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Fleming, M. K.

Publications and source records attributed to Fleming, M. K..

2 recordsLinked to original sources

Closed-loop beta stimulation enhances beta activity and motor behaviour

Movement-related beta event-related synchronization (ERS) has been linked to motor control and learning, showing potential as a therapeutic target for those with movement deficits, such as stroke survivors. However, whether directly modulating beta ERS can causally influence motor performance remains unclear, largely due to the lack of methods designed to specifically target this neural activity. To address this gap, we developed a novel behaviourally-driven, closed-loop transcranial alternating current stimulation (tACS) approach to target movement-related beta ERS during a visuomotor adaptation task. We found that the behaviourally-driven, closed-loop beta-tACS specifically enhances beta ERS without affecting beta event-related desynchronization (ERD). Critically, this targeted enhancement significantly improves retention of motor adaptation. These findings establish a causal relationship between beta ERS and motor behaviour and highlight the potential of behaviourally-driven beta-tACS as a therapeutic approach for improving motor function in clinical populations characterized by impaired beta activity.

neuroscience↗

The effect of pulse shape in theta-burst stimulation: monophasic vs biphasic TBS

BackgroundIntermittent theta-burst stimulation (i)(TBS) is a transcranial magnetic stimulation (TMS) plasticity protocol. Conventionally, TBS is applied using biphasic pulses due to hardware limitations. However, monophasic pulses are hypothesised to recruit cortical neurons more selectively than biphasic pulses, thus yielding stronger plasticity effects. Monophasic and biphasic TBS can be generated using a custom-made pulse-width modulation-based TMS device (pTMS). ObjectiveUsing pTMS, we tested the hypothesis that monophasic iTBS would induce greater plasticity effects than biphasic, measured as induced changes in motor corticospinal excitability. MethodsIn a repeated-measures design, thirty healthy volunteers participated in three separate sessions, where monophasic and biphasic iTBS was applied to the primary motor cortex (M1 condition) or the vertex (control condition). Plasticity was quantified as changes in motor corticospinal excitability after versus before iTBS, by comparing peak-to-peak amplitudes of motor evoked potentials (MEP) measured at baseline and over 60 minutes after iTBS. ResultsBoth monophasic and biphasic M1 iTBS led to significant increases in MEP amplitude. As predicted, monophasic iTBS induced a significantly larger effect than biphasic iTBS (linear mixed effect model analysis: ({chi}2(1) = 7.48, p = 0.006), which persisted even after subtracting each individuals control (vertex) condition data from the M1 conditions ({chi}2(1) = 5.48, p = 0.019). ConclusionsIn this study, monophasic iTBS induced a stronger motor corticospinal excitability increase than biphasic within participants. This greater physiological effect suggests that monophasic iTBS may also have potential for greater functional impact, of interest for future fundamental and clinical applications of TBS.

neuroscience↗