Yuval Nir

Yuval Nir
Tel Aviv University | TAU · Department of Physiology and Pharmacology and Sagol School of Neuroscience

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78
Publications
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Introduction
Skills and Expertise

Publications

Publications (78)
Article
Full-text available
During sleep, sensory stimuli rarely trigger a behavioral response or conscious perception. However, it remains unclear whether sleep inhibits specific aspects of sensory processing, such as feedforward or feedback signaling. Here, we presented auditory stimuli (for example, click-trains, words, music) during wakefulness and sleep in patients with...
Preprint
Epilepsy can be considered a network disorder in which distinct and sometimes widespread brain regions coordinate their activity to generate seizures. Fast ripples (200-600 Hz) are associated with epileptogenic brain tissue and play critical roles in the epileptic network. Using macroelectrode stereo EEG recordings from a cohort of 46 patients we f...
Preprint
Insufficient sleep is commonplace in modern lifestyle and can lead to grave outcomes, yet the changes in neuronal activity accumulating over hours of extended wakefulness remain poorly understood. Specifically, which aspects of cortical processing are affected by sleep deprivation (SD), and whether they also affect early sensory regions, remains un...
Article
Full-text available
Despite extensive knowledge of its molecular and cellular effects, how anesthesia affects sensory processing remains poorly understood. In particular, it remains unclear whether anesthesia modestly or robustly degrades activity in primary sensory regions, and whether such changes are linked to anesthesia drug concentration versus behavioral unrespo...
Article
Full-text available
Dysregulated homeostasis of neural activity has been hypothesized to drive Alzheimer’s disease (AD) pathogenesis. AD begins with a decades-long presymptomatic phase, but whether homeostatic mechanisms already begin failing during this silent phase is unknown. We show that before the onset of memory decline and sleep disturbances, familial AD (fAD)...
Article
The characteristics of the sleep drivers and the mechanisms through which sleep relieves the cellular homeostatic pressure are unclear. In flies, zebrafish, mice, and humans, DNA damage levels increase during wakefulness and decrease during sleep. Here, we show that 6 h of consolidated sleep is sufficient to reduce DNA damage in the zebrafish dorsa...
Article
Sleep involves infra-slow ∼50-second fluctuations between disengagement and sensory reactivity. New findings reveal that the brain’s noradrenaline system controls these dynamics by acting in the thalamus to affect sleep spindles, and by modulating coordinated heart rate variations.
Preprint
Full-text available
Engagement is a major determinant of performance. Hyper-engagement risks impulsivity and is fatiguing over time, while hypo-engagement could lead to missed opportunities. Even in sleep, when engagement levels are minimal, sensory responsiveness varies. Thus, maintaining an optimal engagement level with the environment is a fundamental cognitive abi...
Preprint
Full-text available
Sleep is defined as a reversible, homeostatically-regulated state of a reduced behavioral responsiveness, and a high arousal threshold in response to external sensory stimulation defines sleep across all species. However, it remains unclear whether sleep mainly gates motor output or affects responses along sensory pathways, and if sleep primarily m...
Article
Vagus nerve stimulation (VNS) is widely used to treat drug-resistant epilepsy and depression. While the precise mechanisms mediating its long-term therapeutic effects are not fully resolved, they likely involve locus coeruleus (LC) stimulation via the nucleus of the solitary tract, which receives afferent vagal inputs. In rats, VNS elevates LC firi...
Preprint
Full-text available
Despite extensive knowledge of its molecular and cellular effects, how anesthesia affects sensory processing remains poorly understood. In particular, it remains unclear whether anesthesia modestly or robustly degrades activity in primary sensory regions, and whether such changes are linked to anesthesia drug concentration vs. behavioral unresponsi...
Preprint
Full-text available
Vagus nerve stimulation (VNS) is widely used to treat drug-resistant epilepsy and depression. While the precise mechanisms mediating its long-term therapeutic effects are not fully resolved, they likely involve locus coeruleus (LC) stimulation via the nucleus of the solitary tract (NTS), which receives afferent vagal inputs. In rats, VNS elevates L...
Article
Despite its ubiquitous use in medicine, and extensive knowledge of its molecular and cellular effects, how anesthesia induces loss of consciousness (LOC) and affects sensory processing remains poorly understood. Specifically, it is unclear whether anesthesia primarily disrupts thalamocortical relay or intercortical signaling. Here we recorded intra...
