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Imperio CM, Chua EF. Lack of effects of online HD-tDCS over the left or right DLPFC in an associative memory and metamemory monitoring task. PLoS One 2024; 19:e0300779. [PMID: 38848375 PMCID: PMC11161112 DOI: 10.1371/journal.pone.0300779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 02/20/2024] [Indexed: 06/09/2024] Open
Abstract
Neuroimaging studies have shown that activity in the prefrontal cortex correlates with two critical aspects of normal memory functioning: retrieval of episodic memories and subjective "feelings-of-knowing" about our memory. Brain stimulation can be used to test the causal role of the prefrontal cortex in these processes, and whether the role differs for the left versus right prefrontal cortex. We compared the effects of online High-Definition transcranial Direct Current Stimulation (HD-tDCS) over the left or right dorsolateral prefrontal cortex (DLPFC) compared to sham during a proverb-name associative memory and feeling-of-knowing task. There were no significant effects of HD-tDCS on either associative recognition or feeling-of-knowing performance, with Bayesian analyses showing moderate support for the null hypotheses. Despite past work showing effects of HD-tDCS on other memory and feeling-of-knowing tasks, and neuroimaging showing effects with similar tasks, these findings add to the literature of non-significant effects with tDCS. This work highlights the need to better understand factors that determine the effectiveness of tDCS, especially if tDCS is to have a successful future as a clinical intervention.
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Affiliation(s)
- Casey M Imperio
- The Graduate Center of the City University of New York, New York, New York, United States of America
| | - Elizabeth F Chua
- The Graduate Center of the City University of New York, New York, New York, United States of America
- Brooklyn College of the City University of New York, New York, New York, United States of America
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Imperio CM, Chua EF. HD-tDCS over the left DLPFC increases cued recall and subjective question familiarity rather than other aspects of memory and metamemory. Brain Res 2023; 1819:148538. [PMID: 37595661 PMCID: PMC10548440 DOI: 10.1016/j.brainres.2023.148538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 08/08/2023] [Accepted: 08/15/2023] [Indexed: 08/20/2023]
Abstract
When retrieving information from memory there is an interplay between memory and metamemory processes, and the prefrontal cortex has been implicated in both memory and metamemory. Previous work shown that High Definition transcranial Direct Current Stimulation (HD-tDCS) over the dorsolateral prefrontal cortex (DLPFC) can lead to improvements in memory and metamemory monitoring, but findings are mixed. Our original design targeted metamemory, but because the prefrontal cortex plays a role in both memory and metamemory, we tested for effects of HD-tDCS on multiple memory tasks (e.g., recall, cued recall, and recognition) and multiple aspects of metamemory (e.g., once-knew-it ratings, feeling-of-knowing ratings, metamemory accuracy, and metamemory control). There were HD-tDCS-related improvements in cued recall performance, but not other memory tasks. For metamemory, there were HD-tDCS-related increases in subjective once-knew-it ratings, but not other aspects of metamemory. These results highlight the need to consider the effects of HD-tDCS on memory and metamemory at different timepoints during retrieval, as well as specific conditions that show benefits from HD-tDCS.
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Affiliation(s)
- Casey M Imperio
- The Graduate Center of the City University of New York, Department of Psychology, 365 5th Ave., New York, NY 10016, USA; Brooklyn College of the City University of New York, Department of Psychology, 2900 Bedford Ave., Brooklyn, NY 11210, USA.
| | - Elizabeth F Chua
- The Graduate Center of the City University of New York, Department of Psychology, 365 5th Ave., New York, NY 10016, USA; Brooklyn College of the City University of New York, Department of Psychology, 2900 Bedford Ave., Brooklyn, NY 11210, USA.
