The functional role of beta‐oscillations in the supplementary motor area during reaching and grasping after stroke: A question of structural damage to the corticospinal tract

Abstract

Hand motor function is often severely affected in stroke patients. Non‐satisfying recovery limits reintegration into normal daily life. Understanding stroke‐related network changes and identifying common principles that might underlie recovered motor function is a prerequisite for the development of interventional therapies to support recovery. Here, we combine the evaluation of functional activity (multichannel electroencephalography) and structural integrity (diffusion tensor imaging) in order to explain the degree of residual motor function in chronic stroke patients. By recording neural activity during a reaching and grasping task that mimics activities of daily living, the study focuses on deficit‐related neural activation patterns. The study showed that the functional role of movement‐related beta desynchronization in the supplementary motor area (SMA) for residual hand motor function in stroke patients depends on the microstructural integrity of the corticospinal tract (CST). In particular, in patients with damaged CST, stronger task‐related activity in the SMA was associated with worse residual motor function. Neither CST damage nor functional brain activity alone sufficiently explained residual hand motor function. The findings suggest a central role of the SMA in the motor network during reaching and grasping in stroke patients, the degree of functional relevance of the SMA is depending on CST integrity.

Multimodal Neuroimaging Using Concurrent EEG/fNIRS for Poststroke Recovery Assessment: An Exploratory Study

“…In fact, instead of simply focusing on the difference between healthy and patient groups, biomarkers associated with cortical excitability and connectivity among the patient group are more attractive and are expected to be capable of characterizing the motor recovery pattern of patients during rehabilitation intervention. 43,54 As such, in current study, we not only presented consistent and strong correlations between the identified FC indices and motor gains (Figure 3) but also demonstrated the great potential of these biomarkers in predicting the motor recovery spanning the 4 weeks of intervention (Figure 4), which provided reliable and sensitive biomarkers for the investigation of cortical reorganization after stroke.…”

“…Recent findings have suggested that there is a close association between the cortical excitability and upper extremity function in stroke patients. 10,43 In the current study, using the cortical activation strength as an excitability measure, the ipsilesional PMC was identified as key region associated with the motor recovery. Specifically, the increment of beta strength at ipsilesional PMC was highly correlated with the motor function improvement across the 4-week intervention (R = 0.895, Figure 3B).…”

Normalization of reduced functional connectivity after revascularization of asymptomatic carotid stenosis

“…COIs were chosen based on previous studies investigating network differences in patients with cerebrovascular disease. 18,19 Coordinates for the primary motor cortex (M1), ventral premotor cortex (PMv), supplementary motor area (SMA), anterior part of the intraparietal sulcus (aIPS) and the caudal part of the intraparietal sulcus (cIPS) were derived from a previous fMRI experiment involving a hand grip task in healthy elderly participants and stroke patients (please refer to Supplementary figure 1). 19 Moreover, this motor network of brain regions is located within middle cerebral and anterior cerebral artery territory.…”

“…To avoid effects of lateralization in group comparison, data of randomly assigned healthy controls were flipped from left to right in the same ratio (n ¼ 15/23). Subsequently, data were averaged within the alpha (8-13 Hz) and beta (14-25 Hz) frequency band, as these frequency bands have been shown to contain a high information content in elderly and stroke patients during tasks 18,[25][26][27] as well as in resting-state studies. 28,29 Analysis of perfusion data.…”

“…Connectivity was assessed within a well-described motor network located within the internal carotid artery territory which has been shown to map relevant differences in patients with cerebrovascular disease. 18,19 We further studied brain perfusion by MRI in order to relate changes in functional connectivity to regional brain hypoperfusion resulting from carotid stenosis. Cognitive function was evaluated in order to assess whether patients already showed clinical deficits.…”