Recollection deficiencies in patients with major depressive disorder

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Neuropsychological research suggests that recognition memory (RM) and recall memory are impaired in
patients with a major depressive disorder or a dysphoric mood state. This study examines the proposal that
abnormalities in recollection (a form of recall) result from a breakdown in frontal strategic memory
processes involved in encoding and retrieval, and executive functions linked to reality monitoring, planning,
problem-solving, reasoning and decision-making. We investigated two predictions arising from this theory.
Firstly, patients diagnosed with a major depressive disorder (MDD) will display a dissociation between
(deficient) recollection and (preserved) familiarity. Secondly, if recollection impairments are indicative of a
breakdown in prefrontal strategic memory processes which are dependent, at least in part, on executive
processes, then an explicit correlational approach predicts that recollection will be positively associated with
the severity of executive dysfunction in MDD patients. The remember/know paradigm was used to investigate
RM for words and neutral faces in 16 MDD patients and 16 healthy volunteers, matched for age, gender and
estimates of premorbid IQ. Measures of executive function included working memory, reasoning and
decision-making. Applying the Dual Process Signal Detection interpretation of the remember/know data, the
MDD group displayed significant impairments in RM and recollection rates for both verbal and neutral facial
memoranda. In contrast, familiarity-aware rates were preserved. There was no evidence of executive
dysfunction in the patient group, and little evidence that recollection rates correlated with executive
function. Furthermore, a single process signal detection approach suggested that the MDD patients displayed
a reduction in sensitivity for RM and remember rates but not know responses. The criteria for detecting
studied from unstudied items, and remembering from knowing, were the same in both patient and healthy
control groups. Taken together, these findings are consistent with the view that MDD is marked by a decline
in RM, which is underpinned by an impairment in recollection rather than familiarity processes. The extent
to which the recollection deficiencies arise from disruption of strategic memory and executive processes
requires further investigation.