Navegando por Autor "Scheffer-Teixeira, Robson"
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Artigo Dopamine Modulates Delta-Gamma Phase-Amplitude Coupling in the Prefrontal Cortex of Behaving Rats(2017-05-09) Andino-Pavlovsky, Victoria; Souza, Annie C.; Scheffer-Teixeira, Robson; Tort, Adriano Bretanha Lopes; Etchenique, Roberto; Ribeiro, Sidarta Tollendal GomesDopamine release and phase-amplitude cross-frequency coupling (CFC) have independently been implicated in prefrontal cortex (PFC) functioning. To causally investigate whether dopamine release affects phase-amplitude comodulation between different frequencies in local field potentials (LFP) recorded from the medial PFC (mPFC) of behaving rats, we used RuBiDopa, a light-sensitive caged compound that releases the neurotransmitter dopamine when irradiated with visible light. LFP power did not change in any frequency band after the application of light-uncaged dopamine, but significantly strengthened phase-amplitude comodulation between delta and gamma oscillations. Saline did not exert significant changes, while injections of dopamine and RuBiDopa produced a slow increase in comodulation for several minutes after the injection. The results show that dopamine release in the medial PFC shifts phase-amplitude comodulation from theta-gamma to delta-gamma. Although being preliminary results due to the limitation of the low number of animals present in this study, our findings suggest that dopamine-mediated modification of the frequencies involved in comodulation could be a mechanism by which this neurotransmitter regulates functioning in mPFC.Artigo Ketamine alters oscillatory coupling in the hoppocampus(Nature Publishing Group, 2013-08-02) Caixeta, Fábio; Cornélio, Alianda; Scheffer-Teixeira, Robson; Ribeiro, Sidarta Tollendal Gomes; Tort, Adriano Bretanha LopesArtigo On cross-frequency phase-phase coupling between theta and gamma oscillations in the hippocampus(2016-12-07) Scheffer-Teixeira, Robson; Tort, Adriano Bretanha LopesPhase-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.Artigo On High-Frequency Field Oscillations ( 100 Hz) and the Spectral Leakage of Spiking Activity(2013-01-23) Scheffer-Teixeira, Robson; Belchior, Hindiael; Leão, Richardson Naves; Ribeiro, Sidarta Tollendal Gomes; Tort, Adriano Bretanha LopesRecent reports converge to the idea that high-frequency oscillations in local field potentials (LFPs) represent multiunit activity. In particular, the amplitude of LFP activity above 100 Hz—commonly referred to as “high-gamma” or “epsilon” band—was found to correlate with firing rate. However, other studies suggest the existence of true LFP oscillations at this frequency range that are different from the well established ripple oscillations. Using multisite recordings of the hippocampus of freely moving rats, we show here that high-frequency LFP oscillations can represent either the spectral leakage of spiking activity or a genuine rhythm, depending on recording location. Both spike-leaked, spurious activity and true fast oscillations couple to theta phase; however, the two phenomena can be clearly distinguished by other key features, such as preferred coupling phase and spectral signatures. Our results argue against the idea that all high-frequency LFP activity stems from spike contamination and suggest avoiding defining brain rhythms solely based on frequency range.Artigo Theta-associated high-frequency oscillations (110–160 Hz) in the hippocampus and neocortex(2013) Tort, Adriano Bretanha Lopes; Scheffer-Teixeira, Robson; Souza, Bryan C.; Draguhn, Andreas; Brankacˇk, JurijCapítulo de livro Theta-Gamma Cross-Frequency Analyses (Hippocampus)(2018) Scheffer-Teixeira, Robson; Tort, Adriano Bretanha LopesBrain oscillations of different frequencies can coexist and influence each other. A cross-frequency interaction occurs when a feature from one oscillation (i.e., instantaneous amplitude, phase, or frequency) depends on a feature from another oscillation at a distinct frequency. These phenomena have been collectively called cross-frequency coupling (CFC). There are multiple types of CFC, such as phase-amplitude coupling, amplitude-amplitude coupling, and n:m phase-locking. Several metrics have been devised to quantify CFC.Artigo Unveiling fast field oscillations through comodulation(2017-07-26) Scheffer-Teixeira, Robson; Tort, Adriano Bretanha LopesPhase-amplitude coupling analysis shows that theta phase modulates oscillatory activity not only within the traditional gamma band (30–100 Hz) but also at faster frequencies, called high-frequency oscillations (HFOs; 120–160 Hz). To date, however, theta-associated HFOs have been reported by only a small number of laboratories. Here we characterized coupling patterns during active waking (aWk) and rapid eye movement (REM) sleep in local field potentials (LFPs) from the parietal cortex and hippocampus of rats, focusing on how theta-associated HFOs can be detected. We found that electrode geometry and impedance only mildly influence HFO detection, whereas recording location and behavioral state are main factors. HFOs were most prominent in parietal cortex and during REM sleep, although they could also be detected in stratum oriens-alveus and during aWK. The underreporting of HFOs may thus be a result of higher prevalence of recordings from the pyramidal cell layer. However, at this layer, spike-leaked HFOs (SLHFOs) dominate, which represent spike contamination of the LFP and not genuine oscillations. In contrast to HFOs, high-gamma (HG; 60–100 Hz) coupled to theta below the pyramidal cell layer; theta–HG coupling increased during REM sleep. Theta also weakly modulated low-gamma (LG; 30–60 Hz) amplitude, mainly in the parietal cortex; theta–LG coupling did not vary between aWK and REM sleep. HG and HFOs were maximal near the theta peak, parietal LG at the ascending phase, hippocampal LG at the descending phase, and SLHFOs at the trough. Our results unveil four types of fast LFP activity coupled to theta and outline how to detect theta-associated HFOs.