Effects of Transcranial Direct Current Stimulation (tDCS) on Cognitive Performance and Cerebral Oxygen Hemodynamics: A Systematic Review

Figeys, Mathieu; Zeeman, Michael; Kim, Esther Sung

doi:10.3389/fnhum.2021.623315

Cited by 24 publications

(13 citation statements)

References 83 publications

(116 reference statements)

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“…Most studies using tDCS on human participants tend to report small effect sizes [57][58][59]. Interestingly, we observed that the Cohen's d effect sizes of TN-DCS on hippocampal activity ranged between 0.19 and 0.53, with the mean being 0.26.…”

Section: Tn-dcs Effect Sizesmentioning

confidence: 66%

Trigeminal nerve direct current stimulation causes sustained increase in neural activity in the rat hippocampus

Chen,

Deng,

Asamoah

et al. 2023

Preprint

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Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation method that can modulate many brain functions including learning and memory. Recent evidence suggests that tDCS memory effects may be caused by co-stimulation of scalp nerves such as the trigeminal nerve (TN), and not the electric field in the brain. The TN gives input to brainstem nuclei, including the locus coeruleus that controls noradrenaline release across brain regions, including hippocampus. However, the effects of TN direct current stimulation (TN-DCS) are currently not well understood. In this study we hypothesized that TN-DCS manipulates hippocampal activity via an LC-noradrenergic bottom-up pathway. We recorded neural activity in rat hippocampus using multichannel silicon probes. We applied 3 minutes of 0.25 mA or 1 mA TN-DCS, monitored hippocampal activity for up to 1 hour and calculated spikes-rate and spike-field coherence metrics. Subcutaneous injections of xylocaine were used to block TN and intraperitoneal injection of clonidine to block the LC pathway. We found that 1 mA TN-DCS caused a significant increase in hippocampal spike-rate lasting 45 minutes in addition to significant changes in spike-field coherence, while 0.25 mA TN-DCS did not. TN blockage prevented spike-rate increases, confirming effects were not caused by the electric field in the brain. When 1 mA TN-DCS was delivered during clonidine blockage no increase in spike-rate was observed, suggesting an important role for the LC-noradrenergic pathway. These results provide a neural basis to support a tDCS TN co-stimulation mechanism. TN-DCS emerges as an important tool to potentially modulate learning and memory.HighlightsTrigeminal nerve direct current stimulation (TN-DCS) boosts hippocampal spike ratesTN-DCS alters spike-field coherence in theta and gamma bands across the hippocampus.Blockade experiments indicate that TN-DCS modulated hippocampal activity via the LC-noradrenergic pathway.TN-DCS emerges as a potential tool for memory manipulation.Figure Graphic Abstract

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Section: Tn-dcs Effect Sizesmentioning

confidence: 66%

Trigeminal nerve direct current stimulation causes sustained increase in neural activity in the rat hippocampus

Chen,

Deng,

Asamoah

et al. 2023

Preprint

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“…During the VFT experiment, we used a 52-channel fNIRS device (ETG-4000 Optical Topography System) to estimate changes in regional cortical Hb concentration during the cognitive activation task, as described previously (55). The probes (17 emitters and 16 detectors, alternating) were fixed using 3 × 11 thermoplastic shells with an inter-optode distance of 3.0 cm.…”

Section: Functional Near-infrared Spectroscopy Signal Acquisitionmentioning

confidence: 99%

Increased both cortical activation and functional connectivity after transcranial direct current stimulation in patients with post-stroke: A functional near-infrared spectroscopy study

et al. 2022

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BackgroundPrevious studies have shown that cognitive impairment is common after stroke. Transcranial direct current stimulation (tDCS) is a promising tool for rehabilitating cognitive impairment. This study aimed to investigate the effects of tDCS on the rehabilitation of cognitive impairment in patients with stroke.MethodsTwenty-two mild–moderate post-stroke patients with cognitive impairments were treated with 14 tDCS sessions. A total of 14 healthy individuals were included in the control group. Cognitive function was assessed using the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). Cortical activation was assessed using functional near-infrared spectroscopy (fNIRS) during the verbal fluency task (VFT).ResultsThe cognitive function of patients with stroke, as assessed by the MMSE and MoCA scores, was lower than that of healthy individuals but improved after tDCS. The cortical activation of patients with stroke was lower than that of healthy individuals in the left superior temporal cortex (lSTC), right superior temporal cortex (rSTC), right dorsolateral prefrontal cortex (rDLPFC), right ventrolateral prefrontal cortex (rVLPFC), and left ventrolateral prefrontal cortex (lVLPFC) cortical regions. Cortical activation increased in the lSTC cortex after tDCS. The functional connectivity (FC) between the cerebral hemispheres of patients with stroke was lower than that of healthy individuals but increased after tDCS.ConclusionThe cognitive and brain functions of patients with mild-to-moderate stroke were damaged but recovered to a degree after tDCS. Increased cortical activation and increased FC between the bilateral cerebral hemispheres measured by fNIRS are promising biomarkers to assess the effectiveness of tDCS in stroke.

