Aging and the wandering brain: Age-related differences in the neural correlates of stimulus-independent thoughts

• Published in: PloS one 2019-10, Vol.14 (10), p.e0223981-e0223981
• Main Authors: Maillet, David, Beaty, Roger E, Adnan, Areeba, Fox, Kieran C R, Turner, Gary R, Spreng, R Nathan
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Adults; Age; Aged; Aging; Aging (Biology); Aging - physiology; Biology and Life Sciences; Brain; Brain Mapping; Brain research; Cognition & reasoning; Cortex (cingulate); Cortex (temporal); Diagnostic imaging; Elderly; Female; Functional magnetic resonance imaging; Gyrus Cinguli - physiology; Health aspects; Humans; Magnetic resonance; Magnetic Resonance Imaging; Male; Medicine and Health Sciences; Memory; Neuroimaging; Novels; Objectives; Older people; Parietal Lobe - physiology; People and Places; Physiological aspects; Prefrontal cortex; Psychology; Research and Analysis Methods; Scanners; Social Sciences; Stimuli (Psychology); Studies; Superior temporal gyrus; Temporal gyrus; Temporal lobe; Thinking - physiology; Young Adult; Young adults
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0223981

In recent years, several studies have indicated that healthy older adults exhibit a reduction in task-unrelated thoughts compared to young adults. However, much less is known regarding age-related differences in time spent engaging in stimulus-independent thoughts or in their neural correlates in the absence of an ongoing task. In the current study, we collected functional magnetic resonance imaging (fMRI) data while 29 young (mean age = 22y) and 22 older (mean age = 70y) adults underwent experience sampling in the absence of an ongoing task (i.e., at "rest"). Although both age groups reported spending a similar amount of time engaged in stimulus-independent thoughts, older adults rated their thoughts as more present-oriented (rather than atemporal) and more novel. Moreover, controlling for these age-related differences in content, we found that experiencing stimulus-independent thoughts was associated with increased posterior cingulate and left angular gyrus activation across age groups compared to exhibiting an external focus of attention. When experiencing stimulus-independent thoughts, younger adults engaged medial and left lateral prefrontal cortex as well as left superior temporal gyrus to a greater degree than older adults. Taken together, our results suggest that, in the absence of an ongoing task, although young and older adults spend a similar amount of time engaging in stimulus-independent thoughts, the content and neural correlates of these thoughts differ with age.