An investigation into cortical activity associated with robotic upper limb rehabilitation after stroke

Abstract

Background: Many stroke survivors are left with upper limb impairments that affect their ability to carry out functional tasks. Using neuroimaging and electrophysiological technology, advances have been made in understanding brain function and reorganisation after stroke. These findings provide valuable insights and may provide the key to more effective rehabilitation practices. Objectives: This research aimed to improve understanding of cortical function recovery after stroke, as measured by electroencephalography (EEG) during a reaching movement, before and following robotic upper limb rehabilitation. In particular, the study looked for event-related changes in EEG waves commonly referred to as event-related desynchronisation (ERD) and event-related synchronisation (ERS), which are measured in the frequency domain.
Methods: EEG was recorded over the sensorimotor cortex during a reaching movement with all participants using a customised experimental setup developed for this study. Four studies were carried out: 1) a feasibility study tested data collection methods with four participants, 2) test-retest variability of ERD/ERS measures over three sessions was determined with five healthy participants, 3) averaged ERD/ERS measures were examined in a group of ten healthy participants, 4) ERD/ERS measures of six stroke participants who underwent ten sessions of robotic upper limb rehabilitation over two weeks were examined, and changes following rehabilitation were compared to changes in measures of upper limb impairment (Fugl-Meyer Assessment) and function (Action Research Arm Test).
Results: Results from the stroke participant study show that 1) two participants presented with reduced alpha ERD over the ipsilateral hemisphere, three participants had a predominant alpha and/or beta ERD over the ipsilateral hemisphere, and beta ERS following movement was predominantly found to occur over the ipsilateral hemisphere for four participants, and 2) two participants showed changes in ERD/ERS measures that could be attributed to the effects of rehabilitation, with associations made with measures of upper limb impairment and function. These changes related to hemispheric lateralisation of alpha ERD, as demonstrated by a decrease of excessive contralateral predominance (when compared to healthy participants) as well as to a hypothesised normalisation of interhemispheric inhibitory mechanisms demonstrated by a decrease in abnormal alpha and beta ERS during movement.
Conclusions: Abnormal ERD/ERS measures of hemispheric laterality were a recurrent feature of stroke participants, with some changes that could be attributed to the effects of rehabilitation, indicating that measures of ERD/ERS during reaching using this experimental setup could be used to assess and monitor cortical activity recovery after stroke. Further work is however proposed to determine the responsiveness of the methods used, as improved motor function was not always accompanied by changes in measures of ERD/ERS.

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Identifiers

ORCID for Jane Burridge: orcid.org/0000-0003-3497-6725

ORCID for David Simpson: orcid.org/0000-0001-9072-5088

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