Frequency Entrainment Research Articles

Neuromodulation effect of temporal interference stimulation based on network computational model.

Deep brain stimulation (DBS) has long been the conventional method for targeting deep brain structures, but noninvasive alternatives like transcranial Temporal Interference Stimulation (tTIS) are gaining traction. Research has shown that alternating current influences brain oscillations through neural modulation. Understanding how neurons respond to the stimulus envelope, particularly considering tTIS's high-frequency carrier, is vital for elucidating its mechanism of neuronal engagement. This study aims to explore the focal effects of tTIS across varying amplitudes and modulation depths in different brain regions. An excitatory-inhibitory network using the Izhikevich neuron model was employed to investigate responses to tTIS and compare them with transcranial Alternating Current Stimulation (tACS). We utilized a multi-scale model that integrates brain tissue modeling and network computational modeling to gain insights into the neuromodulatory effects of tTIS on the human brain. By analyzing the parametric space, we delved into phase, amplitude, and frequency entrainment to elucidate how tTIS modulates endogenous alpha oscillations. Our findings highlight a significant difference in current intensity requirements between tTIS and tACS, with tTIS requiring notably higher intensity. We observed distinct network entrainment patterns, primarily due to tTIS's high-frequency component, whereas tACS exhibited harmonic entrainment that tTIS lacked. Spatial resolution analysis of tTIS, conducted via computational modeling and brain field distribution at a 13 Hz stimulation frequency, revealed modulation in deep brain areas, with minimal effects on the surface. Notably, we observed increased power within intrinsic and stimulation bands beneath the electrodes, attributed to the high stimulus signal amplitude. Additionally, Phase Locking Value (PLV) showed slight increments in non-deep areas. Our analysis indicates focal stimulation using tTIS, prompting further investigation into the necessity of high amplitudes to significantly affect deep brain regions, which warrants validation through clinical experiments.

Driven generalized quantum Rayleigh-van der Pol oscillators: Phase localization and spectral response.

Driven classical self-sustained oscillators have been studied extensively in the context of synchronization. Using the master equation, this work considers the classically driven generalized quantum Rayleigh-van der Pol oscillator, which is characterized by linear dissipative gain and loss terms as well as three nonlinear dissipative terms. Since two of the nonlinear terms break the rotational phase space symmetry, the Wigner distribution of the quantum mechanical limit cycle state of the undriven system is, in general, not rotationally symmetric. The impact of the symmetry-breaking dissipators on the long-time dynamics of the driven system are analyzed as functions of the drive strength and detuning, covering the deep quantum to near-classical regimes. Phase localization and frequency entrainment, which are required for synchronization, are discussed in detail. We identify a large parameter space where the oscillators exhibit appreciable phase localization but only weak or no entrainment, indicating the absence of synchronization. Several observables are found to exhibit the analog of the celebrated classical Arnold tongue; in some cases, the Arnold tongue is found to be asymmetric with respect to vanishing detuning between the external drive and the natural oscillator frequency.

Vagus nerve stimulation in bursts can efficiently modulate gastric contractions and contraction frequency at varying gastric pressures.

There has been recent clinical interest in the use of vagus nerve stimulation (VNS) for treating gastrointestinal disorders as an alternative to drugs or gastric electrical stimulation. However, effectiveness of burst stimulation has not been demonstrated. We investigated the ability of bursting and continuous VNS to influence gastric and pyloric activity under a range of stimulation parameters and gastric pressures. The goals of this study were to determine which parameters could optimally excite or inhibit gastric activity. Data were collected from 21 Sprague-Dawley rats. Under urethane anesthesia, a rubber balloon was implanted into the stomach, connected to a pressure transducer and a saline infusion pump. A pressure catheter was inserted at the pyloric sphincter and a bipolar nerve cuff was implanted onto the left cervical vagus nerve. The balloon was filled to 15 cmH2O. Stimulation trials were conducted in a consistent order; the protocol was then repeated at 25 and 35 cmH2O. The nerve was then transected and stimulation repeated to investigate directionality of effects. Bursting stimulation at the bradycardia threshold caused significant increases in gastric contraction amplitude with entrainment to the bursting frequency. Some continuous stimulation trials could also cause increased contractions but without frequency changes. Few significant changes were observed at the pylorus, except for frequency entrainment. These effects could not be uniquely attributed to afferent or efferent activity. Our findings further elucidate the effects of different VNS parameters on the stomach and pylorus and provide a basis for future studies of bursting stimulation for gastric neuromodulation.

