Neural correlates of successful semantic processing during propofol sedation

Adapa, R.; Davis, Matthew H.; Stamatakis, Emmanuel A.; Absalom, Anthony; Menon, David

doi:10.1002/hbm.22375

Cited by 51 publications

(49 citation statements)

References 64 publications

(71 reference statements)

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“…Our results are in line with earlier observations that propofol attenuates stimulus-induced activity during auditory and noxious stimulation [Adapa et al, 2014; Davis et al, 2007; DiFrancesco et al, 2013; Dueck et al, 2005; Frölich et al, 2017; Liu et al, 2012; Mhuircheartaigh et al, 2010; Mhuircheartaigh et al, 2013]. These effects may be due to an overall impairment of hierarchy cortical processing and information integration [Alkire et al, 2008; Davis et al, 2007].…”

Section: Discussionsupporting

confidence: 93%

“…We found a gradual decease of TTM in both amplitude and spatial distribution from wakefulness (widespread brain areas) through sedation (auditory cortex, language, and sensorimotor networks) to deep anesthesia (auditory cortex only). Our results are in line with earlier observations that propofol attenuates stimulus-induced activity during auditory and noxious stimulation (Adapa, Davis, Stamatakis, Absalom, & Menon, 2014;Davis et al, 2007;DiFrancesco, Robertson, Karunanayaka, & Holland, 2013;Dueck et al, 2005;Frölich, Banks, & Ness, 2017;Liu et al, 2012;Mhuircheartaigh et al, 2010;Ní Mhuircheartaigh, Warnaby, Rogers, Jbabdi, & Tracey, 2013). These effects may be due to an overall impairment of hierarchy cortical processing and information integration (Alkire et al, 2008;Davis et al, 2007).…”

Section: Graded Attenuation Of Ttm From Wakefulness Through Sedatiosupporting

confidence: 93%

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Disrupted neural variability during propofol‐induced sedation and unconsciousness

Huang

Zhang

et al. 2018

Human Brain Mapping

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Variability quenching is a widespread neural phenomenon in which trial-to-trial variability (TTV) of neural activity is reduced by repeated presentations of a sensory stimulus. However, its neural mechanism and functional significance remain poorly understood. Recurrent network dynamics are suggested as a candidate mechanism of TTV, and they play a key role in consciousness. We thus asked whether the variability-quenching phenomenon is related to the level of consciousness. We hypothesized that TTV reduction would be compromised during reduced level of consciousness by propofol anesthetics. We recorded functional magnetic resonance imaging signals of resting-state and stimulus-induced activities in three conditions: wakefulness, sedation, and unconsciousness (i.e., deep anesthesia). We measured the average (trial-to-trial mean, TTM) and variability (TTV) of auditory stimulus-induced activity under the three conditions. We also examined another form of neural variability (temporal variability, TV), which quantifies the overall dynamic range of ongoing neural activity across time, during both the resting-state and the task. We found that (a) TTM deceased gradually from wakefulness through sedation to anesthesia, (b) stimulus-induced TTV reduction normally seen during wakefulness was abolished during both sedation and anesthesia, and (c) TV increased in the task state as compared to resting-state during both wakefulness and sedation, but not anesthesia. Together, our results reveal distinct effects of propofol on the two forms of neural variability (TTV and TV). They imply that the anesthetic disrupts recurrent network dynamics, thus prevents the stabilization of cortical activity states. These findings shed new light on the temporal dynamics of neuronal variability and its alteration during anesthetic-induced unconsciousness.

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Section: Discussionsupporting

confidence: 93%

Section: Graded Attenuation Of Ttm From Wakefulness Through Sedatiosupporting

confidence: 93%

Disrupted neural variability during propofol‐induced sedation and unconsciousness

Huang

Zhang

et al. 2018

Human Brain Mapping

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“…The full stimulus set included 120 neutral (i.e., not intrinsically salient) monosyllabic words, half describing living items (e.g., horse, tree) and half describing nonliving items (e.g., table, stone), recorded in a neutral (i.e., nonemotional) female voice. 15 From the set, 50 were randomly chosen and allocated, in subgroups of 5, to each of the 10 blocks (5 baseline, 5 target detection). Within each block, words were randomly selected to repeat 7, 6, 5, or 4 times (with 2 words repeating 4 times), resulting in 26 word presentations per block.…”

mentioning

confidence: 99%

Thalamo-frontal connectivity mediates top-down cognitive functions in disorders of consciousness

