Clarifying frequency-dependent brightness enhancement: delta- and theta-band flicker, not alpha-band flicker, consistently seen as brightest

Bertrand, Jennifer K; Zuk, Alexandra A. Ouellette; Chapman, Craig S.

doi:10.1007/s00221-019-05568-1

Cited by 2 publications

(6 citation statements)

References 52 publications

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“…Perceptual competition between two concurrently presented flickering stimuli of equal luminance was biased in favor of the stimulus with greater inter-trial phase coherence of evoked SSRs [13,14]. Further, flicker evoked response amplitudes were shown to correlate not only with increases in physical luminance contrast [15][16][17][18], but also with the strength of illusory brightness percepts as early as in primary visual cortex [2,3,19,20].…”

Section: Introductionmentioning

confidence: 90%

tACS phase-specifically biases brightness perception of flickering light

et al. 2022

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Section: Introductionmentioning

confidence: 90%

tACS phase-specifically biases brightness perception of flickering light

et al. 2022

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“…Thereby, we controlled for a potential confound of retinal co-stimulation under occipital tACS due to current shunting across the scalp [26][27][28]. As the subjective perception of flicker brightness is known to vary with the temporal modulation frequency [29,30], we first determined the discrimination threshold of perceived brightness differences between the 8 Hz tACS-targeted flicker (LED8Hz) and the 12 Hz reference flicker (LED12Hz) dependent on their luminance ratio. Second, electrophysiological data without tACS were recorded to quantify individual flicker entrainment strength on data segments free of electrical artifacts.…”

Section: Resultsmentioning

confidence: 99%

“…These excitability modulations may influence the net synchrony in population firing to upcoming visual input, that generates SSR amplitude changes on a neural population level. Flicker-evoked response amplitudes have been repeatedly shown to correlate with the subjective experience of brightness [9,13,14]. As electrophysiological recordings during the application of tACS are contaminated by electrical artifacts, the direct measurement of SSR amplitude changes during tACS was not possible [51,52].…”

Section: Discussionmentioning

confidence: 99%

“…Firstly, we determined the point of subjective equality between perceived brightness of the 8 and 12 Hz flicker. Based on previous studies showing interindividual differences in frequency-dependent brightness enhancement [29,30], the point of subjective equality was estimated individually for each participant by applying the method of limits [51]. During eight blocks, the LED8Hz ascended from low to high intensity or descended from high to low intensity, relative to the LED12Hz.…”

Section: Psychophysical Estimation Of Brightness Discrimination Thresholdsmentioning

confidence: 99%

“…Noninvasive recordings in humans of flicker entrained activity, i.e., visually evoked steady-state responses (SSRs), converge with these findings. Perceptual competition between two concurrently presented flickering stimuli of equal luminance was biased in favor of the stimulus with greater inter-trial phase coherence of evoked SSRs [13,14]. Further, flicker evoked response amplitudes were shown to correlate not only with increases in physical luminance contrast [15][16][17][18], but also with the strength of illusory brightness percepts as early as in primary visual cortex [2,3,19,20].…”

Section: Introductionmentioning

confidence: 99%

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tACS phase-specifically biases brightness perception of flickering light

Fiene

Radecke

Misselhorn

et al. 2021

Preprint

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Human brightness estimation often pronouncedly dissociates from objective viewing conditions. Yet, the physiological substrate underlying subjective perception is still poorly understood. Rather than physical illumination, the subjective experience of brightness has been shown to correlate with temporal dynamics in the amplitude of cortical neural responses. Here, we aimed to experimentally manipulate visual flicker-evoked steady-state responses and related perception via concurrent modulation of cortical excitability by transcranial alternating current stimulation. Participants performed a brightness discrimination task of two visual flicker stimuli, one of which was targeted by same-frequency electrical stimulation at varying phase shifts. Transcranial electrical stimulation was applied with an occipital and a periorbital active control montage, based on finite-element method simulations of electric fields. Experimental results reveal that flicker brightness perception is modulated dependent on the phase shift between sensory and electrical stimulation, solely under stable flicker entrainment and exclusively under occipital electrical stimulation. The degree of induced brightness modulation was positively correlated with the strength of neuronal phase locking to the flicker, recorded prior to electrical stimulation. This finding was corroborated by a neural network model, demonstrating a comparable dependency between flicker-evoked phase synchronization and amplitude modulations of entrained neural rhythms by phase shifted visual and electric inputs. Our data suggest a causal role of the amplitude of neural activity in visual cortex for brightness perception in humans. This finding provides an important step towards understanding the basis of visual perception and further confirms electrical stimulation as a tool for advancing controlled modulations of neural excitability and related behavior.

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Clarifying frequency-dependent brightness enhancement: delta- and theta-band flicker, not alpha-band flicker, consistently seen as brightest

Cited by 2 publications

References 52 publications

tACS phase-specifically biases brightness perception of flickering light

tACS phase-specifically biases brightness perception of flickering light

tACS phase-specifically biases brightness perception of flickering light

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