49 results for qubit oscillator frequency
Data from: Input-dependent frequency modulation of cortical gamma oscillations shapes spatial synchronization and enables phase coding
Contributors: Lowet, Eric, Roberts, Mark, Hadjipapas, Avgis, Peter, Alina, van der Eerden, Jan, De Weerd, Peter
phase-oscillator model part 1...phase-oscillator model part 2...phase-oscillator model part 3...phase-oscillator model part 4...oscillation frequencies at nearby spatial locations. Similarly to cortical...oscillation phase codes, may resolve conflicting experimental observations...frequency with increasing input drive. The relates to the experimental...oscillators. The gamma phase-locking, the precise phase relation and the...oscillators, where input drive determines the intrinsic (natural) frequency...oscillation...frequency of gamma oscillations varies with input drive (e.g. visual contrast ... Fine-scale temporal organization of cortical activity in the gamma range (~25–80Hz) may play a significant role in information processing, for example by neural grouping (‘binding’) and phase coding. Recent experimental studies have shown that the precise frequency of gamma oscillations varies with input drive (e.g. visual contrast) and that it can differ among nearby cortical locations. This has challenged theories assuming widespread gamma synchronization at a fixed common frequency. In the present study, we investigated which principles govern gamma synchronization in the presence of input-dependent frequency modulations and whether they are detrimental for meaningful input-dependent gamma-mediated temporal organization. To this aim, we constructed a biophysically realistic excitatory-inhibitory network able to express different oscillation frequencies at nearby spatial locations. Similarly to cortical networks, the model was topographically organized with spatially local connectivity and spatially-varying input drive. We analyzed gamma synchronization with respect to phase-locking, phase-relations and frequency differences, and quantified the stimulus-related information represented by gamma phase and frequency. By stepwise simplification of our models, we found that the gamma-mediated temporal organization could be reduced to basic synchronization principles of weakly coupled oscillators, where input drive determines the intrinsic (natural) frequency of oscillators. The gamma phase-locking, the precise phase relation and the emergent (measurable) frequencies were determined by two principal factors: the detuning (intrinsic frequency difference, i.e. local input difference) and the coupling strength. In addition to frequency coding, gamma phase contained complementary stimulus information. Crucially, the phase code reflected input differences, but not the absolute input level. This property of relative input-to-phase conversion, contrasting with latency codes or slower oscillation phase codes, may resolve conflicting experimental observations on gamma phase coding. Our modeling results offer clear testable experimental predictions. We conclude that input-dependency of gamma frequencies could be essential rather than detrimental for meaningful gamma-mediated temporal organization of cortical activity.
Data from: Detection of transient synchrony across oscillating receptors by the central electrosensory system of mormyrid fish
Contributors: Vélez, Alejandro, Carlson, Bruce A.
oscillations among receptors. We found that electrosensory stimulation...oscillating electroreceptors in weakly electric fish (Mormyridae) respond...oscillation frequencies of the receptors. These frequencies are lower ...Frequency tuning in the midbrain resembled peripheral frequency tuning ... Recently, we reported evidence for a novel mechanism of peripheral sensory coding based on oscillatory synchrony. Spontaneously oscillating electroreceptors in weakly electric fish (Mormyridae) respond to electrosensory stimuli with a phase reset that results in transient synchrony across the receptor population (Baker et al., 2015). Here, we asked whether the central electrosensory system actually detects the occurrence of synchronous oscillations among receptors. We found that electrosensory stimulation elicited evoked potentials in the midbrain exterolateral nucleus at a short latency following receptor synchronization. Frequency tuning in the midbrain resembled peripheral frequency tuning, which matches the intrinsic oscillation frequencies of the receptors. These frequencies are lower than those in individual conspecific signals, and instead match those found in collective signals produced by groups of conspecifics. Our results provide further support for a novel mechanism for sensory coding based on the detection of oscillatory synchrony among peripheral receptors.
