The Experts below are selected from a list of 9969 Experts worldwide ranked by ideXlab platform
Patrick L Purdon - One of the best experts on this subject based on the ideXlab platform.
-
Autonomic predictions by subject from the best logistic regression model for Question 3.
'Public Library of Science (PLoS)', 2021Co-Authors: Sandya Subramanian, Patrick L Purdon, Riccardo Barbieri, Emery N. BrownAbstract:Unlike in Figs 5 and 6, with respect to the behavioral markers, Unconsciousness is 0 and consciousness is 1.
-
quantitative assessment of the relationship between behavioral and autonomic dynamics during propofol induced Unconsciousness
bioRxiv, 2020Co-Authors: Sandya Subramanian, Patrick L Purdon, Riccardo Barbieri, Emery N. BrownAbstract:During general anesthesia, both behavioral and autonomic changes are caused by the administration of anesthetics such as propofol. Propofol produces Unconsciousness by creating highly structured oscillations in brain circuits. The anesthetic also has autonomic effects due to its actions as a vasodilator and myocardial depressant. Understanding how autonomic dynamics change in relation to propofol-induced Unconsciousness is an important scientific and clinical question since anesthesiologists often infer changes in level of Unconsciousness from changes in autonomic dynamics. Therefore, we present a framework combining physiology-based statistical models that have been developed specifically for heart rate variability and electrodermal activity with a robust statistical tool to compare behavioral and multimodal autonomic changes before, during, and after propofol-induced Unconsciousness. We tested this framework on physiological data recorded from nine healthy volunteers during computer-controlled administration of propofol. We studied how autonomic dynamics related to behavioral markers of Unconsciousness: 1) overall, 2) during the transitions of loss and recovery of consciousness, and 3) before and after anesthesia as a whole. Our results show a strong relationship between behavioral state of consciousness and autonomic dynamics. All of our prediction models showed areas under the curve greater than 0.75 despite the presence of non-monotonic relationships among the variables during the transition periods. Our analysis highlighted the specific roles played by fast versus slow changes, parasympathetic vs sympathetic activity, heart rate variability vs electrodermal activity, and even pulse rate vs pulse amplitude information within electrodermal activity. Further advancement upon this work can quantify the complex and subject-specific relationship between behavioral changes and autonomic dynamics before, during, and after anesthesia. However, this work demonstrates the potential of a multimodal, physiologically-informed, statistical approach to characterize autonomic dynamics.
-
broadband slow wave modulation in posterior and anterior cortex tracks distinct states of propofol induced Unconsciousness
Scientific Reports, 2020Co-Authors: Emily P Stephen, Emery N. Brown, Gladia C Hotan, Eric T Pierce, Grace P Harrell, John L Walsh, Patrick L PurdonAbstract:A controversy has developed in recent years over the roles of frontal and posterior cortices in mediating consciousness and Unconsciousness. Disruption of posterior cortex during sleep appears to suppress the contents of dreaming, yet activation of frontal cortex appears necessary for perception and can reverse Unconsciousness under anesthesia. We used anesthesia to study how regional cortical disruption, mediated by slow wave modulation of broadband activity, changes during Unconsciousness in humans. We found that broadband slow-wave modulation enveloped posterior cortex when subjects initially became unconscious, but later encompassed both frontal and posterior cortex when subjects were more deeply anesthetized and likely unarousable. Our results suggest that Unconsciousness under anesthesia comprises several distinct shifts in brain state that disrupt the contents of consciousness distinct from arousal and awareness of those contents.
-
broadband slow wave modulation in posterior and anterior cortex tracks distinct states of propofol induced Unconsciousness
bioRxiv, 2019Co-Authors: Emily P Stephen, Emery N. Brown, Gladia C Hotan, Eric T Pierce, Grace P Harrell, John L Walsh, Patrick L PurdonAbstract:A controversy exists over the roles of frontal and posterior cortices in mediating consciousness and Unconsciousness. Disruption of posterior cortex during sleep appears to suppress the contents of dreaming, yet activation of frontal cortex appears necessary for perception and can reverse Unconsciousness under anesthesia. We used anesthesia to study how regional cortical disruption, mediated by slow wave modulation of broadband activity, changes during un-consciousness in humans. We found that broadband slow-wave modulation enveloped posterior cortex when subjects initially became unconscious, but later encompassed both frontal and posterior cortex when subjects were more deeply anesthetized and likely unarousable. Our results suggest that Unconsciousness under anesthesia comprises several distinct shifts in brain state that disrupt the contents of consciousness distinct from arousal and awareness of those contents.
