14 FMRI Investigation of Metacognitive Processing in Moderate to Severe Traumatic Brain Injury

Abstract

Objective:

Metacognition refers to one’s ability to make online, in-the-moment judgments regarding their own cognitive performance, and has significant implications for one’s abilities to function in daily life. It has been documented that individuals with TBI often present with metacognitive deficits, and are slower than neurotypical peers in making such judgments. Preliminary attempts have been made to determine how neural contributions to metacognitive functioning differ after injury. Studies thus far have found unique roles of prefrontal gray matter volume and inter-network connectivity in metacognitive functioning after injury, but functional activation directly associated with metacognitive processing has yet to be investigated. This event-related functional magnetic resonance imaging (fMRI) study aimed to document differences in functional activation between adults with TBI and neurotypical peers when completing metacognitive confidence judgments.

Participants and Methods:

16 adults with moderate to severe TBI and 10 healthy adults (HCs) completed a metacognitive task while in the fMRI scanner. All participants were exposed to target slides with polygons arranged in various positions, then asked to identify the target slide from a group including 3 other distractor slides. Following each response, participants provided a metacognitive retrospective confidence judgment (RCJ) by rating their confidence that the answer they provided was correct. Meta d', a signal-detection based metric of metacognitive accuracy, was calculated. FSL FEAT was used for processing and analysis of the imaging data. Contrasts were created to model activation that was greater when RCJs were made compared to target recognition, mixed effects modeling was then used to investigate group differences. Cluster based thresholding set to z>2.3, p<0.01 was used for multiple comparisons correction.

Results:

Healthy controls performed significantly better on the target identification task (p<0.01), and were faster at making RCJs (p=0.03). Individuals with TBI had greater meta d’ scores (p=0.03). Significant activation beyond what was present during target recognition (RCJ>recognition) was found in left supramarginal gyrus, left posterior cingulate, and left cerebellum when individuals with TBI made RCJs, while HCs showed significant activation in the left precuneus, and bilateral superior temporal gyri. Individuals with TBI demonstrated more activation in the lateral occipital cortex bilaterally and the left cerebellum than HCs when completing RCJs. HCs presented with more activation in the left supramarginal gyrus than the TBI group when making RCJs.

Conclusions:

The areas of activation present in both the TBI and HC groups are consistent with previous imaging findings from studies of healthy samples. Interestingly, two structures previously implicated in self-directed cognition and consciousness, the posterior cingulate and precuneus, were differentially activated by the groups. The lack of a common network between the two groups suggests that survivors may rely on separate neural substrates to facilitate metacognition after injury. The TBI group was found to recruit more functional areas when completing the RCJs. These findings, paired with the behavioral data indicating metacognitive performance differences, suggests that neural recruitment may occur after injury to allow for survivors to engage in making metacognitive judgments. Future qualitative investigations of the metacognitive judgments are needed to determine the compensatory nature of this postinjury recruitment.