Entanglement signatures for quantum synchronization with single-ion phonon laser

The entanglement properties of quantum synchronization, based on a single-ion phonon laser subjected to an external drive, have been studied. It is found that the maximum value of steady-state entanglement between the ion’s internal and external states occurs near the noiseless boundary from synchronization to unsynchronization, accompanied by noticeable oscillatory behaviors during the corresponding time evolution of entanglement. In addition, the later time dynamics of entanglement also indicates the occurrence of frequency entrainment, as evidenced by the strong consistency between the bending of the observed frequency and the emergence of Liouvillian exceptional points (LEPs) in the first two eigenvalues of the Liouvillian eigenspectrum. Moreover, the emergence of LEPs, which is intimately associated with frequency entrainment, should be widely observed in quantum synchronization and can be explored in LEPs-based applications.

Dynamics of oscillator populations with disorder in the coupling phase shifts

We study populations of oscillators, all-to-all coupled by means of quenched disordered phase shifts. While there is no traditional synchronization transition with a nonvanishing Kuramoto order parameter, the system demonstrates a specific order as the coupling strength increases. This order is characterized by partial phase locking, which is put into evidence by the introduced novel correlation order parameter, which is shown to grow monotonically with the coupling strength, and via frequency entrainment by following concentration of the oscillators frequencies. Simulations with phase oscillators, Stuart–Landau oscillators, and chaotic Roessler oscillators demonstrate similar scaling of the correlation order parameter with the coupling and the system size and also similar behavior of the frequencies with maximal entrainment (at which the standard deviation of the frequencies is reduced by a factor close to four) at some finite coupling.

Quasi-Period Dynamics of Soliton Molecules: Route to Chaos and Intrinsic Frequency Entrainment

Soliton molecules in optical resonators have attracted remarkable attention in nonlinear dynamics, driven by their compelling analogies with matter molecules. So far, while extensive research has been conducted on their generation, pulsations, and dissociation behaviors, the investigation of their quasi-periodic dynamics has been relatively limited. Here, we present a systematic exploration of the quasi-periodic dynamics of soliton molecules using advanced balanced optical cross-correlation techniques. The incommensurable quasi-period bifurcations constituted of cascaded Hopf bifurcations are found, providing an unambiguous pathway toward chaotic soliton molecules. The chaotic intramolecular dynamics are analyzed by time series, radio frequency spectra, phase portraits, and Lyapunov exponent analysis. In addition, we reveal an intrinsic frequency entrainment phenomenon experimentally. Such frequency entrainment provides a novel perspective on synchronization in optical resonators, encompassing the competition and interaction of oscillations across multiple temporal scales. Our experimental findings offer clear proof that the gain dynamics serve as the origin of the binding forces between solitons within the molecule, which are well supported by the numerical simulations. By advancing the understanding of sub-femtosecond resolved quasi-period dynamics of optical soliton molecules, this study contributes to the broader field of complex nonlinear dynamics, paving the way for future explorations into the intricate behaviors of solitons within optical resonators and relevant fields.

How Do Event‐Related Gamma Oscillations Differ in Alzheimer’s Disease From Other Types of Dementia ?