Article
Full-text available
A defining feature of sleep is reduced responsiveness to external stimuli, but the mechanisms mediating sensory-evoked arousal remain unclear. We hypothesized that reduced locus coeruleus (LC) norepinephrine (NE) activity during sleep mediates unresponsiveness, and its action promotes sensory-evoked awakenings. We tested this using electrophysiolog...
Article
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...
Article
Ripple oscillations (80-200 Hz) in the normal hippocampus are involved in memory consolidation during rest and sleep. In the epileptic brain, increased ripple and fast ripple (200-600 Hz) rates serve as a biomarker of epileptogenic brain. We report that both ripples and fast ripples exhibit a preferred phase angle of coupling with the trough-peak (...
Article
Full-text available
A fundamental feature of sleep is reduced behavioral responsiveness to external events, but the extent of processing along sensory pathways remains poorly understood. While responses are comparable across wakefulness and sleep in auditory cortex (AC), neuronal activity in downstream regions remains unknown. Here we recorded spiking activity in 435...
Preprint
Full-text available
Despite its ubiquitous use in medicine, and extensive knowledge of its molecular and cellular effects, how anesthesia induces loss of consciousness (LOC) and affects sensory processing remains poorly understood. Specifically, it is unclear whether anesthesia primarily disrupts thalamocortical relay or intercortical signaling. Here we recorded intra...
Preprint
Full-text available
A fundamental feature of sleep is reduced behavioral responsiveness to external events, but the extent of processing along sensory pathways remains poorly understood. While responses are comparable across wakefulness and sleep in auditory cortex (AC), neuronal activity in downstream regions remains unknown. Here we recorded spiking activity in 435...
Preprint
Full-text available
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...
Preprint
Full-text available
A defining feature of sleep is reduced responsiveness to external stimuli, but the mechanisms gating sensory-evoked arousal remain unclear. We hypothesized that reduced locus-coeruleus norepinephrine (LC-NE) activity during sleep mediates unresponsiveness, and its action promotes sensory-evoked awakenings. We tested this using electrophysiological,...
Preprint
Full-text available
Despite its ubiquitous use in medicine, and extensive knowledge of its molecular and cellular effects, how anesthesia induces loss of consciousness (LOC) and affects sensory processing remains poorly understood. Specifically, it is unclear whether anesthesia primarily disrupts thalamocortical relay or intercortical signaling. Here we recorded intra...
Article
An identical sensory stimulus may or may not be incorporated into perceptual experience, depending on the behavioral and cognitive state of the organism. What determines whether a sensory stimulus will be perceived? While different behavioral and cognitive states may share a similar profile of electrophysiology, metabolism, and early sensory respon...
Article
Full-text available
Sleep deprivation is a major source of morbidity with widespread health effects, including increased risk of hypertension, diabetes, obesity, heart attack, and stroke1. Moreover, sleep deprivation brings about vehicle accidents and medical errors2,3,4 and is therefore an urgent topic of investigation. During sleep deprivation, homeostatic and circa...
Article
Full-text available
The extent to which the sleeping brain processes sensory information remains unclear. This is particularly true for continuous and complex stimuli such as speech, in which information is organized into hierarchically embedded structures. Recently, novel metrics for assessing the neural representation of continuous speech have been developed using n...
Article
Full-text available
During sleep, external sensory events rarely elicit a behavioral response or affect perception. However, how sensory processing differs between wakefulness and sleep remains unclear. A major difficulty in this field stems from using brief auditory stimuli that often trigger nonspecific high-amplitude "K-complex" responses and complicate interpretat...
Article
Significance statement: A long-standing hypothesis is that neurons fire less during slow-wave sleep to recover from the "fatigue" accrued during wake, when overall synaptic activity is higher than in sleep. This idea, however, has rarely been tested and other factors, namely increased cortical synchrony, could explain why sleep slow-wave activity...
Article
Full-text available
Study objectives: Sleep is defined as a reversible state of reduction in sensory responsiveness and immobility. A long-standing hypothesis suggests that a high arousal threshold during nonrapid eye movement (NREM) sleep is mediated by sleep spindle oscillations, impairing thalamocortical transmission of incoming sensory stimuli. Here we set out to...
