FV 6 Sustained GABA reduction induced by anodal Transcranial direct current stimulation (tDCS) in motor cortex – a proton magnetic resonance spectroscopy study

Patel, Harshal; Romanzetti, Sandro; Pellicano, Antonello; Reetz, Kathrin; Binkofski, Ferdinand

doi:10.1016/j.clinph.2017.06.048

Cited by 3 publications

(5 citation statements)

References 4 publications

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“…In addition, as predicted by animal models, GABA may play a role in regulating human cortical plasticity. Magnetic resonance spectroscopy (MRS) studies have shown that the neuromodulation technique anodal transcranial direct current stimulation (a-tDCS) reduces GABA concentration in the adult motor cortex and that larger GABA reductions are associated with increased motor learning (Stagg et al, 2011; Patel et al, 2017). A-tDCS can also temporarily improve vision in adults with amblyopia, perhaps by modulating GABA concentration (Spiegel et al, 2013a, 2013b; Ding et al, 2016; Castaño-Castaño et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Older Adults Exhibit Greater Visual Cortex Inhibition and Reduced Visual Cortex Plasticity Compared to Younger Adults

2019

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Recent evidence indicates that inhibition within the visual cortex is greater in older than young adults. Increased inhibition has been associated with reduced visual cortex plasticity in animal models. We investigated whether age-related increases in human visual cortex inhibition occur in conjunction with reduced visual cortex plasticity. Visual cortex inhibition was measured psychophysically using binocular rivalry alternation rates (AR) for dichoptic gratings. Slower ARs are associated with a greater concentration of the inhibitory neurotransmitter GABA within the human visual cortex. Visual cortex plasticity was measured using an established paradigm for induction of long-term potentiation (LTP) -like increases in visually evoked potential (VEP) amplitude. Following rapid visual stimulation, greater increases in VEP amplitude indicate greater visual cortex plasticity. The study involved two groups; young (18–40 years, n = 29) and older adults (60–80 years, n = 18). VEPs were recorded for a 1 Hz onset/offset checkerboard stimulus before and after 9 Hz visual stimulation with the same stimulus. ARs were slower in older than young adults. In contrast to most previous studies, VEP amplitudes were significantly reduced following the rapid visual stimulation for young adults; older adult VEP amplitudes were unaffected. Our AR results replicate previous observations of increased visual cortex inhibition in the older adults. Rapid visual stimulation significantly altered VEP amplitude in young adults, albeit in the opposite direction than predicted. VEP amplitudes did not change in older adults suggesting an association between increased inhibition and reduced plasticity within the human visual cortex.

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Section: Introductionmentioning

confidence: 99%

Older Adults Exhibit Greater Visual Cortex Inhibition and Reduced Visual Cortex Plasticity Compared to Younger Adults

2019

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“…Although the specific mechanisms that underlie the effects of visual cortex a-tDCS are unknown, the effects of motor cortex a-tDCS are attributed in part to a reduction in cortical inhibition mediated by the neurotransmitter gamma amino-butyric acid (GABA). Specifically, magnetic resonance spectroscopy measures indicate that a-tDCS reduces motor cortex GABA concentration [12][13][14][15][16][17][18]. We anticipated that a similar reduction in GABA concentration occurs when a-tDCS is applied to the visual cortex based on previous results that are consistent with such an effect.…”

Section: Introductionmentioning

confidence: 77%

“…We tested the hypothesis that visual cortex a-tDCS, which has been observed to reduce regional GABA concentration [13,17], acts to reduce GABA-mediated inhibition within visual cortex as evidenced by increased binocular rivalry mixed percept duration [27]. Mixed percept duration during binocular rivalry has been causally linked to visual cortex GABA concentration through pharmacological antagonism of GABA a and GABA b receptors [27].…”

Section: Discussionmentioning

confidence: 99%

Visual cortex cTBS increases mixed percept duration while a-tDCS has no effect on binocular rivalry