-
thalamocortical synchronization during induction and emergence from propofol induced Unconsciousness
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Emery N. Brown, Francisco J Flores, Katharine E Hartnack, Amanda B Fath, Seongeun Kim, Matthew A Wilson, Patrick L PurdonAbstract:General anesthesia (GA) is a reversible drug-induced state of altered arousal required for more than 60,000 surgical procedures each day in the United States alone. Sedation and Unconsciousness under GA are associated with stereotyped electrophysiological oscillations that are thought to reflect profound disruptions of activity in neuronal circuits that mediate awareness and cognition. Computational models make specific predictions about the role of the cortex and thalamus in these oscillations. In this paper, we provide in vivo evidence in rats that alpha oscillations (10–15 Hz) induced by the commonly used anesthetic drug propofol are synchronized between the thalamus and the medial prefrontal cortex. We also show that at deep levels of Unconsciousness where movement ceases, coherent thalamocortical delta oscillations (1–5 Hz) develop, distinct from concurrent slow oscillations (0.1–1 Hz). The structure of these oscillations in both cortex and thalamus closely parallel those observed in the human electroencephalogram during propofol-induced Unconsciousness. During emergence from GA, this synchronized activity dissipates in a sequence different from that observed during loss of consciousness. A possible explanation is that recovery from anesthesia-induced Unconsciousness follows a “boot-up” sequence actively driven by ascending arousal centers. The involvement of medial prefrontal cortex suggests that when these oscillations (alpha, delta, slow) are observed in humans, self-awareness and internal consciousness would be impaired if not abolished. These studies advance our understanding of anesthesia-induced Unconsciousness and altered arousal and further establish principled neurophysiological markers of these states.
Emery N. Brown - One of the best experts on this subject based on the ideXlab platform.
-
neural effects of propofol induced Unconsciousness and its reversal using thalamic stimulation
eLife, 2021Co-Authors: Andre M Bastos, Jacob A Donoghue, Scott L Brincat, Meredith Mahnke, Jorge Yanar, Josefina Correa, Ayan S Waite, Mikael Lundqvist, Jefferson E Roy, Emery N. BrownAbstract:The specific circuit mechanisms through which anesthetics induce Unconsciousness have not been completely characterized. We recorded neural activity from the frontal, parietal, and temporal cortices and thalamus while maintaining Unconsciousness in non-human primates (NHPs) with the anesthetic propofol. Unconsciousness was marked by slow frequency (~1 Hz) oscillations in local field potentials, entrainment of local spiking to Up states alternating with Down states of little or no spiking activity, and decreased coherence in frequencies above 4 Hz. Thalamic stimulation 'awakened' anesthetized NHPs and reversed the electrophysiologic features of Unconsciousness. Unconsciousness is linked to cortical and thalamic slow frequency synchrony coupled with decreased spiking, and loss of higher-frequency dynamics. This may disrupt cortical communication/integration.
-
Autonomic predictions by subject from the best logistic regression model for Question 3.
'Public Library of Science (PLoS)', 2021Co-Authors: Sandya Subramanian, Patrick L Purdon, Riccardo Barbieri, Emery N. BrownAbstract:Unlike in Figs 5 and 6, with respect to the behavioral markers, Unconsciousness is 0 and consciousness is 1.
