Increased cognitive effort costs in healthy aging and preclinical Alzheimer's disease

Abstract

Life-long engagement in cognitively demanding activities may mitigate against declines in cognitive ability observed in healthy or pathological aging. However, the "mental costs" associated with completing cognitive tasks also increase with age and may be partly attributed to increases in preclinical levels of Alzheimer's disease (AD) pathology, specifically amyloid. We test whether cognitive effort costs increase in a domain-general manner among older adults, and further, whether such age-related increases in cognitive effort costs are associated with working memory (WM) capacity or amyloid burden, a signature pathology of AD. In two experiments, we administered a behavioral measure of cognitive effort costs (cognitive effort discounting) to a sample of older adults recruited from online sources (Experiment 1) or from ongoing longitudinal studies of aging and dementia (Experiment 2). Experiment 1 compared age-related differences in cognitive effort costs across two domains, WM and speech comprehension. Experiment 2 compared cognitive effort costs between a group of participants who were rated positive for amyloid relative to those with no evidence of amyloid. Results showed age-related increases in cognitive effort costs were evident in both domains. Cost estimates were highly correlated between the WM and speech comprehension tasks but did not correlate with WM capacity. In addition, older adults who were amyloid positive had higher cognitive effort costs than those who were amyloid negative. Cognitive effort costs may index a domain-general trait that consistently increases in aging. Differences in cognitive effort costs associated with amyloid burden suggest a potential neurobiological mechanism for age-related differences. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Figure 1:

Simplified illustration of the discounting portion of the COG-ED task. Thick lines indicate the choice made by the participant.

Figure 2:

Panel A: Boxplots of the average SVs for each age group, task and difficulty level. Solid lines represent the medians and the dashed lines represent the mean. Panel B: Main effect of age group on Subjective Value in Experiment 1

Figure 3:

Relationship between working memory SV and Speech SV, collapsed across all difficulty levels, in Experiment 1.

Figure 4:

Correlations between cognitive effort cost and working memory capacity (top panels) or Need for Cognition (bottom panels) in Experiment 1.

Figure 5:

Panel A) Boxplots of average SVs for each level of difficulty in Experiment 2. Solid lines represent the median value and the dashed lines represent the means. Panel B) Main effect of amyloid group (collapsed across difficulty).

Figure 6:

Bivariate relationships between Need for Cognition and COG-ED Subjective value (Panel A) and NASA Effort subscale (averages across conditions) and COG-ED Subjective value averaged across conditions (Panel B).