Article
Full-text available
Are rapid eye movements (REMs) in sleep associated with visual-like activity, as during wakefulness? Here we examine single-unit activities (n ¼ 2,057) and intracranial electroencephalography across the human medial temporal lobe (MTL) and neocortex during sleep and wakefulness, and during visual stimulation with fixation. During sleep and wakefuln...
Data
Supplementary Figures 1-6, Supplementary Note 1, Supplementary Methods and Supplementary References
Article
Full-text available
Sleep entails a disconnection from the external environment. By and large, sensory stimuli do not trigger behavioral responses and are not consciously perceived as they usually are in wakefulness. Traditionally, sleep disconnection was ascribed to a thalamic “gate,” which would prevent signal propagation along ascending sensory pathways to primary...
Chapter
Full-text available
Sleep offers a unique opportunity to relate changes in brain activity to changes in consciousness. Indeed, if it were not for sleep, when consciousness fades in and out on a regular basis, it might be hard to imagine that consciousness is not a given but depends somehow on the way our brain is functioning. At the same time as changes in consciousne...
Article
Even in the absence of stimulation or task, the cerebral cortex shows an incessant pattern of ultra slow fluctuations which are coherent across brain regions. In the healthy brain these coherent patterns (also termed resting state functional connectivity) often exhibit spatial similarity to the large scale organization of task-induced functional ne...
Article
Full-text available
Clinical diagnosis of disorders of consciousness (DOC) caused by brain injury poses great challenges since patients are often behaviorally unresponsive. A promising new approach towards objective DOC diagnosis may be offered by the analysis of ultra-slow (<0.1 Hz) spontaneous brain activity fluctuations measured with functional magnetic resonance i...
Data
Voxel-by-voxel differences in Spontaneous BOLD correlations between intact- and impaired-awareness groups. Statistical maps of two-sample t-tests (see Methods) comparing BOLD signal correlations in the two subject groups (intact, n = 12; impaired, n = 7) separately for each voxel. Maps are projected on inflated cortical surfaces as seen from latera...
Data
Correlations between Spontaneous BOLD fluctuations in right post-central gyrus and all other cortical regions. Group correlation maps between a “seed” region in the post-central gyrus (postCG) and all other cortical voxels. (A) Correlations of spontaneous activity in the intact awareness group (n = 12) projected on inflated hemispheres as seen from...
Data
Clinical, electrophysiological and structural imaging data of patients. Abbreviations: LIS, locked-in syndrome; VS, vegetative state; MCS, minimally conscious state. (DOCX)
Data
Correlations between spontaneous BOLD fluctuations in right pre-central gyrus and all other cortical regions. Group correlation maps between a “seed” region in the pre-central gyrus (preCG) and all other cortical voxels. (a) Correlations of spontaneous activity in the intact awareness group (n = 12) projected on inflated hemispheres as seen from a...
Data
Single subject inter-hemispheric correlation maps (seed: right PreCG) ordered according to the ICD values. Correlation maps with a “seed” time-course in the right pre-central gyrus (pre-CG) are shown in flat, left hemisphere (“mirror site”) cortical format for each subject separately. (a) Location of seed (red ellipse) and location of the “mirror s...
Data
Inter-operator correlation of ICD measure. ICD values as computed on a subsample of 11 subjects by two independent operators drawing the ROIs. Abbreviations: CCC, concordance correlation coefficient; r, Pearson correlation. (TIF)
Data
Inter-hemispheric Correlation Index (ICD) in individual subjects in all three groups. Subjects are separated on the x-axis depending on their group (controls1: non-aged matched group; controls2: aged-matched group, and patients). Abbreviations: (*) refers to the VS patient who regained consciousness shortly after scan (VS2 in the supplementary tabl...
Data
Inter-operator variability analysis. (DOC)
Data
Comparison of the ICD to an aged-matched control group. (DOCX)
Data
Correlations between spontaneous BOLD fluctuations in right intra-parietal sulcus and all other cortical regions. Group correlation maps between a “seed” region in the intra-parietal sulcus (IPS) and all other cortical voxels. (A) Correlations of spontaneous activity in the intact awareness group (n = 12) projected on inflated hemispheres as seen f...
