Combined effect of prefrontal transcranial direct current stimulation and a working memory task on heart rate variability

• Published in: PloS one Vol. 12; no. 8; p. e0181833
• Main Authors: Nikolin, Stevan, Boonstra, Tjeerd W., Loo, Colleen K., Martin, Donel
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 03.08.2017; Public Library of Science (PLoS)
• Subjects: Accuracy; Analysis; Autonomic nervous system; Biology and Life Sciences; Blood pressure; Brain; Brain research; Brain stimulation; Cognition; Computer memory; Correlation; Data collection; Electrical stimulation of the brain; ESB; Female; Healthy Volunteers; Heart Rate; Humans; Hyperactivity; Integration; Low frequencies; Male; Mediation; Medicine and Health Sciences; Memory; Memory tasks; Memory, Short-Term - physiology; Mental task performance; Nervous system; Neurosciences; Parasympathetic nervous system; Physiological aspects; Prefrontal cortex; Prefrontal Cortex - physiology; Propagation; Psychiatry; Research and Analysis Methods; Response time; Short term memory; Stimulation; Studies; Sympathetic nervous system; Transcranial Direct Current Stimulation; Variability; Workloads; Young Adult; Australia; Sydney New South Wales Australia
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0181833

Prefrontal cortex activity has been associated with changes to heart rate variability (HRV) via mediation of the cortico-subcortical pathways that regulate the parasympathetic and sympathetic branches of the autonomic nervous system. Changes in HRV due to altered prefrontal cortex functioning can be predicted using the neurovisceral integration model, which suggests that prefrontal hyperactivity increases parasympathetic tone and decreases contributions from the sympathetic nervous system. Working memory (WM) tasks and transcranial direct current stimulation (tDCS) have been used independently to modulate brain activity demonstrating changes to HRV in agreement with the model. We investigated the combined effects of prefrontal tDCS and a WM task on HRV. Bifrontal tDCS was administered for 15 minutes at 2mA to 20 participants in a sham controlled, single-blind study using parallel groups. A WM task was completed by participants at three time points; pre-, during-, and post-tDCS, with resting state data collected at similar times. Frequency-domain HRV was computed for high frequency (HF; 0.15-0.4Hz) and low frequency (LF; 0.04-0.15Hz) power reflecting parasympathetic and sympathetic branch activity, respectively. Response time on the WM task, but not accuracy, improved from baseline to during-tDCS and post-tDCS with sham, but not active, stimulation. HF-HRV was significantly increased in the active tDCS group compared to sham, lasting beyond cessation of stimulation. Additionally, HF-HRV showed a task-related reduction in power during performance on the WM task. Changes in LF-HRV were moderately inversely correlated (r > 0.4) with changes in WM accuracy during and following tDCS compared to baseline levels. Stimulation of the prefrontal cortex resulted in changes to the parasympathetic branch of the nervous system in agreement with a linearly additive interpretation of effects. Sympathetic activity was not directly altered by tDCS, but was correlated with changes in WM performance. This suggests that the parasympathetic and sympathetic branches respond differentially due to similar, but distinct neural pathways. Given the ease of HRV data collection, studies of prefrontal tDCS would benefit from collection of this data as it provides unique insight into tDCS effects resulting from propagation through brain networks.