-
quantitative assessment of the relationship between behavioral and autonomic dynamics during propofol induced Unconsciousness
bioRxiv, 2020Co-Authors: Sandya Subramanian, Patrick L Purdon, Riccardo Barbieri, Emery N. BrownAbstract:During general anesthesia, both behavioral and autonomic changes are caused by the administration of anesthetics such as propofol. Propofol produces Unconsciousness by creating highly structured oscillations in brain circuits. The anesthetic also has autonomic effects due to its actions as a vasodilator and myocardial depressant. Understanding how autonomic dynamics change in relation to propofol-induced Unconsciousness is an important scientific and clinical question since anesthesiologists often infer changes in level of Unconsciousness from changes in autonomic dynamics. Therefore, we present a framework combining physiology-based statistical models that have been developed specifically for heart rate variability and electrodermal activity with a robust statistical tool to compare behavioral and multimodal autonomic changes before, during, and after propofol-induced Unconsciousness. We tested this framework on physiological data recorded from nine healthy volunteers during computer-controlled administration of propofol. We studied how autonomic dynamics related to behavioral markers of Unconsciousness: 1) overall, 2) during the transitions of loss and recovery of consciousness, and 3) before and after anesthesia as a whole. Our results show a strong relationship between behavioral state of consciousness and autonomic dynamics. All of our prediction models showed areas under the curve greater than 0.75 despite the presence of non-monotonic relationships among the variables during the transition periods. Our analysis highlighted the specific roles played by fast versus slow changes, parasympathetic vs sympathetic activity, heart rate variability vs electrodermal activity, and even pulse rate vs pulse amplitude information within electrodermal activity. Further advancement upon this work can quantify the complex and subject-specific relationship between behavioral changes and autonomic dynamics before, during, and after anesthesia. However, this work demonstrates the potential of a multimodal, physiologically-informed, statistical approach to characterize autonomic dynamics.
-
broadband slow wave modulation in posterior and anterior cortex tracks distinct states of propofol induced Unconsciousness
Scientific Reports, 2020Co-Authors: Emily P Stephen, Emery N. Brown, Gladia C Hotan, Eric T Pierce, Grace P Harrell, John L Walsh, Patrick L PurdonAbstract:A controversy has developed in recent years over the roles of frontal and posterior cortices in mediating consciousness and Unconsciousness. Disruption of posterior cortex during sleep appears to suppress the contents of dreaming, yet activation of frontal cortex appears necessary for perception and can reverse Unconsciousness under anesthesia. We used anesthesia to study how regional cortical disruption, mediated by slow wave modulation of broadband activity, changes during Unconsciousness in humans. We found that broadband slow-wave modulation enveloped posterior cortex when subjects initially became unconscious, but later encompassed both frontal and posterior cortex when subjects were more deeply anesthetized and likely unarousable. Our results suggest that Unconsciousness under anesthesia comprises several distinct shifts in brain state that disrupt the contents of consciousness distinct from arousal and awareness of those contents.
-
broadband slow wave modulation in posterior and anterior cortex tracks distinct states of propofol induced Unconsciousness
bioRxiv, 2019Co-Authors: Emily P Stephen, Emery N. Brown, Gladia C Hotan, Eric T Pierce, Grace P Harrell, John L Walsh, Patrick L PurdonAbstract:A controversy exists over the roles of frontal and posterior cortices in mediating consciousness and Unconsciousness. Disruption of posterior cortex during sleep appears to suppress the contents of dreaming, yet activation of frontal cortex appears necessary for perception and can reverse Unconsciousness under anesthesia. We used anesthesia to study how regional cortical disruption, mediated by slow wave modulation of broadband activity, changes during un-consciousness in humans. We found that broadband slow-wave modulation enveloped posterior cortex when subjects initially became unconscious, but later encompassed both frontal and posterior cortex when subjects were more deeply anesthetized and likely unarousable. Our results suggest that Unconsciousness under anesthesia comprises several distinct shifts in brain state that disrupt the contents of consciousness distinct from arousal and awareness of those contents.
Thomas A Gennarelli - One of the best experts on this subject based on the ideXlab platform.
-
new rat model for diffuse brain injury using coronal plane angular acceleration
Journal of Neurotrauma, 2007Co-Authors: Ronald J Fijalkowski, Brian D Stemper, Frank A Pintar, Narayan Yoganandan, Maria J Crowe, Thomas A GennarelliAbstract:A new experimental model was developed to induce diffuse brain injury (DBI) in rats through pure coronal plane angular acceleration. An impactor was propelled down a guide tube toward the lateral extension of the helmet fixture. Upon impactor-helmet contact, helmet and head were constrained to rotate in the coronal plane. In the present experimental series, the model was optimized to generate rotational kinematics necessary for concussion. Twenty-six rats were subjected to peak angular accelerations of 368 ± 30 krad/sec2(mean ± standard deviation) with 2.1 ± 0.5-msec durations. Following rotational loading, Unconsciousness was defined as time between reversal agent administration and return of corneal reflex. All experimental rats demonstrated transient Unconsciousness lasting 8.8 ± 3.7 min that was significantly longer than control rats. Macroscopic damage was noted in 51% of experimental animals: 38% subarachnoid hemorrhage, and 15% intraparenchymal lesion. Microscopic analysis indicated no evidence of ...
