Blunted response to feedback information in depressive illness

Depressive illness is associated with sustained widespread cognitive deficits, in addition to repeated experience of distressing emotions. An accepted theory, which broadly accounts for features of the syndrome, and its delayed response to antidepressantmedication, is lacking.One possibility, which has received considerable atten-tion, is that depressive illness is associated with a specific underlying deficit: a blunted or impaired ability to respond to feedback information.Unlike healthy controls, if patients with a depressive illness commit an error, they can be at increased risk of committing a subsequent error, possibly due to a failure to adjust performance in order to reduce the risk of error. In some speeded tasks, performance adjustment in humans is reliably asso-ciatedwith trial-to-trial change in reaction times (RTs), such as ‘post-error slowing’. Previous studies of abnormal response to feedback have not investigated RT change in any detail.We used a combination of quantitativemod-elling of RTs and fMRI in 15 patients and 14 matched controls to test the hypothesis that depressive illness was associated with a blunted behavioural and neural response to feedback information during a gambling task.The results supported the hypothesis.Controls responded to negative (‘lose’) feedback by an increase in RTand acti-vation of the anterior cingulate, the extent of which correlated with RT change. Patients did not significantly increase their RTs, nor activate the anterior cingulate. Controls responded to positive (‘win’) feedback by a reduction in RTand activation of the ventral striatum, the extent of which correlated with RT change. Patient