Combined effect of prefrontal transcranial direct current stimulation and a working memory task on heart rate variability Nikolin, Stevan ; Boonstra, Tjeerd W. ; Loo, Colleen K. ; Martin, Donel Abstract Publication: PLoS ONE Pub Date: August 2017 DOI: 10.1371/journal.pone.0181833 Bibcode: 2017PLoSO..1281833N