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Wu D, Wang Y, Liu N, Wang P, Sun K, Zhang P. Posttraining anodal tDCS improves early consolidation of visual perceptual learning. Clin Neurophysiol 2023; 146:89-96. [PMID: 36563555 DOI: 10.1016/j.clinph.2022.11.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 11/21/2022] [Accepted: 11/26/2022] [Indexed: 12/12/2022]
Abstract
OBJECTIVE We aimed to investigate the transcranial direct current stimulation (tDCS)-induced facilitation of early consolidation over a period of extended training sessions and explored the effect of tDCS on visual perceptual learning (VPL) improvement during online learning and offline consolidation. METHODS In the current double-blind sham-controlled study, twenty-four healthy participants were trained on coherent motion direction identification for 5 consecutive sessions. Performance was assessed at the pre- and posttests. Anodal or sham tDCS of the left human middle temporal region (hMT+) was applied immediately after the completion of daily training (termed early consolidation). RESULTS The magnitude of improvement between anodal and sham tDCS was marginally significant, supporting the beneficial effect of anodal tDCS on VPL by stimulating early consolidation. Additionally, anodal tDCS induced a larger improvement between the first two training sessions than sham tDCS. No effect of anodal tDCS was found on the within-session improvement. CONCLUSIONS The above results indicated that anodal tDCS facilitates offline consolidation during the early period of the whole training series, not online learning. The possible neural mechanisms and limitations (sample size and persistent effects) were discussed. SIGNIFICANCE Our findings support the use of the combination of tDCS and behavioral training in facilitating visual rehabilitation and contribute to a deeper understanding of learning processes by neuromodulation procedures.
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Affiliation(s)
- Di Wu
- Department of Medical Psychology, Air Force Medical University, Xi'an, China; Department of Neurobiology, Basic Medical School, Air Force Medical University, Xi'an, China
| | - Yifan Wang
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
| | - Na Liu
- Department of Nursing, Air Force Medical University, Xi'an, China
| | - Panhui Wang
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
| | - Kewei Sun
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
| | - Pan Zhang
- Department of Psychology, Hebei Normal University, Shijiazhuang, China.
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2
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Wu D, Zhang P, Wang Y, Liu N, Sun K, Wang P, Xiao W. Anodal online transcranial direct current stimulation facilitates visual motion perceptual learning. Eur J Neurosci 2023; 57:479-489. [PMID: 36511948 DOI: 10.1111/ejn.15895] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Revised: 12/07/2022] [Accepted: 12/08/2022] [Indexed: 12/15/2022]
Abstract
Visual perceptual learning (VPL) has great potential implications for clinical populations, but adequate improvement often takes weeks to months to obtain; therefore, practical applications of VPL are limited. Strategies that enhance visual performance acquisition make great practical sense. Transcranial direct current stimulation (tDCS) could be beneficial to VPL, but thus far, the results are inconsistent. The current study had two objectives: (1) to investigate the effect of anodal tDCS on VPL and (2) to determine whether the timing sequence of anodal tDCS and training influences VPL. Anodal tDCS was applied on the left human middle temporal (hMT+) during training on a coherent motion discrimination task (online), anodal tDCS was also applied before training (offline) and sham tDCS was applied during training (sham). The coherent thresholds were measured without stimulation before, 2 days after and 1 month after training. All participants trained for five consecutive days. Anodal tDCS resulted in more performance improvement when applied during daily training but not when applied before training. Additionally, neither within-session improvement nor between-session improvement differed among the online, offline and sham tDCS conditions. These findings contribute to the development of efficient stimulation protocols and a deep understanding of the mechanisms underlying the effect of tDCS on VPL.