AbstractBackgroundAlthough recent studies showed that gamma frequency entrainment might have therapeutic effects on Alzheimer’s Disease (AD) (Iaccarino et al. 2016), the gamma band abnormalities in AD patients are still poorly understood, while some studies presented increased gamma responses in AD, others showed reduced gamma responses (Güntekin et al., 2022). The differentiation of gamma responses between different dementia types is also not known. The present study aims to analyze the event‐related gamma responses in AD patients and to find out how the event‐related gamma responses differentiate between AD, Parkinson’s disease dementia (PDD), and Lewy Body dementia (DLB).MethodEEG of 17 DLB, 19 PDD, 20 AD patients, and 20 healthy controls was recorded with a 32‐channel EEG device. Subjects had performed visual oddball paradigm during EEG recordings. Event‐related phase locking and Event‐related power were analyzed in three gamma frequency bands (25‐30 Hz, 30‐35 Hz, 35‐48 Hz) in three different time windows (0 200 ms, 200 400 ms, 400‐600 ms) for target and non‐target stimuli. Repeated measures of ANOVA were used with the between‐subjects and within‐subjects factors.ResultTarget responses elicited higher gamma phase locking than the non‐target responses (p<0.05). Healthy subjects had higher gamma phase locking than AD, PDD, and DLB patients (p<0.05). The healthy control group had increased gamma power in the 0‐200 ms time window at frontal and central locations (p<0.05); however, patient groups did not have this early time window increase of gamma responses. Furthermore, although it was non‐significant, gamma phase locking values of PDD and DLB patients were worse than AD.ConclusionThe present study showed that AD, PDD, and DLB patients had reduced event‐related gamma phase locking and power in the early time window compared to healthy elderly controls. The gamma phase locking values of PDD and DLB patients were worse than those of AD patients. The present study showed that similar to AD patients and other dementia types could also have deficits in the gamma frequency band. Since the PDD and DLB patients had even more abnormal gamma band activities, the gamma entrainment could also have positive effects in these groups of patients.

Spontaneity competes with intention to influence the coordination dynamics of interpersonal performance tendencies

Research has shown that spontaneous visual coupling supports frequency entrainment, phase attraction, and intermittent interpersonal coordination when co-actors are switched from a no-vision (NV) to vision (V) context. In two experiments, co-actors started in a NV context while producing the same or different amplitude movements. The same amplitude resulted in similar self-paced frequencies, while different amplitudes resulted in disparate frequencies. In experiment 1, co-actors were instructed to maintain amplitude while receiving no instructions to coordinate their actions. Frequency and phase entrainment was limited in the V context even when co-actors started the NV context with the same amplitude. In experiment 2, co-actors were instructed to maintain amplitude and intentionally coordinate together, but not at a specific pattern. Significant frequency modulations occurred to maintain amplitude as the co-actors sought to coordinate their actions. With the open-ended instructions, co-actors produced in-phase and anti-phase coordination along with intermittent performance exhibited by shifts between a variety of stable relative phase patterns. The proposed hypotheses and findings are discussed within the context of a shared manifold representation for joint action contexts, with the coordination dynamics expressed by the HKB model of relative phase serving to conceptualization the representations in the shared manifold.

Acousto-optic stimuli to promote coherent 40-Hz frequency entrainment effect.

Research has shown that a fundamental frequency of 40 Hz in continuous neural oscillation is indicative of normal brain activity; in Alzheimer disease (AD) patients, these oscillations either disappear or are significantly interrupted. Research has also indicated that the degenerative impacts of AD in mice were mitigated by the synchronization of 40-Hz acousto-optic stimulation (AOS). To examine the impact of employing a 40-Hz AOS intervention on the induction of a substantial 40-Hz frequency entrainment and improvement in working memory performance among a sample of young individuals in good health. We conduct an analysis of event-related potentials (ERPs) derived from electroencephalogram (EEG) data following the presentation of AOS. We recruited 20 healthy volunteers (median age: 25 years; 8 female subjects). Following the administration of various stimuli, including no stimuli, 40-Hz AOS, pink noise, and 40Hz acoustic stimuli (AS), the participants were required to complete a working memory task. A total of 62 electrodes were used to record EEG data, which was subsequently analyzed to investigate the impact of AOS on the activity of working memory. We also aimed to determine if AOS lead to a more pronounced 40-Hz frequency entrainment. Following the administration of AOS, a notable enhancement in the 40-Hz power of pertinent cerebral areas was observed, accompanied by a substantial improvement in the performance of the subjects on working memory tests subsequent to the stimulation. The findings unequivocally establish the efficacy of using AOS to enhance the 40-Hz power and working memory.

