The neural correlates of cognitive fatigue in traumatic brain injury using functional MRI

The present study used fMRI (functional magnetic resonance imaging) to objectively assess cognitive fatigue in persons with traumatic brain injury (TBI). It was hypothesized that while performing a cognitive task, TBI participants would show increased brain activity over time, indicative of increased cerebral 'effort' which might manifest as the subjective feeling of cognitive fatigue.

Functional MRI was used to track brain activity across time while 11 TBI patients with moderate-severe injury and 11 age-matched healthy controls (HCs) performed a modified Symbol Digit Modalities Task (mSDMT). Cognitive fatigue was operationally defined as a relative increase in cerebral activation across time compared to that seen in HCs. ROIs were derived from the Chauduri and Behan model of cognitive fatigue.

While performing the mSDMT, participants with a TBI showed increased activity, while HCs subsequently showed decreased activity in several regions including the middle frontal gyrus, superior parietal cortex, basal ganglia and anterior cingulate.

Increased brain activity exhibited by participants with a TBI might represent increased cerebral effort which may be manifested as cognitive fatigue. Functional MRI appears to be a potentially useful tool for understanding the neural mechanisms associated with cognitive fatigue in TBI.