Biology subjects

Morozova, M.

Publications and source records attributed to Morozova, M..

7 recordsLinked to original sources

bioRxiv2024

Scents Modulate Anxiety Levels, but Electroencephalographic and Electrocardiographic Assessments Could Diverge from Subjective Reports

Scents could modulate anxiety levels, such as anxiety in a medical office. Here we investigated the impact of two scents on the subjective and physiological anxiety markers in the dental office environment, utilizing self-reported anxiety assessments alongside physiological assessment with electroencephalographic (EEG) and electrocardiographic (ECG) measurements. Lavender was the first tested scent with the previously reported calming effect. African stone was the second stimulus with a musky scent. Twenty healthy participants took part in scent exposure sessions. Anxiety levels were assessed using the State-Trait Anxiety Inventory (STAI), EEG-based theta, alpha, and beta power ratios, and heart rate variability (HRV) indices derived from ECG data. Lavender exposure significantly decreased self-reported anxiety whereas African stone reduced physiological indicators of anxiety. Namely, African stone exposure led to decreased theta and increased alpha power in the parietal-occipital EEG signals. Additionally, decreases were observed in low-frequency (LF) HRV power and total HRV power, reflecting lowered autonomic arousal. These findings support the potential effectiveness for olfactory interventions to aid in anxiety management within clinical environments, but draw attention to the issue of proper evaluation of anxiety. In particular, the difference between the subjective reports and traditional EEG and HRV markers indicates that anxiety involves a complexity of factors, which makes its treatment by scents challenging.

neuroscience↗

bioRxiv2024

Human short association fibers are thinner and less myelinated than long fibers

The size and complexity of the human brain requires optimally sized and myelinated fibers. White matter fibers facilitate fast communication between distant areas, but also connect adjacent cortical regions via short association fibers. The fundamental questions of i) how thick these fibers are and ii) how strongly they are myelinated, however, remain unanswered. We present a comprehensive analysis of [~]400,000 fibers of human white matter regions with long (corpus callosum) and short fibers (superficial white matter). We demonstrate a substantially smaller fiber diameter and lower myelination in superficial white matter than in the corpus callosum. Surprisingly, we do not find a difference in the ratio between axon diameter and myelin thickness (g-ratio), which is close to the theoretically optimal value of [~]0.6 in both areas. For the first time, to our knowledge, we shed light on a fundamental principle of brain organization that will be essential to understand the human brain.

neuroscience↗

bioRxiv2023

Tactile vs Motor Imagery: the Effects on Corticospinal Excitability Assessed with single-pulse TMS

Tactile Imagery (TI) remains a fairly understudied phenomenon despite an increased attention to this topic in recent years. Here we investigated the effects of TI on corticospinal excitability by measuring motor evoked potentials (MEPs) induced by single-pulse transcranial magnetic stimulation (TMS). The effects of TI were compared with those of tactile stimulation (TS) and kinesthetic motor imagery (kMI). Twenty-two participants performed three tasks in randomly assigned order: imagine finger tapping (kMI); experience vibratory sensations in the middle finger (TS); and mentally reproduce the sensation of vibration (TI). MEPs increased during both kMI and TI, with a stronger increase for kMI. No statistically significant change in MEP was observed during TS. The demonstrated differential effects of kMI, TI and TS on corticospinal excitability have practical implications for the development of imagery-based and TS-based brain-computer interfaces (BCIs), particularly the ones intended to improve neurorehabilitation by evoking plastic changes in sensorimotor circuitry. Significance StatementWhile it is known that tactile imagery (TI) engages the primary somatosensory cortex similarly to physical tactile perceptions, it is not well understood how TI affects neural processing in the primary motor cortex (M1), the area that controls voluntary movements while receiving somatosensory feedback. This study employed transcranial magnetic stimulation (TMS) to examine the responsiveness of M1 to different types of somatosensory imagery in response to TMS. TI facilitated the responses in the forearm and hand muscles but to a significantly lesser extent compared to kinesthetic motor imagery (kMI). This demonstration of the distinct effects of TI and kMI on corticospinal excitability highlights the importance of selecting an imagery strategy when using imagery to modulate cortical representation of the body. These findings have practical implications for the development of imagery-based brain-computer interfaces (BCIs) intended for rehabilitation of sensorimotor impairments.

neuroscience↗

bioRxiv2023

Tactile Imagery Affects Cortical Responses to Vibrotactile Stimulation of the Fingertip