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Affiliation(s)
- Di Wu
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
- Department of Neurobiology, Basic Medical School, Air Force Medical University, Xi'an, China
| | - Pan Zhang
- Department of Psychology, Hebei Normal University, Shijiazhuang, China
| | - Yifan Wang
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
| | - Na Liu
- Department of Nursing, Air Force Medical University, Xi'an, China
| | - Kewei Sun
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
| | - Panhui Wang
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
| | - Wei Xiao
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
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3
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Bello UM, Wang J, Park ASY, Tan KWS, Cheung BWS, Thompson B, Cheong AMY. Can visual cortex non-invasive brain stimulation improve normal visual function? A systematic review and meta-analysis. Front Neurosci 2023; 17:1119200. [PMID: 36937668 PMCID: PMC10017867 DOI: 10.3389/fnins.2023.1119200] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 02/13/2023] [Indexed: 03/06/2023] Open
Abstract
Objective Multiple studies have explored the use of visual cortex non-invasive brain stimulation (NIBS) to enhance visual function. These studies vary in sample size, outcome measures, and methodology. We conducted a systematic review and meta-analyses to assess the effects of NIBS on visual functions in human participants with normal vision. Methods We followed the PRISMA guidelines, and a review protocol was registered with PROSPERO before study commencement (CRD42021255882). We searched Embase, Medline, PsychInfo, PubMed, OpenGrey and Web of Science using relevant keywords. The search covered the period from 1st January 2000 until 1st September 2021. Comprehensive meta-analysis (CMA) software was used for quantitative analysis. Results Fifty studies were included in the systematic review. Only five studies utilized transcranial magnetic stimulation (TMS) and no TMS studies met our pre-specified criteria for meta-analysis. Nineteen transcranial electrical stimulation studies (tES, 38%) met the criteria for meta-analysis and were the focus of our review. Meta-analysis indicated acute effects (Hedges's g = 0.232, 95% CI: 0.023-0.442, p = 0.029) and aftereffects (0.590, 95% CI: 0.182-0.998, p = 0.005) of tES on contrast sensitivity. Visual evoked potential (VEP) amplitudes were significantly enhanced immediately after tES (0.383, 95% CI: 0.110-0.665, p = 0.006). Both tES (0.563, 95% CI: 0.230-0.896, p = 0.001) and anodal-transcranial direct current stimulation (a-tDCS) alone (0.655, 95% CI: 0.273-1.038, p = 0.001) reduced crowding in peripheral vision. The effects of tES on visual acuity, motion perception and reaction time were not statistically significant. Conclusion There are significant effects of visual cortex tES on contrast sensitivity, VEP amplitude, an index of cortical excitability, and crowding among normally sighted individuals. Additional studies are required to enable a comparable meta-analysis of TMS effects. Future studies with robust experimental designs are needed to extend these findings to populations with vision loss. Clinical trial registration ClinicalTrials.gov/, identifier CRD42021255882.
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Affiliation(s)
- Umar M. Bello
- Centre for Eye and Vision Research, Hong Kong Science Park, Hong Kong, Hong Kong SAR, China
- Department of Physiotherapy and Paramedicine, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, United Kingdom
| | - Jingying Wang
- School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
| | - Adela S. Y. Park
- Centre for Eye and Vision Research, Hong Kong Science Park, Hong Kong, Hong Kong SAR, China
| | - Ken W. S. Tan
- Centre for Eye and Vision Research, Hong Kong Science Park, Hong Kong, Hong Kong SAR, China
| | - Blossom W. S. Cheung
- Centre for Eye and Vision Research, Hong Kong Science Park, Hong Kong, Hong Kong SAR, China
| | - Benjamin Thompson
- Centre for Eye and Vision Research, Hong Kong Science Park, Hong Kong, Hong Kong SAR, China
- School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, Canada
| | - Allen M. Y. Cheong
- Centre for Eye and Vision Research, Hong Kong Science Park, Hong Kong, Hong Kong SAR, China
- School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
- *Correspondence: Allen M. Y. Cheong,
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Perspectives on the Combined Use of Electric Brain Stimulation and Perceptual Learning in Vision. Vision (Basel) 2022; 6:vision6020033. [PMID: 35737420 PMCID: PMC9227313 DOI: 10.3390/vision6020033] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 06/07/2022] [Accepted: 06/08/2022] [Indexed: 11/29/2022] Open
Abstract
A growing body of literature offers exciting perspectives on the use of brain stimulation to boost training-related perceptual improvements in humans. Recent studies suggest that combining visual perceptual learning (VPL) training with concomitant transcranial electric stimulation (tES) leads to learning rate and generalization effects larger than each technique used individually. Both VPL and tES have been used to induce neural plasticity in brain regions involved in visual perception, leading to long-lasting visual function improvements. Despite being more than a century old, only recently have these techniques been combined in the same paradigm to further improve visual performance in humans. Nonetheless, promising evidence in healthy participants and in clinical population suggests that the best could still be yet to come for the combined use of VPL and tES. In the first part of this perspective piece, we briefly discuss the history, the characteristics, the results and the possible mechanisms behind each technique and their combined effect. In the second part, we discuss relevant aspects concerning the use of these techniques and propose a perspective concerning the combined use of electric brain stimulation and perceptual learning in the visual system, closing with some open questions on the topic.
