Brain imaging and psychological disorders
9 February 2009
Abnormal behaviour is seen in many mental conditions and presumably reflects disruptions to normal brain function. Insight into these abnormalities is being gathered by brain imaging - increasing understanding and raising hopes of better diagnosis and treatment.
The basis of conditions such as obsessive-compulsive disorder (OCD) has been difficult to trace, in part because human behaviours are tricky to categorise in a way that makes them amenable to study. A productive way forward, being taken by Sam Chamberlain and colleagues in Cambridge, is to identify patterns of brain activity that can act as robust proxies of behavioural traits.
To this end, they looked to this end, they looked at brain activity in people with OCD and their unaffected relatives, who might be expected to show similar but less marked abnormalities. Indeed, compared with controls, activity in areas within the frontal lobes - known to be involved in decision-making - were lower in both people with OCD and their relatives.
Neural correlates of another mental disorder, depression, have been uncovered by Cynthia Fu and colleagues from the Institute of Psychiatry, London. Ultimately, this may lead to more objective diagnosis of depression. Responses were recorded to faces manipulated digitally to show varying degrees of sadness. By analysing activity across the whole brain, Dr Fu was able to identify patterns consistently seen in people with depression but not controls.
Finally, Senior Research Fellow Paul Fletcher and colleagues in Cambridge have used brain imaging to explore susceptibility to schizophrenia, using ketamine to induce a state of psychosis in healthy volunteers.
Brain activity was monitored in volunteers before and after a dose of ketamine. Some distinctive brain activations seen before ketamine was administered were significantly more common in those reporting psychotic symptoms. Moreover, activation at certain sites seemed to predict which types of symptom an individual experienced.
It may therefore be possible to use brain imaging to identify vulnerabilities to particular psychotic symptoms, before they become clinically apparent.
Image: Areas of abnormal brain activity (blue) in people with OCD or their relatives undertaking a cognitive task. Adapted from Chamberlain et al., reproduced with permission from AAAS.
References
Chamberlain SR et al. Orbitofrontal dysfunction in patients with obsessive-compulsive disorder and their unaffected relatives. Science 2008;321(5887):421-2.
Fu CH et al. Pattern classification of sad facial processing: toward the development of neurobiological markers in depression. Biol Psychiatry 2008;63(7):656-62.
Honey GD et al. Individual differences in psychotic effects of ketamine are predicted by brain function measured under placebo. J Neurosci 2008;28(25):6295-303.