Biology subjects

Levichkina, E.

Publications and source records attributed to Levichkina, E..

4 recordsLinked to original sources

bioRxiv2026

Interactions between hippocampus and visceral organs in sleep and wakefulness

Exteroception is attenuated during sleep, while interoceptive signals may remain active. If so, they can trigger responses in their target areas, including the hippocampus, which is known to receive information from the internal organs and is susceptible to oversynchronization while triggered. We investigated whether the hippocampus is synchronized to various visceral events in sleep and wakefulness. Activity of hippocampal neurons and local field potentials (LFPs) was co-registered with respiration, heart rate and myoelectric signals of the stomach and duodenum in two adult female cats over multiple sleep-wake cycles. Visceral event-triggered and neuronal spike-triggered (bootstrapping-based) analyses were performed in wakefulness and SWS. Synchronization between visceral and hippocampal activities occurred in both wakefulness and SWS. However, hippocampal cells and LFPs showed preferences for one state only. Consistent with prior studies, we found the strongest link between high-amplitude respiratory events and hippocampal activity, with significantly higher occurrence during SWS. Both stomach and duodenal signals were also represented in hippocampal activity. Motility-associated duodenal myoelectric signals correlated with hippocampal activity more during wakefulness where gastrointestinal motility is more active, while synchronization between regular duodenal waves and the hippocampus was more frequent during SWS. We conclude that the interoceptive signals reach the hippocampus in both sleep and wakefulness and suggest that they have the potential to oversynchronize any ongoing synchronized slow-wave activities in the hippocampal network during slow wave sleep (SWS). Significance StatementWhat types of sensory input shapes hippocampal activity and regulates its rhythmical structure is important for understanding both normal and paroxysmal hippocampal dynamics. We find that synchronization between interoceptive signals and hippocampal neural activity exists during wakefulness and is preserved during SWS. Moreover, in some cases, this association increases in SWS for respiratory and periodic duodenal activities. Our data revealed specificity of hippocampal neurons to both type of visceral activity and state of vigilance, suggesting that hippocampal network is shaped by visceral activity in a state-dependent manner. Our results highlight the factors underlying the comorbidities of epilepsy with gastrointestinal, cardiac or respiratory disorders.

neuroscience↗

bioRxiv2025

Nucleus Basalis of Meynert as a DBS target

Several clinical attempts to use deep brain stimulation applied to nucleus basalis of Meynert to reduce cognitive decline in different types of dementia report inconclusive effects. At the same time, experiments in rodents have largely demonstrated cognitive improvement. The hypothesised basis for this difference was the application of different patterns of stimulation - tonic continuous over multiple sleep-wake cycles in human clinical trials vs intermittent bursts over shorter intervals in animal studies. However, since no systematic testing of the effects of different stimulation patterns applied in different states of vigilance was conducted, it remains unclear what specific attributes of cortical responses are associated with these patterns, and the effect of vigilance state on pattern response. We hypothesised that communication between nucleus basalis and its cortical targets involves frequencies in both low and high ranges, making burst-type intermittent patterns potentially more effective. Therefore we studied preferred frequencies of neuronal synchronization within nucleus basalis as well as between nucleus basalis and its cortical targets in B6 mouse strain (N=9, age 4-6 month) by recording neuronal spiking and local field potentials (LFP) from 2 sites of the nucleus basalis and 4 cortical sites simultaneously across multiple sleep-wake cycles. Spike-field coherence (SFC) analysis revealed natural synchronization tendencies of nucleus basalis - all animals demonstrated significant SFC at delta-theta range and gamma coherence peaking between 57 and 88 Hz (SFC > 95% Jackknife confidence interval at frequency range > 2*bandwidth). SFC between cortical cells and local field potentials of nucleus basalis, which reflects cortical feedback, peaked at delta-theta frequencies. Based on these results we constructed "nested" patterns of stimulation that included both delta-theta and individually assessed gamma peak for each animal (N=8). The effects of nested stimulation were compared to the ones of random and tonic (20Hz) stimulation patterns. These patterns of stimulation were applied across multiple sleep-wake cycles to freely behaving animals, and spectral power density in response to stimulation compared between patterns for different states of vigilance. We report significant reduction of delta power during slow wave sleep and theta power in REM for all three patterns. Slow wave suppression was also present during wakefulness. This indicates all patterns may improve levels of alertness but highlights strong likelihood of sleep disturbances in response to stimulation during sleep. Thus, deep brain stimulation of nucleus basalis may be counterproductive during sleep. The nested pattern of stimulation alone demonstrated preservation or even enhancement of gamma activity in the cortex while suppressing low frequencies. Broad-band suppression of cortical activity was shown in response to tonic stimulation, and to some extent to the random pattern as well, suggesting that tonic stimulation may be unsuitable for deep brain stimulation of the nucleus basalis of Meynert.

neuroscience↗

bioRxiv2020

Dynamics of coherent activity between cortical areas defines a two-stage process of selective attention

Analysing a visual scene requires the brain to briefly keep in memory potentially relevant parts and then direct attention to their locations for detailed processing. To reveal the neuronal basis of the underlying working memory and top-down attention processes, we trained macaques to match two patterns presented with a delay between them. As the above processes are likely to require communication between brain regions, and the parietal cortex is involved in spatial attention, we simultaneously recorded neuronal activities from the interconnected parietal and middle temporal areas. We found that mnemonic information about the first pattern was retained in coherent oscillating activity between the areas in high-frequency bands, followed by coherent activity in low-frequency bands that mediate top-down attention on the relevant location. ONE SENTENCE SUMMARYGamma coherence allows retaining object features in a saliency map while lower frequency coherence facilitates attention.

neuroscience↗

bioRxiv2018

Diversity of feature selectivity in macaque visual cortex arising from limited number of broadly-tuned input channels

Spikes (action potential) responses of most primary visual cortical cells in the macaque are sharply tuned for the orientation of a line or an edge and neurons preferring similar orientations are clustered together in cortical columns. The preferred stimulus orientation of these columns span the full range of orientations, as observed in recordings of spikes, which represent the outputs of cortical neurons. However, when we imaged also the thalamic input to these cells that occur on a larger spatial scale, we found that the orientation domain map of the primary visual cortex did not show the diversity of orientations exhibited by signals representing outputs of the cells. This map was dominated by just the one orientation that is most commonly represented in subcortical responses. This supports cortical feature selectivity and columnar architecture being built upon feed-forward signals transmitted from the thalamus in a very limited number of broadly-tuned input channels.

neuroscience↗