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5
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Richard B, Shafto P. Sensitivity to the slope of the amplitude spectrum is dependent on the spectral slopes of recently viewed environments: A visual adaptation study in modified reality. Vision Res 2022; 197:108056. [PMID: 35489239 DOI: 10.1016/j.visres.2022.108056] [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: 09/08/2021] [Revised: 04/06/2022] [Accepted: 04/13/2022] [Indexed: 11/29/2022]
Abstract
Scenes contain many statistical regularities that could benefit visual processing if accounted for by the visual system. One such statistic is the orientation-averaged slope (α) of the amplitude spectrum of natural scenes. Human observers show different discrimination sensitivity to α: sensitivity is highest for α values between 1.0 and 1.2 and decreases as α is steepened or shallowed. The range of α for peak discrimination sensitivity is concordant with the average α of natural scenes, which may indicate that visual mechanisms are optimized to process information at α values commonly encountered in the environment. Here we explore the association between peak discrimination sensitivity and the most viewed αs in natural environments. Specifically, we verified whether discrimination sensitivity depends on the recently viewed environments. Observers were immersed, using a Head-Mounted Display, in an environment that was either unaltered or had its average α steepened or shallowed by 0.4. Discrimination thresholds were affected by the average shift in α, but this effect was most prominent following adaptation to a shallowed environment. We modeled these data with a Bayesian observer and explored whether a change in the prior or a change in the likelihood best explained the psychophysical effects. Change in discrimination thresholds following adaptation could be explained by a shift in the central tendency of the prior concordant with the shift of the environment, in addition to a change in the likelihood. Our findings suggest that expectations on the occurrence of α that result from a lifetime of exposure remain plastic and able to accommodate for the statistical structure of recently viewed environments.
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Affiliation(s)
- Bruno Richard
- Department of Mathematics and Computer Science, Rutgers University - Newark, 101 Warren Street, Rm 216, Newark, NJ 07102, USA.
| | - Patrick Shafto
- Department of Mathematics and Computer Science, Rutgers University - Newark, 101 Warren Street, Rm 216, Newark, NJ 07102, USA; School of Mathematics, Institute for Advanced Study, Princeton, NJ, USA
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Wu D, Zhou Y, Lv H, Liu N, Zhang P. The initial visual performance modulates the effects of anodal transcranial direct current stimulation over the primary visual cortex on the contrast sensitivity function. Neuropsychologia 2021; 156:107854. [PMID: 33823163 DOI: 10.1016/j.neuropsychologia.2021.107854] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 03/09/2021] [Accepted: 03/31/2021] [Indexed: 10/21/2022]
Abstract
Transcranial direct current stimulation (tDCS) has great potential to modulate cortical excitability and further facilitate visual function or rehabilitation. However, tDCS modulation effects are largely variable, possibly because of the individual differences in initial performance. The present study investigated the influence of the initial performance on contrast sensitivity function (CSF) following tDCS. Fifty healthy participants were randomly assigned to three groups: anodal, cathodal and sham stimulation. The CSF was measured through a grating detection task before and immediately after tDCS. Active and reference electrodes were applied to the primary occipital cortex (Oz) and the middle of the head (Cz) for 20 min with an intensity of 1.5 mA, respectively. Compared with sham stimulation, anodal or cathodal stimulation had no effect on the area under the log CSF (AULCSF) or contrast sensitivity (CS) of various spatial frequencies at the group level. However, a negative relationship was found between initial performance and the AULCSF change (or CS change at a spatial of frequency 8 c/°) after the application of anodal tDCS, indicating that the degree of change was dependent on initial performance, with greater gains observed for those with poorer initial performance. Initial performance modulated the effect of anodal tDCS over the Oz on the CSF, indicating that the Oz plays a crucial role in visual function. These results contribute to a deep understanding of the mechanisms of tDCS and to the design of more precise and efficient personalized simulation approaches based on individual differences.
