Inter-muscular coherence and neurogenic tremor as tools to evaluate the effects of motor training, transcranial stimulation and peripheral stimulation on cortical activity

  • Pauline Axford

Student thesis: Doctoral Thesis


The primary aims of this thesis were to develop and use inter-muscular coherence (IMC) and physiological neurogenic tremor (PNT) analysis as investigatory tools of cortico-spinal activity and to investigate the effects, on these outcomes, of transcranial direct current stimulation (tDCS), motor training, and peripheral nerve stimulation. To improve the coherence investigations baseline stability analysis and a robust analysis technique were incorporated and it was demonstrated that, under certain task conditions, IMC and PNT are appropriate investigation tools. The effects of anodal and cathodal tDCS on cortical excitability, IMC and PNT were tested. There was a reduction in cortical excitability after only cathodal tDCS; both polarities caused similar changes to IMC that may be suggestive of an opposing effect on a homeostatic response induced by the motor task; only cathodal tDCS interacted with PNT causing both decreases and increases that may be suggestive of changes to multiple inputs of PNT. The secondary aims of this thesis were to investigate whether any effects could be enhanced through the incorporation of a sinusoidal waveform onto the DC stimulation signal, or through the inclusion of peripheral nerve stimulation. Small sinuosoidal modulations of 5 Hz, 10 Hz and 20 Hz were imposed onto anodal tDCS. The effects on IMC and PNT were different from tDCS alone, but were not larger. Both tDCS and the sinusoidal variants were combined with peripheral nerve stimulation. Again, while there were some similarities, each stimulation protocol caused a different result on IMC and PNT from any other, but none exceeded the magnitude or duration of the effects caused by tDCS alone. It was concluded that IMC and PNT are appropriate tools for the investigation of cortical stimulation and that alterations to the tDCS protocol in the form of sinusoidal varying signals and peripheral nerve stimulation did not enhance the after effects of the stimulation.
Date of Award5 Dec 2016
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council) & University of Strathclyde

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