CONCLUSION. In this review we have considered research on the neuropsychology of bipolar disorder with special attention to the relationship between mood and cognitive

In this review we have considered research on the neuropsychology of bipolar disorder with special attention to the relationship between mood and cognitive functioning. Unlike the more advanced research focusing on major (unipolar) depression, work to date on bipolar disorder has not achieved a satisfactorily comprehensive assessment of cognitive functioning. Patients suffering from depression have been shown to be cognitively impaired on a wide range of tasks, and euthymic patients have demonstrated residual impairments on some tests of attention and visual information processing. Although studies of mania indicate a wide range of possible cognitive deficits, the comprehensive review of cognition suggested by these findings has not yet been undertaken. At the same time, comparative studies of unipolar depression have brought the essential similarity of these conditions into some doubt, with complicating consequences for a perhaps oversimple understanding of the relationship between mood and cognition in affective disorders. In particular, comparative studies have sought to establish distinct neuropsychological profiles for mania, depression and schizophrenia as a way of determining whether general or specific deficits obtain in the affective disorders.

The establishment of such distinct profiles is crucial to our understanding of the neuropsychology of the affective disorders. Until recently, most comparative studies noted striking similarities between schizophrenia, mania and depression. However, these studies employed affectively neutral designs, eliminating emotional processing from the experimental dynamic and thus compromising their usefulness in the investigation of mood and cognition. More recent studies, based on the model of earlier investigations of mood-congruent bias in depression, have attempted to differentiate mania and depression by employing tasks with affective components. These studies have noted biases in informational processing and abnormal responses to feedback that appear to be consistent with other data obtained from neuroimaging work on mania and depression.

Historically, studies of mood disorders have made virtually no reference to basic research on emotion in healthy volunteers, and conventional neuropsychological testing has shied away from emphasising emotional components of cognition. A neuropsychological approach that incorporates both elements in experimental designs requiring both cognitive and emotional processing could go a long way towards a better characterisation of the deficits so far observed in depression and in mania (see, for example, Murphy et al, 1999). Such an integrated approach could benefit greatly by incorporating ideas from emotion theories that emphasise cognition—emotion interactions (e.g. Barnard & Teasdale, 1991; Teasdale & Barnard, 1993; Williams, 1996) and from recent advances in our understanding of the brain mechanisms that underlie emotion (e.g. Damasio, 1994; LeDoux, 1995). Studies focusing on the neural networks involved in such emotional processes in the neuropsychiatric affective disorders of depression and mania may provide the key to resolving these important issues.

Previous SectionNext Section