Amplitude Frequency Modulation Research Articles

Effects of amplitude modulated capacitively coupled discharge Ar plasma on kinetic energy and angular distribution function of ions impinging on electrodes: particle-in-cell/Monte Carlo collision model simulation

We investigated the effects of amplitude modulated (AM) capacitively coupled Ar discharge plasma on the ion energy distribution function (IEDF) and the ion angular distribution function (IADF) incident on electrodes using the particle-in-cell/Monte Carlo collision model. For AM discharge, the electron density and electron temperature and the kinetic energy and angle of ions incident on the ground electrode change periodically with AM frequency, whereas ones for continuous wave discharge are almost constant. For AM discharge, the plasma had hysteresis characteristics. The peak energy of IEDF varies from 53 to 135 eV and the FWHM of IADF varies from 1.82 to 3.34 degrees for gas pressure 10mTorr, the peak-to-peak input voltage 400 V and AM level of 50%. The variation width of the peak energy of IEDF and FWHM of IADF increases with the AM level. These effects of AM method discharge are more noticeable at lower pressures. Thus, the AM discharge offers a way to control simultaneously IEDF and IADF, which opens a new avenue for plasma processes such as an ALD-like PECVD.

Ultra-short-term prediction method of PV power output based on the CNN–LSTM hybrid learning model driven by EWT

This study proposes a new method for ultra-short-term prediction of photovoltaic (PV) power output using a convolutional neural network (CNN) and long short-term memory (LSTM) hybrid model driven by empirical wavelet transform (EWT) to address the intermittent and stochastic nature of PV power generation. Given the differences in the spatial and temporal distribution of features between PV sample data and meteorological conditions, a hybrid learning model for multibranch feature extraction was designed. First, the frequency band of PV output data was adaptively selected using EWT and decomposed into the amplitude modulation–frequency modulation single components with frequencies ranging from low to high. Second, data reconstruction was performed on the obtained power components to exploit the extraction ability of the two-dimensional CNN model for short-term local invariance and periodic features. Third, the combined one-dimensional CNN–LSTM model was used for the sample daily meteorological conditions to extract their spatiotemporal features, and the LSTM model was used to learn the correlation between the power data features and the predicted daily weather conditions and to obtain the corresponding component prediction results. Finally, the prediction results of each component were reconstructed to achieve the ultra-short-term prediction. Using Hangzhou Dianzi University's PV microgrid system as an example, the training and testing sets were randomly selected based on different seasons and weather. The results show that this method outperforms traditional learning models in terms of overall prediction performance. The proposed method of a hybrid deep learning model will provide a novel approach for ultra-short-term prediction of PV output.

Modulation masking produced by a low-frequency pure tone

An intense low-frequency tone can affect the perception of amplitude modulation (AM) applied to a high-frequency carrier. Here, thresholds for detecting AM of a 3000-Hz carrier were measured in the presence of a 50-Hz pure tone at 91 dB SPL. When the carrier was presented at 20 dB sensation level (SL), the thresholds were higher than in the absence of the 50-Hz tone, increased when the AM frequency was increased from 20 to 100 Hz, and did not show a maximum near 50 Hz, as would be expected if the effect of the 50-Hz tone resulted from modulation detection interference. When the AM frequency was fixed at 50 Hz, the AM detection thresholds showed a minimum when the phase of the AM was 90° ahead of the phase of the 50-Hz tone (denoted Δφ = 90°) and a maximum for Δφ = 270°. To assess the role of the outer hair cells (OHCs), AM detection thresholds were measured as a function of Δφ using SLs of 20 and 50 dB for normal-hearing participants and 20 dB for hearing-impaired participants. It was assumed that the latter would have impaired OHC function. The pattern of the results was similar across SLs and groups: AM detection thresholds were 8–10 dB lower for Δφ = 90° than for Δφ = 270° in all cases. This suggests that the OHCs do not play a large role in these effects and supports the idea that the low-frequency tone biases the responses of inner hair cells tuned to high frequencies.