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Affiliation(s)
- Di Wu
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
| | - YingJie Zhou
- Basic Medical School, Air Force Medical University, Xi'an, China
| | - Haixu Lv
- Basic Medical School, Air Force Medical University, Xi'an, China
| | - Na Liu
- Department of Nursing, Air Force Medical University, Xi'an, China
| | - Pan Zhang
- Department of Psychology, Hebei Normal University, Shijiazhuang, China.
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7
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Wu D, Li C, Liu N, Xu P, Xiao W. Visual motion perception improvements following direct current stimulation over V5 are dependent on initial performance. Exp Brain Res 2020; 238:2409-2416. [PMID: 32776173 DOI: 10.1007/s00221-020-05842-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 05/25/2020] [Indexed: 11/26/2022]
Abstract
Transcranial direct current stimulation (tDCS) can improve visual perception. However, the effect of tDCS on visual perception is largely variable, possibly due to individual differences in initial performance. The goal of the present study was to evaluate the dependency of visual motion perception improvements on initial performance. Twenty-eight observers were randomly divided into two groups. Anodal tDCS and sham stimulation were separately applied to V5 (1.5 mA, 20 min), while observers performed a coherent motion direction identification task. The results showed that compared to sham stimulation, anodal tDCS induced a significant improvement in motion perception that lasted at least 20 min. In addition, the degree of improvement was dependent on initial performance, with a greater improvement magnitude observed for those with poorer initial performance. These results may have implications for understanding the nature of the stimulation rule and for the use of a customised stimulation protocol to enhance tDCS efficiency in practical applications.
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Affiliation(s)
- Di Wu
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
| | - Chenxi Li
- Scholl of Nursing, Yueyang Vocational Technical College, Yueyang, China
| | - Na Liu
- Department of Nursing, Air Force Medical University, Xi'an, China
| | - Pengbo Xu
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
| | - Wei Xiao
- Department of Medical Psychology, Air Force Medical University, Xi'an, China.
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8
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Wu D, Zhang P, Li C, Liu N, Jia W, Chen G, Ren W, Sun Y, Xiao W. Perceptual Learning at Higher Trained Cutoff Spatial Frequencies Induces Larger Visual Improvements. Front Psychol 2020; 11:265. [PMID: 32153473 PMCID: PMC7047335 DOI: 10.3389/fpsyg.2020.00265] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 02/04/2020] [Indexed: 12/29/2022] Open
Abstract
It is well known that extensive practice of a perceptual task can improve visual performance, termed perceptual learning. The goal of the present study was to evaluate the dependency of visual improvements on the features of training stimuli (i.e., spatial frequency). Twenty-eight observers were divided into training and control groups. Visual acuity (VA) and contrast sensitivity function (CSF) were measured and compared before and after training. All observers in the training group were trained in a monocular grating detection task near their individual cutoff spatial frequencies. The results showed that perceptual learning induced significant visual improvement, which was dependent on the cutoff spatial frequency, with a greater improvement magnitude and transfer of perceptual learning observed for those trained with higher spatial frequencies. However, VA significantly improved following training but was not related to the cutoff spatial frequency. The results may broaden the understanding of the nature of the learning rule and the neural plasticity of different cortical areas.