et al. 2015

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Objective: We employed functional MRI (fMRI) to assess whether (1) patients with disorders of consciousness (DOC) retain the ability to willfully engage in top-down processing and (2) what neurophysiologic factors distinguish patients who can demonstrate this ability from patients who cannot.Methods: Sixteen volunteers, 8 patients in vegetative state (VS), 16 minimally conscious patients (MCS), and 4 exit from MCS (eMCS) patients were enrolled in a prospective cross-sectional fMRI study. Participants performed a target detection task in which they counted the number of times a (changing) target word was presented amidst a set of distractors.Results: Three of 8 patients diagnosed as being in a VS exhibited significant activations in response to the task, thereby demonstrating a state of consciousness. Differential activations across tasks were also observed in 6 MCS patients and 1 eMCS patient. A psycho-physiologic interaction analysis revealed that the main factor distinguishing patients who responded to the task from those who did not was a greater connectivity between the anterior section of thalamus and prefrontal cortex.Conclusions: In our sample of patients, the dissociation between overt behavior observable in clinical assessments and residual cognitive faculties is prevalent among DOC patients (37%). A substantial number of patients, including some diagnosed with VS, can demonstrate willful engagement in top-down cognition. While neuroimaging data are not the same as observable behavior, this suggests that the mental status of some VS patients exceeds what can be appreciated clinically. Furthermore, thalamo-frontal circuits might be crucial to sustaining top-down functions. Neurology ® 2015;84:167-173 GLOSSARY DOC 5 disorders of consciousness; eMCS 5 exit from minimally conscious state; FA 5 flip angle; fMRI 5 functional MRI; GLM 5 generalized linear model; MCS 5 minimally conscious state; MNI 5 Montreal Neurological Institute; PPI 5 psychophysiologic interaction approach; ROI 5 region of interest; TE 5 echo time; TR 5 repetition time; VS 5 vegetative state.

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“…Twenty five healthy volunteer subjects were recruited for scanning. The acquisition procedures are described in detail in (Stamatakis et al, 2010;Adapa et al, 2014): MRI data were acquired on a Siemens Trio 3T scanner Of the 25 healthy subjects datasets, 10 were excluded, either because of missing scans (n=2), or due of excessive motion in the scanner (n=8, 5mm maximum motion threshold). For this study, we only used the awake, control condition described in the original Stamatakis study, ignoring the drug conditions.…”

Section: Healthy Control Datamentioning

confidence: 99%

Fractal Dimension of Cortical Functional Connectivity Networks Predicts Severity in Disorders of Consciousness

Varley

Craig

Adapa

et al. 2019

Preprint

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Recent evidence suggests that the quantity and quality of conscious experience may be a function of the complexity of activity in the brain, and that consciousness emerges in a critical zone on the axes of order/randomness and integration/differentiation. We propose fractal shapes as a measure of proximity to this critical point, as fractal dimension encodes information about complexity beyond simple entropy or randomness, and fractal structures are known to emerge in systems nearing a critical point. To validate this, we tested the several measures of fractal dimension on the brain activity from healthy volunteers and patients with disorders of consciousness of varying severity. We used a Compact Box Burning algorithm to compute the fractal dimension of cortical functional connectivity networks as well as computing the fractal dimension of the associated adjacency matrices using a 2D box-counting algorithm. To test whether brain activity is fractal in time as well as space, we used the Higuchi temporal fractal dimension on BOLD time-series. We found significant decreases in the fractal dimension between healthy volunteers (n=15), patients in a minimally conscious state (n=10), and patients in a vegetative state (n=8), regardless of the mechanism of injury. We also found significant decreases in adjacency matrix fractal dimension and Higuchi temporal fractal dimension, which correlated with decreasing level of consciousness. These results suggest that cortical functional connectivity networks display fractal character and that this is predictive of level of consciousness in a clinically relevant population, with more fractal (i.e. more complex) networks being associated with higher levels of consciousness. This supports the hypothesis that level of consciousness and system complexity are positively associated, and is consistent with previous EEG, MEG, and fMRI studies.

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Neural correlates of successful semantic processing during propofol sedation

Cited by 51 publications

References 64 publications

Disrupted neural variability during propofol‐induced sedation and unconsciousness

Disrupted neural variability during propofol‐induced sedation and unconsciousness

Thalamo-frontal connectivity mediates top-down cognitive functions in disorders of consciousness

Fractal Dimension of Cortical Functional Connectivity Networks Predicts Severity in Disorders of Consciousness

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