Effects of amplitude modulated discharge on growth of nanoparticles in TEOS/O2/Ar capacitively coupled plasma

We investigate the effects of the amplitude modulation (AM) discharge method on the growth of nanoparticles and the relation between growth of nanoparticles and plasma generation in tetraethylorthosilicate (TEOS)/O2/Ar plasma. The laser-light scattering (LLS) intensity, which is proportional to the density and the sixth power of the size of nanoparticles in the Rayleigh scattering regime, decreases by 18% at an AM level of 10% and by 60% at an AM level of 50%. On the other hand, the ArI emission intensity, which is roughly proportional to plasma density, is higher than that for the continuous wave discharge. Thus, AM discharges suppress growth of nanoparticles in TEOS plasma. We have shown oscillations of the axial electric field Ez with the AM frequency for AM discharge by electric field measurement using an electro-optic probe. We have discussed that these fluctuations of Ez mainly lead to the vertical oscillation of the levitation position of nanoparticles trapped in the plasma sheath boundary region by taking into account the force balance equation in the axial direction on these negatively charged nanoparticles.

Species diversity and systematics of the Leptodactylus melanonotus group (Anura, Leptodactylidae): review of diagnostic traits and a new species from the Eastern Guiana Shield

The Leptodactylus melanonotus species group is an anuran clade widely distributed in the Neotropics. This clade harbours many species that are difficult to identify because of incomplete taxonomic knowledge, ambiguous species boundaries and distribution. Here we expand the understanding of species diversity of this Leptodactylus clade by analysing mtDNA sequences for over 600 individuals, delimiting Operational Taxonomic Units (OTUs), and updating species identifications and distributions by linking sequences to morphotypes and calls. Also, we review the morphological and acoustic traits traditionally used as diagnostic characters of species within this group. The DNA-based species delimitation analyses yielded 57 OTUs. Given that only 19 taxa are currently recognized as valid species, our results suggest the existence of many unnamed species within the L. melanonotus group. After reassessing morphological traits in the group, we concluded that the combined use of dorsolateral fold, upper lip stripe, and belly colouration is sufficiently informative for species identification in most cases, especially when associated with data on geographic distribution and habitat use. Regarding advertisement calls, the patterns of amplitude and frequency modulation, calling rate, and dominant frequency were also informative for species discrimination. Furthermore, we designate a neotype for L. wagneri, for which we also describe the advertisement call, and make comparisons with congeners of the L. melanonotus group, especially with the partially sympatric L. leptodactyloides. Lastly, we name and describe a new species endemic to the Eastern Guiana Shield. Patterns of distribution and habitat use in the L. melanonotus group revealed that sympatric occurrences are more commonly found among distantly related species, whereas allopatric occurrences correspond to closely related ones. Speciation between closely related species of the group seems to be related to ecological divergence (open vs. forest habitats) in parallel with clear morphological and acoustic differentiation. http://www.zoobank.org/urn:lsid:zoobank.org:pub:867A8EA9-A8F2-4FA4-8746-A0D9BB2E4286

The Full Informational Spectral Analysis for Auditory Steady-State Responses in Human Brain Using the Combination of Canonical Correlation Analysis and Holo-Hilbert Spectral Analysis.