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“…Interestingly, the literature enables us to make a connection between the processes underlying the reduction in aerobic performance due to hypoxia and the ones underlying the beneficial effect of tDCS on endurance performance. For instance, while hypoxia has been shown to impose cognitive and perceptual burden [ 30 ], reduce neurovascular coupling in the brain, and decrease the central drive to the periphery [ 31 , 36 ], tDCS can increase cognitive function [ 37 ], corticospinal excitability [ 1 , 38 ], motor unit recruitment [ 39 ], brain blood supply [ 40 ], reduce RPE, and improve exercise performance [ 6 ].…”

Section: Introductionmentioning

confidence: 99%

Anodal tDCS over the left DLPFC but not M1 increases muscle activity and improves psychophysiological responses, cognitive function, and endurance performance in normobaric hypoxia: a randomized controlled trial

et al. 2023

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Background Transcranial direct current stimulation (tDCS) has been shown to have positive effects on exercise performance and cognitive function in the normal ambient condition. Hypoxia is deemed a stressful situation with detrimental effects on physiological, psychological, cognitive, and perceptual responses of the body. Nevertheless, no study has evaluated the efficacy of tDCS for counteracting the negative effects of hypoxic conditions on exercise performance and cognition so far. Hence, in the present study, we investigated the effects of anodal tDCS on endurance performance, cognitive function, and perceptual responses in hypoxia. Participants and methods Fourteen endurance-trained males participated in five experimental sessions. After familiarization and measuring peak power output in hypoxia, in the first and second sessions, through the 3rd to 5th sessions, participants performed a cycling endurance task until exhaustion after 30 min hypoxic exposure at resting position followed by 20 min of anodal stimulation of the motor cortex (M1), left dorsolateral prefrontal cortex (DLPFC), or sham-tDCS. Color-word Stroop test and choice reaction time were measured at baseline and after exhaustion. Time to exhaustion, heart rate, saturated O2, EMG amplitude of the vastus lateralis, vastus medialis, and rectus femoris muscles, RPE, affective response, and felt arousal were also measured during the task under hypoxia. Results The results showed a longer time to exhaustion (+ 30.96%, p=0.036), lower RPE (− 10.23%, p = 0.045) and higher EMG amplitude of the vastus medialis muscle (+ 37.24%, p=0.003), affective response (+ 260%, p=0.035) and felt arousal (+ 28.9%, p=0.029) in the DLPFC tDCS compared to sham. The choice reaction time was shorter in DLPFC tDCS compared to sham (− 17.55%, p=0.029), and no differences were seen in the color-word Stroop test among the conditions under hypoxia. M1 tDCS resulted in no significant effect for any outcome measure. Conclusions We concluded that, as a novel finding, anodal stimulation of the left DLPFC might provide an ergogenic aid for endurance performance and cognitive function under the hypoxic condition probably via increasing neural drive to the working muscles, lowering RPE, and increasing perceptual responses.

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Effects of Transcranial Direct Current Stimulation (tDCS) on Cognitive Performance and Cerebral Oxygen Hemodynamics: A Systematic Review

Cited by 24 publications

References 83 publications

Trigeminal nerve direct current stimulation causes sustained increase in neural activity in the rat hippocampus

Trigeminal nerve direct current stimulation causes sustained increase in neural activity in the rat hippocampus

Increased both cortical activation and functional connectivity after transcranial direct current stimulation in patients with post-stroke: A functional near-infrared spectroscopy study

Anodal tDCS over the left DLPFC but not M1 increases muscle activity and improves psychophysiological responses, cognitive function, and endurance performance in normobaric hypoxia: a randomized controlled trial

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