Contributors: Lowet, Eric, Roberts, Mark Jonathan, Peter, Alina, Gips, Bart, de Weerd, Peter
frequency modulations applies to gamma in V1, and is likely generalizable...frequency by increasing input current) and coupling on their phase dynamics...frequency difference. Crucially, the precise dynamics of frequencies and...frequencies. When similar enough, these frequencies continually attracted...oscillators influence each other’s phase relations. Hence, the fundamental...oscillators. With this code the effects of detuning and coupling are illustrated...oscillating neuronal populations to optimize information transmission ... Gamma-band synchronization coordinates brief periods of excitability in oscillating neuronal populations to optimize information transmission during sensation and cognition. Commonly, a stable, shared frequency over time is considered a condition for functional neural synchronization. Here, we demonstrate the opposite: instantaneous frequency modulations are critical to regulate phase relations and synchronization. In monkey visual area V1, nearby local populations driven by different visual stimulation showed different gamma frequencies. When similar enough, these frequencies continually attracted and repulsed each other, which enabled preferred phase relations to be maintained in periods of minimized frequency difference. Crucially, the precise dynamics of frequencies and phases across a wide range of stimulus conditions was predicted from a physics theory that describes how weakly coupled oscillators influence each other’s phase relations. Hence, the fundamental mathematical principle of synchronization through instantaneous frequency modulations applies to gamma in V1, and is likely generalizable to other brain regions and rhythms.
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Data from: The impact of pathological high-frequency oscillations on hippocampal network activity in rats with chronic epilepsy
Contributors: Ewell, Laura A., Fischer, Kyle B., Leibold, Christian, Leutgeb, Stefan, Leutgeb, Jill K.
oscillations, which by comparison to control animals we could classify...high-frequency oscillations (pHFOs) during interictal periods. To understand...oscillations in overlapping frequency bands and potentially perturb hippocampal...oscillations ... In epilepsy, brain networks generate pathological high-frequency oscillations (pHFOs) during interictal periods. To understand how pHFOs differ from normal oscillations in overlapping frequency bands and potentially perturb hippocampal processing, we performed high-density single unit and local field potential recordings from hippocampi of behaving rats with and without chronic epilepsy. In epileptic animals, we observed two types of co-occurring fast oscillations, which by comparison to control animals we could classify as ‘ripple-like’ or ‘pHFO’. We compared their spectral characteristics, brain state dependence, and cellular participants. Strikingly, pHFO occurred irrespective of brain state, were associated with interictal spikes, engaged distinct subnetworks of principal neurons compared to ripple-like events, increased the sparsity of network activity, and initiated both general and immediate disruptions in spatial information coding. Taken together, our findings suggest that events that result in pHFOs have an immediate impact on memory processes, corroborating the need for proper classification of pHFOs to facilitate therapeutic interventions that selectively target pathological activity.
Contributors: Bos, Hannah, Diesmann, Markus, Helias, Moritz
frequency. The low-γ peak turns out to be generated in a sub-circuit located...oscillations visible in all populations. Since locally generated frequencies...frequency of the observed oscillations and identifies the minimal circuit...Oscillations are omnipresent in neural population signals, like multi-unit...oscillations...frequency-dependent connectivity map that reveals connections crucial ... Oscillations are omnipresent in neural population signals, like multi-unit recordings, EEG/MEG, and the local field potential. They have been linked to the population firing rate of neurons, with individual neurons firing in a close-to-irregular fashion at low rates. Using a combination of mean-field and linear response theory we predict the spectra generated in a layered microcircuit model of V1, composed of leaky integrate-and-fire neurons and based on connectivity compiled from anatomical and electrophysiological studies. The model exhibits low- and high-γ oscillations visible in all populations. Since locally generated frequencies are imposed onto other populations, the origin of the oscillations cannot be deduced from the spectra. We develop an universally applicable systematic approach that identifies the anatomical circuits underlying the generation of oscillations in a given network. Based on a theoretical reduction of the dynamics, we derive a sensitivity measure resulting in a frequency-dependent connectivity map that reveals connections crucial for the peak amplitude and frequency of the observed oscillations and identifies the minimal circuit generating a given frequency. The low-γ peak turns out to be generated in a sub-circuit located in layer 2/3 and 4, while the high-γ peak emerges from the inter-neurons in layer 4. Connections within and onto layer 5 are found to regulate slow rate fluctuations. We further demonstrate how small perturbations of the crucial connections have significant impact on the population spectra, while the impairment of other connections leaves the dynamics on the population level unaltered. The study uncovers connections where mechanisms controlling the spectra of the cortical microcircuit are most effective.