Auditory steady-state response (ASSR) is a translational biomarker for several neurological and psychiatric disorders, such as hearing loss, schizophrenia, bipolar disorder, autism, etc. The ASSR is sinusoidal electroencephalography (EEG)/magnetoencephalography (MEG) responses induced by periodically presented auditory stimuli. Traditional frequency analysis assumes ASSR is a stationary response, which can be analyzed using linear analysis approaches, such as Fourier analysis or Wavelet. However, recent studies have reported that the human steady-state responses are dynamic and can be modulated by the subject’s attention, wakefulness state, mental load, and mental fatigue. The amplitude modulations on the measured oscillatory responses can result in the spectral broadening or frequency splitting on the Fourier spectrum, owing to the trigonometric product-to-sum formula. Accordingly, in this study, we analyzed the human ASSR by the combination of canonical correlation analysis (CCA) and Holo-Hilbert spectral analysis (HHSA). The CCA was used to extract ASSR-related signal features, and the HHSA was used to decompose the extracted ASSR responses into amplitude modulation (AM) components and frequency modulation (FM) components, in which the FM frequency represents the fast-changing intra-mode frequency and the AM frequency represents the slow-changing inter-mode frequency. In this paper, we aimed to study the AM and FM spectra of ASSR responses in a 37 Hz steady-state auditory stimulation. Twenty-five healthy subjects were recruited for this study, and each subject was requested to participate in two auditory stimulation sessions, including one right-ear and one left-ear monaural steady-state auditory stimulation. With the HHSA, both the 37 Hz (fundamental frequency) and the 74 Hz (first harmonic frequency) auditory responses were successfully extracted. Examining the AM spectra, the 37 Hz and the 74 Hz auditory responses were modulated by distinct AM spectra, each with at least three composite frequencies. In contrast to the results of traditional Fourier spectra, frequency splitting was seen at 37 Hz, and a spectral peak was obscured at 74 Hz in Fourier spectra. The proposed method effectively corrects the frequency splitting problem resulting from time-varying amplitude changes. Our results have validated the HHSA as a useful tool for steady-state response (SSR) studies so that the misleading or wrong interpretation caused by amplitude modulation in the traditional Fourier spectrum can be avoided.

Electromagnetic omnidirectional scanning micromirror with multi jet fusion printed structures for smart factory applications

This paper presents a new omnidirectional scanning micromirror fabricated with a multi jet fusion three-dimensional (3D) printing process. The proposed electromagnetically actuated wobbling scanner has an aluminum-coated 6 mm-diameter mirror supported by quadpod springs and magnets for actuation. The analytic model for optimizing the driving coil is presented and compared with the finite element analysis results. The core part of the structural layer is fabricated by the 3D printing process and assembled with a separately fabricated reflective surface, permanent magnets, and coils. Three different combinations of magnets are tested to improve the optical scan angle of the device and provide a wider field of view (FOV). The one-dimensional (1D) horizontal (H) scan angle of 15.2° is obtained at 415 Hz, and 14.5° is obtained at the vertical (V) scan mode at 406 Hz. The applied current at both scan modes is less than 100 mA rms . The two-dimensional (2D) scan capability is also analyzed by generating the Lissajous, circular, and spiral scan patterns. For the spiral scan, a 2D FOV of 8° is achieved with the driving frequency of 400 Hz and the phase difference of 120°, which is equivalent to the FOV of 360° × 4°, the vertical angular resolution of 0.01°, and frame rate of 1 fps for light detection and ranging (LiDAR) system optics. The amplitude modulation depth and frequency are 100% and 1 Hz, respectively. The developed device can potentially be utilized in various LiDAR applications for the smart factory. • A 6 mm-diameter omnidirectional scanning micromirror has been fabricated by multi jet fusion 3D printing. • Operation principle of the scanner has been analyzed and spiral scan pattern with 8° field-of-view has been generated. • Surface morphology and characteristics of the MJF fabricated device have been analyzed. • Tested various 2D scan capabilities, including of Lissajous, circle, and spiral scan.

