Abstract
ObjectiveIntermittent theta burst stimulation (iTBS) has been widely used as a neural modulation approach in stroke rehabilitation. Concurrent use of transcranial magnetic stimulation and electroencephalography (TMS-EEG) offers a chance to directly measure cortical reactivity and oscillatory dynamics and allows for investigating neural effects induced by iTBS in all stroke survivors including individuals without recordable MEPs. Here, we used TMS-EEG to investigate aftereffects of iTBS following stroke.MethodsWe studied 22 stroke survivors (age: 65.2 ± 11.4 years; chronicity: 4.1 ± 3.5 months) with upper limb motor deficits. Upper-extremity component of Fugl-Meyer motor function assessment and action research arm test were used to measure motor function of stroke survivors. Stroke survivors were randomly divided into two groups receiving either Active or Sham iTBS applied over the ipsilesional primary motor cortex. TMS-EEG recordings were performed at baseline and immediately after Active or Sham iTBS. Time and time-frequency domain analyses were performed for quantifying TMS-evoked EEG responses.ResultsAt baseline, natural frequency was slower in the ipsilesional compared with the contralesional hemisphere (P = 0.006). Baseline natural frequency in the ipsilesional hemisphere was positively correlated with upper limb motor function following stroke (P = 0.007). After iTBS, natural frequency in the ipsilesional hemisphere was significantly increased (P < 0.001).ConclusionsThis is the first study to investigate the acute neural adaptations after iTBS in stroke survivors using TMS-EEG. Our results revealed that natural frequency is altered following stroke which is related to motor impairments. iTBS increases natural frequency in the ipsilesional motor cortex in stroke survivors. Our findings implicate that iTBS holds the potential to normalize natural frequency in stroke survivors, which can be utilized in stroke rehabilitation.
Highlights
Stroke is a debilitating acquired neurological injury and the leading cause of adult disability over the world (Lloyd-Jones et al, 2010)
We hypothesized that (1) natural frequency is slower in the ipsilesional compared with the contralesional hemisphere (CH); (2) there is a positive correlation between ipsilesional hemisphere (IH) natural frequency and motor function; (3) IH natural frequency is increased after the application of Intermittent theta burst stimulation (iTBS)
Natural frequency in the IH was significantly slower compared with the CH (P = 0.006, power = 0.67) (Figure 4)
Summary
Stroke is a debilitating acquired neurological injury and the leading cause of adult disability over the world (Lloyd-Jones et al, 2010). Neural effects of iTBS are typically investigated by motor evoked potentials (MEP), which are muscular responses elicited by single-pulse TMS (Talelli et al, 2007; Di Lazzaro et al, 2008; Ding et al, 2021b). This approach is not applicable to stroke survivors in whom MEPs are not elicitable. As TMS-EEG can directly measure cortical reactivity and oscillatory dynamics regardless of the integrity of corticospinal tracts (Borich et al, 2016), it allows for investigating neural effects induced by iTBS in stroke survivors without recordable MEPs (Pellicciari et al, 2018)
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