Emergence of Synchronization in a Driven-Dissipative Hot Rydberg Vapor.

We observe synchronization in a thermal (35-60 °C) atomic (Rb) ensemble driven to a highly excited Rydberg state (principle quantum number n ranging from 43 to 79). Synchronization in this system is unexpected due to the atomic motion; however, we show theoretically that sufficiently strong interactions via a global Rydberg density mean field cause frequency and phase entrainment. The emergent oscillations in the vapor's bulk quantities are detected in the transmission of the probe laser for a two-photon excitation scheme.

Phonetic entrainment in L2 human-robot interaction: an investigation of children with and without autism spectrum disorder.

Phonetic entrainment is a phenomenon in which people adjust their phonetic features to approach those of their conversation partner. Individuals with Autism Spectrum Disorder (ASD) have been reported to show some deficits in entrainment during their interactions with human interlocutors, though deficits in terms of significant differences from typically developing (TD) controls were not always registered. One reason related to the inconsistencies of whether deficits are detected or not in autistic individuals is that the conversation partner's speech could hardly be controlled, and both the participants and the partners might be adjusting their phonetic features. The variabilities in the speech of conversation partners and various social traits exhibited might make the phonetic entrainment (if any) of the participants less detectable. In this study, we attempted to reduce the variability of the interlocutors by employing a social robot and having it do a goal-directed conversation task with children with and without ASD. Fourteen autistic children and 12 TD children participated the current study in their second language English. Results showed that autistic children showed comparable vowel formants and mean fundamental frequency (f0) entrainment as their TD peers, but they did not entrain their f0 range as the TD group did. These findings suggest that autistic children were capable of exhibiting phonetic entrainment behaviors similar to TD children in vowel formants and f0, particularly in a less complex situation where the speech features and social traits of the interlocutor were controlled. Furthermore, the utilization of a social robot may have increased the interest of these children in phonetic entrainment. On the other hand, entrainment of f0 range was more challenging for these autistic children even in a more controlled situation. This study demonstrates the viability and potential of using human-robot interactions as a novel method to evaluate abilities and deficits in phonetic entrainment in autistic children.

Phase switching phenomenon in a system of three coupled DC glow discharge plasmas.

We report the first experimental observations of phase switching in a system of three coupled plasma sources. Two of the plasma sources are inductively coupled to each other while the third one is directly coupled to one of them. The coupled system acquires a frequency pulling synchronized state following which a transition occurs to a frequency entrainment state with an increase in the frequency of the directly coupled system. We also observe a sudden jump from a lower to a higher frequency entrainment state and a concomitant phase switching between the oscillations of the two directly coupled sources while the phase difference between the inductively coupled sources remains constant. These experimental findings are established using various diagnostic tools, such as the Fourier spectra, frequency bifurcation plots, Lissajous plots, and Hilbert transforms of the data. The experimental results are qualitatively modeled using three coupled van der Pol equations, in which two of them are environmentally coupled while the third one is directly coupled with one of them.

Gamma frequency entrainment rescues cognitive impairment by decreasing postsynaptic transmission after traumatic brain injury.