-
new rat model for diffuse brain injury using coronal plane angular acceleration
Journal of Neurotrauma, 2007Co-Authors: Ronald J Fijalkowski, Brian D Stemper, Frank A Pintar, Narayan Yoganandan, Maria J Crowe, Thomas A GennarelliAbstract:A new experimental model was developed to induce diffuse brain injury (DBI) in rats through pure coronal plane angular acceleration. An impactor was propelled down a guide tube toward the lateral extension of the helmet fixture. Upon impactor-helmet contact, helmet and head were constrained to rotate in the coronal plane. In the present experimental series, the model was optimized to generate rotational kinematics necessary for concussion. Twenty-six rats were subjected to peak angular accelerations of 368 +/- 30 krad/sec2 (mean +/- standard deviation) with 2.1 +/- 0.5-msec durations. Following rotational loading, Unconsciousness was defined as time between reversal agent administration and return of corneal reflex. All experimental rats demonstrated transient Unconsciousness lasting 8.8 +/- 3.7 min that was significantly longer than control rats. Macroscopic damage was noted in 51% of experimental animals: 38% subarachnoid hemorrhage, and 15% intraparenchymal lesion. Microscopic analysis indicated no evidence of axonal swellings at sacrifice times of 24, 48, 72, and 96 h. All rats survived rotational loading without skull fracture. Injuries were classified as concussion based on transient Unconsciousness, scaled biomechanics, limited macroscopic damage, and minimal histological abnormalities. The experimental methodology remains adjustable, permitting investigation of increasing DBI severities through modulation of model parameters, and inclusion of further functional and histological outcome measures.
George A Mashour - One of the best experts on this subject based on the ideXlab platform.
-
long range temporal correlations in the brain distinguish conscious wakefulness from induced Unconsciousness
NeuroImage, 2018Co-Authors: Thomas Thiery, George A Mashour, Stefanie Blainmoraes, Tarek Lajnef, Etienne Combrisson, Arthur Dehgan, Pierre Rainville, Karim JerbiAbstract:Rhythmic neuronal synchronization across large-scale networks is thought to play a key role in the regulation of conscious states. Changes in neuronal oscillation amplitude across states of consciousness have been widely reported, but little is known about possible changes in the temporal dynamics of these oscillations. The temporal structure of brain oscillations may provide novel insights into the neural mechanisms underlying consciousness. To address this question, we examined long-range temporal correlations (LRTC) of EEG oscillation amplitudes recorded during both wakefulness and anesthetic-induced Unconsciousness. Importantly, the time-varying EEG oscillation envelopes were assessed over the course of a sevoflurane sedation protocol during which the participants alternated between states of consciousness and Unconsciousness. Both spectral power and LRTC in oscillation amplitude were computed across multiple frequency bands. State-dependent differences in these features were assessed using non-parametric tests and supervised machine learning. We found that periods of Unconsciousness were associated with increases in LRTC in beta (15-30Hz) amplitude over frontocentral channels and with a suppression of alpha (8-13Hz) amplitude over occipitoparietal electrodes. Moreover, classifiers trained to predict states of consciousness on single epochs demonstrated that the combination of beta LRTC with alpha amplitude provided the highest classification accuracy (above 80%). These results suggest that loss of consciousness is accompanied by an augmentation of temporal persistence in neuronal oscillation amplitude, which may reflect an increase in regularity and a decrease in network repertoire compared to the brain's activity during resting-state consciousness.
