Modulation of event-related desynchronization in robot-assisted hand performance: brain oscillatory changes in active, passive and imagined movements

Abstract

Background: Robot-assisted therapy in patients with neurological disease is an attempt to improve function in a moderate to severe hemiparetic arm. A better understanding of cortical modifications after robot-assisted training could aid in refining rehabilitation therapy protocols for stroke patients. Modifications of cortical activity in healthy subjects were evaluated during voluntary active movement, passive robot-assisted motor movement, and motor imagery tasks performed under unimanual and bimanual protocols.

Methods: Twenty-one channel electroencephalography (EEG) was recorded with a video EEG system in 8 subjects. The subjects performed robot-assisted tasks using the Bi-Manu Track robot-assisted arm trainer. The motor paradigm was executed during one-day experimental sessions under eleven unimanual and bimanual protocols of active, passive and imaged movements. The event-related-synchronization/desynchronization (ERS/ERD) approach to the EEG data was applied to investigate where movement-related decreases in alpha and beta power were localized.

Results: Voluntary active unilateral hand movement was observed to significantly activate the contralateral side; however, bilateral activation was noted in all subjects on both the unilateral and bilateral active tasks, as well as desynchronization of alpha and beta brain oscillations during the passive robot-assisted motor tasks. During active-passive movement when the right hand drove the left one, there was predominant activation in the contralateral side. Conversely, when the left hand drove the right one, activation was bilateral, especially in the alpha range. Finally, significant contralateral EEG desynchronization was observed during the unilateral task and bilateral ERD during the bimanual task.

Conclusions: This study suggests new perspectives for the assessment of patients with neurological disease. The findings may be relevant for defining a baseline for future studies investigating the neural correlates of behavioral changes after robot-assisted training in stroke patients.

Figure 1

Bi-Manu-Track arm trainer and Video-EEG system.

Figure 2

EEG acquired during different tasks. A) active movement with the right hand (subject no. 4), B) bimanual active movement (subject no. 2), C) passive movement with the right hand (subject no. 4), and D) imagination of movement with the right hand (subject no. 4). The vertical line represents the beginning of the task.

Figure 3

Time schedule for measuring EEG data during a task. Six runs of rest alternating with six runs of execution.

Figure 4

Topographic maps showing ERD and t values. Grand average maps of ERD/ERS in alpha and beta bands during active (A) and passive (B) movements, imagination of movement (C), active-passive movement (D) (R: right, L: left, BI: bimanual). Blue color coding indicates maximal ERD. T-maps of ERD/ERS in alpha and beta bands thresholded at p<0.05 (|t|>2.306).