scholarly journals Frequency but not phase specific modulation of binocular rivalry with transcranial alternating current stimulation

2019 ◽  
Author(s):  
Jorge Delgado ◽  
Guillaume Riesen ◽  
Vladimir Y. Vildavski ◽  
Anthony M. Norcia
Keyword(s):  
Visual Stimulus ◽  
Binocular Rivalry ◽  
Control Experiment ◽  
Visual Stimuli ◽  
Alternating Current ◽  
Specific Model ◽  
Transcranial Alternating Current Stimulation ◽  
The Right

ABSTRACTRecent transcranial alternating current stimulation (tACS) literature suggests that tACS effects can in principle be both frequency and phase specific. In a series of three experiments using 69 participants used binocular rivalry percepts as a read-out for the effects of phase-synchronized tACS stimulation. To test for phase specificity, with frequency the same in each eye, we visually stimulated each eye with 3Hz, with stimuli in each eye presented in temporal in antiphase. The frequency-specific paradigm visually stimulated the right eye with 3Hz, and the left eye with 5Hz. Each experiment was accompanied by 3Hz tACS, whose phase with respect to the visual stimulus was varied by 0°, 90°, 180°, or 270° in relation to the right eye’s stimulus. A baseline no-tACS block preceded the stimulation blocks and two more followed, immediately and ten minutes after. Individual blocks lasted 4 minutes. Additionally, a no-tACS control experiment identical to the 3 Hz anti-phase visual stimuli setup was conducted, keeping all parameters the same but eliminating tACS. During stimulation, the 3 Hz anti-phase visual stimuli setup slowed the rate of rivalry in both eyes. Conversely, the 3Hz-right, 5Hz-left setup slowed the right (targeted) eye significantly while leaving the left (unstimulated) eye unchanged. In both experiments, durations returned to baseline after 10 minutes. Our results are consistent with the frequency-specific model of tACS, and with the Leveltian hypothesis that stimulation weakens the stimulated eye, as the right eye got weaker when it was directly targeted, and both eyes got weaker when targeted in antiphase. tACS does not appear to preferentially modulating percept durations in one phase more than in another.

scholarly journals Amplitude modulated transcranial alternating current stimulation (AM-TACS) efficacy evaluation via phosphene induction

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Carsten Thiele ◽  
Tino Zaehle ◽  
Aiden Haghikia ◽  
Philipp Ruhnau
Keyword(s):  
Amplitude Modulation ◽  
Carrier Frequency ◽  
Alternating Current ◽  
Efficacy Evaluation ◽  
Electrophysiological Signals ◽  
Transcranial Alternating Current Stimulation ◽  
Novel Method ◽  
The Right

AbstractAmplitude modulated transcranial alternating current stimulation (AM-tACS) is a novel method of electrostimulation which enables the recording of electrophysiological signals during stimulation, thanks to an easier removable stimulation artefact compared to classical electrostimulation methods. To gauge the neuromodulatory potential of AM-tACS, we tested its capacity to induce phosphenes as an indicator of stimulation efficacy. AM-tACS was applied via a two-electrode setup, attached on FpZ and below the right eye. AM-tACS waveforms comprised of different carrier (50 Hz, 200 Hz, 1000 Hz) and modulation frequencies (8 Hz, 16 Hz, 28 Hz) were administered with at maximum 2 mA peak-to-peak stimulation strength. TACS conditions in the same frequencies were used as a benchmark for phosphene induction. AM-tACS conditions using a 50 Hz carrier frequency were able to induce phosphenes, but with no difference in phosphene thresholds between modulation frequencies. AM-tACS using a 200 Hz or 1000 Hz carrier frequency did not induce phosphenes. TACS conditions induced phosphenes in line with previous studies. Stimulation effects of AM-tACS conditions were independent of amplitude modulation and instead relied solely on the carrier frequency. A possible explanation may be that AM-tACS needs higher stimulation intensities for its amplitude modulation to have a neuromodulatory effect.

scholarly journals Alpha and Theta Transcranial Alternating Current Stimulation Over the Right Dorsolateral Prefrontal Cortex Modulates Vigilance Performance, but Only When Arousal Levels Are Non-optimal

2021 ◽  
Author(s):  
Víctor Martínez-Pérez ◽  
Miriam Tortajada ◽  
Lucía B. Palmero ◽  
Guillermo Campoy ◽  
Luis J. Fuentes
Keyword(s):  
Prefrontal Cortex ◽  
Dorsolateral Prefrontal Cortex ◽  
Alternating Current ◽  
Time Of Day ◽  
Time On Task ◽  
Frontoparietal Network ◽  
Dorsolateral Prefrontal ◽  
Transcranial Alternating Current Stimulation ◽  
The Right