Retention of Intrafibrillar Minerals Improves Resin–Dentin Bond Durability

The concept of extrafibrillar demineralization involves selective removal of apatite crystallites from the extrafibrillar spaces of mineralized dentin without disturbing the intrafibrillar minerals within collagen. This helps avoiding activation of endogenous proteases and enables air-drying of partially demineralized dentin without causing collapse of completely demineralized collagen matrix that adversely affects resin infiltration. The objective of the present study was to evaluate the potential of quaternized carboxymethyl chitosan (QCMC)–based extrafibrillar demineralization in improving resin–dentin bond durability. Isothermal titration calorimetry indicated that QCMC synthesized by quaternization of O-carboxymethyl chitosan had moderate affinity for Ca2+ (binding constant: 8.9 × 104 M−1). Wet and dry bonding with the QCMC-based demineralization produced tensile bond strengths equivalent to the phosphoric acid (H3PO4)–based etch-and-rinse technique. Those bond strengths were maintained after thermocycling. Amide I and PO43− mappings of QCMC-conditioned dentin were performed with atomic force microscope–infrared spectroscopy (AFM-IR). Whereas H3PO4-etched dentin exhibited an extensive reduction in PO43− signals corresponding to apatite depletion, QCMC-conditioned dentin showed scattered dark areas and bright PO43− streak signals. The latter were consistent with areas identified as collagen fibrils in the amide I mapping and were suggestive of the presence of intrafibrillar minerals in QCMC-conditioned dentin. Young’s modulus mapping of QCMC-demineralized dentin obtained by AFM-based amplitude modulation–frequency modulation recorded moduli that were the same order of magnitude as those in mineralized dentin and at least 1 order higher than H3PO4-etched dentin. In situ zymography of the gelatinolytic activity within hybrid layers created with QCMC conditioning revealed extremely low signals before and after thermocycling, compared with H3PO4-etched dentin for both wet and dry bonding. Confocal laser scanning microscopy identified the antibacterial potential of QCMC against Streptococcus mutans and Enterococcus faecalis biofilms. Taken together, the QCMC-based demineralization retains intrafibrillar minerals, preserves the elastic modulus of collagen fibrils, reduces endogenous proteolytic activity, and inhibits bacteria biofilms to extend dentin bond durability.

Comparison of age-related declines in behavioral auditory responses versus electrophysiological measures of amplitude modulation

Amplitude and frequency modulations are important for speech intelligibility, especially in noise. Neurophysiological responses assessed by envelope following responses (EFRs) are smaller at faster amplitude modulation frequencies (AMF) in older subjects compared to younger subjects. A typical assumption is that a decline in EFRs necessarily results in corresponding perceptual deficits. To test this in an animal model, we investigated the behavioral AMF discrimination of young and aged Fischer-344 rats and compared those abilities to their EFRs. A modified version of prepulse inhibition of the acoustic startle reflex was used to measure behavior. When AMF differences and modulation depths were large, young and aged animals’ behavioral performances were comparable. Aged animals’ discrimination abilities declined as the difference between background and prepulse AMF decreased and as modulation depth decreased. These declines were larger than in younger animals, even compared to young rats with similar peripheral activation (ABR wave I amplitudes), whose EFR amplitudes were smaller than the aged animals. The results revealed larger age-related deficits in behavioral perception compared to EFRs, suggesting additional factors that affect perception in aging.

Localization of Mechanisms of Amplitude-Frequency Modulation of Pulse Blood Perfusion of the Soft Tissue Microvasculature. Pilot Study.

Peripheral blood flow analysis is used for noninvasive assessment of the cardiovascular system. The aim was to investigate the possibility of applying Hilbert-Huang spectral analysis (HH) to localize the mechanisms of nonlinear regulation of blood perfusion dynamics in the soft tissues of distal areas of the hands in human. In 9 healthy subjects, synchronous recording of photoplethysmograms (PPG) from the index fingers of the hands was performed. Using a band-pass filter, a cardiac signal was extracted from the PPG, which was separated into the carrier and modulating components. The latter was subjected to decomposition into empirical modes by HH method. Five modes were detected, for which the coherence between the hands was evaluated. The frequencies of the modes fell within the conventional frequency intervals of skin blood flow oscillations, and the coherence was 0.6. A decreased depth of modulation in the left hand compared to the right hand was shown. The results indicate a central origin of the nonlinear regulation of the dynamics of tissue blood perfusion in the hands.

