Strengthened Corticosubcortical Functional Connectivity during Muscle Fatigue

Abstract

The present study examined functional connectivity (FC) between functional MRI (fMRI) signals of the primary motor cortex (M1) and each of the three subcortical neural structures, cerebellum (CB), basal ganglia (BG), and thalamus (TL), during muscle fatigue using the quantile regression technique. Understanding activation relation between the subcortical structures and the M1 during prolonged motor performance should help delineate how central motor control network modulates acute perturbations at peripheral sensorimotor system such as muscle fatigue. Ten healthy subjects participated in the study and completed a 20-minute intermittent handgrip motor task at 50% of their maximal voluntary contraction (MVC) level. Quantile regression analyses were carried out to compare the FC between the contralateral (left) M1 and CB, BG, and TL in the minimal (beginning 100 s) versus significant (ending 100 s) fatigue stages. Widespread, statistically significant increases in FC were found in bilateral BG, CB, and TL with the left M1 during significant versus minimal fatigue stages. Our results imply that these subcortical nuclei are critical components in the motor control network and actively involved in modulating voluntary muscle fatigue, possibly, by working together with the M1 to strengthen the descending central command to prolong the motor performance.

Functional brain connectivity of remembered fatigue or happiness in healthy adults: Use of arterial spin labeling

“…Although the most common conceptualization of cerebellar function relates to its role in coordinating motor activity, evidence suggests that the cerebellum is also involved in the encoding and perception of aversive stimuli, including pain (Moulton et al, 2011). Increased frontocortical FC with cerebellum following exercise-based fatigue induction has been previously reported (Jiang, Wang, & Yue, 2016; Jiang, Oathes, et al, 2016), as well as disruptions in inferior frontal gyrus FC with a large cluster including bilateral cerebellum and vermis over the course of a fatiguing cognitive task in ME/CFS patients (Boissoneault et al, in press). Furthermore, Caseras et al found that ME/CFS patients had greater cerebellar activation than controls while viewing fatigue-related video clips (Caseras et al, 2008).…”

Fatigue in multiple sclerosis: The role of thalamus

“…The specific role for thalamus in the pathogenesis of fatigue has been confirmed in both healthy subjects, 54 and patients with different (and more focal) neurological diseases (e.g., stroke, traumatic brain injury). 55,56 Indeed, a relatively-small damage to the thalamic network, independently from the extent of diffuse brain involvement, could generate fatigue.…”

Mapping cortical network effects of fatigue during a handgrip task by functional near-infrared spectroscopy in physically active and inactive subjects

“…Physical fatigue induced by intermittent muscle contractions and its effect on force has been studied extensively in physiology 35,36 and recent neuroimaging studies. 3,6,8,17,22,37,38 Fatigue has been defined as "any decline in muscle performance associated with muscle activity at the original intensity." 36 Both inactive and active subjects' muscle performance adhered to this definition vis-à-vis the gradual decline in MVC throughout the exercise.…”

“…3 Moreover, brain activation changes in deeper subcortical structures participating in motor regulation (i.e., bilateral basal ganglia, cerebellum, and thalamus) are known to occur as a coordinated effort to optimize motor unit recruitment and activation level for prolonged fatiguing exercise. 38,42 Although it would be reasonable to expect that these structures could also be activated as the handgrip task progressed, those regions were not accessible by fNIRS.…”

“…The application of FC analysis to the fNIRS data collected in this study provided details of cortical area interconnectedness during the entire duration of the handgrip task than seen in prior neuroimaging studies using similar protocols, which only reported results for the beginning and the end of the task period. 7,8,22,38 In our work, seed regions were specifically placed at locations with significant hemodynamic activity namely, the lM1, the lDLPFC, and the rDLPFC. These seed regions are all known to be connected to the descending motor pathways that control hand and arm movements.…”