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Imperio CM, Chua EF. Differential effects of remotely supervised transcranial direct current stimulation on recognition memory depending on task order. Front Hum Neurosci 2023; 17:1239126. [PMID: 37635805 PMCID: PMC10450219 DOI: 10.3389/fnhum.2023.1239126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 07/26/2023] [Indexed: 08/29/2023] Open
Abstract
Background Prior work has shown positive effects of High Definition transcranial direct current stimulation (HD-tDCS) over the dorsolateral prefrontal cortex (DLPFC) on semantic memory performance and metamemory monitoring accuracy. However, HD-tDCS requires setup by a trained researcher, which is not always feasible. Few studies have used remotely supervised (rs) tDCS in healthy populations, and remote supervision has strong practical benefits. Objective/hypothesis The goal of the current study was to test if previously shown effects of HD-tDCS over the left DLPFC on semantic memory performance and metamemory monitoring accuracy extended to conventional rs-tDCS, which is less focal than HD-tDCS, and to episodic memory and metamemory tasks. Materials and methods A total of 36 healthy participants completed 6 weeks of rs-tDCS sessions, with either active left or right anodal DLPFC stimulation, or sham. Participants completed semantic and episodic memory and metamemory tasks, which each lasted for three consecutive sessions, and session order was counterbalanced across participants. Results Overall, there were no main effects of rs-tDCS on metamemory monitoring accuracy or memory performance for either the semantic or the episodic tasks. However, there were effects of rs-tDCS that depended on the order of completing the episodic and semantic task sessions. When participants completed the semantic task sessions after the episodic task sessions, semantic recognition was greater in the left anodal DLPFC condition. In a parallel effect, when participants completed the episodic task sessions after the semantic task sessions, episodic recognition was greater in the right anodal DLPFC condition. Conclusion Prior experience with tDCS is a factor for effects of rs-tDCS on cognition. Additionally, the current experiment provides evidence for the feasibility of fully remotely supervised tDCS in healthy participants.
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Affiliation(s)
- Casey M. Imperio
- Department of Psychology, Brooklyn College, Brooklyn, NY, United States
- Department of Psychology, The Graduate Center of the City University of New York, New York, NY, United States
| | - Elizabeth F. Chua
- Department of Psychology, Brooklyn College, Brooklyn, NY, United States
- Department of Psychology, The Graduate Center of the City University of New York, New York, NY, United States
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Oliver-Mas S, Delgado-Alonso C, Delgado-Álvarez A, Díez-Cirarda M, Cuevas C, Fernández-Romero L, Matias-Guiu A, Valles-Salgado M, Gil-Martínez L, Gil-Moreno MJ, Yus M, Matias-Guiu J, Matias-Guiu JA. Transcranial direct current stimulation for post-COVID fatigue: a randomized, double-blind, controlled pilot study. Brain Commun 2023; 5:fcad117. [PMID: 37091591 PMCID: PMC10116605 DOI: 10.1093/braincomms/fcad117] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Revised: 02/19/2023] [Accepted: 04/05/2023] [Indexed: 04/25/2023] Open
Abstract
Fatigue is one of the most frequent and disabling symptoms of the post-COVID syndrome. In this study, we aimed to assess the effects of transcranial direct current stimulation on fatigue severity in a group of patients with post-COVID syndrome and chronic fatigue. We conducted a double-blind, parallel-group, sham-controlled study to evaluate the short-term effects of anodal transcranial direct current stimulation (2 mA, 20 min/day) on the left dorsolateral prefrontal cortex. The modified fatigue impact scale score was used as the primary endpoint. Secondary endpoints included cognition (Stroop test), depressive symptoms (Beck depression inventory) and quality of life (EuroQol-5D). Patients received eight sessions of transcranial direct current stimulation and were evaluated at baseline, immediately after the last session, and one month later. Forty-seven patients were enrolled (23 in the active treatment group and 24 in the sham treatment group); the mean age was 45.66 ± 9.49 years, and 37 (78.72%) were women. The mean progression time since the acute infection was 20.68 ± 6.34 months. Active transcranial direct current stimulation was associated with a statistically significant improvement in physical fatigue at the end of treatment and 1 month as compared with sham stimulation. No significant effect was detected for cognitive fatigue. In terms of secondary outcomes, active transcranial direct current stimulation was associated with an improvement in depressive symptoms at the end of treatment. The treatment had no effects on the quality of life. All the adverse events reported were mild and transient, with no differences between the active stimulation and sham stimulation groups. In conclusion, our results suggest that transcranial direct current stimulation on the dorsolateral prefrontal cortex may improve physical fatigue. Further studies are needed to confirm these findings and optimize stimulation protocols.
