The hippocampus is implicated in the pathophysiology of major depressive disorder (MDD), with evidence that morphological changes occur with disease progression. It was hypothesized that treatment-naive patients with depression would show performance deficits in hippocampus-dependent memory trials, with concurrent hippocampal activation deficits on functional magnetic resonance imaging, compared with control participants. Thirteen treatment-naive patients with MDD and 13 control participants completed a hippocampus-dependent memory functional magnetic resonance imaging process-dissociation task. On behavioural measures of habit memory and guessing, there were no significant differences between groups. Functional magnetic resonance imaging analysis indicated that compared with the control group, the MDD group showed increased activation in the parahippocampal gyrus and hippocampus on habit memory and nonitem trials. These alterations in hippocampal functioning with preserved cognitive performance on a test of hippocampus-dependent memory in MDD may be indicative of a compensatory mechanism.
aDepartment of Psychiatry and Behavioural Neurosciences, Faculty of Health Sciences
bDepartment of Psychology, Neuroscience and Behaviour, Faculty of Sciences, McMaster University
cMood Disorders Research Unit, St. Joseph’s Centre for Integrated Healthcare, Hamilton, Ontario
dDepartment of Psychiatry, Faculty of Medicine, University of Calgary, Foothills Hospital, Calgary, Alberta, Canada
Correspondence to Geoffrey B. Hall, PhD, Psychology Building (PC) Room 307, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada Tel: +1 905 525 9140; e-mail: firstname.lastname@example.org
Received September 17, 2018
Accepted October 22, 2018