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2.4 Depression
Depression is a mental disorder presenting with symptoms such as depressed mood
and loss of interest or joy. In the cognitive theory proposed by Beck [
11
], cogni-
tions causing depressed mood are divided into depressive schemas, cognitive dis-
tortions, and automatic thoughts. Automatic thoughts, which are suf
!
cient to cause
depressed mood, are negative ideas regarding oneself, the world, and the future. Of
the cognitive impairments in these forms of depression, we have focused on neg-
ative cognition regarding the future and have examined the underlying functional
brain mechanisms. We used fMRI to assess brain activation during the performance
of a decision-making task requiring the prediction of future rewards in 12 patients
with depression and 12 healthy control subjects. When healthy control subjects
predicted future rewards, activation was observed in the prefrontal cortex, anterior
cingulate gyrus, parietal lobe, thalamus, basal ganglia, and cerebellum. These brain
networks are considered important for prediction of future rewards. In patients with
depression, on the other hand, no signi
!
cant activation was observed in any of the
above-mentioned areas of the brain. In patients with depression, decreased activity
of the cerebral network (including areas such as the prefrontal cortex) is considered
to result in reduced cognitive function related to the prediction of future rewards;
this, in turn, is inferred to contribute to negative cognition with regard to the future.
In addition, we have performed group cognitive behavioral therapy for patients
with depression and examined brain activation during the performance of future
reward prediction tasks before and after therapy (Fig.
3
). Before therapy, brain
Fig. 3 Areas of brain activation in prediction of future rewards
