No Modulation of Visual Cortex Excitability by Transcranial Direct Current Stimulation

Brückner, Sabrina; Kammer, Thomas

doi:10.1371/journal.pone.0167697

Cited by 16 publications

(10 citation statements)

References 43 publications

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“…As in a recently published study of Brückner and Kammer ( 2016 ), previous tDCS studies showed high inter-individual variability in the response to tDCS applied over the visual cortex. Given the high anatomic variability of the visual cortex in relation to the skull (Stensaas et al, 1974 ; Dougherty et al, 2003 ), the approach of referencing the stimulation electrode with the skull-based standard 10/20 EEG system (Brückner and Kammer, 2016 ) seems questionable but is widely used. In a recently published review about tDCS use within the sensory perceptual processing areas (Costa et al, 2015 ), only 6% of all 82 listed studies used an exact electrode position via MRI (3%) or transcranial magnetic stimulation (3%).…”

Section: Discussionmentioning

confidence: 53%

Long-Lasting Enhancement of Visual Perception with Repetitive Noninvasive Transcranial Direct Current Stimulation

Behrens

Kraft

Irlbacher³

et al. 2017

Front. Cell. Neurosci.

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Understanding processes performed by an intact visual cortex as the basis for developing methods that enhance or restore visual perception is of great interest to both researchers and medical practitioners. Here, we explore whether contrast sensitivity, a main function of the primary visual cortex (V1), can be improved in healthy subjects by repetitive, noninvasive anodal transcranial direct current stimulation (tDCS). Contrast perception was measured via threshold perimetry directly before and after intervention (tDCS or sham stimulation) on each day over 5 consecutive days (24 subjects, double-blind study). tDCS improved contrast sensitivity from the second day onwards, with significant effects lasting 24 h. After the last stimulation on day 5, the anodal group showed a significantly greater improvement in contrast perception than the sham group (23 vs. 5%). We found significant long-term effects in only the central 2–4° of the visual field 4 weeks after the last stimulation. We suspect a combination of two factors contributes to these lasting effects. First, the V1 area that represents the central retina was located closer to the polarization electrode, resulting in higher current density. Second, the central visual field is represented by a larger cortical area relative to the peripheral visual field (cortical magnification). This is the first study showing that tDCS over V1 enhances contrast perception in healthy subjects for several weeks. This study contributes to the investigation of the causal relationship between the external modulation of neuronal membrane potential and behavior (in our case, visual perception). Because the vast majority of human studies only show temporary effects after single tDCS sessions targeting the visual system, our study underpins the potential for lasting effects of repetitive tDCS-induced modulation of neuronal excitability.

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Section: Discussionmentioning

confidence: 53%

Long-Lasting Enhancement of Visual Perception with Repetitive Noninvasive Transcranial Direct Current Stimulation

Behrens

Kraft

Irlbacher³

et al. 2017

Front. Cell. Neurosci.

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“…Early studies showed that cathodal stimulation of hMT+ improved visuomotor co‐ordination, while either anodal or cathodal reduced the motion after‐effect . An improvement in acuity has recently been demonstrated following anodal tDCS, but another study did not find any effect of tDCS on visual cortex excitability …”

Section: Discussionmentioning

confidence: 99%

Visual training in hemianopia alters neural activity in the absence of behavioural improvement: a pilot study

Larcombe

Kulyomina

Antonova

et al. 2018

Ophthalmic Physiologic Optic

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BackgroundDamage to the primary visual cortex (V1) due to stroke often results in permanent loss of sight affecting one side of the visual field (homonymous hemianopia). Some rehabilitation approaches have shown improvement in visual performance in the blind region, but require a significant time investment.MethodsSeven patients with cortical damage performed 400 trials of a motion direction discrimination task daily for 5 days. Three patients received anodal transcranial direct current stimulation (tDCS) during training, three received sham stimulation and one had no stimulation. Each patient had an assessment of visual performance and a functional magnetic resonance imaging (fMRI) scan before and after training to measure changes in visual performance and cortical activity.ResultsNo patients showed improvement in visual function due to the training protocol, and application of tDCS had no effect on visual performance. However, following training, the neural response in motion area hMT+ to a moving stimulus was altered. When the stimulus was presented to the sighted hemifield, activity decreased in hMT+ of the damaged hemisphere. There was no change in hMT+ response when the stimulus was presented to the impaired hemifield. There was a decrease in activity in the inferior precuneus after training when the stimulus was presented to either the impaired or sighted hemifield. Preliminary analysis of tDCS data suggested that anodal tDCS interacted with the delivered training, modulating the neural response in hMT+ in the healthy side of the brain.ConclusionTraining can affect the neural responses in hMT+ even in the absence of change in visual performance.

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“…In the oddball task, subjects heard a sequence of two beep tones with different frequencies (300 and 500 Hz, 0.2 s each, every 2.5 seconds) through in-ear-headphones, and were asked to silently count the rare beeps without using their fingers [cf. 16,23]. The number of rare beeps was adjusted between 20 and 30 in a 10 minutes train.…”

Section: Experimental Designmentioning

confidence: 99%

“…This notion does not only hold for iTBS. In a former study [23] we investigated the effects of transcranial direct current stimulation (tDCS) on visual cortex excitability. Subjects took part in…”

Section: Plos Onementioning

confidence: 99%

“…two sessions, which only differed after the tDCS intervention, but included an identical poststimulation measurement. Only for cathodal tDCS a medium reliability was observed in the post-stimulation measurement, and overall a high variability in response to tDCS was found [23]. Therefore any study investigating the modulatory effect of a cortical stimulation including tSMS would be well advised to repeat the intervention in order to estimate the real effect.…”

Section: Plos Onementioning

confidence: 99%

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Ten minutes of transcranial static magnetic field stimulation does not reliably modulate motor cortex excitability

2020

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Recently, modulatory effects of static magnetic field stimulation (tSMS) on excitability of the motor cortex have been reported. In our previous study we failed to replicate these results. It was suggested that the lack of modulatory effects was due to the use of an auditory oddball task in our study. Thus, we aimed to evaluate the role of an oddball task on the effects of tSMS on motor cortex excitability. In a within-subject-design we compared 10 minutes tSMS with and without oddball task. In one of the two sessions subjects had to solve an auditory oddball task during the exposure to the magnet, whereas there was no task during exposure in the other session. Motor cortex excitability was measured before and after tSMS. No modulation was observed in any condition. However, when data were pooled regarding the order of the sessions, a trend for an increase of excitability was observed in the first session compared to the second session. We now can rule out that the auditory oddball task destroys tSMS effects, as postulated. Our results rather suggest that fluctuations in the amplitudes of single pulse motor evoked potentials may possibly mask weak modulatory effects but may also lead to false positive results if the number of subjects in a study is too low. In addition, there might be a habituation effect to the whole procedure, resulting in less variability when subjects underwent the same experiment twice.

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No Modulation of Visual Cortex Excitability by Transcranial Direct Current Stimulation

Cited by 16 publications

References 43 publications

Long-Lasting Enhancement of Visual Perception with Repetitive Noninvasive Transcranial Direct Current Stimulation

Long-Lasting Enhancement of Visual Perception with Repetitive Noninvasive Transcranial Direct Current Stimulation

Visual training in hemianopia alters neural activity in the absence of behavioural improvement: a pilot study

Ten minutes of transcranial static magnetic field stimulation does not reliably modulate motor cortex excitability

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