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Subramaniam A, Liu S, Lochhead L, Appelbaum LG. A systematic review of transcranial direct current stimulation on eye movements and associated psychological function. Rev Neurosci 2022; 34:349-364. [PMID: 36310385 DOI: 10.1515/revneuro-2022-0082] [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: 07/05/2022] [Accepted: 09/07/2022] [Indexed: 11/05/2022]
Abstract
Abstract
The last decades have seen a rise in the use of transcranial direct current stimulation (tDCS) approaches to modulate brain activity and associated behavior. Concurrently, eye tracking (ET) technology has improved to allow more precise quantitative measurement of gaze behavior, offering a window into the mechanisms of vision and cognition. When combined, tDCS and ET provide a powerful system to probe brain function and measure the impact on visual function, leading to an increasing number of studies that utilize these techniques together. The current pre-registered, systematic review seeks to describe the literature that integrates these approaches with the goal of changing brain activity with tDCS and measuring associated changes in eye movements with ET. The literature search identified 26 articles that combined ET and tDCS in a probe-and-measure model and are systematically reviewed here. All studies implemented controlled interventional designs to address topics related to oculomotor control, cognitive processing, emotion regulation, or cravings in healthy volunteers and patient populations. Across these studies, active stimulation typically led to changes in the number, duration, and timing of fixations compared to control stimulation. Notably, half the studies addressed emotion regulation, each showing hypothesized effects of tDCS on ET metrics, while tDCS targeting the frontal cortex was widely used and also generally produced expected modulation of ET. This review reveals promising evidence of the impact of tDCS on eye movements and associated psychological function, offering a framework for effective designs with recommendations for future studies.
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Affiliation(s)
- Ashwin Subramaniam
- Department of Psychiatry and Behavioral Sciences, Duke University, Durham, NC 27710, USA
| | - Sicong Liu
- Department of Psychiatry and Behavioral Sciences, Duke University, Durham, NC 27710, USA
- Annenberg School of Communication, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Liam Lochhead
- Department of Psychiatry, University of California, San Diego, CA 92093, USA
| | - Lawrence Gregory Appelbaum
- Department of Psychiatry and Behavioral Sciences, Duke University, Durham, NC 27710, USA
- Department of Psychiatry, University of California, San Diego, CA 92093, USA
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Orcioli-Silva D, Islam A, Baker MR, Gobbi LTB, Rochester L, Pantall A. Bi-Anodal Transcranial Direct Current Stimulation Combined With Treadmill Walking Decreases Motor Cortical Activity in Young and Older Adults. Front Aging Neurosci 2021; 13:739998. [PMID: 34924993 PMCID: PMC8681021 DOI: 10.3389/fnagi.2021.739998] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 11/01/2021] [Indexed: 01/05/2023] Open
Abstract
Background: Walking in the "real world" involves motor and cognitive processes. In relation to this, declines in both motor function and cognition contribute to age-related gait dysfunction. Transcranial direct current stimulation (tDCS) and treadmill walking (STW) have potential to improve gait, particularly during dual-task walking (DTW); walking whilst performing a cognitive task. Our aims were to analyze effects of combined anodal tDCS + STW intervention on cortical activity and gait during DTW. Methods: Twenty-three young adults (YA) and 21 older adults (OA) were randomly allocated to active or sham tDCS stimulation groups. Participants performed 5-min of mixed treadmill walking (alternating 30 s bouts of STW and DTW) before and after a 20-min intervention of active or sham tDCS + STW. Anodal electrodes were placed over the left prefrontal cortex (PFC) and the vertex (Cz) using 9 cm2 electrodes at 0.6 mA. Cortical activity of the PFC, primary motor cortex (M1), premotor cortex (PMC), and supplementary motor area (SMA) bilaterally were recorded using a functional near-infrared spectroscopy (fNIRS) system. Oxygenated hemoglobin (HbO2) levels were analyzed as indicators of cortical activity. An accelerometer measured gait parameters. We calculated the difference between DTW and STW for HbO2 and gait parameters. We applied linear mixed effects models which included age group (YA vs. OA), stimulation condition (sham vs. active), and time (pre- vs. post-intervention) as fixed effects. Treadmill belt speed was a covariate. Partial correlation tests were also performed. Results: A main effect of age group was observed. OA displayed higher activity bilaterally in the PFC and M1, unilaterally in the right PMC and higher gait variability than YA. M1 activity decreased in both YA and OA following active tDCS + STW. There was no overall effect of tDCS + STW on PFC activity or gait parameters. However, negative correlations were observed between changes in left PFC and stride length variability following active tDCS + STW intervention. Conclusion: Increased activity in multiple cortical areas during DTW in OA may act as a compensatory mechanism. Reduction in M1 activity following active tDCS + STW with no observed gait changes suggests improved neural efficiency.
