Differences between Han Chinese and Caucasians in transcranial magnetic stimulation parameters

Xiang Yi,Kashif Mansoor,Stuart N Baker,Ming Lai,R Bicker,Karen M Fisher

doi:10.1007/s00221-013-3763-2

Xiang Yi, Kashif Mansoor + Show 4 more

Open Access

https://doi.org/10.1007/s00221-013-3763-2

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Abstract

The study was conducted to investigate the difference between Han Chinese and Caucasians on various parameters measured from responses to transcranial magnetic brain stimulation (TMS). Sixteen subjects were studied in each group. A circular coil at the vertex was used for stimulation, whilst recording surface electromyograms from right first dorsal interosseous. In the passive state, motor-evoked potential (MEP) threshold, MEP recruitment, short-interval intracortical inhibition (SICI) and intracortical facilitation were measured. The MEP threshold, recruitment and silent period were also measured in the active state. Chinese subjects showed significantly higher passive thresholds (P < 0.005), less inhibition of the motor response (SICI, P < 0.0005) and a shorter silent period (P < 0.05). Differences in SICI appeared to be a consequence of the differences in passive threshold and were not seen when active threshold was used to determine the conditioning stimulus intensity. Differences in silent period may also reflect differences in cortical excitability rather than inhibitory processes, as they were not seen when the silent-period duration was expressed as a function of MEP size, rather than TMS intensity. There appears to be a significant difference in some TMS parameters between Han Chinese and Caucasian subjects. This may reflect an underlying difference in cortical excitability.

Highlights

Transcranial magnetic brain stimulation (TMS) is an important neurophysiological method
Parameter k was found to be significantly different between groups (Fig. 1h; P < 0.05) By contrast, there were no significant differences in I50 (Fig. 1g, P > 0.05) or in the population variance
This study provides the first objective evidence that there are differences between TMS measurements across different racial groups, supporting anecdotal accounts from several laboratories

Summary

Introduction

Transcranial magnetic brain stimulation (TMS) is an important neurophysiological method. As well as extensive use in the basic sciences, TMS has found a useful role in diagnosis of a wide range of diseases (Chen et al 2008) Such use relies on detecting abnormal measurements in patient populations compared to normative control data. We were intrigued by anecdotal observations within our own group, confirmed by conversations with other centres that healthy Chinese subjects often have high TMS thresholds compared with other races. If true, this would have obvious and important implications for the diagnostic use of TMS. We show that there are significant differences, which should be taken into account when interpreting the results of investigations in individual patients

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Conclusion