Cutaneous retinal activation and neural entrainment in transcranial alternating current stimulation: A systematic review

Schutter, Dennis J.L.G.

doi:10.1016/j.neuroimage.2015.09.067

Cited by 75 publications

(76 citation statements)

References 47 publications

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“…Importantly, photic stimulation has been shown to improve cognitive performance (Elliott and Müller, 1998;Knez, 2014;Williams et al, 2006;Williams, 2001). These findings indicate a possible confounding factor of tACS-induced changes in behavioural and cognitive improvements, since they may not be "solely attributable to the direct neuromodulatory effects" (Schutter, 2016) of tACS, but could potentially be caused by retinal phosphenes.…”

Section: Introductionmentioning

confidence: 89%

“…The current understanding is that phosphenes are generated in the retina by current spreading from the stimulation electrodes. Alongside empirical work (Kar and Krekelberg, 2012;Schutter, 2016;Schutter and Hortensius, 2010;Schwiedrzik, 2009), this hypothesis is supported by computational models suggesting that even distant electrodes can result in small portions of current flowing through the eyes, sufficient to induce retinal phosphenes due to the high sensitivity of the retina to electrical stimulation (Laakso and Hirata, 2013). However, alongside the evidence for the retinal origin of phosphene perceptions, possible interaction effects with ongoing cortical oscillations cannot be fully dismissed.…”

Section: Introductionmentioning

confidence: 97%

“…The importance of studying phosphene perception induced by tACS was recently highlighted by Schutter (2016), who pointed to an emergent body of evidence suggesting that retinal phosphenes can induce neural entrainment. Therefore, visual phosphenes may be both a byproduct of entrainment and may themselves cause patterns of entrainment in the same way as exogenous photic stimulation (Schutter, 2016). Importantly, photic stimulation has been shown to improve cognitive performance (Elliott and Müller, 1998;Knez, 2014;Williams et al, 2006;Williams, 2001).…”

Section: Introductionmentioning

confidence: 99%

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Assessing tACS-induced phosphene perception using closed-loop Bayesian optimization

Lorenz

et al. 2017

Preprint

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Transcranial alternating current stimulation (tACS) can evoke illusory flash-like visual percepts known as phosphenes. The perception of phosphenes represents a major experimental challenge when studying tACS-induced effects on cognitive performance. Besides growing concerns that retinal phosphenes themselves could potentially have neuromodulatory effects, the perception of phosphenes may also modify the alertness of participants. Past research has shown that stimulation intensity, frequency and electrode montage affect phosphene perception. However, to date, the effect of an additional tACS parameter on phosphene perception has been completely overlooked: the relative phase difference between stimulation electrodes. This is a crucial and timely topic given the confounding nature of phosphene perception and the increasing number of studies reporting changes in cognitive function following tACS phase manipulations. However, studying phosphene perception for different frequencies and phases simultaneously is not tractable using standard approaches, as the physiologically plausible range of parameters results in a combinatorial explosion of experimental conditions, yielding impracticable experiment durations. To overcome this limitation, here we applied a Bayesian optimization approach to efficiently sample an exhaustive tACS parameter space. Moreover, unlike conventional methodology, which involves subjects judging the perceived phosphene intensity on a rating scale, our study leveraged the strength of human perception by having the optimization driven based on a subject's relative judgement.Applying Bayesian optimization for two different montages, we found that phosphene perception was affected by differences in the relative phase between cortical electrodes. The results were replicated in a second study involving new participants and validated using computational modelling. In summary, our results have important implications for the experimental design and conclusions drawn from future tACS studies investigating the effects of phase on cognition.

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Section: Introductionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Assessing tACS-induced phosphene perception using closed-loop Bayesian optimization

Lorenz

et al. 2017

Preprint

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“…e l s e v i e r . c o m / l o c a t e / y n i m g The diversity and complexity of possible mechanisms underlying tES effects is well exemplified by Dennis Schutter, who provided a systematic review on cutaneous retinal activation and neural entrainment in transcranial alternating current stimulation (tACS) (Schutter, 2016). Schutter argues that peripheral photic stimulation can at least in part explain the central effects that are attributed to classical tACS.…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

Transcranial electric stimulation (tES) and NeuroImaging: the state-of-the-art, new insights and prospects in basic and clinical neuroscience

2016

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Transcranial electric stimulation (tES) of the brain has attracted an increased interest in recent years. Yet, despite remarkable research efforts to date, the underlying neurobiological mechanisms of tES' effects are still incompletely understood. This Special Issue aims to provide a comprehensive and up-to-date overview of the state-of-the-art in studies combining tES and neuroimaging, while introducing most recent insights and outlining future prospects related to this new and rapidly growing field. The findings reported here combine methodological advancements with insights into the underlying mechanisms of tES itself. At the same time, they also point to the many caveats and specific challenges associated with such studies, which can arise from both technical and biological sources. Besides promising to advance basic neuroscience, combined tES and neuroimaging studies may also substantially change previous conceptions about the methods of action of electric or magnetic stimulation on the brain.

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“…We therefore 43 applied transcranial alternating current stimulation (TACS) at individual alpha frequency (IAF) to the 44 visual cortex (Oz-Cz montage) in human volunteers performing a visual detection task to mimic the 45 impact of alpha phase-related cortical excitability fluctuations on endogenous gamma activity during 46 visual stimulus processing. A second goal of this study was to test (i) whether TACS is capable of 47 modulating behaviorally relevant neuronal activity in the human brain at commonly used stimulation 48 intensities, an assumption recently called into question by modelling work (Opitz et al, 2016) and 49 cadaver studies (Underwood, 2016), and (ii) whether its effect can be attributed to transcranial as opposed 50 to mere retinal stimulation (Schutter, 2015). While simultaneous TACS-EEG recordings (Helfrich et al, and TACS artifact suppression techniques, we extracted gamma-band oscillatory signals from the visual cortex during TACS and estimated cross-frequency TACS-phase-to-gamma-amplitude-coupling.…”

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confidence: 99%

Low-frequency alternating current stimulation rhythmically suppresses stimulus-induced gamma-band oscillations in visual cortex and impairs perceptual performance

Herring

Esterer

Marshall

et al. 2017

Preprint

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Cutaneous retinal activation and neural entrainment in transcranial alternating current stimulation: A systematic review

Cited by 75 publications

References 47 publications

Assessing tACS-induced phosphene perception using closed-loop Bayesian optimization

Assessing tACS-induced phosphene perception using closed-loop Bayesian optimization

Transcranial electric stimulation (tES) and NeuroImaging: the state-of-the-art, new insights and prospects in basic and clinical neuroscience

Low-frequency alternating current stimulation rhythmically suppresses stimulus-induced gamma-band oscillations in visual cortex and impairs perceptual performance

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