Cognitive control and conflict processes in geriatric depression

Major depressive disorder is often accompanied by disturbances in aspects of cognitive control that impair goal-directed behavior. In particular, depressed individuals have been found to have deficits in conflict processing, which manifest as inadequate inhibition of maladaptive environmental stimuli and thought patterns. Insufficient cognitive inhibition of irrelevant negative information may contribute to, and perpetuate the depressive syndrome. Prior studies have hypothesized that the neural network that underlies conflict processing consists of the dorsal anterior cingulate and dorsolateral prefrontal cortex. This network has been shown to be compromised by depression in young adults, as well as by the aging process. However, the temporal properties of conflict processing, within this conflict-control network, have not been fully examined in geriatric depression.;In this study, the N2 event-related potential was recorded during a Stroop paradigm administered to 44 depressed and 24 healthy older adults. Depressed subjects exhibited smaller N2 amplitudes to incongruent relative to congruent stimuli. Among healthy non-depressed subjects, there was no difference in N2 amplitudes between conditions. Notably, there were no overall differences in task accuracy or reaction time between the depressed and non-depressed groups. Larger N2 amplitudes were associated with executive dysfunction (i.e., poorer performance on a set-shifting measure) in healthy older adults; however, this relationship was not observed in the depressed group. These results suggest that neural processing abnormalities within the conflict-control network may exist in geriatric depression, above and beyond those attributable to normal age related changes. Furthermore, alternate neural networks may be recruited for successful conflict processing in depressed older adults. Additional characterization of abnormalities within specific conflict processing networks, as well as examination of how these abnormalities relate to the course and treatment of depression can help inform pharmacological and psychotherapeutic interventions.