The relationship between oscillatory activity in hippocampus and cognitive impairment in traumatic brain injury (TBI) remains unclear. Although TBI decreases gamma oscillations and 40 Hz light flicker improves TBI prognosis, the effects and mechanism of rhythmic flicker on TBI remain unclear. In this study, we aimed to explore whether light flicker could reverse cognitive deficits, and further explore its potential mechanisms in TBI mouse model. The Morris water maze test (MWM), step-down test (SDT), and novel object recognition test (NOR) were applied to evaluate the cognitive ability. The local field potential (LFP) recording was applied to measure low gamma reduction of CA1 in hippocampus after TBI. And electrophysiological experiments were applied to explore effects of the gamma frequency entrainment on long-term potentiation (LTP), postsynaptic transmission, and intrinsic excitability of CA1 pyramidal cells (PCs) in TBI mice. Immunofluorescence staining and western blotting were applied to explore the effects of 40 Hz light flicker on the expression of PSD95 in hippocampus of TBI mice. We found that 40 Hz light flicker restored low gamma reduction of CA1 in hippocampus after TBI. And 40 Hz, but not random or 80 Hz light flicker, reversed cognitive impairment after TBI in behavioral tests. Moreover, 40 Hz light flicker improved N-methyl-D-aspartate (NMDA) receptor-dependent LTP (LTPNMDAR ) and L-type voltage-gated calcium channel-dependent LTP (LTPL-VGCC ) after TBI treatment. And gamma frequency entrainment decreased excitatory postsynaptic currents (EPSCs) of CA1 PCs in TBI mice. Our results have illustrated that 40 Hz light flicker could decrease intrinsic excitability of PCs after TBI treatment in mice. Furthermore, 40 Hz light flicker decreased the expression of PSD95 in hippocampus of TBI mice. These results demonstrated that 40 Hz light flicker rescues cognitive impairment by decreasing postsynaptic transmission in PCs after TBI treatment in mice.

Frequency entrainment and suppression of stick–slip vibrations in a 3 DoF discontinuous disc brake model

Friction-induced stick–slip vibration has been identified as the main reason for various types of disc brake noises like creep groan, squeak and creak. In this work, we investigate the suppression of stick–slip vibrations in disc brakes due to the application of a small-amplitude normal harmonic force on the brake pad. The discontinuity induced bifurcations that lead to such suppression are studied in detail. The frequency range of the normal force in which suppression of stick–slip vibration occur is identified. A 3 DoF discontinuous model of the disc brake is considered. The discontinuous oscillator is modelled as a Filippov system with smooth vector fields separated by a discontinuity surface. It is shown that the normal harmonic force entrains the non-smooth limit cycle even for very small forcing amplitudes. Different frequency intervals exhibiting harmonic, super-harmonic, and sub-harmonic entrainments are identified. It is demonstrated that the initiation and termination of these entrainment intervals are associated with Neimark–Sacker bifurcations. It is also shown that discontinuity induced grazing-sliding mechanism brings about these bifurcations. Switching-sliding bifurcations happening in the entrainment region give rise to a sub-interval which is associated with suppression of stick–slip vibrations. We also report interesting discontinuity induced bifurcation scenarios in higher order entrainment regimes like grazing-sliding involving different orbit loops at lower and upper limits of the interval and splitting–merging of the sliding surface. • Stick–slip vibration suppression in disc brakes by using normal force is studied. • Various entrainment regions are detected and studied by Filippov’s method. • Discontinuity induced bifurcations causing these entrainments are analysed. • Entrainment sub-intervals with suppressed stick–slip vibration are identified.

