefrontal cortices. Such models provide potentially testable hypotheses, which can be addressed using recent technological advances in neuroimaging and cognitive neuropsychology and can be interpreted with respect to anatomical connectivity between the areas of interest.

Introduction

Schizophrenia is a serious psychiatric disorder presenting in the late teens and early twenties, with a lifetime prevalence of greater than 1% (review: Jablensky2). It is characterized clinically by abnormal experiences and beliefs, disturbances of emotion and affect, and behavioral disturbances and impaired social functioning. These symptoms usually include abnormal experiences, termed ‘positive symptoms’, such as prominent auditory and/or other sensory hallucinations, experiences of alien control, delusional ideas, and a characteristic disorder of thinking. There is also a loss of normal functioning, often termed ‘negative symptoms’, characterized by avolition and apathy, blunting of affect, and poverty of speech. The latter are particularly dif.cult to manage and treat and have been associated with neuropsychological de.cits and a poorer prognosis. Up to 50% of patients have a severe illness with a relatively poor outcome, with about 5–10% having progressive, treatment-resistant illness. Despite the high heritability of the disorder,5 other etiological factors are apparent and have been considered relevant to a neurodevelopmental pathogenesis. Thus, the prevailing current view is that schizophrenia is a neurodevelopmental disorder in which structural brain changes, caused by an early antenatal or perinatal insult, confer a predisposition to the development of schizophrenia, but are not progressive beyond the onset of symptoms.