Towards a Functional Neuroanatomy of Symptoms and Cognitive Deficits of Schizophrenia

Abstract

The techniques of neuroimaging and non-invasive neurophysiology, alone or in combination, provide unprecedented access to the mechanisms of normal and pathological perception and cognition in the human brain. They are especially useful for the investigation of the neural basis of psychiatric symptoms, for which animal models cannot be obtained, for example hallucinations. Functional magnetic resonance imaging has revealed that auditory cortex, frontal language areas and parts of the limbic system are commonly active during auditory verbal hallucinations. The anatomical connectivity underlying this pathophy-siological network can be studied with another magnetic resonance imaging technique, diffusion tensor imaging. A similar rationale of combining functional and structural methods can be applied to other core symptoms of schizophrenia. The study of the pathophysiology of psychotic symptoms is closely linked to that of perceptual and cognitive deficits, which probably contribute to the generation of the clinical symptoms, but often precede or outlast them, making them important trait markers. Deficits of working memory and executive function have been associated with characteristic changes in late components of the event-related potential of the electroencephalogram (EEG) and distinctive patterns of pre-frontal metabolic activity. However, recent studies also showed differences at earlier stages of perceptual processing, affecting sensory cortices in both the auditory and the visual domain. In addition to overall activity, coherence within and across areas, as evidenced by synchronous oscillations of the EEG, seems to be impaired in schizophrenia during certain cognitive tasks. These findings from neuroimaging and electrophysiology are not only important for the cognitive neuroscience of schizophrenia, but can also inform models that explain schizophrenia at the molecular level.