Background. Recent studies have suggested that subjects
with depression suffer a diagnosis-specific
motivational deficit, characterized by an abnormal response to negative
feedback that endures
beyond clinical recovery. Furthermore, it has been suggested that negative
feedback may motivate
non-depressed controls, but not depressed patients, to improve their performance
in neuropsychological tests.
Methods. We describe two studies. The first compared performance
on the simultaneous and
delayed match to sample (SDMS) task from the CANTAB neuropsychological
test battery, in 20
patients with severe depression with 20 with acute schizophrenia, 40 with
chronic schizophrenia and
40 healthy controls. The second examined the performance of depressed patients
with diurnal
variation in symptoms and cognitive function.
Results. All patients groups showed impairments on the simultaneous
and delayed match to sample
task compared to controls. Depressed patients did not show an abnormal
response to negative
feedback. Controls did not show a motivational effect of negative feedback.
Depressed patients with
diurnal variation showed no variation in their response to perceived failure.
There was no evidence
of abnormal response to negative feedback in any patient group using the
‘runs test’ or of a
motivational effect in controls. Conditional probability analysis was not
independent of the total
number of errors made in the SDMS task.
Conclusions. Further studies are suggested to examine whether
an abnormal response to negative
feedback characterizes particular subgroups of patients suffering from
depression.