Navegando por Autor "Brankačk, Jurij"
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Artigo Impaired theta-gamma coupling in APP-defcient mice(2016-02-24) Zhang, Xiaomin; Zhong, Wewei; Brankačk, Jurij; Weyer, Sascha W.; Müller, Ulrike C.; Tort, Adriano Bretanha Lopes; Draguhn, AndreasAmyloid precursor protein (APP) is critically involved in the pathophysiology of Alzheimer's disease, but its physiological functions remain elusive. Importantly, APP knockout (APP-KO) mice exhibit cognitive deficits, suggesting that APP plays a role at the neuronal network level. To investigate this possibility, we recorded local field potentials (LFPs) from the posterior parietal cortex, dorsal hippocampus and lateral prefrontal cortex of freely moving APP-KO mice. Spectral analyses showed that network oscillations within the theta- and gamma-frequency bands were not different between APP-KO and wild-type mice. Surprisingly, however, while gamma amplitude coupled to theta phase in all recorded regions of wild-type animals, in APP-KO mice theta-gamma coupling was strongly diminished in recordings from the parietal cortex and hippocampus, but not in LFPs recorded from the prefrontal cortex. Thus, lack of APP reduces oscillatory coupling in LFP recordings from specific brain regions, despite not affecting the amplitude of the oscillations. Together, our findings reveal reduced cross-frequency coupling as a functional marker of APP deficiency at the network level.Artigo Parallel detection of theta and respiration-coupled oscillations throughout the mouse brain(2018-04-24) Tort, Adriano Bretanha Lopes; Ponsel, Simon; Jessberger, Jakob; Yanovsky, Yevgenij; Brankačk, Jurij; Draguhn, AndreasSlow brain oscillations are usually coherent over long distances and thought to link distributed cell assemblies. In mice, theta (5–10 Hz) stands as one of the most studied slow rhythms. However, mice often breathe at theta frequency, and we recently reported that nasal respiration leads to local field potential (LFP) oscillations that are independent of theta. Namely, we showed respiration-coupled oscillations in the hippocampus, prelimbic cortex, and parietal cortex, suggesting that respiration could impose a global brain rhythm. Here we extend these findings by analyzing LFPs from 15 brain regions recorded simultaneously with respiration during exploration and REM sleep. We find that respiration-coupled oscillations can be detected in parallel with theta in several neocortical regions, from prefrontal to visual areas, and also in subcortical structures such as the thalamus, amygdala and ventral hippocampus. They might have escaped attention in previous studies due to the absence of respiration monitoring, the similarity with theta oscillations, and the highly variable peak frequency. We hypothesize that respiration-coupled oscillations constitute a global brain rhythm suited to entrain distributed networks into a common regime. However, whether their widespread presence reflects local network activity or is due to volume conduction remains to be determined.Artigo Respiration and rapid eye movement (REM) sleep substructure: short versus long episodes(Wiley, 2022-11) Hammer, Maximilian; Jung, Felix; Brankačk, Jurij; Yanovsky, Yevgenij; Tort, Adriano Bretanha Lopes; Draguhn, AndreasRapid eye movement (REM) sleep in rodents is defined by the presence of theta rhythm in the absence of movement. The amplitude and frequency of theta oscillations have been used to distinguish between tonic and phasic REM sleep. However, tonic REM sleep has not been further subdivided, although characteristics of network oscillations such as cross-frequency coupling between theta and gamma vary within this sub-state. Recently, it has been shown that theta-gamma coupling depends on an optimal breathing rate of ~5 Hz. The frequency of breathing varies strongly throughout REM sleep, and the duration of single REM sleep episodes ranges from several seconds to minutes, whereby short episodes predominate. Here we studied the relation between breathing frequency, accelerometer activity, and the length of REM sleep periods. We found that small movements detected with three-dimensional accelerometry positively correlate with breathing rate. Interestingly, breathing is slow in short REM sleep episodes, while faster respiration regimes exclusively occur after a certain delay in longer REM sleep episodes. Thus, merging REM sleep episodes of different lengths will result in a predominance of slow respiration due to the higher occurrence of short REM sleep periods. Moreover, our results reveal that not only do phasic REM sleep epochs predominantly occur during long REM sleep episodes, but that the long episodes also have faster theta and higher gamma activity. These observations suggest that REM sleep can be further divided from a physiological point of view depending on its duration. Higher levels of arousal during REM sleep, indicated by higher breathing rates, can only be captured in long REM sleepArtigo Similarities and differences between natural sleep and urethane anesthesia(Springer Science and Business Media LLC, 2025) Brankačk, Jurij; Yanovsky, Yevgenij; Tort, Adriano Bretanha Lopes; Draguhn, Andreas; https://orcid.org/0000-0002-9877-7816Slow oscillations dominate the EEG or local field potential (LFP) of mammals during specific periods within natural sleep and anesthesia. Such similarities have led to the use of anesthesia as a model to study sleep and state-dependent changes of consciousness. Previous research has documented the similarities between the activated state of urethane anesthesia and natural REM sleep, particularly with respect to network oscillations in the theta (θ) frequency domain. Likewise, the deactivated states, characterized by large amplitude slow waves in both urethane anesthesia and non-REM sleep, have generally been regarded as similar. Here, we report striking differences between slow oscillations in the mouse parietal cortex during the deactivated state of urethane anesthesia and natural non-REM sleep. These differences are notable in the LFP, the underlying current sources, and in the modulation of unit activity. Our data show that slow network oscillations in natural sleep and anesthesia are generated by different mechanisms, despite phenomenological similaritiesArtigo Theta-gamma coupling during REM sleep depends on breathing rate(Oxford University Press, 2021-07-23) Hammer, Maximilian; Schwale, Chrysovalandis; Brankačk, Jurij; Draguhn, Andreas; Tort, Adriano Bretanha LopesTemporal coupling between theta and gamma oscillations is a hallmark activity pattern of several cortical networks and becomes especially prominent during REM sleep. In a parallel approach, nasal breathing has been recently shown to generate phase-entrained network oscillations which also modulate gamma. Both slow rhythms (theta and respiration-entrained oscillations) have been suggested to aid large-scale integration but they differ in frequency, display low coherence, and modulate different gamma sub-bands. Respiration and theta are therefore believed to be largely independent. In the present work, however, we report an unexpected but robust relation between theta-gamma coupling and respiration in mice. Interestingly, this relation takes place not through the phase of individual respiration cycles, but through respiration rate: the strength of theta-gamma coupling exhibits an inverted V-shaped dependence on breathing rate, leading to maximal coupling at breathing frequencies of 4-6 Hz. Noteworthy, when subdividing sleep epochs into phasic and tonic REM patterns, we find that breathing differentially relates to theta-gamma coupling in each state, providing new evidence for their physiological distinctiveness. Altogether, our results reveal that breathing correlates with brain activity not only through phase-entrainment but also through rate-dependent relations with theta-gamma coupling. Thus, the link between respiration and other patterns of cortical network activity is more complex than previously assumed