The Effects of Non-invasive Brain Stimulation on Autonomic Regulation

Book excerpt: The autonomic nervous system is an important physiological system in the context of health. Heart rate variability is a non-invasive measure of autonomic function. Empirical evidence indicates that reduced heart rate variability may mediate the relationship between psychological states and pathological conditions. This relationship may be indicative of topdown influences on autonomic regulation. Non-invasive brain stimulation offers potential tools to explore top-down pathways that are involved in autonomic regulation. The main aim of this study was to investigate whether transcranial direct current stimulation (tDCS) over the ventral medial pre frontal cortex (vMPFC) could modulate autonomic regulation during psychological stress (Situational HRV) as well as at rest (Tonic HRV) after receiving tDCS. Sixteen participants received either anodal, cathodal or sham tDCS across three, two hour sessions that were counterbalanced across participants. In each session, participants were also asked to complete a mental arithmetic task prior to and after receiving tDCS. Participants also completed questionnaires that assessed their level of fitness, health behaviours and state anxiety. The results showed that there were no after-effects of tDCS on HRV during the cognitive stressor task, despite participants experiencing an increase in heart rate in response to task, prior to receiving the stimulation. Unexpectedly, while HRV returned back to baseline after receiving tDCS, participants showed an increase in HRV during cathodal stimulation over the vMPFC. This suggests that the effects of tDCS on autonomic regulation while not long lasting may occur during the stimulation period itself, thus providing evidence to support the notion of top-down regulation. The findings from this study provide interesting opportunities for future investigations in health psychology in relation to mind-body medicine.