Assessment of movement skills and perceptual judgent in atypical aging.

Abstract

This study investigated if individuals with either mild cognitive impairment (MCI) or early-stage Alzheimer’s disease (AD) exhibit higher levels of postural motion when engaged in a perceptually demanding visual task, compared to a similar group of typically aging individuals. Participants were well-characterized patients currently enrolled in the Minneapolis Veteran Affairs Medical Center’s, existing protocols for patients (Protocol-Cognitive Changes in Older Adults: A Minneapolis VA Medical Center Database [the GRECC Memory Loss Clinic database]) and normal controls (Protocol-Normative Changes in Older Adults). Fifty-nine volunteer participants enrolled from these protocols. Groups were assigned according to a consensus diagnosis of AD, MCI, and Normal. Twenty-five AD, 19 MCI and 15 Normal participated in the study. Participants completed a visual task comprising two conditions: a control condition (Inspection) - looking only within the perimeter of the blank (white board) target; and an experimental condition (Search) – which required counting the frequency of a designated letter within a text block of randomly presented alphabet letters. Postural motion was recorded as center of pressure (COP) in centimeters, in both the medial-lateral (ML) and anterior-posterior (AP) planes of motion, using a stable motion detecting platform. Results indicate that the AD group was less able to modulate postural motion in the ML plane (postural motion increased when switching from the Inspection task to the Search task); both the MCI and Normal group decreased their postural motion when switching from the Inspection task to the Search task. All groups, in the AP plane, were able to modulate their postural motion when engaged in the more demanding Search task, but the AD recorded significantly higher postural motion than the Normal group. There was no significant difference between the Normal and MCI group; or between the AD and MCI group in the AP plane. When groups were reclassified according to their current Mini-Mental State Exam (MMSE) scores, there was a significant difference between the “Low” MMSE group and the “High” MMSE group, in which the Low group increased their postural motion in the ML plane when engaged in the more demanding Search task. Consistent with the previous analysis, in the AP, all groups were able to reduce their postural motion when engaged in the more demanding Search task. However, both the “Low” and “Middle” MMSE groups, who recorded higher postural motion, differed significantly from the “High” MMSE group. The results extend previous findings with respect to the strength of the perception-action link in aging individuals who experience cognitive change. Deficits in cognitive function related to postural motion, indicate an ‘embodied’ relationship that may be a sensitive measure to early-stage dementia.