Effects of focal muscle vibration on corticospinal excitability

In two experiments, we compared the dynamics of corticospinal excitability when processing visually or linguistically presented tool-oriented hand actions in native speakers and sequential bilinguals. In a third experiment we used the same procedure to test non-motor, low-level stimuli, i.e. scrambled images and pseudo-words. Stimuli were presented in sequence: pictures (tool + tool-oriented hand action or their scrambled counterpart) and words (tool noun + tool-action verb or pseudo-words). Experiment 1 presented German linguistic stimuli to native speakers, while Experiment 2 presented English stimuli to non-natives. Experiment 3 tested Italian native speakers. Single-pulse trascranial brain stimulation (spTMS) was applied to the left motor cortex at five different timings: baseline, 200ms after tool/noun onset, 150, 350 and 500ms after hand/verb onset with motor-evoked potentials (MEPs) recorded from the first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles.We report strong similarities in the dynamics of corticospinal excitability across the visual and linguistic modalities. MEPs’ suppression started as early as 150ms and lasted for the duration of stimulus presentation (500ms). Moreover, we show that this modulation is absent for stimuli with no motor content. Overall, our study supports the notion of a core, overarching system of action semantics shared by different modalities.

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Motor cortex disinhibition in normal-pressure hydrocephalus

Journal of Neurosurgery ◽

10.3171/2011.9.jns11678 ◽

2012 ◽

Vol 116 (2) ◽

pp. 453-459 ◽

Cited By ~ 10

Author(s):

Andrei V. Chistyakov ◽

Hava Hafner ◽

Alon Sinai ◽

Boris Kaplan ◽

Menashe Zaaroor

Keyword(s):

Motor Cortex ◽

Healthy Volunteers ◽

Normal Pressure Hydrocephalus ◽

Close Association ◽

Motor Evoked Potential ◽

Normal Pressure ◽

Corticospinal Excitability ◽

Conduction Time ◽

Shunt Placement ◽

Resting Motor Threshold

Object Previous studies have shown a close association between frontal lobe dysfunction and gait disturbance in idiopathic normal-pressure hydrocephalus (iNPH). A possible mechanism linking these impairments could be a modulation of corticospinal excitability. The aim of this study was 2-fold: 1) to determine whether iNPH affects corticospinal excitability; and 2) to evaluate changes in corticospinal excitability following ventricular shunt placement in relation to clinical outcome. Methods Twenty-three patients with iNPH were examined using single- and paired-pulse transcranial magnetic stimulation of the leg motor area before and 1 month after ventricular shunt surgery. The parameters of corticospinal excitability assessed were the resting motor threshold (rMT), motor evoked potential/M-wave area ratio, central motor conduction time, intracortical facilitation, and short intracortical inhibition (SICI). The results were compared with those obtained in 8 age-matched, healthy volunteers, 19 younger healthy volunteers, and 9 age-matched patients with peripheral neuropathy. Results Significant reduction of the SICI associated with a decrease of the rMT was observed in patients with iNPH at baseline evaluation. Ventricular shunt placement resulted in significant enhancement of the SICI and increase of the rMT in patients who markedly improved, but not in those who failed to improve. Conclusions This study demonstrates that iNPH affects corticospinal excitability, causing disinhibition of the motor cortex. Recovery of corticospinal excitability following ventricular shunt placement is correlated with clinical improvement. These findings support the view that reduced control of motor output, rather than impairment of central motor conduction, is responsible for gait disturbances in patients with iNPH.

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