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Affiliation(s)
- Silvia Oliver-Mas
- Department of Neurology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Cristina Delgado-Alonso
- Department of Neurology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Alfonso Delgado-Álvarez
- Department of Neurology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - María Díez-Cirarda
- Department of Neurology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Constanza Cuevas
- Department of Neurology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Lucía Fernández-Romero
- Department of Neurology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Andreu Matias-Guiu
- Department of Neurology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - María Valles-Salgado
- Department of Neurology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Lidia Gil-Martínez
- Department of Radiology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - María José Gil-Moreno
- Department of Neurology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Miguel Yus
- Department of Radiology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Jorge Matias-Guiu
- Department of Neurology, Hospital Clínico San Carlos, San Carlos Health Research Institute (IdISCC), Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Jordi A Matias-Guiu
- Correspondence to: Jordi A. Matias-Guiu Department of Neurology, Hospital Clínico San Carlos C/Profesor Martín Lagos, 28040 Madrid, Spain E-mails: ;
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Steinmann I, Williams KA, Wilke M, Antal A. Detection of Transcranial Alternating Current Stimulation Aftereffects Is Improved by Considering the Individual Electric Field Strength and Self-Rated Sleepiness. Front Neurosci 2022; 16:870758. [PMID: 35833087 PMCID: PMC9272587 DOI: 10.3389/fnins.2022.870758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 05/04/2022] [Indexed: 11/13/2022] Open
Abstract
Non-invasive electrical stimulation methods, such as transcranial alternating current stimulation (tACS), are increasingly used in human neuroscience research and offer potential new avenues to treat neurological and psychiatric disorders. However, their often variable effects have also raised concerns in the scientific and clinical communities. This study aims to investigate the influence of subject-specific factors on the alpha tACS-induced aftereffect on the alpha amplitude (measured with electroencephalography, EEG) as well as on the connectivity strength between nodes of the default mode network (DMN) [measured with functional magnetic resonance imaging (fMRI)]. As subject-specific factors we considered the individual electrical field (EFIELD) strength at target regions in the brain, the frequency mismatch between applied stimulation and individual alpha frequency (IAF) and as a covariate, subject’s changes in mental state, i.e., sleepiness. Eighteen subjects participated in a tACS and a sham session conducted on different days. Each session consisted of three runs (pre/stimulation/). tACS was applied during the second run at each subject’s individual alpha frequency (IAF), applying 1 mA peak-to-peak intensity for 7 min, using an occipital bihemispheric montage. In every run, subjects watched a video designed to increase in-scanner compliance. To investigate the aftereffect of tACS on EEG alpha amplitude and on DMN connectivity strength, EEG data were recorded simultaneously with fMRI data. Self-rated sleepiness was documented using a questionnaire. Conventional statistics (ANOVA) did not show a significant aftereffect of tACS on the alpha amplitude compared to sham stimulation. Including individual EFIELD strengths and self-rated sleepiness scores in a multiple linear regression model, significant tACS-induced aftereffects were observed. However, the subject-wise mismatch between tACS frequency and IAF had no contribution to our model. Neither standard nor extended statistical methods confirmed a tACS-induced aftereffect on DMN functional connectivity. Our results show that it is possible and necessary to disentangle alpha amplitude changes due to intrinsic mechanisms and to external manipulation using tACS on the alpha amplitude that might otherwise be overlooked. Our results suggest that EFIELD is really the most significant factor that explains the alpha amplitude modulation during a tACS session. This knowledge helps to understand the variability of the tACS-induced aftereffects.
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Affiliation(s)
- Iris Steinmann
- Department of Cognitive Neurology, University Medical Center Göttingen, Göttingen, Germany
- *Correspondence: Iris Steinmann,
| | - Kathleen A. Williams
- Department of Cognitive Neurology, University Medical Center Göttingen, Göttingen, Germany
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Melanie Wilke
- Department of Cognitive Neurology, University Medical Center Göttingen, Göttingen, Germany
- German Primate Center, Leibniz Institute for Primate Research, Göttingen, Germany
| | - Andrea Antal
- Department of Neurology, University Medical Center Göttingen, Göttingen, Germany
- Andrea Antal,
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Bolling AJ, King VL, Enam T, McDonough IM. Using transcranial direct current stimulation (tDCS) on the dorsolateral prefrontal cortex to promote long-term foreign language vocabulary learning. Brain Cogn 2021; 154:105789. [PMID: 34509124 DOI: 10.1016/j.bandc.2021.105789] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 08/22/2021] [Accepted: 08/27/2021] [Indexed: 11/26/2022]
Abstract
Transcranial direct current stimulation (tDCS) on the dorsolateral prefrontal cortex (DLPFC) was used to improve foreign-langue learning while using mental imagery. Participants underwent two sessions of 1 mA, 1.5 mA, or sham stimulation prior to learning Swahili-English word pairs two consecutive days. During learning, participants were encouraged to create a mental image of the associated English word. Twenty-four hours after learning and one week later, participants received a cued recall test. A linear dose-response effect of stimulation was found across both tests that occurred long after the immediate effects of stimulation. Follow-up comparisons revealed that only the 1.5 mA condition differed from the sham group. Exploratory moderating effects revealed interactions with sleep quality and handedness. Those with poorer sleep and who were left-handed showed greater recall after 1.5 mA of stimulation than those with better sleep and right-handers. A follow-up behavioral study probing strategy usage indicated that mental imagery strategy use did not strongly impact learning but point to other possible mechanisms including the importance of attending to multimodal perceptual details and memory consolidation. This preliminary evidence supports the role of the DLPFC or connected regions in foreign language vocabulary learning and verbal memory encoding.
