The Effects of tDCS on Speech Motor Control in Younger and Older Adults

  • Author / Creator
    Freitag, Ian J
  • Purpose. The present study focused on modulating features of speech motor control using transcranial direct current stimulation (tDCS). Recent studies have shown that tDCS modulates cortical activity within the brain, leading to changes in both cognitive and motor performance. More specific to the present study, tDCS has been shown to reduce vocal reaction times and increase speaking accuracy in healthy individuals (Fiori, Cipollari, Caltagirone, & Marangolo, 2014). The present study was designed to examine whether there is a differential effect on speech motor control performance (i.e., producing tongue twisters) following tDCS in younger versus older healthy adults. Method. Two groups of healthy individuals participated in the study. The first included younger adults (N = 30; range 18-43) and the second included older adults (N = 30; range 54-77). Each participant was asked to read a series of tongue twisters before and after one of three different stimulation conditions, with target stimulation over the left precentral gyrus: offline anodal tDCS (13 min, 1 mA); offline cathodal tDCS (13 min, 1 mA), and a sham condition. Accuracy, vocal reaction time, and rate of speech were measured. Results. The results showed no significant effects for stimulation type, or any significant interactions between age and stimulation type. There was a significant effect of age on rate of speech, showing that the older adults spoke, on average, slower than their younger counterparts. There was a significant effect of time (i.e., pre- and post-stimulation) on reaction time, showing that both younger and older adults (regardless of stimulation condition) displayed faster reaction times post-stimulation; this was believed to have been a practice effect. Finally, there was a statistical trend showing that individuals tended to become less accurate post stimulation, possibly due to fatigue or other non-stimulation conditions. Discussion. Given the complicated nature of tDCS, there are multiple reasons as to why no significant effects of stimulation were elicited. It is possible that this study did not feature optimal stimulation parameters, in which the factors of current density, electrode position, stimulation duration, and neural resting state need to be addressed. However, other factors such as the variation of results of tDCS on different groups, should be considered as well. Finally, the fact that older adults spoke at a slower rate than younger adults was consistent with previous speech literature.

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  • Graduation date
    Spring 2018
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.