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Affiliation(s)
- Di Wu
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
| | - Pan Zhang
- Department of Psychology, The Ohio State University, Columbus, OH, United States
| | - Chenxi Li
- School of Nursing, Yueyang Vocational Technical College, Yueyang, China
| | - Na Liu
- Department of Nursing, Air Force Medical University, Xi'an, China
| | - Wuli Jia
- Department of Psychology, School of Education Science, Huaiyin Normal University, Huai'an, China
| | - Ge Chen
- School of Arts and Design, Zhengzhou University of Light Industry, Zhengzhou, China
| | - Weicong Ren
- Department of Psychology, Hebei Normal University, Shijiazhuang, China
| | - Yuqi Sun
- Department of Systems Neuroscience, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Wei Xiao
- Department of Medical Psychology, Air Force Medical University, Xi'an, China
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9
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Battaglini L, Contemori G, Penzo S, Maniglia M. tRNS effects on visual contrast detection. Neurosci Lett 2020; 717:134696. [PMID: 31846733 DOI: 10.1016/j.neulet.2019.134696] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 11/21/2019] [Accepted: 12/13/2019] [Indexed: 12/21/2022]
Abstract
In recent years, transcranial electrical stimulation (tES) has been used to improve cognitive and perceptual abilities and to boost learning. In the visual domain, transcranial random noise stimulation (tRNS), a type of tES in which electric current is randomly alternating in between two electrodes at high frequency, has shown potential in inducing long lasting perceptual improvements when coupled with tasks such as contrast detection. However, its cortical mechanisms and online effects have not been fully understood yet, and it is still unclear whether these long-term improvements are due to early-stage perceptual enhancements of contrast sensitivity or later stage mechanisms such as learning consolidation. Here we tested tRNS effects on multiple spatial frequencies and orientation, showing that tRNS enhances detection of a low contrast Gabor, but only for oblique orientation and high spatial frequency (12 cycles per degree of visual angle). No improvement was observed for low contrast and vertical stimuli. These results indicate that tRNS can enhance contrast sensitivity already after one training session, however this early onset is dependent on characteristics of the stimulus such as spatial frequency and orientation. In particular, the shallow depth of tRNS is likely to affect superficial layers of the visual cortex where neurons have higher preferred spatial frequencies than cells in further layers, while the lack of effect on vertical stimuli might reflect the optimization of the visual system to see cardinally oriented low contrast stimuli, leaving little room for short-term improvement. Taken together, these results suggest that online tRNS effects on visual perception are the result of a complex interaction between stimulus intensity and cortical anatomy, consistent with previous literature on brain stimulation.
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Affiliation(s)
- Luca Battaglini
- Department of General Psychology, University of Padova, Padova, Italy; Neuro.Vis.U.S. Laboratory, University of Padova, Padova, Italy.
| | - Giulio Contemori
- Department of General Psychology, University of Padova, Padova, Italy; Neuro.Vis.U.S. Laboratory, University of Padova, Padova, Italy; Université de Toulouse-UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France
| | - Sofia Penzo
- Department of General Psychology, University of Padova, Padova, Italy
| | - Marcello Maniglia
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA.
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10
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He Q, Lin BR, Zhao J, Shi YZ, Yan FF, Huang CB. No effects of anodal transcranial direct current stimulation on contrast sensitivity function. Restor Neurol Neurosci 2019; 37:109-118. [DOI: 10.3233/rnn-180881] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Qing He
- Key Laboratory of Behavioral Sciences, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Bo-Rong Lin
- Key Laboratory of Behavioral Sciences, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Jin Zhao
- Key Laboratory of Behavioral Sciences, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Ying-Zhen Shi
- Key Laboratory of Behavioral Sciences, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Fang-Fang Yan
- Key Laboratory of Behavioral Sciences, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Chang-Bing Huang
- Key Laboratory of Behavioral Sciences, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
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11