Abstract BackgroundCurrent theoretical accounts on the oscillatory nature of sustained attention predict that entrainment via transcranial alternating current stimulation (tACS) at alpha and theta frequencies on the frontoparietal network could prevent the drops in vigilance across time-on-task. Nonetheless, most previous studies have neglected both the fact that vigilance comprises two dissociable components (i.e. arousal and executive vigilance) and the potential role of differences in arousal baseline. MethodWe examined the effects of theta- and alpha-tACS over the right dorsolateral prefrontal cortex on both components of vigilance and on participants that differed in arousal baseline according to their chronotype and the time of testing. Intermediate-types performed the vigilance tasks when their arousal baseline was at the optimal level, whereas evening-types performed the vigilance tasks when their arousal baseline was at non-optimal levels. ResultsBoth theta- and alpha-tACS improved arousal vigilance, whereas alpha-tACS, but not theta-tACS, improved accuracy and attenuated the typical vigilance decrement in the executive vigilance task. Importantly, these stimulation effects were only found when arousal baseline was low (i.e., with evening-types performing the tasks at their non-optimal time of day).ConclusionThe results support the multicomponent view of vigilance, the relevance of heeding individual differences in arousal baseline, and the role of alpha oscillations as a long-range cortical scale synchronization mechanism that compensates the decrements in performance as a function of time-on-task by exerting and maintaining cognitive control attributed to activation of the frontoparietal network.

scholarly journals Theta Phase-dependent Modulation of Perception by Concurrent Transcranial Alternating Current Stimulation and Periodic Visual Stimulation

2020 ◽  
Vol 32 (6) ◽  
pp. 1142-1152
Author(s):  
Elif Somer ◽  
John Allen ◽  
Joseph L. Brooks ◽  
Vaughan Buttrill ◽  
Amir-Homayoun Javadi
Keyword(s):  
Visual Cortex ◽  
Visual Stimulus ◽  
Auditory Perception ◽  
Visual Stimulation ◽  
Alternating Current ◽  
Matching Task ◽  
Phase 0 ◽  
Theta Frequency ◽  
Transcranial Alternating Current Stimulation ◽  
Visual Matching

Sensory perception can be modulated by the phase of neural oscillations, especially in the theta and alpha ranges. Oscillatory activity in the visual cortex can be entrained by transcranial alternating current stimulation (tACS) as well as periodic visual stimulation (i.e., flicker). Combined tACS and visual flicker stimulation modulates BOLD response, and concurrent 4-Hz auditory click train, and tACS modulate auditory perception in a phase-dependent way. In this study, we investigated whether phase synchrony between concurrent tACS and periodic visual stimulation (i.e., flicker) can modulate performance on a visual matching task. Participants completed a visual matching task on a flickering visual stimulus while receiving either in-phase (0°) or asynchronous (180°, 90°, or 270°) tACS at alpha or theta frequency. Stimulation was applied over either occipital cortex or dorsolateral pFC. Visual performance was significantly better during theta frequency tACS over the visual cortex when it was in-phase (0°) with visual stimulus flicker, compared with antiphase (180°). This effect did not appear with alpha frequency flicker or with dorsolateral pFC stimulation. Furthermore, a control sham group showed no effect. There were no significant performance differences among the asynchronous (180°, 90°, and 270°) phase conditions. Extending previous studies on visual and auditory perception, our results support a crucial role of oscillatory phase in sensory perception and demonstrate a behaviorally relevant combination of visual flicker and tACS. The spatial and frequency specificity of our results have implications for research on the functional organization of perception.

scholarly journals Effects of transcranial alternating current stimulation over right-DLPFC on vigilance tasks depend on the arousal level

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Víctor Martínez-Pérez ◽  
Miriam Tortajada ◽  
Lucía B. Palmero ◽  
Guillermo Campoy ◽  
Luis J. Fuentes
Keyword(s):  
Prefrontal Cortex ◽  
Sustained Attention ◽  
Dorsolateral Prefrontal Cortex ◽  
Alternating Current ◽  
Arousal Level ◽  
Time On Task ◽  
Dorsolateral Prefrontal ◽  
Transcranial Alternating Current Stimulation ◽  
The Right