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Affiliation(s)
- A Jordan Bolling
- Department of Psychology, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Victoria L King
- Department of Psychology, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Tasnuva Enam
- Department of Psychology, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Ian M McDonough
- Department of Psychology, The University of Alabama, Tuscaloosa, AL 35487, USA.
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Non-invasive cortical stimulation: Transcranial direct current stimulation (tDCS). INTERNATIONAL REVIEW OF NEUROBIOLOGY 2021; 159:1-22. [PMID: 34446242 DOI: 10.1016/bs.irn.2021.01.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Transcranial direct current stimulation (tDCS) is a re-emerging non-invasive brain stimulation technique that has been used in animal models and human trials aimed to elucidate neurophysiology and behavior interactions. It delivers subthreshold electrical currents to neuronal populations that shift resting membrane potential either toward depolarization or hyperpolarization, depending on stimulation parameters and neuronal orientation in relation to the induced electric field (EF). Although the resulting cerebral EFs are not strong enough to induce action potentials, spontaneous neuronal firing in response to inputs from other brain areas is influenced by tDCS. Additionally, tDCS induces plastic synaptic changes resembling long-term potentiation (LTP) or long-term depression (LTD) that outlast the period of stimulation. Such properties place tDCS as an appealing intervention for the treatment of diverse neuropsychiatric disorders. Although findings of clinical trials are preliminary for most studied conditions, there is already convincing evidence regarding its efficacy for unipolar depression. The main advantages of tDCS are the absence of serious or intolerable side effects and the portability of the devices, which might lead in the future to home-use applications and improved patient care. This chapter provides an up-to-date overview of a number tDCS relevant topics such as mechanisms of action, contemporary applications and safety. Furthermore, we propose ways to further develop tDCS research.
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No Effect of Anodal tDCS on Verbal Episodic Memory Performance and Neurotransmitter Levels in Young and Elderly Participants. Neural Plast 2020; 2020:8896791. [PMID: 33029128 PMCID: PMC7528151 DOI: 10.1155/2020/8896791] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 08/14/2020] [Accepted: 09/01/2020] [Indexed: 01/05/2023] Open
Abstract
Healthy ageing is accompanied by cognitive decline that affects episodic memory processes in particular. Studies showed that anodal transcranial direct current stimulation (tDCS) to the left dorsolateral prefrontal cortex (DLPFC) may counteract this cognitive deterioration by increasing excitability and inducing neuroplasticity in the targeted cortical region. While stimulation gains are more consistent in initial low performers, relying solely on behavioural measures to predict treatment benefits does not suffice for a reliable implementation of this method as a therapeutic option. Hence, an exploration of the underlying neurophysiological mechanisms regarding the differential stimulation effect is warranted. Glutamatergic metabolites (Glx) and γ-aminobutyric acid (GABA) are involved in learning and memory processes and can be influenced with tDCS; wherefore, they present themselves as potential biomarkers for tDCS-induced behavioural gains, which are affiliated with neuroplasticity processes. In the present randomized, double-blind, sham-controlled, crossover study, 33 healthy young and 22 elderly participants received anodal tDCS to their left DLPFC during the encoding phase of a verbal episodic memory task. Using MEGA-PRESS edited magnetic resonance spectroscopy (MRS), Glx and GABA levels were measured in the left DLPFC before and after the stimulation period. Further, we tested whether baseline performance and neurotransmitter levels predicted subsequent gains. No beneficial group effects of tDCS emerged in either verbal retrieval performances or neurotransmitter concentrations. Moreover, baseline performance levels did not predict stimulation-induced cognitive gains, nor did Glx or GABA levels. Nevertheless, exploratory analyses suggested a predictive value of the Glx : GABA ratio, with lower ratios at baseline indicating greater tDCS-related gains in delayed recall performance. This highlights the importance of further studies investigating neurophysiological mechanisms underlying previously observed stimulation-induced cognitive benefits and their respective interindividual heterogeneity.
