Brain-movement relationship during upper-limb functional movements in chronic post-stroke patients

Abstract

Background: Following a stroke, brain activation reorganisation, movement compensatory strategies, motor performance and their evolution through rehabilitation are matters of importance for clinicians. Two non-invasive neuroimaging methods allow for recording task-related brain activation: functional near-infrared spectroscopy (fNIRS) and electroencephalography (fEEG), respectively based on hemodynamic response and neuronal electrical activity. Their simultaneous measurement during movements could allow a better spatiotemporal mapping of brain activation, and when associated to kinematic parameters could unveil underlying mechanisms of functional upper limb (UL) recovery. This study aims to depict the motor cortical activity patterns using combined fNIRS-fEEG and their relationship to motor performance and strategies during UL functional tasks in chronic post-stroke patients.

Methods: Twenty-one healthy old adults and 21 chronic post-stroke patients were recruited and completed two standardised functional tasks of the UL: a paced-reaching task where they had to reach a target in front of them and a circular steering task where they had to displace a target using a hand-held stylus, as fast as possible inside a circular track projected on a computer screen. The activity of the bilateral motor cortices and motor performance were recorded simultaneously utilizing a fNIRS-fEEG and kinematics platform.

Results and conclusions: Kinematic analysis revealed that post-stroke patients performed worse in the circular steering task and used more trunk compensation in both tasks. Brain analysis of bilateral motor cortices revealed that stroke individuals over-activated during the paretic UL reaching task, which was associated with more trunk usage and a higher level of impairment (clinical scores). This work opens up avenues for using such combined methods to better track and understand brain-movement evolution through stroke rehabilitation.

Keywords: Neuroplasticity; Reaching and tracing tasks; Sensorimotor cortex; Stroke; Upper limb; fEEG; fNIRS.

Fig. 1

Circular steering task performances and strategies (mean ± SD) for the two groups and according to hand trial. (A) Index of performance (IP_e); (B) Range of trunk anterior flexion; and (C) Time per lap. (* for statistically significant differences at p < .05)

Fig. 2

Paced reaching task upper limb movement strategies (mean ± SD) for the healthy and stroke groups and according to hand trial and condition (for condition interaction and/or effects). (A) Proximal-arm non-use, PANU; (B) Range of elbow extension; (C) Hand mean velocity; and (D) Range of trunk anterior flexion. (* for statistically significant differences at p < .05)

Fig. 3

Paced reaching task fNIRS mean ΔHbO₂ peak (mean ± SD) for the healthy and stroke groups as a function of hand and hemisphere (ipsilateral in orange; contralateral in cyan). * For statistically significant differences at p < .05: hand effect in the stroke group and hemisphere effect for all groups and conditions

Fig. 4

fEEG Beta event-related spectral perturbation (ERSP) (mean ± SD) for the healthy and stroke groups. Circular steering task: lower Beta event-related synchronization (ERS) in contralateral (ipsilesional) hemisphere of the stroke group after paretic arm movement (A). Paced reaching task: Beta event-related desynchronisation (ERD) with a tendency to lower ERD in the stroke group (B), higher Beta ERS in the stroke group for both hemispheres (C), and a higher Alpha ERS for the stroke group in the Ipsilateral hemisphere. (* for statistically significant differences at p < .05)

Fig. 5

Stroke group correlation between (A) Alpha ERD and the trunk use, and (B) Beta ERS and the index of effective performance (IP_e) during the circular steering task with the paretic arm

Fig. 6

Stroke group correlation between (A) Peak of ΔHbO₂ and elbow extension and (B) Mean Beta ERS and elbow extension during the paced-reaching task with the paretic arm

Fig. 7

Stroke group correlation between (A) Alpha ERD during the circular steering task and the FM-UE test and, (B) Peak of ΔHbO₂ during the maximal paced-reaching task and the FM-UE test