Insular Connectivity Is Associated With Self-Appraisal of Cognitive Function After a Concussion

Abstract

Concussion is associated with acute cognitive impairments, with declines in processing speed and reaction time being common. In the clinical setting, these issues are identified via symptom assessments and neurocognitive test (NCT) batteries. Practice guidelines recommend integrating both symptoms and NCTs into clinical decision-making, but correlations between these measures are often poor. This suggests that many patients experience difficulties in the self-appraisal of cognitive issues. It is presently unclear what neural mechanisms give rise to appraisal mismatch after a concussion. One promising target is the insula, which regulates aspects of cognition, particularly interoception and self-monitoring. The present study tested the hypothesis that appraisal mismatch is due to altered functional connectivity of the insula to frontal and midline structures, with hypo-connectivity leading to under-reporting of cognitive issues and hyper-connectivity leading to over-reporting. Data were collected from 59 acutely concussed individuals and 136 normative controls, including symptom assessments, NCTs and magnetic resonance imaging (MRI) data. Analysis of resting-state functional MRI supported the hypothesis, identifying insular networks that were associated with appraisal mismatch in concussed athletes that included frontal, sensorimotor, and cingulate connections. Subsequent analysis of diffusion tensor imaging also determined that symptom over-reporting was associated with reduced fractional anisotropy and increased mean diffusivity of posterior white matter. These findings provide new insights into the mechanisms of cognitive appraisal mismatch after a concussion. They are of particular interest given the central role of symptom assessments in the diagnosis and clinical management of concussion.

A review of brain regions and associated post-concussion symptoms

“…Untreated insular damage could lead to empathy or emotional deficits ( 86 ), disruptive behavior disorders in adolescents ( 86 , 152 ), depression in adults ( 34 , 153 ), anxiety ( 154 ), and a tendency toward substance abuse ( 155 ). A recent MRI study found significantly reduced insular functional connectivity and damaged white matter connections along with slower times on completing all cognitive tasks and lower test scores compared to controls ( 156 ). Another recent study on post-concussion headaches compared persistent concussion symptoms patients with migraine patients and identified numerous functional connectivity differences between brain regions, including the insula, cingulate, temporal pole, cuneus, secondary somatosensory cortex, ventro-medial prefrontal cortex, and others ( 46 ).…”

“…Another recent study on post-concussion headaches compared persistent concussion symptoms patients with migraine patients and identified numerous functional connectivity differences between brain regions, including the insula, cingulate, temporal pole, cuneus, secondary somatosensory cortex, ventro-medial prefrontal cortex, and others ( 46 ). In summary, insular damage caused by a concussion could result in somatic [e.g., headache ( 46 , 157 ), nausea, vomiting ( 67 , 130 ), noise sensitivity ( 105 , 134 ), and motor problems ( 120 , 134 ), or bodily pain ( 145 , 148 )], cognitive (e.g., feeling “slow” or “foggy” ( 156 ), or language problems ( 120 , 134 )], or emotional symptoms [e.g., irritability or feeling more emotional ( 86 , 142 , 153 )] ( Table 2 ).…”