Data from: Cross-frequency synchronization connects networks of fast and slow oscillations during visual working memory maintenance
Contributors: Siebenhühner, Felix, Wang, Sheng H., Palva, J. Matias, Palva, Satu
within-frequency-synchronized networks and its strength predicted individual...frequencies to link sensory and attentional functions....oscillations during VWM maintenance among visual, FP, and dorsal attention...Cross-frequency coupling...cross-frequency phase synchrony (CFS). Using concurrent magneto- and electroencephalography...frequencies and thereby the sensory and attentional functions. We investigated...cross-frequency amplitude-amplitude correlations. ... Neuronal activity in sensory and fronto-parietal (FP) areas underlies the representation and attentional control, respectively, of sensory information maintained in visual working memory (VWM). Within these regions, beta/gamma phase-synchronization supports the integration of sensory functions, while synchronization in theta/alpha bands supports the regulation of attentional functions. A key challenge is to understand which mechanisms integrate neuronal processing across these distinct frequencies and thereby the sensory and attentional functions. We investigated whether such integration could be achieved by cross-frequency phase synchrony (CFS). Using concurrent magneto- and electroencephalography, we found that CFS was load-dependently enhanced between theta and alpha–gamma and between alpha and beta-gamma oscillations during VWM maintenance among visual, FP, and dorsal attention (DA) systems. CFS also connected the hubs of within-frequency-synchronized networks and its strength predicted individual VWM capacity. We propose that CFS integrates processing among synchronized neuronal networks from theta to gamma frequencies to link sensory and attentional functions.
Data from: Genomic evidence of rapid and stable adaptive oscillations over seasonal time scales in Drosophila
Contributors: Bergland, Alan O., Behrman, Emily L., O'Brien, Katherine R., Schmidt, Paul S., Petrov, Dmitri A.
frequency and read depths of the 14 samples described in Bergland et al...frequencies; and, quality filters. This VCF file only contains SNPs with...frequency oscillates among seasons and argue that these loci are subject...oscillations at balanced polymorphisms. We identified hundreds of polymorphisms...frequency > 0.15....frequencies for long periods. So called “balanced polymorphisms” have ...oscillating polymorphisms are likely millions of years old, with some ... In many species, genomic data have revealed pervasive adaptive evolution indicated by the fixation of beneficial alleles. However, when selection pressures are highly variable along a species' range or through time adaptive alleles may persist at intermediate frequencies for long periods. So called “balanced polymorphisms” have long been understood to be an important component of standing genetic variation, yet direct evidence of the strength of balancing selection and the stability and prevalence of balanced polymorphisms has remained elusive. We hypothesized that environmental fluctuations among seasons in a North American orchard would impose temporally variable selection on Drosophila melanogaster that would drive repeatable adaptive oscillations at balanced polymorphisms. We identified hundreds of polymorphisms whose frequency oscillates among seasons and argue that these loci are subject to strong, temporally variable selection. We show that these polymorphisms respond to acute and persistent changes in climate and are associated in predictable ways with seasonally variable phenotypes. In addition, our results suggest that adaptively oscillating polymorphisms are likely millions of years old, with some possibly predating the divergence between D. melanogaster and D. simulans. Taken together, our results are consistent with a model of balancing selection wherein rapid temporal fluctuations in climate over generational time promotes adaptive genetic diversity at loci underlying polygenic variation in fitness related phenotypes.
