Ralentissement cognitif dans le vieillissement : fonctions exécutives et apprentissage procédural lors d'une tâche informatisée de labyrinthe

Abstract

General slowing of performance speed is a common finding associated with normal aging. However, which aspects of information processing are playing a major role in this decline are not well understood. Impairment in maze learning has been shown in patients with neurological disorders. Hippocampal bilateral lesions are associated mith larger deficits and interfere with both storage and retrieval of spatial information. Frontal lesions also produce similar effects and are characterized by perseverative errors. Reduced working memory has also been implicated in cognitive aging and is reflected in difficulties encountered in the execution of a task in real time when alterning between encoding and retrieval of information. A computerized maze learning task (Groton Maze Learning Task, GMLT) was developed specifically to determine the extent to which perseverative behaviors, working memory difficulties or other factors are implicated in the cognitive slowing generally observed in aging. Two groups of right-handed subjects (20 young adults: M =22.6; SD =1.54; 19 older adults: M =64; SD3 =0.93) were compared looking at speed of learning and perseverative errors. Subjects were also assessed on tasks of procedural learning (Tower of Toronto), working memory (Paced Auditory Serial Addition Test; PASAT), and four subtests of the Wechsler Memory Scale-III (logical memory, faces, paired associates, family pictures) with immediate and delayed recall. With respect to the GMLT, subjects were required to find the correct path through a hidden maze by pressing on the computer’s touchscreen to move to the location of their choice. After practice trials, all subjects underwent ten consecutive trials followed, ten minutes later, by one last trial. Results of interest showed significant differences between the two groups in the time needed to complete all trials and in the number of perseverative errors. More specifically, the older subjects made more perseverative errors and were slower in learning the maze. In addition, a canonical correlation analysis was performed to determine the relationship between maze learning and the cognitive systems involved (executive function, working memory, procedural learning). The analysis revealed a canonical variate explaining 49% of the total variance, showing that the number of perseverative errors and number of moves on the Tower of Toronto test are the main components principally implicated in the performance of subjects on the GMLT. We conclude that the tendency for healthy elderly adults to make perseverative errors while completing the learning trials, often related to frontal-lobe dysexecutive syndromes, may also be associated with normal aging. It is suggested that the poorer monitoring of errors and/or the inhibition of a choice in response to new information observed in the elderly accounts, at least in part, for the overall finding of slowed information processing speed.