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Santander T, Leslie S, Li LJ, Skinner HE, Simonson JM, Sweeney P, Deen KP, Miller MB, Brunye TT. Towards optimized methodological parameters for maximizing the behavioral effects of transcranial direct current stimulation. Front Hum Neurosci 2024; 18:1305446. [PMID: 39015825 PMCID: PMC11250584 DOI: 10.3389/fnhum.2024.1305446] [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: 10/01/2023] [Accepted: 06/12/2024] [Indexed: 07/18/2024] Open
Abstract
Introduction Transcranial direct current stimulation (tDCS) administers low-intensity direct current electrical stimulation to brain regions via electrodes arranged on the surface of the scalp. The core promise of tDCS is its ability to modulate brain activity and affect performance on diverse cognitive functions (affording causal inferences regarding regional brain activity and behavior), but the optimal methodological parameters for maximizing behavioral effects remain to be elucidated. Here we sought to examine the effects of 10 stimulation and experimental design factors across a series of five cognitive domains: motor performance, visual search, working memory, vigilance, and response inhibition. The objective was to identify a set of optimal parameter settings that consistently and reliably maximized the behavioral effects of tDCS within each cognitive domain. Methods We surveyed tDCS effects on these various cognitive functions in healthy young adults, ultimately resulting in 721 effects across 106 published reports. Hierarchical Bayesian meta-regression models were fit to characterize how (and to what extent) these design parameters differentially predict the likelihood of positive/negative behavioral outcomes. Results Consistent with many previous meta-analyses of tDCS effects, extensive variability was observed across tasks and measured outcomes. Consequently, most design parameters did not confer consistent advantages or disadvantages to behavioral effects-a domain-general model suggested an advantage to using within-subjects designs (versus between-subjects) and the tendency for cathodal stimulation (relative to anodal stimulation) to produce reduced behavioral effects, but these associations were scarcely-evident in domain-specific models. Discussion These findings highlight the urgent need for tDCS studies to more systematically probe the effects of these parameters on behavior to fulfill the promise of identifying causal links between brain function and cognition.
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Affiliation(s)
- Tyler Santander
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, Santa Barbara, CA, United States
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Sara Leslie
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Luna J. Li
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Henri E. Skinner
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Jessica M. Simonson
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, Santa Barbara, CA, United States
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Patrick Sweeney
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Kaitlyn P. Deen
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Michael B. Miller
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, Santa Barbara, CA, United States
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Tad T. Brunye
- U. S. Army DEVCOM Soldier Center, Natick, MA, United States
- Center for Applied Brain and Cognitive Sciences, Tufts University, Medford, MA, United States
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Ehrhardt SE, Ballard T, Wards Y, Mattingley JB, Dux PE, Filmer HL. tDCS augments decision-making efficiency in an intensity dependent manner: A training study. Neuropsychologia 2022; 176:108397. [DOI: 10.1016/j.neuropsychologia.2022.108397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 10/10/2022] [Accepted: 10/14/2022] [Indexed: 11/15/2022]
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Penalver-Andres J, Buetler KA, Koenig T, Müri RM, Marchal-Crespo L. Providing Task Instructions During Motor Training Enhances Performance and Modulates Attentional Brain Networks. Front Neurosci 2021; 15:755721. [PMID: 34955719 PMCID: PMC8695982 DOI: 10.3389/fnins.2021.755721] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 10/18/2021] [Indexed: 11/21/2022] Open
Abstract
Learning a new motor task is a complex cognitive and motor process. Especially early during motor learning, cognitive functions such as attentional engagement, are essential, e.g., to discover relevant visual stimuli. Drawing participant's attention towards task-relevant stimuli-e.g., with task instructions using visual cues or explicit written information-is a common practice to support cognitive engagement during training and, hence, accelerate motor learning. However, there is little scientific evidence about how visually cued or written task instructions affect attentional brain networks during motor learning. In this experiment, we trained 36 healthy participants in a virtual motor task: surfing waves by steering a boat with a joystick. We measured the participants' motor performance and observed attentional brain networks using alpha-band electroencephalographic (EEG) activity before and after training. Participants received one of the following task instructions during training: (1) No explicit task instructions and letting participants surf freely (implicit training; IMP); (2) Task instructions provided through explicit visual cues (explicit-implicit training; E-IMP); or (3) through explicit written commands (explicit training; E). We found that providing task instructions during training (E and E-IMP) resulted in less post-training motor variability-linked to enhanced performance-compared to training without instructions (IMP). After training, participants trained with visual cues (E-IMP) enhanced the alpha-band strength over parieto-occipital and frontal brain areas at wave onset. In contrast, participants who trained with explicit commands (E) showed decreased fronto-temporal alpha activity. Thus, providing task instructions in written (E) or using visual cues (E-IMP) leads to similar motor performance improvements by enhancing activation on different attentional networks. While training with visual cues (E-IMP) may be associated with visuo-attentional processes, verbal-analytical processes may be more prominent when written explicit commands are provided (E). Together, we suggest that training parameters such as task instructions, modulate the attentional networks observed during motor practice and may support participant's cognitive engagement, compared to training without instructions.
