Transcranial Direct Current Stimulation May Reduce Prefrontal Recruitment During Dual Task Walking in Functionally Limited Older Adults – A Pilot Study

Abstract

IntroductionTranscranial direct current stimulation (tDCS) targeting the left dorsolateral prefrontal cortex (dlPFC) improves dual task walking in older adults, when tested just after stimulation. The acute effects of tDCS on the cortical physiology of walking, however, remains unknown.MethodsIn a previous study, older adults with slow gait and executive dysfunction completed a dual task walking assessment before and after 20 min of tDCS targeting the left dlPFC or sham stimulation. In a subset of seven participants per group, functional near-infrared spectroscopy (fNIRS) was used to quantify left and right prefrontal recruitment defined as the oxygenated hemoglobin response to usual and dual task walking (ΔHbO2), as well as the absolute change in this metric from usual to dual task conditions (i.e., ΔHbO2cost). Paired t-tests examined pre- to post-stimulation differences in each fNIRS metric within each group.ResultsThe tDCS group exhibited pre- to post-stimulation reduction in left prefrontal ΔHbO2cost (p = 0.03). This mitigation of dual task “cost” to prefrontal recruitment was induced primarily by a reduction in left prefrontal ΔHbO2 specifically within the dual task condition (p = 0.001), an effect that was observed in all seven participants within this group. Sham stimulation did not influence ΔHbO2cost or ΔHbO2 in either walking condition (p > 0.35), and neither tDCS nor sham substantially influenced right prefrontal recruitment (p > 0.16).DiscussionThis preliminary fNIRS data suggests that tDCS over the left dlPFC may modulate prefrontal recruitment, as reflected by a relative reduction in the oxygen consumption of this brain region in response to dual task walking.

Uncorking the limitation—improving dual tasking using transcranial electrical stimulation and task training in the elderly: a systematic review

“…In the above-mentioned studies, L-DLPFC was the main target area as it is highly related to executive function (Zhou et al, 2014). A combined tDCS and functional near-infrared spectroscopy study revealed lower oxygenated hemoglobin response in the left prefrontal cortex within DT condition after 2 mA, 20 min tDCS over L-DLPFC was applied, suggesting that L-DLPFC tDCS modulates the prefrontal recruiting, and the reduction of DTC may be due to the reduced oxygen consumption (Jor'dan et al, 2022) as neuroimaging study which mentioned above reported a higher activation in the healthy elderly during DT condition. Compared to tDCS over the right DLPFC or sham stimulation, anodal tDCS over the L-DLPFC can significantly enhance executive functions within conflict-related tasks (Dubreuil-Vall et al, 2019).…”