Analysis of Video Transmission Capabilities in a Simulated OFDM-Based Supplementary BPL-PLC System

The design and maintenance of a reliable communication system, especially in harsh working conditions for the oil and mining industry, brings many challenges. With the use of a video transmission system, one can monitor the crew and their working environment. Broadband over power line–power line communication (BPL-PLC) seems an ideal medium for such a service, since it enables the use of the existing wired infrastructure for supplementary applications. In this paper, we perform a set of simulations for a dedicated wired medium as well as analyses of a visual data transmission system, designed to deliver video content with quadrature amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM). We investigate a set of video sequences at 480 × 270 resolution under varying network conditions, including signal-to-noise ratio (SNR) and bit error rate (BER). We perform a subjective evaluation study of video content transmitted over our simulated communication link. The results of this study may aid parties involved in designing additional services for portable devices and user terminals, including reliable means of contact, surveillance and monitoring. The obtained results may be of particular interest to researchers and professionals related to the Industry 4.0 and Internet of things (IoT) concepts.

An all-optical phase detector by amplitude modulation of the local field in a Rydberg atom-based mixer

Recently, a Rydberg atom-based mixer was developed to measure the phase of a radio frequency (RF) field. The phase of the signal RF (SIG RF) field is down-converted directly to the phase of a beat signal created by the presence of a local RF (LO RF) field. In this study, we propose that the Rydberg atom-based mixer can be converted to an all-optical phase detector by amplitude modulation (AM) of the LO RF field; that is, the phase of the SIG RF field is related to both the amplitude and phase of the beat signal. When the AM frequency of the LO RF field is the same as the frequency of the beat signal, the beat signal will further interfere with the AM of the LO RF field inside the atom, and then the amplitude of the beat signal is related to the phase of the SIG RF field. The amplitude of the beat signal and the phase of the SIG RF field show a linear relationship within the range of 0 to π/2 when the phase of the AM is set with a difference π/4 from the phase of the LO RF field. The minimum phase resolution can be as small as 0.6° by optimizing the experimental conditions according to a simple theoretical model. This study will expand and contribute to the development of RF measurement devices based on Rydberg atoms.

Effects of interferential current on autonomic nervous system in healthy volunteers: randomized clinical trial

To evaluate the effects of different amplitude-modulated frequency (AMF-100Hz and AMF-10Hz) of the interferential current (IC) on autonomic nervous system (ANS) in healthy volunteers. Thirty healthy volunteers (23.7 ±2.7 years old) were randomized into placebo interventions (turned off), IC with AMF-100Hz and IC with AMF-10Hz. Interventions ware applied in the paravertebral ganglionar region for 30 minutes. ANS evaluated by the heart rate variability before and immediately after the interventions. 10Hz intervention reduced the sympathetic activity in 6% and an increase in the parasympathetic in 6%. 100Hz intervention increased 12% to sympathetic activity and decreased 12% to parasympathetic activity. IC changes the autonomic balance in healthy volunteers. 10Hz reduces the sympathetic activity and increases parasympathetic, although the 100Hz has opposite results. The IC at 10Hz improves the autonomic balance and presents potential effects to be tested in hypertensive patients.

Simulating acoustic waves in acoustic black hole analogues

We present a physical model and a numerical method to simulate nonlinear acoustic waves emitted from moving boundaries in a moving background flow field with transition from subsonic to supersonic flow speeds. The physical model is based on a convective form of the Westervelt equation and accounts for the motion of the background medium and the progressive distortion of a finite amplitude acoustic wave. A suitable coordinate transformation in physical space allows us to accommodate the motion of the wave emitting boundary, while solving the governing equation in a fixed computational domain using standard finite difference techniques. We present the case of an oscillating spherical wave emitting boundary with an induced spherical flow as a prototypical example of an acoustic black hole analogue, where the acoustic waves cannot escape from the horizon of sonic flow speed during the contraction phase. It is demonstrated that the accelerating motion of the wave emitting boundary gives rise to frequency sidebands and amplitude modulations of the acoustic wave. The influence of the background flow speed on this nonlinear Doppler effect is investigated with the present methodology, thus contributing to an improved understanding of the acoustic wave behavior in the proximity of a sonic horizon.

