Biology subjects

Cavelli, M.

Publications and source records attributed to Cavelli, M..

11 recordsLinked to original sources

bioRxiv2026

State-dependent top-down and bottom-up processes in gamma-band (~40 Hz) oscillations of the cat EEG

Cognitive processes rely on extensive thalamocortical and corticocortical recurrent interactions. The gamma frequency band ([~]40 Hz) of the electroencephalogram (EEG) emerges from these interactions. Importantly, cognitive processing depends on the interplay between bottom-up sensory inputs and top-down influences from higher-order cortical areas. However, the extent to which gamma-band oscillations are associated with directional patterns of functional interactions remains unclear. Therefore, the aim of this study was to investigate the directionality of gamma-band information flow during wakefulness (W) and sleep, under spontaneous conditions and in response to auditory stimulation. Cats were chronically implanted for polysomnographic recordings, with electrodes placed in multiple cortical and thalamic regions. Information-flow directionality was assessed using two complementary methods: (i) time-lag analysis of gamma-band amplitude envelopes between pairs of channels, and (ii) Granger Causality analysis of the same channel pairs. During quiet W gamma-band oscillations exhibited a predominantly top-down directional organization, from higher- to lower-order cortical areas, as well as from cortical regions to thalamic nuclei. Following auditory stimulation, a prominent gamma response emerged between 0.5 and 1.5 s after stimulus onset. Within this time window, distinct patterns of gamma-band information flow were observed depending on the nature of the stimulus. Specifically, a bottom-up directional predominance was observed for simple auditory stimuli (clicks), whereas top-down processing prevailed for complex variable stimuli. In contrast, no consistent directionality of information flow was observed during either NREM or REM sleep, regardless of whether auditory stimulation was present. These findings extend our understanding of gamma-band information-flow dynamics during wakefulness and sleep.

neuroscience↗

bioRxiv2024

Differential Effects of Haloperidol on Neural Oscillations During Wakefulness and Sleep

The electrical activity of the brain, characterized by its frequency components, reflects a complex interplay between periodic (oscillatory) and aperiodic components. These components are associated with various neurophysiological processes, such as the excitation-inhibition balance (aperiodic activity) or interregional communication (oscillatory activity). However, we do not fully understand whether these components are truly independent or if different neuromodulators modulate them in different ways. The dopaminergic system has a critical role for cognition and motivation, being a potential modulator of these power spectrum components. To improve our understanding of these questions, we investigated the differential effects of this system on these components using electrocorticogram recordings in cats, which show clear oscillations and aperiodic 1/f activity. Specifically, we focused on the effects of haloperidol (a D2 receptor antagonist) on oscillatory and aperiodic dynamics during wakefulness and sleep. By parameterizing the power spectrum into these two components, our findings reveal a state-dependent modulation of oscillatory activity by the D2 receptor across the brain. Surprisingly, aperiodic activity was not significantly affected and exhibited inconsistent changes across the brain. This suggests a nuanced interplay between neuromodulation and the distinct components of brain oscillations, providing insights into the selective regulation of oscillatory dynamics in awake states.

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bioRxiv2023

Characterizing the power spectrum dynamics of the NREM to REM sleep transition

The transition from NREM to REM sleep is considered a transitional or intermediate stage (IS), characterized by high amplitude spindles in the frontal cortex and theta activity in the occipital cortex. Early reports in rats showed an IS lasting from 1 to 5 s, but recent studies suggested a longer duration of this stage. To further characterize the IS, we analyzed its spectral characteristics on electrocorticogram (ECoG) recordings of the olfactory bulb (OB), motor (M1), somato-sensory (S1) and secondary visual cortex (V2) in twelve Wistar male adult rats. By comparing the IS to consolidated NREM/REM epochs, our results reveal that the IS has specific power spectral patterns that statistically differ from both NREM and REM sleep states. Specifically, the main findings were that sigma (11-16 Hz) and beta (17-30 Hz) power in OB, M1, and S1 increased during the IS compared to NREM and REM sleep and began 55 s before REM sleep onset. Additionally, low gamma (31-48 Hz) in the OB started transitioning from NREM levels to REM ones 65 s before its onset. Finally, the high-frequency oscillations (102-198 Hz) in OB, M1, and S1 showed a power increase that began 40 s before REM sleep and reached REM sleep values 10 s after its onset. Thus, we argue that the NREM to REM transition contains its own spectral profile and is more extended than previously described.