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Affiliation(s)
- Joaquin Penalver-Andres
- Motor Learning and Neurorehabilitation Laboratory, ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
- Psychosomatic Medicine, Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Karin A. Buetler
- Motor Learning and Neurorehabilitation Laboratory, ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | - Thomas Koenig
- Translational Research Center, University Hospital of Psychiatry and Psychotherapy, University of Bern, Bern, Switzerland
| | - René Martin Müri
- Gerontechnology and Rehabilitation Group, ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
- Perception and Eye Movement Laboratory, Department of Neurology and BioMedical Research, University of Bern, Bern, Switzerland
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Laura Marchal-Crespo
- Motor Learning and Neurorehabilitation Laboratory, ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
- Department of Cognitive Robotics, Delft University of Technology, Delft, Netherlands
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Ehrhardt SE, Filmer HL, Wards Y, Mattingley JB, Dux PE. The influence of tDCS intensity on decision-making training and transfer outcomes. J Neurophysiol 2020; 125:385-397. [PMID: 33174483 DOI: 10.1152/jn.00423.2020] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Transcranial direct current stimulation (tDCS) has been shown to improve single- and dual-task performance in healthy participants and enhance transferable training gains following multiple sessions of combined stimulation and task practice. However, it has yet to be determined what the optimal stimulation dose is for facilitating such outcomes. We aimed to test the effects of different tDCS intensities, with a commonly used electrode montage, on performance outcomes in a multisession single/dual-task training and transfer protocol. In a preregistered study, 123 participants, who were pseudorandomized across four groups, each completed six sessions (pre- and posttraining sessions and four combined tDCS and training sessions) and received 20 min of prefrontal anodal tDCS at 0.7, 1.0, or 2.0 mA or 15-s sham stimulation. Response time and accuracy were assessed in trained and untrained tasks. The 1.0-mA group showed substantial improvements in single-task reaction time and dual-task accuracy, with additional evidence for improvements in dual-task reaction times, relative to sham performance. This group also showed near transfer to the single-task component of an untrained multitasking paradigm. The 0.7- and 2.0-mA intensities varied in which performance measures they improved on the trained task, but in sum, the effects were less robust than for the 1.0-mA group, and there was no evidence for the transfer of performance. Our study highlights that training performance gains are augmented by tDCS, but their magnitude and nature are not uniform across stimulation intensity.NEW & NOTEWORTHY Using techniques such as transcranial direct current stimulation to modulate cognitive performance is an alluring endeavor. However, the optimal parameters to augment performance are unknown. Here, in a preregistered study with a large sample (123 subjects), three different stimulation dosages (0.7, 1.0, and 2.0 mA) were applied during multitasking training. Different cognitive training performance outcomes occurred across the dosage conditions, with only one of the doses (1.0 mA) leading to training transfer.
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Affiliation(s)
- Shane E Ehrhardt
- School of Psychology, The University of Queensland, St. Lucia, Australia
| | - Hannah L Filmer
- School of Psychology, The University of Queensland, St. Lucia, Australia
| | - Yohan Wards
- School of Psychology, The University of Queensland, St. Lucia, Australia
| | - Jason B Mattingley
- School of Psychology, The University of Queensland, St. Lucia, Australia.,Queensland Brain Institute, The University of Queensland, St. Lucia, Australia.,Canadian Institute for Advanced Research, Toronto, Ontario, Canada
| | - Paul E Dux
- School of Psychology, The University of Queensland, St. Lucia, Australia
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Nydam AS, Sewell DK, Dux PE. Effects of tDCS on visual statistical learning. Neuropsychologia 2020; 148:107652. [PMID: 33069791 DOI: 10.1016/j.neuropsychologia.2020.107652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 09/25/2020] [Accepted: 10/03/2020] [Indexed: 11/25/2022]
Abstract
Visual statistical learning describes the encoding of structure in sensory input, and it has important consequences for cognition and behaviour. Higher-order brain regions in the prefrontal and posterior parietal cortices have been associated with statistical learning behaviours. Yet causal evidence of a cortical contribution remains limited. In a recent study, the modulation of cortical activity by transcranial direct current stimulation (tDCS) disrupted statistical learning in a spatial contextual cueing phenomenon; supporting a cortical role. Here, we examined whether the same tDCS protocol would influence statistical learning assessed by the Visual Statistical Learning phenomenon (i.e., Fiser and Aslin, 2001), which uses identity-based regularities while controlling for spatial location. In Experiment 1, we employed the popular exposure-test design to tap the learning of structure after passive viewing. Using a large sample (N = 150), we found no effect of the tDCS protocol when compared to a sham control nor to an active control region. In Experiment 2 (N = 80), we developed an online task that was sensitive to the timecourse of learning. Under these task conditions, we did observe a stimulation effect on learning, consistent with the previous work. The way tDCS affected learning appeared to be task-specific; expediting statistical learning in this case. Together with the existing evidence, these findings support the hypothesis that cortical areas are involved in the visual statistical learning process, and suggest the mechanisms of cortical involvement may be task-dependent and dynamic across time.
