Transcranial direct current stimulation over the right dorsolateral prefrontal cortex increases oxyhemoglobin concentration and cognitive performance dependent on cognitive load

• Published in: Behavioural brain research 2023-04, Vol.443, p.114343-114343, Article 114343
• Main Authors: Figeys, Mathieu, Loucks, Torrey M., Leung, Ada W.S., Kim, Esther S.
• Format: Article
• Language: English
• Subjects: Adult; Cerebral oxygenation; Cognition; Dorsolateral Prefrontal Cortex; Functional near-infrared spectroscopy; Humans; Memory, Short-Term - physiology; Oxyhemoglobins; Prefrontal Cortex - physiology; Toulouse n-back; Transcranial direct current stimulation; Transcranial Direct Current Stimulation - methods
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2023.114343

Transcranial direct current stimulation (tDCS) has been explored as a potential method for cognitive enhancement. tDCS may induce a cascade of neurophysiological changes including alterations in cerebral oxygenation. However, the effects of tDCS on the cognitive-cerebral oxygenation interaction remains unclear. Further, oxygenation variability across individuals remains minimally controlled for. The purpose of this sham-controlled study was to test the effects of anodal tDCS over the right dorsolateral prefrontal cortex (DLPFC) on the interaction between working memory and cerebral oxygenation while controlling for individual oxygenation variability. Thirty-three adults received resting-state functional near-infrared spectroscopy (fNIRS) recordings over bilateral prefrontal cortices. Following this, working memory was tested using a Toulouse n-back task concurrently paired with fNIRS, with measurements taken before and after 20 min of anodal or sham tDCS at 1.5 mA. With individual oxygenation controlled for, anodal tDCS was found to increase the oxyhemoglobin concentration over the right DLPFC during the 2-back (q = .015) and 3-back (q = .008) conditions. Additionally, anodal tDCS was found to improve accuracy during the 3-back task by 13.4 % (p = .028) and decrease latency by 250 ms (p = .013). The increase in oxyhemoglobin was strongly correlated with increases in accuracy (p = .041) and decreases in latency during the 3-back span (p = .017). Taken together, anodal tDCS over the right DLPFC was found to regionally increase oxyhemoglobin concentrations and improve working memory performance in higher cognitive load conditions. •tDCS over the DLPFC may augment cognitive processing and cerebral oxygenation.•Individual cerebral oxygenation is variable and should be controlled for.•tDCS was found to increase oxyhemoglobin (HbO) over the stimulated right DLPFC.•tDCS increased working memory and decreased reaction time in higher load phases.•Increases in HbO are correlated with cognitive improvement in higher load phases.