Contributors: Lin, Genghong, Jiao, Feng, Sun, Qiwen, Tang, Moxun, Yu, Jianshe, Zhou, Zhan
Oscillation and noise filtration...frequency, but the magnitude decreases in the frequency and is almost...oscillation and the noise in the random promoter state selection, as observed...oscillate periodically, $m(t)$ also oscillates later, almost periodically...frequencies. This gives a surprising indication that multiple promoter ... The transcription of inducible genes involves signaling pathways that induce DNA binding of the downstream transcription factors to form functional promoter states. How the transcription dynamics is linked to the temporal variations of activation signals is far to be fully understood. In this work, we develop a mathematical model with multiple promoter states to address this question. Each promoter state has its own activation and inactivation rates, and is selected randomly with a probability that may change in time. Under the activation of constant signals, our analysis shows that if only the activation rates differ among the promoter states, then the mean transcription level $m(t)$ displays only a monotone or monophasic growth pattern. In a sharp contrast, if the inactivation rates change with the promoter states, then $m(t)$ may display multiphasic growth patterns. Upon the activation of signals that oscillate periodically, $m(t)$ also oscillates later, almost periodically in the same frequency, but the magnitude decreases in the frequency and is almost completely attenuated at large frequencies. This gives a surprising indication that multiple promoter states could filter out the signal oscillation and the noise in the random promoter state selection, as observed in the transcription of a gene activated by p53 in breast carcinoma cells. Our approach may help develop a theoretical framework to integrate coherently the genetic circuit with the promoter states to elucidate the linkage from the activation signal to the temporal profile of transcription outputs.
Data from: On cross-frequency phase-phase coupling between theta and gamma oscillations in the hippocampus
Contributors: Scheffer-Teixeira, Robson, Tort, Adriano B. L.
oscillations were also reported to exhibit phase-phase coupling, or n:...frequency harmonics may generate artifactual n:m phase-locking. Studies ... Phase-amplitude coupling between theta and multiple gamma sub-bands is a hallmark of hippocampal activity and believed to take part in information routing. More recently, theta and gamma oscillations were also reported to exhibit phase-phase coupling, or n:m phase-locking, suggesting an important mechanism of neuronal coding that has long received theoretical support. However, by analyzing simulated and actual LFPs, here we question the existence of theta-gamma phase-phase coupling in the rat hippocampus. We show that the quasi-linear phase shifts introduced by filtering lead to spurious coupling levels in both white noise and hippocampal LFPs, which highly depend on epoch length, and that significant coupling may be falsely detected when employing improper surrogate methods. We also show that waveform asymmetry and frequency harmonics may generate artifactual n:m phase-locking. Studies investigating phase-phase coupling should rely on appropriate statistical controls and be aware of confounding factors; otherwise, they could easily fall into analysis pitfalls.
Contributors: Baker, Christa A., Huck, Kevin R., Carlson, Bruce A.
oscillating potentials. We found that oscillating receptors respond to...oscillations...frequencies found only in the collective signals of groups of conspecifics...frequencies. Thus, different perceptual capabilities correspond to different ... Adaptations to an organism's environment often involve sensory system modifications. In this study, we address how evolutionary divergence in sensory perception relates to the physiological coding of stimuli. Mormyrid fishes that can detect subtle variations in electric communication signals encode signal waveform into spike-timing differences between sensory receptors. In contrast, the receptors of species insensitive to waveform variation produce spontaneously oscillating potentials. We found that oscillating receptors respond to electric pulses by resetting their phase, resulting in transient synchrony among receptors that encodes signal timing and location, but not waveform. These receptors were most sensitive to frequencies found only in the collective signals of groups of conspecifics, and this was correlated with increased behavioral responses to these frequencies. Thus, different perceptual capabilities correspond to different receptor physiologies. We hypothesize that these divergent mechanisms represent adaptations for different social environments. Our findings provide the first evidence for sensory coding through oscillatory synchrony.