Neuroimaging in the field of psychoses.

This review looks at the recent findings in the neuroimaging of the psychoses, with a view to clarifying the question of the unitary versus the two-disorder theory of psychosis. Schizophrenia is associated with significantly more cortical grey matter loss than bipolar disorder. The distribution of these losses is different; schizophrenia is characteristically associated with loss of the medial and middle frontal, the superior temporal gyri, and the dorsolateral prefrontal cortex, while bipolar disorder has particular loss in the medial frontal gyrus and the anterior cingulate cortex. Both disorders were associated with extensive white matter deficits. In summary, neuroimaging indicates different patterns of grey matter loss for schizophrenia and bipolar disorder. However, neuroimaging of white matter reveals a good deal of overlap between these two disorders. Thus, neuroimaging does not suggest a unitary psychosis or a two-psychosis model, instead it suggests a two-dimensional psychosis field, on which disorders are located according to two dimensions, the degree of grey matter loss and the degree of white matter abnormality.