Introduction: To study working memory function in major depression using identification and memory tests with event-related potentials (ERP).
Methods: We compared behavioral performance and event-related potentials during the processing of the Sternberg working memory task in 26 patients with major depression and 64 healthy matched control subjects.
Results: Depressed patients had more errors and had an increase in reaction time that was superior to the control subjects during the memory test of 5 letters presented. The depressive patients showed increased event-related potentials (P300 and N400) between 300-700 milliseconds registered in Pz. The prolonged positive activity in the patients ERPs suggests specific deficit in cortical activity and the large prolonged negativity activity in the patients' ERPs suggests abnormal activation of additional neuronal assemblies than those normally participating in the memory task. These data could reflect either compensatory mechanisms of dysfunction of inhibitory systems.
Conclusions: This study provides objective evidence that major depression significantly affects working memory. The ERP changes in depression could be accounted for by cortical activity dysfunction of the central executive control of working memory.