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Rabipour S, Vidjen PS, Remaud A, Davidson PSR, Tremblay F. Examining the Interactions Between Expectations and tDCS Effects on Motor and Cognitive Performance. Front Neurosci 2019; 12:999. [PMID: 30666182 PMCID: PMC6330301 DOI: 10.3389/fnins.2018.00999] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 12/11/2018] [Indexed: 11/13/2022] Open
Abstract
Background: Despite a growing literature and commercial market, the effectiveness of transcranial direct current stimulation (tDCS) remains questionable. Notably, studies rarely examine factors such as expectations of outcomes, which may influence tDCS response through placebo-like effects. Here we sought to determine whether expectations could influence the behavioral outcomes of a tDCS intervention. Methods: Through an initial study and self-replication, we recruited 121 naïve young adults 18-34 years of age (M = 21.14, SD = 3.58; 88 women). We evaluated expectations of tDCS and of motor and cognitive performance at three times: (i) at baseline; (ii) after being primed to have High or Low expectations of outcomes; and (iii) after a single session of sham-controlled anodal tDCS over the left or right motor cortex. Before and after stimulation, participants performed the Grooved Pegboard Test and a choice reaction time task as measures of motor dexterity, response time, and response inhibition. Results: Repeated measures ANOVA revealed that participants had varying, largely uncertain, expectations regarding tDCS effectiveness at baseline. Expectation ratings significantly increased or decreased in response to High or Low priming, respectively, and decreased following the intervention. Response times and accuracy on motor and cognitive measures were largely unaffected by expectation or stimulation conditions. Overall, our analysis revealed no effect attributable to baseline expectations, belief of group assignment, or experimental condition on behavioral outcomes. Subjective experience did not differ based on expectation or stimulation condition. Conclusions: Our results suggest no clear effects of tDCS or of expectations on our performance measures, highlighting the need for further investigations of such stimulation methods.
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Affiliation(s)
- Sheida Rabipour
- School of Psychology, University of Ottawa, Ottawa, ON, Canada
| | | | - Anthony Remaud
- Bruyère Research Institute, Bruyère Continuing Care, Ottawa, ON, Canada
| | - Patrick S. R. Davidson
- School of Psychology, University of Ottawa, Ottawa, ON, Canada
- Bruyère Research Institute, Bruyère Continuing Care, Ottawa, ON, Canada
| | - François Tremblay
- Bruyère Research Institute, Bruyère Continuing Care, Ottawa, ON, Canada
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Lattari E, Oliveira BRR, Monteiro Júnior RS, Marques Neto SR, Oliveira AJ, Maranhão Neto GA, Machado S, Budde H. Acute effects of single dose transcranial direct current stimulation on muscle strength: A systematic review and meta-analysis. PLoS One 2018; 13:e0209513. [PMID: 30586389 PMCID: PMC6306262 DOI: 10.1371/journal.pone.0209513] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 12/06/2018] [Indexed: 11/19/2022] Open
Abstract
Previous studies investigating the effects of transcranial direct current stimulation (tDCS) on muscle strength showed no consensus. Therefore, the purpose of this article was to systematically review the literature on the effects of single dose tDCS to improve muscle strength. A systematic literature search was conducted on PubMeb, ISI Web of Science, SciELO, and Scopus using search terms regarding tDCS and muscle strength. Studies were included in accordance with Population, Intervention, Comparison, Outcomes, and Setting (PICOS) including criteria. Healthy men and women, strength training practitioners or sedentary were selected. The acute effects of single dose anode stimulus of tDCS (a-tDCS) and the placebo stimulus of tDCS (sham) or no interventions were considered as an intervention and comparators, respectively. Measures related to muscle strength were analyzed. To conduct the analyses a weighted mean difference (WMD) and the standardized mean difference (SMD) were applied as appropriate. A total of 15 studies were included in this systematic review and 14 in meta-analysis. Regarding the maximal isometric voluntary contraction (MIVC), a small effect was seen between tDCS and Sham with significant difference between the conditions (SMD = 0.29; CI95% = 0.05 to 0.54; Z = 2.36; p = 0.02). The muscular endurance measured by the seconds sustaining a percentage of MIVC demonstrated a large effect between tDCS and Sham (WMD = 43.66; CI95% = 29.76 to 57.55; Z = 6.16; p < 0.001), showing an improvement in muscular endurance after exposure to tDCS. However, muscular endurance based on total work showed a trivial effect between tDCS and Sham with no significant difference (SMD = 0.22; CI95% = -0.11 to 0.54; Z = 1.32, p = 0.19). This study suggests that the use of tDCS may promote increase in maximal voluntary contraction and muscular endurance through isometric contractions.
