Biology subjects

Deboer, T.

Publications and source records attributed to Deboer, T..

3 recordsLinked to original sources

bioRxiv2026

Is torpor a quiescent state? Periodic motility and transient brain activation during daily torpor in Djungarian hamsters

Torpor is a hypometabolic state employed by many mammalian and non-mammalian species to cope with harsh environments. When exposed to a short photoperiod, Djungarian hamsters (Phodopus sungorus) enter daily torpor with body temperatures dropping to as low as 15{degrees}C. Despite the widely-held notion that torpor is a form of deep sleep, torpid animals are not completely inactive but exhibit occasional movements reflected in an increase in EMG tone. Little is known about these EMG events during torpor and whether they have a functional role during the torpid state. We here analysed EEG, EMG, and brain temperature data from Djungarian hamsters, and used an automatic detection algorithm to identify periods of EMG activation during spontaneous daily torpor. The hamsters exhibited regular periods of motility that were invariably initiated during a decline in brain temperature and were followed by a brain temperature increase. The frequency of EMG events exhibited a negative correlation with brain temperature, such that lower brain temperature was associated with a higher frequency of EMG events. In addition, EMG events were associated with a pronounced increase in EEG power, especially between 9.5-15.5 Hz, which often started with an EEG pattern similar to an evoked potential preceding the increase in the EMG activity. On the contrary, micro-arousals during normothermic NREM sleep were associated with a decrease in EEG power, a decrease in brain temperature and were of shorter duration than torpor EMG events, indicating that the two phenomena may serve different purposes. We speculate that periodic motility associated with increased brain activity during torpor may play a role in thermoregulation, and help retain vigilance to potentially mitigate predation risk during this hypometabolic state.

neuroscience↗

bioRxiv2025

Dim Light at Night Disrupts the Sleep-Wake Cycle and Exacerbates Seizure Activity in Cntnap2 Knockout Mice: Implications for Autism Spectrum Disorders

Epilepsy is one of the most common comorbidities in individuals with autism spectrum disorders (ASDs). Many patients with epilepsy as well as ASD experience disruptions in their sleep-wake cycle and exhibit daily rhythms in expression of symptoms. Chronic exposure to light at nighttime can disrupt sleep and circadian rhythms. Contactin associated protein-like 2 knockout (Cntnap2 KO) mice, a model for autism spectrum disorder (ASD) and epilepsy, exhibit sleep and circadian disturbances and seizure-like events. This study examines how chronic dim light at night (DLaN) exposure affects sleep architecture, EEG power spectra, and seizure activity in Cntnap2 KO and wildtype (WT) mice. Using electroencephalography (EEG) recordings, male and female Cntnap2 KO and WT mice were exposed to DLaN (5 lux) for 2 or 6 weeks. EEG recordings were analyzed to assess sleep architecture, power spectrum, and seizure-like events. DLaN exposure delays the wake onset and disrupts sleep patterns in a sex-dependent manner, with females being more affected. DLaN significantly increased slow-wave activity (SWA, 0.5-4 Hz) in both WT and KO mice, indicating increased sleep pressure. Finally, we found that DLaN dramatically increased the frequency of seizure-like events in the Cntnap2 KO mice and even increased the occurrence rate in the WT mice. Spectral analysis of seizure-like events revealed increased theta power, suggesting the involvement of hippocampus. Chronic DLaN exposure disrupts sleep and increases seizure-like events in Cntnap2 KO mice, with sex-specific differences. These findings emphasize the potential risks of nighttime light exposure for individuals with ASD and epilepsy, reinforcing the need to manage light exposure to improve sleep quality and reduce seizure risk.

neuroscience↗

bioRxiv2022

Behavioral activity increases neuronal activity in the circadian clock of diurnal Arvicanthis ansorgei

2.The central circadian clock, located in the suprachiasmatic nucleus (SCN) within the brain, regulates daily patterns of activity and physiology. Many studies indicate that exercise at specific times throughout the day can help maintain proper circadian rhythms. In nocturnal animals, even moderate levels of physical activity suppress the neuronal discharge rate of the SCN. Given that such a mechanism would likely be counter-effective in diurnal animals, we measured the firing rate of SCN neurons in freely moving diurnal Arvicanthis ansorgei using implanted microelectrodes. We found that SCN firing was acutely increased rather than decreased both during brief (seconds) and long (hours) bouts of activity, and returned to baseline levels after behavioral activity ceased. We also found that daytime activity increases the strength of the SCN rhythm, as expected for day-active animals. To determine whether the acute increases in firing are produced within the SCN or in response to input from outside the SCN, we performed ex vivo recordings in which afferent inputs are severed. We found no intrinsic increment occurring in the isolated SCN. These findings suggest that the excitatory effect on the SCNs neuronal firing rate comes from areas that lie outside the SCN, presumably those that are affected by the animals activity. We conclude that exercise has opposite effects on the clock between nocturnal and diurnal rodents, and identified how exercise strengthens the neuronal discharge rhythm in the clock of a diurnal animal. 3. Significance statementOur biological clock controls behavioral activity rhythms by generating a 24-pattern of electrical activity. The electrical activity serves as output of the clock and is high during the day and low during the night. Physical activity, being under strong control of the clock, acts vice versa, and affects the electrical activity of the clock. In nocturnal animals, behavioral activity inhibits the clocks firing rate. Here, we examined the effect of behavioral activity on the brains clock in the diurnal rodent, Arvicanthis. When the animal is active, the clocks electrical activity is enhanced, rather than decreased. Thus, a diurnal animal can increase the strength of its own clock, by being active during the day. Preprint ServersThe manuscript was deposited as a preprint in bioRxiv preprint doi: https://doi.org/10.1101/2022.05.31.493966; this version posted June 1, 2022. The copyright holder for this preprintin bioRxiv, made available under aCC-BY-NC-ND 4.0 International license (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. ClassificationBiological Sciences, Physiology

neuroscience↗