Biology subjects

Ondracek, J. M.

Publications and source records attributed to Ondracek, J. M..

5 recordsLinked to original sources

bioRxiv2024

Neural population dynamics during sleep in a songbird vocal circuit resemble sharp wave ripple activity

Similar to motor skill learning in mammals, vocal learning in songbirds requires a set of interconnected brain areas that make up an analogous basal ganglia-thalamocortical circuit known as the anterior forebrain pathway (AFP). Although neural activity in the AFP has been extensively investigated during awake singing, very little is known about its neural activity patterns during other behavioral states. Here, we used chronically implanted Neuropixels probes to investigate spontaneous neural activity in the AFP during natural sleep and awake periods in male zebra finches. We found that during sleep, neuron populations in the pallial region LMAN (lateral magnocellular nucleus of the nidopallium) spontaneously exhibited synchronized bursts that were characterized by a negative sharp deflection in the local field potential (LFP) and a transient increase in gamma power. LMAN population bursts occurred primarily during non-rapid eye movement (NREM) sleep and were highly reminiscent of sharp-wave ripple (SWR) activity observed in rodent hippocampus. We also examined the functional connectivity within the AFP by calculating the pairwise LFP coherence. As expected, delta and theta band coherence within LMAN and Area X was higher during sleep compared to awake periods. Contrary to our expectations, we did not observe strong coherence between LMAN and Area X during sleep, suggesting that the input from LMAN into Area X is spatially restricted. Overall, these results provide the first description of spontaneous neural dynamics within the AFP across behavioral states. Significance statementAlthough cortical and basal ganglia circuits are known to be required for learning in both mammals and birds, little is known about the ongoing spontaneous activity patterns within these circuits, or how they are modulated by behavioral state. Here we prove the first description of cortical-basal ganglia network activity during sleep and awake periods in birds. Within the pallial area LMAN, we observed population-wide bursting events that were highly reminiscent of hippocampal sharp-wave ripple (SWR) activity, suggesting that large-scale population events have diverse functions across vertebrates.

neuroscience↗

bioRxiv2023

Local sleep in songbirds: Different simultaneous sleep states across the avian pallium

Wakefulness and sleep have often been treated as distinct and global brain states. However, an emerging body of evidence on the local regulation of sleep stages challenges this conventional view. Apart from unihemispheric sleep, the current data that support local variations of neural oscillations during sleep are focused on the homeostatic regulation of local sleep, i.e., the role preceding awake activity. Here, to examine local differences in brain activity during natural sleep, we recorded the electroencephalogram (EEG) and the local field potential (LFP) across multiple sites within the avian pallium of zebra finches without perturbing the previous awake state. We scored the sleep stages independently in each pallial site and found that the sleep stages are not pallium-wide phenomena but rather deviate widely across electrode sites. Importantly, deeper electrode sites had a dominant role in defining the temporal aspects of sleep state congruence. Altogether, these findings show that local regulation of sleep oscillations also occurs in the avian brain without prior awake recruitment of specific pallial circuits and in the absence of mammalian cortical neural architecture.

neuroscience↗

bioRxiv2023

Nociception in chicken embryos, Part III: Analysis of movements before and after application of a noxious stimulus

Many potentially noxious interventions are performed on chicken embryos in research and in the poultry industry. It is therefore in the interest of animal welfare to define the point at which a chicken embryo is capable of nociception. The present part III of a comprehensive study examined the movements of developing chicken embryos with the aim of identifying behavioral responses to aww noxious stimulus. For this purpose, a noxious mechanical stimulus and a control stimulus were applied. The recorded movements of the embryos were evaluated using the markerless pose estimation software DeepLabCut and manual observations. After the application of the noxious stimulus, a significant increase in beak movement was identified in 15- to 18-day-old embryos. In younger embryos, no behavioral changes related to the noxious stimulus were observed. The results indicate that noxious stimuli at the beak base evoke a nocifensive reaction in chicken embryos starting at embryonic day 15.

animal behavior and cognition↗

bioRxiv2022

Multi-channel EEG recordings during sleep in juvenile zebra finches highlight developmental changes in sleep structure and functional connectivity similar to mammals

Despite their phylogenetic differences and distinct pallial structures, mammals and birds show similar electroencephalography (EEG) traces during sleep, consisting of distinct rapid eye movement (REM) sleep and slow wave sleep (SWS) stages. Studies in human and a limited number of other mammalian species shows that this organization of sleep into interleaving stages undergoes radical changes during lifetime. Do these age-dependent variations in sleep patterns also occur in the avian brain? Does vocal learning have an effect on sleep patterns in birds? To answer this question, we recorded multi-channel sleep EEG from juveniles and adult zebra finches for several nights. Whereas adults spent more time in SWS and REM sleep, juveniles spent more time in intermediate sleep (IS). The amount of IS sleep was significantly larger in male juveniles engaged in vocal learning compared to female juveniles, which suggest that IS sleep could be important for learning. In addition, we observed that the functional connectivity increased rapidly during maturation of young juveniles, and was stable or declined at older ages. Synchronous activity during sleep was larger for recording sites in the left hemisphere for both juveniles and adults, and generally intra-hemispheric synchrony was larger than inter-hemispheric synchrony during sleep. A graph theory analysis revealed that in adults, highly correlated EEG activity tends to be distributed across fewer networks that are spread across a wider area of the brain, whereas in juveniles, highly correlated EEG activity is distributed across more numerous, albeit smaller, networks in the brain. Overall, our results reveal significant changes in the neural signatures of sleep during maturation in an avian brain.

neuroscience↗

bioRxiv2019

Hippocampal-like network dynamics underlie avian sharp wave-ripples

Sharp wave ripples (SWR) represent one of the most synchronous population patterns in the mammalian brain. Although SWRs are highly conserved throughout mammalian evolution, the existence of SWRs in non-mammalian species remains controversial. We reexamined the existence of avian SWRs by recording the brain activity during sleep and under anesthesia in two species of birds, the zebra finch and the chicken. Electrophysiological recordings using silicon probes implanted in the avian telencephalon revealed highly dynamic switching between high and low delta phases during sleep. High delta phases were composed of large-amplitude, negative deflections (sharp waves) that coincided with a high frequency oscillation (ripple). Correlation analysis revealed that these events were highly synchronous and spanned a large anatomical range of the avian telencephalon. Finally, detailed spike analysis revealed that an increase in the population spiking activity coincided with the occurrence of SWRs, that this spiking activity occurred in specific sequences of spike patterns locked to the SWRs, and that the mean population spiking activity peaked prior to the trough of the negative deflection. These results provide the first evidence of avian SWRs during natural sleep and under anesthesia, and suggest that the evolutionary origin of SWR activity may precede the mammalian-sauropsid bifurcation.

neuroscience↗