Fig 1.
Neurovisceral integration model.
(A) Simplified depiction of the neurovisceral integration model described by Thayer and Sternberg [1]. (B) Brain regions relevant to the neurovisceral integration model. PC, prefrontal cortex; CC, cingulate cortex; Hyp, hypothalamus; Ins, insula; Amy, amygdala; BS, brainstem.
Fig 2.
Study design using parallel groups.
HRV data was collected at five epochs, each lasting five minutes. ECG data were recorded at periods of rest occurring at baseline, as well as during-tDCS and post-tDCS, in addition to task-related activity during-tDCS and post-tDCS. Shaded block indicates period during which tDCS was administered.
Table 1.
Working memory (WM) performance calculated using the percentage and response time (RT) of correct responses; LF (ln(ms2)), low-frequency (log transformed); HF (ln(ms2)), high-frequency (log transformed).
Fig 3.
(A) Participants receiving sham-tDCS improved in response time from baseline to during-tDCS and post-tDCS time points. (B) Working memory accuracy scores calculated as percentage of correct responses. Error bars represent standard deviations. * p < .05.
Table 2.
Observed heart rate variability values expressed in frequency-domain values.
All HRV metrics were natural log transformed. LFln (ms2), low-frequency; HFln (ms2), high-frequency.
Fig 4.
Results of baseline-corrected electrocardiogram HRV analyses using estimated marginal means from mixed effects model analysis.
(A) High frequency (HF) power. (B) Low frequency (LF) power. Error bars represent standard deviations. * p < .05.
Fig 5.
Correlation between the change in working memory accuracy and change in LF power.
(A) change from baseline to during-tDCS task period; and (B) change from baseline to post-tDCS task period.