Temporal Modulation Transfer Functions of Amplitude-Modulated Cervical Vestibular-Evoked Myogenic Potentials in Young Adults.

Cervical vestibular-evoked myogenic potentials (cVEMPs) are widely used to evaluate saccular function in clinical and research applications. Typically, transient tonebursts are used to elicit cVEMPs. In this study, we used bone-conducted amplitude-modulated (AM) tones to elicit AMcVEMPs. This new approach allows the examination of phase-locked vestibular responses across a range of modulation frequencies. Currently, cVEMP temporal modulation transfer functions (TMTFs) are not well defined. The purposes of the present study were (1) to characterize the AMcVEMP TMTF in young, healthy individuals, (2) to compare AMcVEMP TMTFs across different analysis approaches, and (3) to determine the upper frequency limit of the AMcVEMP TMTF. Young adults (ages 21 to 25) with no history of vestibular lesions or middle ear pathologies participated in this study. Stimuli were amplitude-modulated tones with a carrier frequency of 500 Hz and modulation frequencies ranging from 7 to 403 Hz. Stimuli were presented at 65 dB HL via a B81 bone-oscillator. AMcVEMP waveforms consisted of transient onset responses, steady-state responses, and transient offset responses; the behavior of these different types of responses varied with modulation frequency. Differences in the TMTF shape were noted across different measures. The amplitude TMTF had a sharp peak, while signal-to-noise ratio and phase coherence TMTFs had broader shapes with plateaus across a range of modulation frequencies. Amplitude was maximal at modulation frequencies of 29 and 37 Hz. Signal-to-noise ratio maintained its peak value at modulation frequencies between 17 Hz and 127 Hz. Phase coherence and modulation gain maintained their peak values at modulation frequencies between 17 Hz and 143 Hz. AMcVEMPs reflect transient onset and offset responses, as well as a sustained response with the periodicity of an amplitude-modulation frequency. AMcVEMP TMTFs had variable shapes depending on the analysis being applied to the response; amplitude had a narrow shape while others were broader. Average upper frequency limits of the AMcVEMP TMTF were as high as approximately 300 Hz in young, healthy adults.

A Novel Fault Diagnosis Method for Analog Circuits Based on Multi-Input Deep Residual Networks with an Improved Empirical Wavelet Transform

Analog circuits play an essential role in electronic systems. To strengthen the reliability of sophisticated electronic circuits, this paper proposes a novel analog circuit fault diagnosis method. Compared with traditional fault diagnosis, the fault diagnosis process in this paper uses a square wave as the stimulus of the circuit under test (CUT), which is beneficial for obtaining the response of the CUT with rich time and frequency domain information. The improved empirical wavelet transform (EWT), which can more accurately extract the amplitude modulated–frequency modulated (AM-FM) components, is used to preprocess the original response. Finally, based on the preprocessed data, a multi-input deep residual network (ResNet) is constructed for fault feature extraction and fault classification. The multi-input ResNet is a powerful approach for learning the fault characteristics of the CUT under different faults by learning the characteristics of the AM-FM components. The effectiveness of the method proposed in this paper is verified by comparing different fault diagnosis methods.

Wideband Rydberg atom-based receiver for amplitude modulation radio frequency communication

Based on Autler–Townes splitting and AC Stark shifts, we present a Rydberg atom-based receiver for determining the amplitude modulation (AM) frequency among a wideband carrier range utilizing a cesium atomic vapor cell. To verify this approach, we measured the signal-to-noise ratio and the data capacity with a 10 kHz AM frequency in the carrier range from 2 GHz to 18 GHz. Without changing the lasers, the working band can be easily extended to a higher range by optimizing the feed antenna and experimental configurations.

