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Electrical Stimulation of Visual Cortex Can Immediately Improve Spatial Vision.

ABSTRACT: We can improve human vision by correcting the optics of our lenses [1-3]. However, after the eye transduces the light, visual cortex has its own limitations that are challenging to correct [4]. Overcoming these limitations has typically involved innovative training regimes that improve vision across many days [5, 6]. In the present study, we wanted to determine whether it is possible to immediately improve the precision of spatial vision with noninvasive direct-current stimulation. Previous work suggested that visual processing could be modulated with such stimulation [7-9]. However, the short duration and variability of such effects made it seem unlikely that spatial vision could be improved for more than several minutes [7, 10]. Here we show that visual acuity in the parafoveal belt can be immediately improved by delivering noninvasive direct current to visual cortex. Twenty minutes of anodal stimulation improved subjects' vernier acuity by approximately 15% and increased the amplitude of the earliest visually evoked potentials in lockstep with the behavioral effects. When we reversed the orientation of the electric field, we impaired resolution and reduced the amplitude of visually evoked potentials. Next, we found that anodal stimulation improved acuity enough to be measurable with the relatively coarse Snellen test and that subjects with the poorest acuity benefited the most from stimulation. Finally, we found that stimulation-induced acuity improvements were accompanied by changes in contrast sensitivity at high spatial frequencies.

SUBMITTER: Reinhart RM

PROVIDER: S-EPMC4961578 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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Electrical Stimulation of Visual Cortex Can Immediately Improve Spatial Vision.

Reinhart Robert M G RM Xiao Wenxi W McClenahan Laura J LJ Woodman Geoffrey F GF

Current biology : CB 20160630 14

We can improve human vision by correcting the optics of our lenses [1-3]. However, after the eye transduces the light, visual cortex has its own limitations that are challenging to correct [4]. Overcoming these limitations has typically involved innovative training regimes that improve vision across many days [5, 6]. In the present study, we wanted to determine whether it is possible to immediately improve the precision of spatial vision with noninvasive direct-current stimulation. Previous work ...[more]

PMID: 27374337

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Project description:ObjectiveMultiple 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.MethodsWe 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.ResultsFifty 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.ConclusionThere 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 registrationClinicalTrials.gov/, identifier CRD42021255882.

Project description:Current standards for safe delivery of electrical stimulation to the central nervous system are based on foundational studies which examined post-mortem tissue for histological signs of damage. This set of observations and the subsequently proposed limits to safe stimulation, termed the “Shannon limits,” allow for a simple calculation (using charge per phase and charge density) to determine the intensity of electrical stimulation that can be delivered safely to brain tissue. In the three decades since the Shannon limits were reported, advances in molecular biology have allowed for more nuanced and detailed approaches to be used to expand current understanding of the physiological effects of stimulation. Here, we investigated spatial transcriptomics as a new approach to assess the safety and efficacy of electrical stimulation in the brain. Electrical stimulation was delivered to the rat visual cortex with either acute or chronic electrode implantation procedures (acute: tissue collection 3 hours post-stimulation on the day of surgery; chronic: stimulation delivered 1-month post-implantation, and tissue collection 24 hours later). To explore the influence of device type and stimulation parameters, we used carbon fiber ultramicroelectrode arrays (7 µm diameter) and microwire electrode arrays (50 µm diameter) delivering charge and charge density levels selected above and below reported tissue damage thresholds (range: 2-20 nC, 0.1-1 mC/cm2). Spatial transcriptomics was performed using Visium Spatial Gene Expression Slides (10x Genomics), which enabled simultaneous immunohistochemistry and spatial transcriptomics to directly compare traditional histological metrics to transcriptional profiles within each tissue sample. Our data revealed unique spatial patterns of differentially expressed genes that are related to cellular processes including inflammation, cell cycle progression, and plasticity. Effects were dependent on stimulation parameters and were localized to both traditional and ultra-small device locations. The abundance of data gathered using this approach allows for sophisticated analysis that can be used to generate new hypotheses while also revealing novel potential biomarkers of neurostimulation.

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Electrical Stimulation of Visual Cortex Can Immediately Improve Spatial Vision.

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Electrical Stimulation of Visual Cortex Can Immediately Improve Spatial Vision.

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