Cortical thickness and metacognition in cognitively diverse older adults

Abstract

Objective: Metacognition, or the ability to accurately identify, appraise, and monitor one's deficits, is commonly impaired in Alzheimer's disease (AD). Poor metacognition prevents correct appraisal of a range of physical, cognitive, and emotional symptoms and facilitates anosognosia, which has important clinical implications for individuals (e.g., diminished treatment adherence, increased engagement in high-risk situations) and caregivers (e.g., higher burden). However, the neural correlates of metacognitive disturbance are still debated in the literature, partly because of the subjective nature of traditional awareness measures.

Method: An objective Feeling of Knowing (FOK) task was used to measure metamemory capacity in a group of cognitively diverse older adults, including 14 with mild to moderate AD and 20 cognitively healthy older adults. The association between three different objective metamemory measures of the FOK task and regional cortical thickness (12 bilateral regions of interest [ROIs] hypothesized to support self-awareness) was analyzed using partial correlations.

Results: Less accurate metamemory at the local and global levels was associated with reduced right posterior cingulate cortical thickness, r = -0.42, p = .02 and reduced right medial prefrontal, r = -0.39, p = .029, respectively.

Conclusions: To our knowledge, this was the first study to examine metacognition in relation to cortical thickness. Both global and local metamemory functions appear to rely on the integrity of right sided midline regions, known to be important for processing self-referential information. Findings are conceptualized with regard to the Default Mode Network, and also considered in relation to recent findings pointing to the right insula as a region critical for self-awareness. (PsycINFO Database Record

Figure 1

A 3-dimensional representation of the brain’s white matter derived in FreeSurfer with the cortical areas used in the study superimposed and labeled by color. Blue = medial prefrontal lobe (medial orbital and frontal pole); Red = temporal (entorhinal cortex, parahippocampus, temporal pole); Orange = parietal (superior parietal lobule, precuneus); purple = anterior cingulate cortex (caudal and rostral anterior cingulate cortex); magenta = posterior cingulate cortex; green = insula.

Figure 2

Association between global calibration scores and right prefrontal cortex thickness

Figure 3

Association between item calibration scores and right posterior cingulate cortex thickness