EFECTO ANALGÉSICO INMEDIATO DE LA CORRIENTE INTERFERENCIAL DE 4 KHZ (AMF) EN EL DOLOR CRÓNICO DE LA REGIÓN LOMBAR

ABSTRACT Objective: To analyze the immediate effect of amplitude modulation frequencies (AMFs) of 4kHz interferential current (IFC) on chronic low back pain (CLBP). Method: This is a randomized controlled clinical trial. Sixty-three subjects with CLBP were recruited. The subjects were randomized into 3 groups: the placebo group (PG, n=21) and 2 intervention groups (IG), IG4kHz/2Hz (n=21) and IG4kHz/100Hz (n=21). All groups were submitted to a single session of 30 minutes. Pain was evaluated using a numerical rating scale (NRS), the McGill Pain Questionnaire (MPQ), and pressure algometry. Flexibility was evaluated using the Modified Schober Test (MST), the Sit-and-Reach Test (SRT), the Fingertip-to-Floor Test (FTF), and the Passive Straight-Leg Raise Test (PSLR). Results: Comparing IG4kHz/100Hz with PG, we found a significant difference (p<0.05) in NRS in the total and in the MPQ categories, whereas in the comparison between IG4kHz/2Hz and PG, we found a significant difference only in the sensory and evaluative categories of MPQ. Regarding the flexibility tests, we observed a significant difference of both IG4kHz/100Hz and IG4kHz/2Hz in comparison to PG in MST and PSLR, and of IG4kHz/2Hz in comparison to PG in SRT. The 4kHz IFC was effective in immediately reducing CLBP and, consequently, in increasing the flexibility of the lumbar spine and lower limbs. Conclusion: Conclusion: There was a greater number of significant positive outcomes when the 100Hz AMF was adopted. Level of Evidence I; High quality randomized clinical trial with or without statistically significant differences, but with narrow confidence intervals.

Modern hybrid-integrated autodyne oscillators of microwave and mm-wave ranges and its applications. Part 14. Autodynes with amplitude-frequency modulation

Modern hybrid-integrated autodyne oscillators of microwave and mm-wave ranges and its applications. Part 14. Autodynes with amplitude-frequency modulation

Critical role of rhythms in prefrontal transcranial magnetic stimulation for depression: A randomized sham-controlled study.

Repetitive transcranial magnetic stimulation (rTMS) is an alternative treatment for depression, but the neural correlates of the treatment are currently inconclusive, which might be a limit of conventional analytical methods. The present study aimed to investigate the neurophysiological evidence and potential biomarkers for rTMS and intermittent theta burst stimulation (iTBS) treatment. A total of 61 treatment‐resistant depression patients were randomly assigned to receive prolonged iTBS (piTBS; N = 19), 10 Hz rTMS (N = 20), or sham stimulation (N = 22). Each participant went through a treatment phase with resting state electroencephalography (EEG) recordings before and after the treatment phase. The aftereffects of stimulation showed that theta‐alpha amplitude modulation frequency (f am) was associated with piTBS_Responder, which involves repetitive bursts delivered in the theta frequency range, whereas alpha carrier frequency (f c) was related to 10 Hz rTMS, which uses alpha rhythmic stimulation. In addition, theta‐alpha amplitude modulation frequency was positively correlated with piTBS antidepressant efficacy, whereas the alpha frequency was not associated with the 10 Hz rTMS clinical outcome. The present study showed that TMS stimulation effects might be lasting, with changes of brain oscillations associated with the delivered frequency. Additionally, theta‐alpha amplitude modulation frequency may be as a function of the degree of recovery in TRD with piTBS treatment and also a potential EEG‐based predictor of antidepressant efficacy of piTBS in the early treatment stage, that is, first 2 weeks.