Prefrontal activity and impaired memory encoding strategies in schizophrenia.
Schizophrenia patients have significant memory difficulties that have far-reaching implications in their daily life. These impairments are partly attributed to an inability to self-initiate effective memory encoding strategies, but its core neurobiological correlates remain unknown. The current study addresses this critical gap in our knowledge of episodic memory impairments in schizophrenia. Schizophrenia patients (n = 35) and healthy controls (n = 23) underwent a Semantic Encoding Memory Task (SEMT) during an fMRI scan. Brain activity was examined for conditions where participants were a) prompted to use semantic encoding strategies, or b) not prompted but required to self-initiate such strategies. When prompted to use semantic encoding strategies, schizophrenia patients exhibited similar recognition performance and brain activity as healthy controls. However, when required to self-initiate these strategies, patients had significant reduced recognition performance and brain activity in the left dorsolateral prefrontal cortex, as well as in the left temporal gyrus, left superior parietal lobule, and cerebellum. When patients were divided based on performance on the SEMT, the subgroup with more severe deficits in self-initiation also showed greater reduction in left dorsolateral prefrontal activity. These results suggest that impaired self-initiation of elaborative encoding strategies is a driving feature of memory deficits in schizophrenia. We also identified the neural correlates of impaired self-initiation of semantic encoding strategies, in which a failure to activate the left dorsolateral prefrontal cortex plays a key role. These findings provide important new targets in the development of novel treatments aiming to improve memory and ultimately patients' outcome.
Department of Psychology, McGill University, Montréal, Canada; Douglas Mental Health University Institute, Montréal, Canada; Department of Psychiatry, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, USA.
Synthia
S
Guimond
Campbell Family Mental Health Institute, Centre for Addiction and Mental Health, Toronto, Canada.
Colin
C
Hawco
Douglas Mental Health University Institute, Montréal, Canada; Department of Psychiatry, McGill University, Montréal, Canada. Electronic address: martin.lepage@mcgill.ca.
Martin
M
Lepage
D000328:Adult; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007206:Individuality; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders / Q000000981:diagnostic imaging / Q000209:etiology*; D061212:Memory, Episodic; D008875:Middle Aged; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D017397:Prefrontal Cortex / Q000000981:diagnostic imaging / Q000503:physiopathology*; D021641:Recognition, Psychology; D012559:Schizophrenia / Q000150:complications* / Q000000981:diagnostic imaging / Q000473:pathology*; D012565:Schizophrenic Psychology; D055815:Young Adult
D010100:Oxygen
Associative encoding; Dorsolateral prefrontal cortex; Encoding strategies; Episodic memory; Schizophrenia