Biology subjects

Arzi, A.

Publications and source records attributed to Arzi, A..

5 recordsLinked to original sources

bioRxiv2023

Brain network dynamics in transitions of consciousness reorganize according to task engagement

Substantial changes in behavior, physiology, and brain function occur when alertness decreases 1- 5. These changes in brain function involve increased synchronization between cortical areas 6,7 as well as alterations in sensory processing pathways and networks connecting the thalamus and cortex 5,8-11. Cognitive tasks engage overlapping functional networks with sensory pathways facilitating information processing 12,13, and thalamocortical and corticocortical networks supporting task performance 14,15. Frontoparietal circuits play a crucial role in cognitive tasks 16 and states of decreased consciousness 17. To develop an integrated framework of consciousness and cognition, it is important to understand how fluctuations in alertness and cognitive processing interact in these shared circuits 18. Our hypothesis is that during periods of low alertness, individuals who actively maintain task engagement would recruit additional frontoparietal and sensory processing networks, while thalamocortical dynamics that typically change during sleep onset would remain unaffected. Our findings demonstrated that as alertness decreased, passively listening to auditory tones led to increased synchronization in the parietal lobe, whereas actively performing an auditory task resulted in increased long-range frontoparietal synchronization. During decreasing alertness, passive listening (but not active task engagement) was associated with widespread increased synchronization between the thalamus and cortex. In contrast, active task engagement (but not passive listening) led to increased synchronization between the auditory cortex and the rest of the brain. These results reveal the functional mechanisms of the brains flexible reorganization during transitions of consciousness when individuals are actively engaged in cognitive processes.

neuroscience↗

bioRxiv2023

Respiration-Triggered Olfactory Stimulation ReducesObstructive Sleep Apnea Symptoms Severity: A Prospective Pilot Study

Obstructive sleep apnea (OSA) is a prevalent sleep-disordered breathing condition characterized by repetitive reduction in breathing during sleep. Current care standard for OSA is continuous positive air pressure devices, often suffering from low tolerance due to limited adherence. Capitalizing on the unique neurocircuitry of olfactory perception and its retained function during sleep, we conducted a pilot study to test transient, respiration-based olfactory stimulation as a treatment for OSA markers. Thirty-two OSA patients (Apnea-Hypopnea Index (AHI)[≥]15 events/hour) underwent two polysomnography sessions, Odor and Control, in random order. In Odor nights, patients were presented with transient respiratory-based olfactory stimulation delivered via a computer-controlled commercial olfactometer (Scentific). The olfactometer, equipped with a wireless monitoring, analyzed respiratory patterns and presented odor upon detection of respiratory events. No odors were presented in Control nights. Following exclusions, 17 patients entered analysis (4 women, 47.4 (10.5) years, BMI: 33.8 (7.8)). We observed that olfactory stimulation during sleep reduced AHI ( Odor:17.2 (20.9), Control: 28.2 (18.6), z=- 3.337, p=0.000846, BF10=57.9), reflecting an average decrease of 31.3% in event number. Relatedly, stimulation reduced the oxygen desaturation index (ODI) by 26.9% ( Odor: 12.5 (15.8), Control: 25.7 (25.9), z=-3.337, p=0.000846, BF10=9.522. This effect was not linked to baseline OSA markers severity ({rho}=-0.042, p=0.87). Olfactory stimulation did not arouse from sleep or affect sleep structure, measured as time per sleep stage (F(1,16)=0.088, p=0.77). In conclusion, olfactory stimulation during sleep was effective in reducing OSA markers severity without inducing arousals and may provide a novel treatment for OSA, prompting continued research.

physiology↗

bioRxiv2021

Dynamic Auditory Remapping Across the Sleep-Wake Cycle

In a single day we transition from vigilant wakefulness to unconscious sleep and dreaming, undergoing diverse behavioural, physiological and neural changes. While during the awake state, exogenous stimuli and endogenous changes lead to sensory reorganisation, this remapping has not been charted throughout the sleep-wake cycle. We recorded neural activity in response to a range of tones using electroencephalography during a full nights sleep, and examined whether auditory responses become more similar, dissimilar or remain unchanged between wakefulness, non-rapid (NREM) and rapid eye movement (REM) sleep. We found that neural similarities between pairs of auditory evoked potentials differed by conscious state in both early and late auditory processing stages. Furthermore, tone-pairs neural similarities were modulated by conscious state as a function of tone frequency, where some tone-pairs changed similarity between states and others continued unaffected. These findings demonstrate a state-, stimulus- and time-dependent functional reorganization of auditory processing across the sleep-wake cycle.

neuroscience↗

bioRxiv2019

Local Targeted Memory Reactivation in Human Sleep

Memory consolidation can be promoted via Targeted Memory Reactivation (TMR) that re-presents training cues or context during sleep. Whether TMR acts locally or globally on cortical sleep oscillations remains unknown. Here we exploit the unique functional neuroanatomy of olfaction with its ipsilateral stimulus processing to perform local TMR in one brain hemisphere. Participants learned associations between words and locations in left or right visual fields with contextual odor throughout. During post-learning naps, odors were presented to one nostril throughout NREM sleep. We found improved memory for specific words processed in the cued hemisphere (ipsilateral to stimulated nostril). Unilateral odor cues locally modulated slow wave activity (SWA) such that regional SWA increase in the cued hemisphere negatively correlated with select memories for cued words. Moreover, local TMR improved slow wave-spindle coupling specifically in the cued hemisphere. Thus, TMR in human sleep transcends global action by selectively promoting specific memories associated with local sleep oscillations.

neuroscience↗

bioRxiv2018

Neural signatures of classical conditioning during human sleep

Recent evidence indicate that humans can learn entirely new information during sleep. To elucidate the neural dynamics underlying sleep-learning we investigated brain activity during auditory-olfactory discriminatory associative learning in human sleep. We found that learning-related delta and sigma neural changes are involved in early acquisition stages, when new associations are being formed. In contrast, learning-related theta activity emerged in later stages of the learning process, after tone-odour associations were already established. These findings suggest that learning new associations during sleep is signalled by a dynamic interplay between slow-waves, sigma and theta activity.

neuroscience↗