BACKGROUND AND OBJECTIVES: Prospective memory (PM) is the ability to remember to perform intended activities in the future. Impairment of PM can be a limiting factor for daily life, including social integration. PM deficits among stroke survivors are ...
BACKGROUND AND OBJECTIVES: Prospective memory (PM) is the ability to remember to perform intended activities in the future. Impairment of PM can be a limiting factor for daily life, including social integration. PM deficits among stroke survivors are a poorly understood contributor to disability. This study assessed PM function in stroke survivors without dementia.
METHODS: Twelve stroke patients and twelve controls, matched for age and education, were included for the first clinical part of the study. Background neuropsychological measures included MMSE, Trails A and B, Verbal Fluency phonemic (FAS) and semantic categories, Sustained Attention to Response Task (SART), Revised Strategy Application Test (R-SAT), Verbal Paired Associates I, II (Verbal PA), and California Verbal Learning Test (CVLT). PM was assessed by: the Memory for Intentions task (MIT), Virtual Week (VW), Remembering a Belonging subtest from the Rivermead Behavioural Memory Test(RBMT), Prospective and Retrospective Memory Questionnaire(PRMQ). For the second part of the study, we have conducted functional imaging study. Six stroke patients and seven age matched elderly controls from the clinical part of the study participated. In addition, seven young controls were included. Two PM tasks, a number and a picture tasks were administered to each participant while measuring brain activity using functional MRI.
RESULTS: Patients performed significantly poor in FAS (p=0.024), Verbal PA I (p=0.045) and CVLT T-score(p=0.002), short-delay free recall(p=0.005), long-delay free recall(p=0.002) compared to controls and made more SART commission error(p=0.013). There was no statistically significant difference in RBMT and PRMQ scores between two groups. MIT provided two measures: PM and RM components for the intentions. As a result, group difference was significant only in the PM component (p<0.01) but not in the RM component. Associative recall performance showed patients performing worse than controls (p=0.019) but an ANCOVA with associative recall as a covariate did not change the result. For VW, patients performed poorly on the time-check task compare to controls; statistically significant differences in proportions of correct responses and misses were shown (p<0.01). In the case of time-check responses, about 1/4 of PM errors were late responses in the control group, and major source of errors was a failure to response in the patient group. These findings may suggest that the major difference is in the prospective component of the task; that is, in remembering some response is required when a specific time or event is encountered. Patients’ performance drop was substantially less in the repeated ‘regular’ tasks than in the non-recurring ‘irregular’ tasks. In time-check task, the drop in performance was even larger. Concurrent performance of the board game and the time-check task resulted in a divided attention situation, and this may be especially troublesome for patients.
Over all functional MRI analysis revealed more activation in the frontal area in the patient group compared with the control groups. Areas of overactivity in these patients could infer that these regions might take over the function of damaged regions.