Neural systems underlying affective disorders

Simon Surguladze is a research worker in the Section of Neuroscience and Emotion, King’s College London, based at the Institute of Psychiatry (De Crespigny Park, Denmark Hill, London SE5 8AF, UK). Paul Keedwell is an honorary clinical research worker and specialist registrar at the Mood Disorder Clinic of the Maudsley Hospital, London. Mary Phillips is Head of the Section of Neuroscience and Emotion and professor and honorary consultant psychiatrist in the Division of Psychological Medicine, Institute of Psychiatry and GKT School of Medicine. The Section’s research programme includes studies of neurobiological mechanisms underlying mood dysregulation in patients with affective disorders, schizophrenia, depersonalisation and obsessive–compulsive disorder.

Three main approaches are used to explore the neural correlates of mood disorder: neuropsychological studies, neuroimaging studies and post-mortem investigations. Lesion studies implicate disturbances in the frontal lobe, basal ganglia, striatum and anterior temporal cortex. Early neurocognitive and neuropathological investigations led to a ‘hypofrontality’ hypothesis of unipolar and bipolar depression, but functional neuroimaging has revealed a more complex picture. Thus, increased metabolism may occur in the subgenual anterior cingulate gyrus in resting-state studies of depression and sad-mood induction. Antidepressants may reduce this activity. Amygdala hyperactivation also is associated with affective disorders. Task-related studies reveal abnormal biases in memory, the experience of pleasure and the perception of emotional facial expressions. There is still little clarity whether the abnormalities in brain activation represent state or trait characteristics of affective disorders.