Effect of harmonic inflow perturbation on the wake vortex dynamics of a cylinder undergoing two-degree-of-freedom vortex-induced vibration near a plane boundary

The influence of inflow perturbations on the wake dynamics and structural response is investigated for a cylinder undergoing vortex-induced vibrations (VIV) in oscillatory flows in the proximity of a solid boundary. Numerical simulations are conducted at a Reynolds number of 200, based on the cylinder diameter and free-stream velocity, for perturbation frequencies fp up to four times the natural shedding frequency fo. Three response regimes are identified: a lock-on regime at fp=2fo, with maximum cylinder displacement and forces, a force-amplification regime for 1.8<fp<2.3 characterized by shedding frequency entrainment, and a weakly coupled regime. The wake and structural response dynamics differ from those for unperturbed VIV in uniform flow. The primary mechanism underlying these differences is due to the symmetric instability of the shear layers forced by the perturbations. This instability results in the shedding of vortex pairs at fp in the cylinder base region, which interact with the Kármán formation process and, in the amplification regimes, reinforce the natural instability at 2fo. These mechanisms give rise to distinct wake topology, which is then related to the structural dynamics.

Quantum synchronization in quadratically coupled quantum van der Pol oscillators

We implement nonlinear anharmonic interaction in the coupled van der Pol oscillators to investigate the quantum synchronization behavior of the systems. We study the quantum synchronization in two oscillator models, coupled quantum van der Pol oscillators and anharmonic self-oscillators. We demonstrate that the considered systems exhibit a high-order synchronization through coupling in both classical and quantum domains. We show that, due to the anharmonicity of the nonlinear interaction between the oscillators, the system exhibits phonon blockade in the phase-locking regime, which is a pure nonclassical effect and has not been observed in the classical domain. We also demonstrate that, for coupled anharmonic oscillators, the system shows a multiple resonance phase-locking behavior due to nonlinear interaction. We point out that the synchronization blockade arises due to strong anticorrelation between the oscillators, which leads to phonon antibunching in the same parametric regime. In the anharmonic oscillator case we illustrate the simultaneous occurrence of bunching and antibunching effects as a consequence of simultaneous negative and positive correlation between the anharmonic oscillators. We examine the aforementioned characteristic features in the frequency entrainment of the oscillators using a power spectrum where one can observe normal mode splitting and the Mollow triplet in the strong coupling regime. Finally, we propose a possible experimental realization for the considered system in the trapped ion and optomechanical setting.

Role of coherence and degeneracies in quantum synchronization

Progress on the study of synchronisation in quantum systems has been largely driven by specific examples which resulted in several examples of frequency entrainment as well as mutual synchronisation. Here we study quantum synchronisation by utilising Liouville space perturbation theory. We begin by clarifying the role of centers, symmetries and oscillating coherences in the context of quantum synchronisation. We then analyse the eigenspectrum of the Liouville superoperator generating the dynamics of the quantum system and determine the conditions under which synchronisation arises. We apply our framework to derive a powerful relationship between energy conservation, degeneracies and synchronisation in quantum systems. Finally, we demonstrate our approach by analysing two mutually coupled thermal machines and the close relationship between synchronisation and thermodynamic quantities.

A Multi-Component Physiotherapeutic Intervention among Schoolchildren with Myopia: 3D-Based Vision Training Program with Auditory Frequency Entrainment and Electrical Stimulation

Purpose. This study evaluated whether 3D-based vision training (VT) with visual cortex-activated auditory frequency entrainment and bilateral orbital electrical stimulation (ES) could prevent the progression of myopia among schoolchildren. Methods. In this two-stage, randomized, crossover, single-blind study, pre- and post-logMAR visual acuity and refractive error from 27 schoolchildren with myopia (≤−0.50 D) were evaluated among four groups: (1) sham control with no VT, frequency following response (FFR), or ES (control group); (2) 3D-based VT only (VT group); (3) VT with FFR generated through visual cortex-activated auditory entrainment (VT-FFR group); and (4) VT with FFR and bilateral orbital ES (VT-FFR-ES group). In stage 1, the intervention was administered for 30 min to all groups using a randomized crossover design. In stage 2, the intervention was administered for 30 min/day, 3 days a week, for 4 weeks to evaluate the effectiveness of intervention. Results. Compared with the pre-test, post-test logMAR visual acuity after a single intervention was not significantly different in control and VT groups, but significantly improved in the VT-FFR (−0.08 ± 0.11) and VT-FFR-ES groups (−0.13 ± 0.14). Compared with the pre-test, post-test refractive error by spherical equivalent in VT-FFR-ES group for the 4-week intervention was significantly (<0.001) improved (0.21 D) compared with the control group (−0.1 D). Conclusions. The multicomponent physiotherapeutic intervention of 3D-based VT with auditory FFR and bilateral orbital ES can inhibit the progression of myopia. This intervention can be used as a noninvasive physiotherapeutic approach to prevent or reduce the severity of myopia.