-
neural correlates of Unconsciousness in large scale brain networks
Trends in Neurosciences, 2018Co-Authors: George A Mashour, Anthony G HudetzAbstract:The biological basis of consciousness is one of the most challenging and fundamental questions in 21st century science. A related pursuit aims to identify the neural correlates and causes of Unconsciousness. We review current trends in the investigation of physiological, pharmacological, and pathological states of Unconsciousness at the level of large-scale functional brain networks. We focus on the roles of brain connectivity, repertoire, graph-theoretical techniques, and neural dynamics in understanding the functional brain disconnections and reduced complexity that appear to characterize these states. Persistent questions in the field, such as distinguishing true correlates, linking neural scales, and understanding differential recovery patterns, are also addressed.
-
Human neural correlates of sevoflurane-induced Unconsciousness.
BJA: British Journal of Anaesthesia, 2017Co-Authors: Ben Julian A. Palanca, Michael S. Avidan, George A MashourAbstract:Sevoflurane, a volatile anaesthetic agent well-tolerated for inhalation induction, provides a useful opportunity to elucidate the processes whereby halogenated ethers disrupt consciousness and cognition. Multiple molecular targets of sevoflurane have been identified, complementing imaging and electrophysiologic markers for the mechanistically obscure progression from wakefulness to Unconsciousness. Recent investigations have more precisely detailed scalp EEG activity during this transition, with practical clinical implications. The relative timing of scalp potentials in frontal and parietal EEG signals suggests that sevoflurane might perturb the propagation of neural information between underlying cortical regions. Spatially distributed brain activity during general anaesthesia has been further investigated with positron emission tomography (PET) and resting-state functional magnetic resonance imaging (fMRI). Combined EEG and PET investigations have identified changes in cerebral blood flow and metabolic activity in frontal, parietal, and thalamic regions during sevoflurane-induced loss of consciousness. More recent fMRI investigations have revealed that sevoflurane weakens the signal correlations among brain regions that share functionality and specialization during wakefulness. In particular, two such resting-state networks have shown progressive breakdown in intracortical and thalamocortical connectivity with increasing anaesthetic concentrations: the Default Mode Network (introspection and episodic memory) and the Ventral Attention Network (orienting of attention to salient feature of the external world). These data support the hypotheses that perturbations in temporally correlated activity across brain regions contribute to the transition between states of sevoflurane sedation and general anaesthesia.
-
neural correlates of wakefulness sleep and general anesthesia an experimental study in rat
Anesthesiology, 2016Co-Authors: Dinesh Pal, Brian H Silverstein, Heonsoo Lee, George A MashourAbstract:Background:Significant advances have been made in our understanding of subcortical processes related to anesthetic- and sleep-induced Unconsciousness, but the associated changes in cortical connectivity and cortical neurochemistry have yet to be fully clarified.Methods:Male Sprague–Dawley rats were
-
electroencephalographic coherence and cortical acetylcholine during ketamine induced Unconsciousness
BJA: British Journal of Anaesthesia, 2015Co-Authors: Dinesh Pal, Brian H Silverstein, Viviane S Hambrechtwiedbusch, George A MashourAbstract:Background There is limited understanding of cortical neurochemistry and cortical connectivity during ketamine anaesthesia. We conducted a systematic study to investigate the effects of ketamine on cortical acetylcholine (ACh) and electroencephalographic coherence. Methods Male Sprague–Dawley rats ( n =11) were implanted with electrodes to record electroencephalogram (EEG) from frontal, parietal, and occipital cortices, and with a microdialysis guide cannula for simultaneous measurement of ACh concentrations in prefrontal cortex before, during, and after ketamine anaesthesia. Coherence and power spectral density computed from the EEG, and ACh concentrations, were compared between conscious and unconscious states. Loss of righting reflex was used as a surrogate for Unconsciousness. Results Ketamine-induced Unconsciousness was associated with a global reduction of power ( P =0.02) in higher gamma bandwidths (>65 Hz), a global reduction of coherence ( P ≤0.01) across a broad frequency range (0.5–250 Hz), and a significant increase in ACh concentrations ( P =0.01) in the prefrontal cortex. Compared with the unconscious state, recovery of righting reflex was marked by a further increase in ACh concentrations ( P =0.0007), global increases in power in theta (4–10 Hz; P =0.03) and low gamma frequencies (25–55 Hz; P =0.0001), and increase in power ( P ≤0.01) and coherence ( P ≤0.002) in higher gamma frequencies (65–250 Hz). Acetylcholine concentrations, coherence, and spectral properties returned to baseline levels after a prolonged recovery period. Conclusions Ketamine-induced Unconsciousness is characterized by suppression of high-frequency gamma activity and a breakdown of cortical coherence, despite increased cholinergic tone in the cortex.