2021

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Neuromodulation of the primary visual cortex using anodal transcranial direct current stimulation (a-tDCS) can alter visual perception and enhance neuroplasticity. However, the mechanisms that underpin these effects are currently unknown. When applied to the motor cortex, a-tDCS reduces the concentration of the inhibitory neurotransmitter gamma aminobutyric acid (GABA), an effect that has been linked to increased neuroplasticity. The aim of this study was to assess whether a-tDCS also reduces GABA-mediated inhibition when applied to the human visual cortex. Changes in visual cortex inhibition were measured using the mixed percept duration in binocular rivalry. Binocular rivalry mixed percept duration has recently been advocated as a direct and sensitive measure of visual cortex inhibition whereby GABA agonists decrease mixed percept durations and agonists of the excitatory neurotransmitter acetylcholine (ACH) increase them. Our hypothesis was that visual cortex a-tDCS would increase mixed percept duration by reducing GABA-mediated inhibition and increasing cortical excitation. In addition, we measured the effect of continuous theta-burst transcranial magnetic stimulation (cTBS) of the visual cortex on binocular rivalry dynamics. When applied to the motor or visual cortex, cTBS increases GABA concentration and we therefore hypothesized that visual cortex cTBS would decrease the mixed percept duration. Binocular rivalry dynamics were recorded before and after active and sham a-tDCS (N = 15) or cTBS (N = 15). Contrary to our hypotheses, a-tDCS had no effect, whereas cTBS increased mixed percepts during rivalry. These results suggest that the neurochemical mechanisms of a-tDCS may differ between the motor and visual cortices.

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“…Although the specific mechanisms that underlie the effects of visual cortex a-tDCS are unknown, the effects of motor cortex a-tDCS are attributed in part to a reduction in cortical inhibition mediated by the neurotransmitter gamma amino-butyric acid (GABA). Specifically, magnetic resonance spectroscopy measures indicate that a-tDCS reduces motor cortex GABA concentration (12)(13)(14)(15)(16)(17)(18). We anticipated that a similar reduction in GABA concentration occurs when a-tDCS is applied to the visual cortex on the basis of previous results that are consistent with such an effect.…”

Section: Introductionmentioning

confidence: 82%

“…We also hypothesized that visual cortex cTBS would have the opposite effect to a-tDCS and increase mixed percept duration. This is because while motor cortex a-tDCS has been observed to reduce regional GABA concentration (13,17), cTBS applied to the motor cortex (28) or visual cortex (25) increases GABA concentration.…”

Section: Discussionmentioning

confidence: 99%

Visual cortex cTBS increases mixed percept duration while a-tDCS has no effect on binocular rivalry

Abuleil

McCulloch

Thompson

2020

Preprint

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Neuromodulation of the primary visual cortex using anodal transcranial direct current stimulation (a-tDCS) can alter visual perception and enhance neuroplasticity. However, the mechanisms that underpin these effects are currently unknown. When applied to the motor cortex, a-tDCS reduces the concentration of the inhibitory neurotransmitter gamma aminobutyric acid (GABA), an effect that has been linked to increased neuroplasticity. The aim of this study was to assess whether a-tDCS also reduces GABA-mediated inhibition when applied to the human visual cortex. Changes in visual cortex inhibition were measured using the mixed percept duration in binocular rivalry. Binocular rivalry mixed percept duration has recently been advocated as a direct and sensitive measure of visual cortex inhibition whereby GABA agonists decrease mixed percept durations and agonists of the excitatory neurotransmitter acetylcholine increase them. Our hypothesis was that visual cortex a-tDCS would increase mixed percept duration by reducing GABA-mediated inhibition and increasing cortical excitation. In addition, we measured the effect of continuous theta-burst transcranial magnetic stimulation (cTBS) of the visual cortex on binocular rivalry dynamics. When applied to the motor or visual cortex, cTBS increases GABA concentration and we therefore hypothesized that visual cortex cTBS would decrease the mixed percept duration. Binocular rivalry dynamics were recorded before and after active and sham a-tDCS (N=15) or cTBS (N=15). Contrary to our hypotheses, a-tDCS had no effect, whereas cTBS significantly increased mixed percepts during rivalry. These results suggest that the neurochemical mechanisms of a-tDCS may differ between the motor and visual cortices.

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FV 6 Sustained GABA reduction induced by anodal Transcranial direct current stimulation (tDCS) in motor cortex – a proton magnetic resonance spectroscopy study

Cited by 3 publications

References 4 publications

Older Adults Exhibit Greater Visual Cortex Inhibition and Reduced Visual Cortex Plasticity Compared to Younger Adults

Older Adults Exhibit Greater Visual Cortex Inhibition and Reduced Visual Cortex Plasticity Compared to Younger Adults

Visual cortex cTBS increases mixed percept duration while a-tDCS has no effect on binocular rivalry

Visual cortex cTBS increases mixed percept duration while a-tDCS has no effect on binocular rivalry

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