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Affiliation(s)
- Diego Orcioli-Silva
- Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, Brazil.,Graduate Program in Movement Sciences, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Aisha Islam
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Mark R Baker
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Lilian Teresa Bucken Gobbi
- Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, Brazil.,Graduate Program in Movement Sciences, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Lynn Rochester
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Annette Pantall
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
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Machado L. Understanding cognition and how it changes with aging, brain disease, and lifestyle choices. J R Soc N Z 2020. [DOI: 10.1080/03036758.2020.1796102] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Liana Machado
- Department of Psychology and Brain Health Research Centre, University of Otago, Dunedin, New Zealand
- Brain Research New Zealand, Auckland, New Zealand
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Chen PL, Stenling A, Machado L. Evidence Transcranial Direct Current Stimulation Can Improve Saccadic Eye Movement Control in Older Adults. Vision (Basel) 2018; 2:E42. [PMID: 31735905 PMCID: PMC6835567 DOI: 10.3390/vision2040042] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 11/23/2018] [Accepted: 11/29/2018] [Indexed: 11/16/2022] Open
Abstract
Objectives: Ageing is associated with declines in voluntary eye movement control, which negatively impact the performance of daily activities. Therapies treating saccadic eye movement control deficits are currently lacking. To address the need for an effective therapy to treat age-related deficits in saccadic eye movement control, the current study investigated whether saccadic behaviour in older adults can be improved by anodal transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex using a montage that has been proven to be effective at improving nonoculomotor control functions. Method: The tDCS protocol entailed a 5 cm × 7 cm anodal electrode and an encephalic cathodal reference electrode positioned over the contralateral supraorbital area. In two experiments, healthy older men completed one active (1.5 mA current for 10 min) and one sham stimulation session, with the session order counterbalanced across participants, and eye movement testing following stimulation. In the first experiment, participants rested during the tDCS (offline), whereas in the follow-up experiment, participants engaged in antisaccades during the tDCS (online). Results: Analyses revealed improvements in saccadic performance following active anodal tDCS relative to sham stimulation in the online experiment, but not in the offline experiment, which was presumably due to the activation of the relevant networks during tDCS promoting more targeted effects. Discussion: These outcomes converge with findings pertaining to nonoculomotor cognitive functions, and provide evidence that tDCS can improve saccadic eye movement control in older adults.
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Affiliation(s)
- Po Ling Chen
- Department of Psychology and Brain Health Research Centre, University of Otago, Dunedin 9054, New Zealand
- Brain Research New Zealand, Auckland 1142, New Zealand
| | - Andreas Stenling
- Department of Psychology and Brain Health Research Centre, University of Otago, Dunedin 9054, New Zealand
- Brain Research New Zealand, Auckland 1142, New Zealand
- Department of Psychology, Umeå University, 901 87 Umeå, Sweden
- Department of Psychology, University of Gothenburg, SE405 30 Gothenburg, Sweden
| | - Liana Machado
- Department of Psychology and Brain Health Research Centre, University of Otago, Dunedin 9054, New Zealand
- Brain Research New Zealand, Auckland 1142, New Zealand
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Reteig LC, Knapen T, Roelofs FJFW, Ridderinkhof KR, Slagter HA. No Evidence That Frontal Eye Field tDCS Affects Latency or Accuracy of Prosaccades. Front Neurosci 2018; 12:617. [PMID: 30233300 PMCID: PMC6135207 DOI: 10.3389/fnins.2018.00617] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 08/14/2018] [Indexed: 12/13/2022] Open
Abstract
Transcranial direct current stimulation (tDCS) may be used to directly affect neural activity from outside of the skull. However, its exact physiological mechanisms remain elusive, particularly when applied to new brain areas. The frontal eye field (FEF) has rarely been targeted with tDCS, even though it plays a crucial role in control of overt and covert spatial attention. Here, we investigate whether tDCS over the FEF can affect the latency and accuracy of saccadic eye movements. Twenty-six participants performed a prosaccade task in which they made eye movements to a sudden-onset eccentric visual target (lateral saccades). After each lateral saccade, they made an eye movement back to the center (center saccades). The task was administered before, during, and after anodal or cathodal tDCS over the FEF, in a randomized, double-blind, within-subject design. One previous study (Kanai et al., 2012) found that anodal tDCS over the FEF decreased the latency of saccades contralateral to the stimulated hemisphere. We did not find the same effect: neither anodal nor cathodal tDCS influenced the latency of lateral saccades. tDCS also did not affect accuracy of lateral saccades (saccade endpoint deviation and saccade endpoint variability). For center saccades, we found some differences between the anodal and cathodal sessions, but these were not consistent across analyses (latency, endpoint variability), or were already present before tDCS onset (endpoint deviation). We tried to improve on the design of Kanai et al. (2012) in several ways, including the tDCS duration and electrode montage, which could explain the discrepant results. Our findings add to a growing number of null results, which have sparked concerns that tDCS outcomes are highly variable. Future studies should aim to establish the boundary conditions for FEF-tDCS to be effective, in addition to increasing sample size and adding additional controls such as a sham condition. At present, we conclude that it is unclear whether eye movements or other aspects of spatial attention can be affected through tDCS of the frontal eye fields.
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Affiliation(s)
- Leon C. Reteig
- Department of Psychology, University of Amsterdam, Amsterdam, Netherlands
- Amsterdam Brain and Cognition, Amsterdam, Netherlands
| | - Tomas Knapen
- Department of Experimental and Applied Psychology, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
- Institute for Brain and Behavior Amsterdam, Amsterdam, Netherlands
| | | | - K. Richard Ridderinkhof
- Department of Psychology, University of Amsterdam, Amsterdam, Netherlands
- Amsterdam Brain and Cognition, Amsterdam, Netherlands
| | - Heleen A. Slagter
- Department of Psychology, University of Amsterdam, Amsterdam, Netherlands
- Amsterdam Brain and Cognition, Amsterdam, Netherlands
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