Van der Pol equation with sine nonlinearity: dynamical behavior and real time control to a target trajectory

In this work, the dynamical behavior and real time control of a target trajectory of a modified Van der Pol model so the potential is proportional to the term is proposed. A generalization in the case of small oscillations on the function is studied. Due to function, the system presents periodical regions of stability and unstability, a very rich dynamical behavior. Analytical investigations based on the harmonic balance method came out some specific values of the excitation frequency for which the model is subjected to a phenomenon of frequency entrainment. Also, under effect of the sine function power, chaos appears for even small value of the nonlinearity coefficient, in contrast to the classical Van der Pol oscillator. An investigation as an artificial pacemaker is done based on the real frequency of the natural pacemaker. We found that the modified Van der Pol model, like the classic Van der Pol model, can play the role of an artificial pacemaker with some approximations. Due to the complexity of the analogical sine function, an experimental study was made by real implementation of an Arduino Card based on the Runge–Kutta 4th order algorithm. The results obtained show a good correlation with the numerical results.

No Evidence for Entrainment: Endogenous Gamma Oscillations and Rhythmic Flicker Responses Coexist in Visual Cortex.

Over the past decades, numerous studies have linked cortical gamma oscillations (∼30–100 Hz) to neurocomputational mechanisms. Their functional relevance, however, is still passionately debated. Here, we asked whether endogenous gamma oscillations in the human brain can be entrained by a rhythmic photic drive >50 Hz. Such a noninvasive modulation of endogenous brain rhythms would allow conclusions about their causal involvement in neurocognition. To this end, we systematically investigated oscillatory responses to a rapid sinusoidal flicker in the absence and presence of endogenous gamma oscillations using magnetoencephalography (MEG) in combination with a high-frequency projector. The photic drive produced a robust response over visual cortex to stimulation frequencies of up to 80 Hz. Strong, endogenous gamma oscillations were induced using moving grating stimuli as repeatedly done in previous research. When superimposing the flicker and the gratings, there was no evidence for phase or frequency entrainment of the endogenous gamma oscillations by the photic drive. Unexpectedly, we did not observe an amplification of the flicker response around participants' individual gamma frequencies (IGFs); rather, the magnitude of the response decreased monotonically with increasing frequency. Source reconstruction suggests that the flicker response and the gamma oscillations were produced by separate, coexistent generators in visual cortex. The presented findings challenge the notion that cortical gamma oscillations can be entrained by rhythmic visual stimulation. Instead, the mechanism generating endogenous gamma oscillations seems to be resilient to external perturbation.SIGNIFICANCE STATEMENT We aimed to investigate to what extent ongoing, high-frequency oscillations in the gamma-band (30–100 Hz) in the human brain can be entrained by a visual flicker. Gamma oscillations have long been suggested to coordinate neuronal firing and enable interregional communication. Our results demonstrate that rhythmic visual stimulation cannot hijack the dynamics of ongoing gamma oscillations; rather, the flicker response and the endogenous gamma oscillations coexist in different visual areas. Therefore, while a visual flicker evokes a strong neuronal response even at high frequencies in the gamma-band, it does not entrain endogenous gamma oscillations in visual cortex. This has important implications for interpreting studies investigating the causal and neuroprotective effects of rhythmic sensory stimulation in the gamma-band.