Seongwhan Lee - One of the best experts on this subject based on the ideXlab platform.
-
assessment of Unconsciousness for memory consolidation using eeg signals
Systems Man and Cybernetics, 2020Co-Authors: Gihwan Shin, Minji Lee, Seongwhan LeeAbstract:The assessment of consciousness and Unconsciousness is a challenging issue in modern neuroscience. Consciousness is closely related to memory consolidation in that memory is a critical component of conscious experience. So far, many studies have been reported on memory consolidation during consciousness, but there is little research on memory consolidation during Unconsciousness. Therefore, we aim to assess the Unconsciousness in terms of memory consolidation using electroencephalogram signals. In particular, we used unconscious state during the nap; because sleep is the only state in which consciousness disappears under normal physiological conditions. Seven participants performed two memory tasks (word-pairs and visuo-spatial) before and after the nap to assess the memory consolidation during Unconsciousness. As a result, spindle power in central, parietal, occipital regions during Unconsciousness was positively correlated with the difference in location memory performance. With the difference in memory performance, there was also a negative correlation between delta connectivity and word-pairs memory, alpha connectivity and location memory, and spindle connectivity and word-pairs memory. Additionally, brain activity and connectivity for differences according to nap and Unconsciousness during memory recall were explored. These findings could help present new insights into the assessment of Unconsciousness by exploring the relationship with memory consolidation.
-
assessment of Unconsciousness for memory consolidation using eeg signals
arXiv: Signal Processing, 2020Co-Authors: Gihwan Shin, Minji Lee, Seongwhan LeeAbstract:The assessment of consciousness and Unconsciousness is a challenging issue in modern neuroscience. Consciousness is closely related to memory consolidation in that memory is a critical component of conscious experience. So far, many studies have been reported on memory consolidation during consciousness, but there is little research on memory consolidation during Unconsciousness. Therefore, we aim to assess the Unconsciousness in terms of memory consolidation using electroencephalogram signals. In particular, we used unconscious state during a nap; because sleep is the only state in which consciousness disappears under normal physiological conditions. Seven participants performed two memory tasks (word-pairs and visuo-spatial) before and after the nap to assess the memory consolidation during Unconsciousness. As a result, spindle power in central, parietal, occipital regions during Unconsciousness was positively correlated with the performance of location memory. With the memory performance, there was also a negative correlation between delta connectivity and word-pairs memory, alpha connectivity and location memory, and spindle connectivity and word-pairs memory. We additionally observed the significant relationship between Unconsciousness and brain changes during memory recall before and after the nap. These findings could help present new insights into the assessment of Unconsciousness by exploring the relationship with memory consolidation.
-
connectivity differences between consciousness and Unconsciousness in non rapid eye movement sleep a tms eeg study
Scientific Reports, 2019Co-Authors: Minji Lee, Mélanie Boly, Olivia Gosseries, Benjamin Baird, Jaakko O Nieminen, Bradley R Postle, Giulio Tononi, Seongwhan LeeAbstract:The neuronal connectivity patterns that differentiate consciousness from Unconsciousness remain unclear. Previous studies have demonstrated that effective connectivity, as assessed by transcranial magnetic stimulation combined with electroencephalography (TMS–EEG), breaks down during the loss of consciousness. This study investigated changes in EEG connectivity associated with consciousness during non-rapid eye movement (NREM) sleep following parietal TMS. Compared with Unconsciousness, conscious experiences during NREM sleep were associated with reduced phase-locking at low frequencies (<4 Hz). Transitivity and clustering coefficient in the delta and theta bands were also significantly lower during consciousness compared to Unconsciousness, with differences in the clustering coefficient observed in scalp electrodes over parietal–occipital regions. There were no significant differences in Granger-causality patterns in frontal-to-parietal or parietal-to-frontal connectivity between reported Unconsciousness and reported consciousness. Together these results suggest that alterations in spectral and spatial characteristics of network properties in posterior brain areas, in particular decreased local (segregated) connectivity at low frequencies, is a potential indicator of consciousness during sleep.