Although imagery of tactile sensations is not so well studied compared to other types of mental imagery, it is potentially very useful for brain computer interfaces (BCIs) where it could produce neural modulations needed for BCI operations. Here we assessed neural modulations associated with tactile imagery (TI) by comparing its effects on cortical responses to the effects of actual vibrotactile stimulation of the fingertip. We found that both TI and vibrostimulation evoked event-related frequency changes of the electroencephalographic (EEG) activity. Moreover, TI affected somatosensory evoked potentials (SEPs) evoked by short pulses of vibration. EEG data were collected in 29 participants trained to perform tactile imagery task. Responses to vibratory pulses were measured with and without TI. These SEPs consisted of three prominent components: a P100 response in the centro-parietal regions, a P200 response in the frontal region, and a P300 response in the central regions. The TI consistently resulted in an increase in ipsilateral P100, ipsi- and contralateral P300 and frontal P200. Moreover, TI strengthened the {theta}-band ERS in the frontal region that occurred in response to vibration. These findings suggest that TI not only modulates EEG patterns by itself but also affects cortical processing of physical somatosensory stimuli. Such conjoint processing of both real and imagined somatic sensations could be utilized in BCIs, particularly in clinically relevant BCI that strive to restore somatosensory processing by combining centrally-induced and peripheral activities. Significance StatementWhile it is known that tactile imagery (TI) engages the same cortical areas that are active during the processing of real tactile inputs, neural mechanisms of such shared representation are not well understood. This study employed EEG recordings to examine the interaction between real and imagined somatic sensations. It was found that TI both changes EEG oscillatory activity and facilitates cortical responses to real tactile stimuli. Therefore combining TI with tactile stimulation could be useful for tactile-based brain-computer interfaces (BCIs), particularly the ones of clinical utility for neurorehabilitation and sensory substitution.

neuroscience↗

bioRxiv2022

EEG Changes during Odor Perception and Discrimination

Brain-Computer Interfaces (BCIs) are devices designed for communication between the central nervous system and a computer. The communication can occur through different sensory modalities, and most commonly visual and auditory systems are used. We suggest that BCIs can be expanded by the incorporation of olfactory modality. To probe the modulation of EEG activity by odorants, we implemented two olfactory tasks: one that required attention to perception of odors, and the second one where participants discriminated consecutively presented odors. EEG recordings were conducted in 13 healthy participants while they performed the tasks following computer-generated verbal instructions. Respiratory activity was recorded to relate EEG modulations to the breath cycle. Theta activity responses were observed over the frontal EEG leads approximately 2 s after the inhalation. This theta activity was different depending on whether or not the inhaled air contained an odorant, and cognitive load also had an effect. We conclude that the frontal theta rhythm is reflective of the neural processing of odors. As such, it could be incorporated in the olfactory-based BCIs which take odors either as inputs or outputs. These BCIs could improve olfactory training needed for conditions like anosmia and hyposmia, and mild cognitive impairment.

neuroscience↗

bioRxiv2022

Colitis-associated intestinal microbiota regulates brain glycine and host behavior in mice.

Inflammatory bowel diseases (IBD) are chronic and relapsing inflammatory disorders of the gastrointestinal tract with complex etiology and no strategies for complete cure. IBD are often complicated by mental disorders like anxiety and depression, indicating substantial shifts in the gut-brain axis. However, the mechanisms connecting IBD to mental diseases are still under debate. Here we use Muc2 mutant mouse model of chronic colitis to uncouple the effects of the intestinal microbiota on host behavior from chronic inflammation in the gut. Muc2 mutant male mice exhibit high exploratory activity, reduced anxiety-related behaviors, impaired sensorimotor gating, and altered social preference towards males and females. Microbial transfer to wild-type mice via littermate co-housing shows that colitis-associated microbiota rather than inflammation per se defines behavioral features in Muc2 colitis model. Metagenomic profiling and combination of antibiotic treatments revealed that bacterial species Akkermansia muciniphila is associated with the behavioral phenotype in mutants, and that its intestinal abundance correlates with social preference towards males. Metabolomic analysis together with pharmacological inhibition of Gly and NMDA receptors helped us to determine that brain glycine is responsible for the behavioral phenotype in Muc2 mice. Blood and brain metabolic profiles suggest that microbiota-dependent changes in choline metabolism might be involved in regulation of central glycine neurotransmission. Taken together, our data demonstrates that colitis-associated microbiota controls anxiety, sensorimotor gating and social behavior via metabolic regulation of the brain glycinergic system, providing new venues to combat neurological complications of IBD.

animal behavior and cognition↗

bioRxiv2021

A representative reference for MRI-based human axon radius assessment using light microscopy

Non-invasive assessment of axon radii via MRI bears great potential for clinical and neuroscience research as it is a main determinant of the neuronal conduction velocity. However, there is a lack of representative histological reference data on the scale of the cross-section of MRI voxels for validating the MRI-visible, effective radius (reff). Because the current gold standard stems from neuroanatomical studies designed to estimate the frequency-weighted arithmetic mean radius (rarith) on small ensembles of axons, it is unsuited to estimate the tail-weighted reff. We propose CNN-based segmentation on high-resolution, large-scale light microscopy (lsLM) data to generate a representative reference for reff. In a human corpus callosum, we assessed estimation accuracy and bias of rarith and reff. Furthermore, we investigated whether mapping anatomy-related variation of rarith and reff is confounded by low-frequency variation of the image intensity, e.g., due to staining heterogeneity. Finally, we analyzed the potential error due to outstandingly large axons in reff. Compared to rarith, reff was estimated with higher accuracy (normalized-root-mean-square-error of reff: 7.2 %; rarith: 21.5 %) and lower bias (normalized-mean-bias-error of reff: -1.7 %; rarith: 16 %). While rarith was confounded by variation of the image intensity, variation of reff seemed anatomy-related. The largest axons contributed between 0.9 % and 3 % to reff. In conclusion, the proposed method accurately estimates reff at MRI voxel resolution across a human corpus callosum sample. Further investigations are required to assess generalization to brain areas with different axon radii ensembles.

neuroscience↗