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bioRxiv2021

Low Frequency Oscillations drive EEG's complexity changes during wakefulness and sleep

Recently, the sleep-wake states have been analysed using novel complexity measures, complementing the classical analysis of EEGs by frequency bands. This new approach consistently shows a decrease in EEGs complexity during slow-wave sleep, yet it is unclear how cortical oscillations shape these complexity variations. In this work, we analyse how the frequency content of brain signals affects the complexity estimates in freely moving rats. We find that the low-frequency spectrum - including the Delta, Theta, and Sigma frequency bands - drives the complexity changes during the sleep-wake states. This happens because low-frequency oscillations emerge from neuronal population patterns, as we show by recovering the complexity variations during the sleep-wake cycle from micro, meso, and macroscopic recordings. Moreover, we find that the lower frequencies reveal synchronisation patterns across the neocortex, such as a sensory-motor decoupling that happens during REM sleep. Overall, our works shows that EEGs low frequencies are critical in shaping the sleep-wake states complexity across cortical scales.

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bioRxiv2021

Urethane Anesthesia Exhibits Neurophysiological Correlates of Unconsciousness and is Distinct from Sleep

Urethane is a general anesthetic widely used in animal research. It is unique among anesthetics because urethane anesthesia alternates between macroscopically distinct electrographic states: a slow-wave state that resembles NREM sleep (NREMure), and an activated state with features of both REM sleep and wakefulness (REMure). However, the relationship between urethane anesthesia and physiological sleep is still unclear. In this study, electroencephalography (EEG) and electromyography were recorded in chronically prepared rats during natural sleep-wake states and during urethane anesthesia. We subsequently analyzed the EEG signatures associated with the loss of consciousness and found that, in comparison to natural sleep-wake states, the power, coherence, directed connectivity and complexity of brain oscillations are distinct during urethane. We also demonstrate that both urethane states have clear EEG signatures of general anesthesia. Thus, despite superficial similarities that have led others to conclude that urethane is a model of sleep, the electrocortical traits of depressed and activated states during urethane anesthesia differ from physiological sleep states.

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bioRxiv2021

OFF-periods reduce the complexity of neocortical activity during sleep

Complexity of electroencephalographic signals decreases during slow-wave sleep (SWS), however, the neural mechanism for this decrease remains elusive. Here, we show that this complexity reduction is caused by synchronous neuronal OFF-periods. We analyse in-vivo recordings from neocortical neuronal populations, finding that OFF-periods in SWS trap cortical dynamics, making the population activity more recurrent, deterministic, and less chaotic than during REM sleep or Wakefulness. Importantly, when we exclude OFF-periods, SWS becomes indistinguishable from Wakefulness or REM sleep. In fact, we show that spiking activity for all states has a universal scaling compatible with critical phenomena. We complement these results by a critical branching model that replicates our experimental findings, where we show that forcing OFF-periods to a percentage of neurons suffices to generate a decrease in complexity that replicates SWS.

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bioRxiv2020

Power and coherence in the EEG of the rat: impact of behavioral states, cortical area, lateralization and light/dark phases

The sleep-wake cycle is constituted by three behavioral states: wakefulness (W), non-REM (NREM) and REM sleep. These states are associated with drastic changes in cognitive capacities, mostly determined by the function of the thalamo-cortical system. Thalamo-cortical activity can be examined by means of the intra-cranial electroencephalogram (iEEG). With the purpose to study in depth the basal activity of the iEEG in adult rats, we analyzed the spectral power and coherence of the iEEG during W and sleep in the paleocortex (olfactory bulb), as well as in motor, somatosensory and visual neocortical areas. We also analyzed the laterality (right Vs. left hemispheres) of the signals, as well as the iEEG in function of the light and dark phases. We found that the iEEG power and coherence of the whole spectrum were largely affected by behavioral states and were highly dependent on the cortical areas recorded. We also determined that there are night/day differences in power and coherence during sleep, but not in W. Finally, while we did not find right/left differences in power either in W or sleep, we observed that during REM sleep intra-hemispheric coherence differs between both hemispheres. We conclude that the iEEG dynamics is highly dependent on the cortical area and behavioral states. We also determine that there are light/dark phases disparities in the iEEG that emerge during sleep, and that intra-hemispheric connectivity differs between both hemispheres only during REM sleep.