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Affiliation(s)
- Abbey S Nydam
- School of Psychology, The University of Queensland, Brisbane, Australia.
| | - David K Sewell
- School of Psychology, The University of Queensland, Brisbane, Australia
| | - Paul E Dux
- School of Psychology, The University of Queensland, Brisbane, Australia
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Grasso PA, Tonolli E, Miniussi C. Effects of different transcranial direct current stimulation protocols on visuo-spatial contextual learning formation: evidence of homeostatic regulatory mechanisms. Sci Rep 2020; 10:4622. [PMID: 32165722 PMCID: PMC7067887 DOI: 10.1038/s41598-020-61626-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 02/27/2020] [Indexed: 11/09/2022] Open
Abstract
In the present study we tested the effects of different transcranial direct current stimulation (tDCS) protocols in the formation of visuo-spatial contextual learning (VSCL). The study comprised three experiments designed to evaluate tDCS-induced changes in VSCL measures collected during the execution of a visual search task widely used to examine statistical learning in the visuo-spatial domain. In Experiment 1, we probed for the effects of left-posterior parietal cortex (PPC) anodal-tDCS (AtDCS) at different timings (i.e. offline and online) and intensities (i.e. 3 mA and 1.5 mA). The protocol producing the more robust effect in Experiment 1 was used in Experiment 2 over the right-PPC, while in Experiment 3, cathodal-tDCS (CtDCS) was applied over the left-PPC only at a high intensity (i.e. 3 mA) but varying timing of application (offline and online). Results revealed that high intensity offline AtDCS reduced VSCL regardless of the stimulation side (Experiment 1 and 2), while no significant behavioral changes were produced by both online AtDCS protocols (Experiment 1) and offline/online CtDCS (Experiment 3). The reduced VSCL could result from homeostatic regulatory mechanisms hindering normal task-related neuroplastic phenomena.
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Affiliation(s)
- Paolo A Grasso
- Centre for Mind/Brain Sciences - CIMeC, University of Trento, Rovereto, TN, Italy.
| | - Elena Tonolli
- Centre for Mind/Brain Sciences - CIMeC, University of Trento, Rovereto, TN, Italy
| | - Carlo Miniussi
- Centre for Mind/Brain Sciences - CIMeC, University of Trento, Rovereto, TN, Italy.
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Zinchenko A, Conci M, Taylor PCJ, Müller HJ, Geyer T. Taking Attention Out of Context: Frontopolar Transcranial Magnetic Stimulation Abolishes the Formation of New Context Memories in Visual Search. J Cogn Neurosci 2018; 31:442-452. [PMID: 30457915 DOI: 10.1162/jocn_a_01358] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
This study investigates the causal contribution of the left frontopolar cortex (FPC) to the processing of violated expectations from learned target-distractor spatial contingencies during visual search. The experiment consisted of two phases: learning and test. Participants searched for targets presented either among repeated or nonrepeated target-distractor configurations. Prior research showed that repeated encounters of identically arranged displays lead to memory about these arrays, which then can come to guide search (contextual cueing effect). The crucial manipulation was a change of the target location, in a nevertheless constant distractor layout, at the transition from learning to test. In addition to this change, we applied repetitive transcranial magnetic stimulation (rTMS) over the left lateral FPC, over a posterior control site, or no rTMS at all (baseline; between-group manipulation) to see how FPC rTMS influences the ability of observers to adapt context-based memories acquired in the training phase. The learning phase showed expedited search in repeated relative to nonrepeated displays, with this context-based facilitation being comparable across all experimental groups. For the test phase, the recovery of cueing was critically dependent on the stimulation site: Although there was evidence of context adaptation toward the end of the experiment in the occipital and no-rTMS conditions, observers with FPC rTMS showed no evidence of relearning at all after target location changes. This finding shows that FPC plays an important role in the regulation of prediction errors in statistical context learning, thus contributing to an update of the spatial target-distractor contingencies after target position changes in learned spatial arrays.
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Affiliation(s)
| | | | | | - Hermann J Müller
- Ludwig-Maximilians-Universität München.,Birkbeck, University of London
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