Impaired implicit sequence learning in depression: A probe for frontostriatal dysfunction?

Sharon L. Naismith, Ian B. Hickie, Philip B. Ward, Elizabeth Scott, Craig Little

Research output: Contribution to journalArticlepeer-review

54 Citations (Scopus)

Abstract

Background. Implicit learning through motor sequencing tasks is sensitive to basal ganglia dysfunction. Consequently, it is ideally suited for testing elements of the frontostriatal model of major depression and performance can be related to key clinical, neuropsychological, vascular and biochemical data. Method. Twenty-one subjects with moderate to severe unipolar depression and 21 age-, sex- and education-matched controls were recruited. Clinical, vascular and biochemical data were recorded. Subjects were administered a battery of neuropsychological tests that assessed speed of processing, working memory, learning, memory, language, perceptual organization and executive functioning. Additionally, subjects were administered a motor sequencing implicit learning task. Implicit learning is assumed when reaction times improve during the sequenced condition as compared to the pseudo-random baseline condition. Results. The rate of implicit learning in persons with depression was only half that of control subjects (3·6% ν 7·3%). Lower rates of implicit learning in patients were associated with poorer performance on neuropsychological tests of visuomotor speed and mental flexibility, longer duration of depressive episode and severity of acute stress. In a small number of subjects, poorer performance was also related to past suicide attempt. Conclusions. Impaired implicit learning in persons with depression is consistent with frontostriatal dysfunction. Performance is related to some clinical characteristics and to neuropsychological functioning on tests of visuomotor speed and mental flexibility.

Original languageEnglish
Pages (from-to)313-323
Number of pages11
JournalPsychological Medicine
Volume36
Issue number3
DOIs
Publication statusPublished - Mar 2006
Externally publishedYes

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