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bioRxiv2020

Gamma band alterations and REM-like traits underpin the acute effect of the atypical psychedelic ibogaine

Ibogaine is a psychedelic alkaloid that has attracted scientific interest because of its important antiaddictive properties evidenced in observational studies in humans, and in models for substance-use-disorders in rodents. Its subjective effect has been described as intense vivid dream-like experiences occurring while awake; hence, ibogaine is often referred to as an oneirogenic psychedelic. While this unique dream-like profile has been hypothesized to aid the antiaddictive effects in the past, the electrophysiological signatures of the ibogaine psychedelic state remain unknown. In our previous work, we showed in rats that ibogaine administration promotes a waking state with abnormal motor behavior, accompanied by a decrease in NREM and REM sleep. Here, we performed an in-depth analysis of the intracranial electroencephalogram during "ibogaine wakefulness". Ibogaine induced gamma oscillations with larger power than control levels but less coherent and less complex; i.e., this state shows clear REM sleep traits within the gamma frequency band. Thus, our results provide novel biological evidence for the association between the psychedelic state and REM sleep, and an empirical basis for the oneirogenic conjecture of ibogaine.

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bioRxiv2020

Communication through coherence by means of cross-frequency coupling

The theory of communication through coherence (CTC) posits the synchronization of brain oscillations as a key mechanism for information sharing and perceptual binding. In a parallel literature, hippocampal theta activity (4 - 10 Hz) has been shown to modulate the appearance of neocortical fast gamma oscillations (100 - 150 Hz), a phenomenon known as cross-frequency coupling (CFC). Even though CFC has also been previously associated with information routing, it remains to be determined whether it directly relates to CTC. In particular, for the theta-fast gamma example at hand, a critical question is to know if the phase of the theta cycle influences gamma synchronization across the neocortex. To answer this question, we designed a new screening method for detecting the modulation of the cross-regional high-frequency synchronization by the phase of slower oscillations. Upon applying the method, we found that the long-distance synchronization of neocortical fast gamma during REM sleep depends on the instantaneous phase of the theta rhythm. These results show that CFC is likely to aid long-range information transfer by facilitating the cross-regional synchronization of faster rhythms, thus consistent with classical CTC views.

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bioRxiv2020

Electrocortical temporal complexity during wakefulness and sleep: an updated account

The states of sleep and wakefulness are critical physiological processes associated with different brain patterns of activity. The intracranial electroencephalogram allows us to measure these changes, thus, it is a critical tool for its study. Recently, we showed that the electrocortical temporal complexity decreased from wakefulness to sleep. Nevertheless, the origin of this complex activity remains a controversial topic due to the existence of possible artifacts contaminating the brain signals. In this work, we showed that complexity decreases during sleep, independently of the electrode configuration employed. This fact strongly suggests that the basis for the behavioral-state differences in complexity does not have an extracranial origin; i.e., generated from the brain.

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bioRxiv2018

Nasal respiration entrains neocortical long-range gamma coherence during wakefulness

Recent studies have shown that slow cortical potentials in archi-, paleo- and neocortex, can phase-lock with nasal respiration. In some of these areas, gamma activity ({gamma}: 30-100 Hz) is also coupled to the animals respiration. It has been hypothesized that this interaction plays a role in coordinating distributed neural activity. In a similar way, inter-cortical interactions at {gamma} frequency has been also associated as a binding mechanism by which the brain generates temporary opportunities necessary for implementing cognitive functions. The aim of the present study is to explore if nasal respiration entrains inter-cortical interactions at {gamma} frequency.\n\nSix adult cats chronically prepared for electrographic recordings were employed in this study. Our results show that slow cortical respiratory potentials are present in several areas of the neocortex and olfactory bulb during wakefulness. Also, we found cross-frequency coupling between the respiratory phase and the amplitude of {gamma} activity in all recorded areas. These oscillatory entrainments are independent of muscular activity, because are maintained during cataplexy induced by carbachol microinjection into the nucleus pontis oralis. Importantly, we observed that respiratory phase modulates the inter-cortical gamma coherence between neocortical pairs of electrodes during wakefulness. However, during NREM and REM sleep, breathing was unable to entrain the oscillatory activity, neither in the olfactory bulb nor in the neocortex. These results suggest a single unified phenomenon involving cross frequency coupling and long-range {gamma} coherence across the neocortex. This fact could be related to a temporal binding process necessary for cognitive functions during wakefulness.

neuroscience↗