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Transcranial Random Noise Stimulation of Visual Cortex: Stochastic Resonance Enhances Central Mechanisms of Perception. J Neurosci 2017; 36:5289-98. [PMID: 27170126 DOI: 10.1523/jneurosci.4519-15.2016] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/26/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Random noise enhances the detectability of weak signals in nonlinear systems, a phenomenon known as stochastic resonance (SR). Though counterintuitive at first, SR has been demonstrated in a variety of naturally occurring processes, including human perception, where it has been shown that adding noise directly to weak visual, tactile, or auditory stimuli enhances detection performance. These results indicate that random noise can push subthreshold receptor potentials across the transfer threshold, causing action potentials in an otherwise silent afference. Despite the wealth of evidence demonstrating SR for noise added to a stimulus, relatively few studies have explored whether or not noise added directly to cortical networks enhances sensory detection. Here we administered transcranial random noise stimulation (tRNS; 100-640 Hz zero-mean Gaussian white noise) to the occipital region of human participants. For increasing tRNS intensities (ranging from 0 to 1.5 mA), the detection accuracy of a visual stimuli changed according to an inverted-U-shaped function, typical of the SR phenomenon. When the optimal level of noise was added to visual cortex, detection performance improved significantly relative to a zero noise condition (9.7 ± 4.6%) and to a similar extent as optimal noise added to the visual stimuli (11.2 ± 4.7%). Our results demonstrate that adding noise to cortical networks can improve human behavior and that tRNS is an appropriate tool to exploit this mechanism. SIGNIFICANCE STATEMENT Our findings suggest that neural processing at the network level exhibits nonlinear system properties that are sensitive to the stochastic resonance phenomenon and highlight the usefulness of tRNS as a tool to modulate human behavior. Since tRNS can be applied to all cortical areas, exploiting the SR phenomenon is not restricted to the perceptual domain, but can be used for other functions that depend on nonlinear neural dynamics (e.g., decision making, task switching, response inhibition, and many other processes). This will open new avenues for using tRNS to investigate brain function and enhance the behavior of healthy individuals or patients.
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12
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Wang X, Wang H, Huang J, Zhou Y, Tzvetanov T. Bayesian Inference of Two-Dimensional Contrast Sensitivity Function from Data Obtained with Classical One-Dimensional Algorithms Is Efficient. Front Neurosci 2017; 10:616. [PMID: 28119563 PMCID: PMC5222793 DOI: 10.3389/fnins.2016.00616] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 12/26/2016] [Indexed: 11/13/2022] Open
Abstract
The contrast sensitivity function that spans the two dimensions of contrast and spatial frequency is crucial in predicting functional vision both in research and clinical applications. In this study, the use of Bayesian inference was proposed to determine the parameters of the two-dimensional contrast sensitivity function. Two-dimensional Bayesian inference was extensively simulated in comparison to classical one-dimensional measures. Its performance on two-dimensional data gathered with different sampling algorithms was also investigated. The results showed that the two-dimensional Bayesian inference method significantly improved the accuracy and precision of the contrast sensitivity function, as compared to the more common one-dimensional estimates. In addition, applying two-dimensional Bayesian estimation to the final data set showed similar levels of reliability and efficiency across widely disparate and established sampling methods (from classical one-dimensional sampling, such as Ψ or staircase, to more novel multi-dimensional sampling methods, such as quick contrast sensitivity function and Fisher information gain). Furthermore, the improvements observed following the application of Bayesian inference were maintained even when the prior poorly matched the subject's contrast sensitivity function. Simulation results were confirmed in a psychophysical experiment. The results indicated that two-dimensional Bayesian inference of contrast sensitivity function data provides similar estimates across a wide range of sampling methods. The present study likely has implications for the measurement of contrast sensitivity function in various settings (including research and clinical settings) and would facilitate the comparison of existing data from previous studies.
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Affiliation(s)
- Xiaoxiao Wang
- CAS Key Laboratory of Brain Function and Diseases and School of Life Sciences, University of Science and Technology of ChinaHefei, China; Centers for Biomedical Engineering, University of Science and Technology of ChinaHefei, China
| | - Huan Wang
- CAS Key Laboratory of Brain Function and Diseases and School of Life Sciences, University of Science and Technology of China Hefei, China
| | - Jinfeng Huang
- CAS Key Laboratory of Brain Function and Diseases and School of Life Sciences, University of Science and Technology of China Hefei, China
| | - Yifeng Zhou
- CAS Key Laboratory of Brain Function and Diseases and School of Life Sciences, University of Science and Technology of China Hefei, China
| | - Tzvetomir Tzvetanov
- CAS Key Laboratory of Brain Function and Diseases and School of Life Sciences, University of Science and Technology of China Hefei, China
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