Data
ICD values and Crawford and Howell test results for the age-matched sample. Abbreviations: LIS, locked-in syndrome; VS, vegetative state; MCS, minimally conscious state. (DOCX)
Data
Inter-operator variability data. Abbreviations: IPS, intra-parietal sulcus; preCG, pre-central gyrus; postCG, post-central gyrus. (DOCX)
Article
Recent fMRI studies have shown that it is possible to reliably identify the default-mode network (DMN) in the absence of any task, by resting-state connectivity analyses in healthy volunteers. We here aimed to identify the DMN in the challenging patient population of disorders of consciousness encountered following coma. A spatial independent compo...
Article
The neural basis of syntax is a matter of substantial debate. In particular, the inferior frontal gyrus (IFG), or Broca's area, has been prominently linked to syntactic processing, but the anterior temporal lobe has been reported to be activated instead of IFG when manipulating the presence of syntactic structure. These findings are difficult to re...
Article
Full-text available
Sleep spindles are an electroencephalographic (EEG) hallmark of non-rapid eye movement (NREM) sleep and are believed to mediate many sleep-related functions, from memory consolidation to cortical development. Spindles differ in location, frequency, and association with slow waves, but whether this heterogeneity may reflect different physiological p...
Article
The effect of stimulus modulation rate on the underlying neural activity in human auditory cortex is not clear. Human studies (using both invasive and noninvasive techniques) have demonstrated that at the population level, auditory cortex follows stimulus envelope. Here we examined the effect of stimulus modulation rate by using a rare opportunity...
Article
Full-text available
In an awake state, neurons in the cerebral cortex fire irregularly and electroencephalogram (EEG) recordings display low-amplitude, high-frequency fluctuations. During sleep, neurons oscillate between 'on' periods, when they fire as in an awake brain, and 'off' periods, when they stop firing altogether and the EEG displays high-amplitude slow waves...
Article
The most prominent EEG events in sleep are slow waves, reflecting a slow (<1 Hz) oscillation between up and down states in cortical neurons. It is unknown whether slow oscillations are synchronous across the majority or the minority of brain regions--are they a global or local phenomenon? To examine this, we recorded simultaneously scalp EEG, intra...
Article
Dreams are a remarkable experiment in psychology and neuroscience, conducted every night in every sleeping person. They show that the human brain, disconnected from the environment, can generate an entire world of conscious experiences by itself. Content analysis and developmental studies have promoted understanding of dream phenomenology. In paral...
Article
Disorders of consciousness (DOC) raise profound scientific, clinical, ethical, and philosophical issues. Growing knowledge on fundamental principles of brain organization in healthy individuals offers new opportunities for a better understanding of residual brain function in DOCs. We here discuss new perspectives derived from a recently proposed sc...
Article
Human recognition performance is characterized by abrupt changes in perceptual states. Understanding the neuronal dynamics underlying such transitions could provide important insights into mechanisms of recognition and perceptual awareness. Here we examined patients monitored for clinical purposes with multiple subdural electrodes. The patients par...
Article
Objectives: Recent fMRI studies have shown that it is possible to reliably identify the default-mode network (DMN) in the absence of any task, by resting-state connectivity analyses in healthy volunteers. We here aimed to identify the DMN in the challenging patient population of disorders of consciousness encountered following coma. Experimental de...
Article
Full-text available
Animal studies have shown robust electrophysiological activity in the sensory cortex in the absence of stimuli or tasks. Similarly, recent human functional magnetic resonance imaging (fMRI) revealed widespread, spontaneously emerging cortical fluctuations. However, it is unknown what neuronal dynamics underlie this spontaneous activity in the human...
Article
Functional magnetic resonance adaptation (fMR-A, also termed repetition suppression) is a reduction in activity due to repeated image presentations which has been extensively studied in human visual areas. Here we tested whether fMR-A dynamics during sustained image presentations is determined by cortical region or by stimulus category. Nine subjec...
Article
Recent functional magnetic resonance imaging (fMRI) studies reveal the presence of spontaneous fluctuations of activity in human sensory cortex emerging in the complete absence of external stimuli or task. Such fluctuations show remarkable selectivity for functional networks, coherence across large cortical distances and across hemispheres, yet it...
Article
To what extent is activity of individual neurons coupled to the local field potential (LFP) and to blood-oxygenation-level dependent (BOLD) functional magnetic resonance imaging (fMRI)? This issue is of high significance for understanding brain function and for relating animal studies to fMRI, yet it is still under debate. Here we report data from...