Neural Correlates of Impaired Self-awareness of Deficits after Acquired Brain Injury: A Systematic Review

Abstract

Self-awareness is essential for the process and outcome of rehabilitation but is often affected by acquired brain injury (ABI). While many studies investigated the psychological aspects of self-awareness deficits, the biological underpinnings are not well understood. The aim of this systematic review was to identify the neural correlates of self-awareness after ABI. Results indicate that anticipation of future problems is associated with lesions and decreased neural functioning in the right frontal lobe, as well as increased diffusivity throughout the white matter of the brain. Poor behavioral adjustment on implicit awareness tasks is associated with less functional connectivity of anterior cingulate cortex and right or middle inferior frontal gyri to the fronto-parietal control network, as well as more activation in the left insula and left parietal operculum during error processing. Recognition of mistakes is associated with internetwork connectivity of anterior or posterior default mode network to salience network. In conclusion, after ABI, different results in brain activation and connectivity are found depending on level of awareness measured. Future studies are necessary to confirm these findings.

Keywords: Acquired brain injury; Magnetic resonance imaging; Neural correlates; Self-awareness; Unawareness.

Fig. 1

Flowchart of selection procedure

Fig. 2

Quality assessment scores per study. Based on nine criteria described in Wolters et al. (2019). Each criterion could be scored with 1 point (+), 0.5 points (±) or 0 points (-). Total score was calculated based on number of applicable criteria. A score of 7.5 or higher was considered as good quality (green), 4–7.5 as fair quality (orange) and 4 or less as poor quality (red)

Fig. 3

Structural and functional neural correlates of impaired self-awareness as measured with self-proxy discrepancy scores after ABI. 1. Lesions in frontal cortical areas associated with impaired self-awareness (Bivona et al., 2014). 2. Right hemisphere lesions associated with impaired self-awareness (Tezuka et al., 2013). 3a. Right frontal lobe gray and white matter damage associated with impaired self-awareness. 3b. Less BOLD activation in right superior frontal gyrus during self-evaluation task associated with impaired self-awareness (Schmitz et al., 2006). 4. Higher mean diffusivity in the whole white matter associated with impaired self-awareness (Lesimple et al., 2019)

Fig. 4

Structural and functional neural correlates of impaired implicit self-awareness as measured with performance-based discrepancy scores after ABI. 1. Fronto-temporo-insular lesions associated with impaired implicit self-awareness (Garcia-cordero et al., 2019). 2. Less functional connectivity of the 2a. dorsal anterior cingulate cortex and 2b. right middle and inferior frontal gyri to the rest of the FPCN in resting state associated with impaired implicit self-awareness. 2c. Increased activation in left insula and left parietal operculum during error processing (stop-signal task) associated with impaired implicit self-awareness (Ham et al., 2014)

Fig. 5

Structural and functional neural correlates of impaired explicit self-awareness as measured with performance-based discrepancy scores after ABI. 1. Ventromedial frontal lesions associated with explicit self-awareness (Garcia-cordero et al., 2019). 2. Lack of positive association, that is present in healthy controls, between explicit self-awareness and gray matter volume in the: 2a. left posterior region (posterior dorsal and ventral parts of the cingulate cortex, angular gyrus and supramarginal gyrus); 2b. left orbital region (orbital gyrus and orbital H-shaped sulcus); 2c. left dorsolateral region (superior & middle frontal gyrus, middle frontal sulcus) in TBI patients (Grossner et al., 2018). 3. During self-related task, increased activation in 3a. right anterior temporal pole, 3b. anterior cingulate cortex, and 3c. precuneus in TBI compared to healthy controls (Schmitz et al., 2006). 4. Explicit self-awareness is positively associated with internetwork connectivity between 4a. anterior default mode network (blue; middle and superior frontal regions) and 4c. salience network (purple; insular cortex and anterior cingulate); and between 4b. posterior default mode network (yellow; posterior cingulate, precuneus and temporal pole) and 4c. salience network (purple; insular cortex and anterior cingulate) in TBI patients (opposite associations for controls) (Grossner et al., 2019)