AbstractCurrent theoretical accounts on the oscillatory nature of sustained attention predict that entrainment via transcranial alternating current stimulation (tACS) at alpha and theta frequencies on specific areas of the prefrontal cortex could prevent the drops in vigilance across time-on-task. Nonetheless, most previous studies have neglected both the fact that vigilance comprises two dissociable components (i.e., arousal and executive vigilance) and the potential role of differences in arousal levels. We examined the effects of theta- and alpha-tACS over the right dorsolateral prefrontal cortex in both components of vigilance and in participants who differed in arousal level according to their chronotype and time of testing. Intermediate-types performed the vigilance tasks when their arousal level was optimal, whereas evening-types performed the vigilance tasks when their arousal levels were non-optimal. Both theta- and alpha-tACS improved arousal vigilance in the psychomotor vigilance task (PVT), whereas alpha-tACS, but not theta-tACS, improved executive vigilance in the sustained attention to response task (SART), and counteracted the typical vigilance decrement usually observed in this task. Importantly, these stimulation effects were only found when arousal was low (i.e., with evening-types performing the tasks at their non-optimal time of day). The results support the multicomponent view of vigilance, the relevance of heeding individual differences in arousal, and the role of alpha oscillations as a long-range cortical scale synchronization mechanism that compensates the decrements in performance as a function of time-on-task by exerting and maintaining cognitive control attributed to activation of the right dorsolateral prefrontal cortex.

scholarly journals A specific phase of transcranial alternating current stimulation at the β frequency boosts repetitive paired-pulse TMS-induced plasticity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hisato Nakazono ◽  
Katsuya Ogata ◽  
Akinori Takeda ◽  
Emi Yamada ◽  
Shinichiro Oka ◽  
...  
Keyword(s):  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Single Pulse ◽  
Alternating Current ◽  
Dependent Manner ◽  
Synaptic Efficacy ◽  
Paired Pulse ◽  
Transcranial Alternating Current Stimulation ◽  
In Trans ◽  
Specific Phase

AbstractTranscranial alternating current stimulation (tACS) at 20 Hz (β) has been shown to modulate motor evoked potentials (MEPs) when paired with transcranial magnetic stimulation (TMS) in a phase-dependent manner. Repetitive paired-pulse TMS (rPPS) with I-wave periodicity (1.5 ms) induced short-lived facilitation of MEPs. We hypothesized that tACS would modulate the facilitatory effects of rPPS in a frequency- and phase-dependent manner. To test our hypothesis, we investigated the effects of combined tACS and rPPS. We applied rPPS in combination with peak or trough phase tACS at 10 Hz (α) or β, or sham tACS (rPPS alone). The facilitatory effects of rPPS in the sham condition were temporary and variable among participants. In the β tACS peak condition, significant increases in single-pulse MEPs persisted for over 30 min after the stimulation, and this effect was stable across participants. In contrast, β tACS in the trough condition did not modulate MEPs. Further, α tACS parameters did not affect single-pulse MEPs after the intervention. These results suggest that a rPPS-induced increase in trans-synaptic efficacy could be strengthened depending on the β tACS phase, and that this technique could produce long-lasting plasticity with respect to cortical excitability.

scholarly journals Online and offline effects of transcranial alternating current stimulation of the primary motor cortex

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ivan Pozdniakov ◽  
Alicia Nunez Vorobiova ◽  
Giulia Galli ◽  
Simone Rossi ◽  
Matteo Feurra
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Random Noise ◽  
Single Pulse ◽  
Alternating Current ◽  
Online Application ◽  
Transcranial Random Noise Stimulation ◽  
Transcranial Alternating Current Stimulation

AbstractTranscranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that allows interaction with endogenous cortical oscillatory rhythms by means of external sinusoidal potentials. The physiological mechanisms underlying tACS effects are still under debate. Whereas online (e.g., ongoing) tACS over the motor cortex induces robust state-, phase- and frequency-dependent effects on cortical excitability, the offline effects (i.e. after-effects) of tACS are less clear. Here, we explored online and offline effects of tACS in two single-blind, sham-controlled experiments. In both experiments we used neuronavigated transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) as a probe to index changes of cortical excitability and delivered M1 tACS at 10 Hz (alpha), 20 Hz (beta) and sham (30 s of low-frequency transcranial random noise stimulation; tRNS). Corticospinal excitability was measured by single pulse TMS-induced motor evoked potentials (MEPs). tACS was delivered online in Experiment 1 and offline in Experiment 2. In Experiment 1, the increase of MEPs size was maximal with the 20 Hz stimulation, however in Experiment 2 neither the 10 Hz nor the 20 Hz stimulation induced tACS offline effects. These findings support the idea that tACS affects cortical excitability only during online application, at least when delivered on the scalp overlying M1, thereby contributing to the development of effective protocols that can be applied to clinical populations.

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