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Affiliation(s)
- Eduardo Lattari
- Physical Activity Sciences Post-Graduate Program (PGCAF), Salgado de Oliveira University (UNIVERSO), Niterói, RJ, Brazil
| | | | - Renato Sobral Monteiro Júnior
- Physical Education and Sport Department, State University of Montes Claros, Montes Claros, Minas Gerais, Brazil
- Post-graduation Program of Health Sciences, State University of Montes Claros, Montes Claros, Minas Gerais, Brazil
| | - Silvio Rodrigues Marques Neto
- Physical Activity Sciences Post-Graduate Program (PGCAF), Salgado de Oliveira University (UNIVERSO), Niterói, RJ, Brazil
| | - Aldair J. Oliveira
- School of Physical Activity, Rural Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Geraldo A. Maranhão Neto
- Physical Activity Sciences Post-Graduate Program (PGCAF), Salgado de Oliveira University (UNIVERSO), Niterói, RJ, Brazil
| | - Sergio Machado
- Physical Activity Sciences Post-Graduate Program (PGCAF), Salgado de Oliveira University (UNIVERSO), Niterói, RJ, Brazil
- * E-mail:
| | - Henning Budde
- Faculty of Human Sciences, Medical School Hamburg, Hamburg, Germany
- Lithuanian Sports University, Kaunas, Lithuania
- Physical Activity, Physical Education, Health and Sport Research Centre (PAPESH), Sports Science Department, School of Science and Engineering, Reykjavik University, Reykjavik, Iceland
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Galli G, Vadillo MA, Sirota M, Feurra M, Medvedeva A. A systematic review and meta-analysis of the effects of transcranial direct current stimulation (tDCS) on episodic memory. Brain Stimul 2018; 12:231-241. [PMID: 30503376 DOI: 10.1016/j.brs.2018.11.008] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 10/26/2018] [Accepted: 11/11/2018] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND In the past decade, several studies have examined the effects of transcranial direct current stimulation (tDCS) on long-term episodic memory formation and retrieval. These studies yielded conflicting results, likely due to differences in stimulation parameters, experimental design and outcome measures. OBJECTIVES In this work we aimed to assess the robustness of tDCS effects on long-term episodic memory using a meta-analytical approach. METHODS We conducted four meta-analyses to analyse the effects of anodal and cathodal tDCS on memory accuracy and response times. We also used a moderator analysis to examine whether the size of tDCS effects varied as a function of specific stimulation parameters and experimental conditions. RESULTS Although all selected studies reported a significant effect of tDCS in at least one condition in the published paper, the results of the four meta-analyses showed only statistically non-significant close-to-zero effects. A moderator analysis suggested that for anodal tDCS, the duration of the stimulation and the task used to probe memory moderated the effectiveness of tDCS. For cathodal tDCS, site of stimulation was a significant moderator, although this result was based on only a few observations. CONCLUSIONS To warrant theoretical advancement and practical implications, more rigorous research is needed to fully understand whether tDCS reliably modulates episodic memory, and the specific circumstances under which this modulation does, and does not, occur.
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Affiliation(s)
- Giulia Galli
- Department of Psychology, Kingston University, Penrhyn Road, Kingston Upon Thames, KT1 2EE, United Kingdom.
| | - Miguel A Vadillo
- Departamento de Psicología Básica, Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain
| | - Miroslav Sirota
- Department of Psychology, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, United Kingdom
| | - Matteo Feurra
- School of Psychology, Centre for Cognition and Decision Making, National Research University Higher School of Economics, 101000, Moscow, Armyanskiy per. 4, c2, Russian Federation
| | - Angela Medvedeva
- Department of Psychology, Kingston University, Penrhyn Road, Kingston Upon Thames, KT1 2EE, United Kingdom
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