De Doncker, W. | Search bioRxiv

bioRxiv2020

Role of left motor cortex in post-stroke fatigue: a corticospinal excitability study

BackgroundThe neural mechanisms that underlie post-stroke fatigue are poorly understood. Previous work show an inverse relationship between motor cortex excitability and post-stroke fatigue, however, it is unclear if the side of lesion influences this relationship. The left hemisphere plays a dominant role in motor control, therefore we hypothesised that left hemisphere strokes are more likely to show a significant inverse relationship between corticospinal excitability and fatigue. MethodsResting motor threshold (measure of corticospinal excitability) using transcranial magnetic stimulation was measured in the affected hemisphere of 98 stroke survivors. Fatigue was measured using the fatigue severity scale. The effect of fatigue and hemisphere affected on corticospinal excitability was analysed using a multiple linear regression. ResultsA multiple linear regression with trait fatigue as the outcome variable (F(4,93)=12.04, p < 0.001, adj R2 = 0.313) revealed that RMT was not a significant predictor of FSS-7 ({beta} = -0.063, p = 0.706, CI[-0.394, 0.268]), while the interaction between lesioned hemisphere and RMT was a significant predictor of FSS-7 ({beta} = 0.339, p = 0.039, CI[0.018, 0.659]). The additional explanatory variables of HADSDepression and sex were also significant predictors of FSS-7 ({beta} = 903, p < 0.001, CI[0.584, 1.223] and {beta} = 1.127, p = 0.002, CI[0.425, 1.830] respectively). ConclusionLower corticospinal excitability of the left hemisphere may indicate altered perception of effort and reduced sensory attenuation. This provides evidence to support the sensory attenuation model of fatigue.

neuroscience↗

bioRxiv2020

Influence of fatigue on reaction times and corticospinal excitability during movement preparation

Slower self-selected ballistic movement speeds and reduced corticospinal excitability at rest are associated with post-stroke fatigue (PSF). It is unclear if fatigue-related differences in corticospinal excitability, measured using transcranial magnetic stimulation, prior to a movement will explain slower movement speeds. We hypothesized that the levels of PSF explains the modulation of corticospinal excitability during movement preparation and altered behaviour. In this study, 73 non-depressed, high functioning, chronic, first-time stroke survivors performed a simple warned and unwarned auditory reaction time task. We show a reduced suppression of corticospinal excitability during movement preparation, an increased facilitation immediately prior to movement onset and slower reaction times in those with greater levels of PSF. Reduced suppression and increased facilitation of corticospinal excitability prior to movement onset in high fatigue is an indicator of poor modulation of pre-movement excitability which may in turn reflect poor sensory processing, supporting the sensory attenuation model of fatigue.

neuroscience↗