Comparison of Anesthetic Depth Indexes Based on Thalamocortical Local Field Potentials in Rats

Silva, Aura; Cardoso‐Cruz, Helder; Silva, Francisco; Galhardo, Vasco; Antunes, Luís

doi:10.1097/aln.0b013e3181ca3196

Cited by 61 publications

(75 citation statements)

References 28 publications

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“…During the transition from awake to unresponsive, a clear reduction in functional connectivity between the putamen and a wide range of other cortical and subcortical regions occurred, while the connectivity of the thalamus with these regions was maintained. This preservation of thalamocortical connectivity has recently been observed in animals (Silva et al, 2010).…”

Section: Discussionmentioning

confidence: 86%

Cortical and Subcortical Connectivity Changes during Decreasing Levels of Consciousness in Humans: A Functional Magnetic Resonance Imaging Study using Propofol

Mhuircheartaigh¹,

Rosenorn-Lanng²,

Wise³

et al. 2010

Journal of Neuroscience

199

144

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. We investigated the effects of propofol, widely used for anesthesia and sedation, on spontaneous and evoked cerebral activity using functional magnetic resonance imaging (fMRI). A series of auditory and noxious stimuli was presented to eight healthy volunteers at three behavioral states: awake, "sedated" and "unresponsive." Performance in a verbal task and the absence of a response to verbal stimulation, rather than propofol concentrations, were used to define these states clinically. Analysis of stimulus-related blood oxygenation level-dependent signal changes identified reductions in cortical and subcortical responses to auditory and noxious stimuli in sedated and unresponsive states. A specific reduction in activity within the putamen was noted and further investigated with functional connectivity analysis. Progressive failure to perceive or respond to auditory or noxious stimuli was associated with a reduction in the functional connectivity between the putamen and other brain regions, while thalamo-cortical connectivity was relatively preserved. This result has not been previously described and suggests that disruption of subcortical thalamo-regulatory systems may occur before, or even precipitate, failure of thalamo-cortical transmission with the induction of unconsciousness.

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Section: Discussionmentioning

confidence: 86%

Cortical and Subcortical Connectivity Changes during Decreasing Levels of Consciousness in Humans: A Functional Magnetic Resonance Imaging Study using Propofol

Mhuircheartaigh¹,

Rosenorn-Lanng²,

Wise³

et al. 2010

Journal of Neuroscience

199

144

View full text Add to dashboard Cite

show abstract

“…Indeed, the volatile agent isoflurane has also been shown to yield increased thalamocortical coherence (33). Thus, our model may not be limited to propofol and predicts an important role of GABAergic pathways in propagating more general anesthetic-induced rhythms.…”

Section: Discussionmentioning

confidence: 95%

Thalamocortical model for a propofol-induced α-rhythm associated with loss of consciousness

Ching

Cimenser

Purdon

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

354

405

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Recent data reveal that the general anesthetic propofol gives rise to a frontal α-rhythm at dose levels sufficient to induce loss of consciousness. In this work, a computational model is developed that suggests the network mechanisms responsible for such a rhythm. It is shown that propofol can alter the dynamics in thalamocortical loops, leading to persistent and synchronous α-activity. The synchrony that forms in the cortex by virtue of the involvement of the thalamus may impede responsiveness to external stimuli, thus providing a correlate for the unconscious state.general anesthesia | oscillations | global coherence | GABA T he anesthetic agent propofol (2,6-di-isopropylphenol) is known to elicit frontal α-rhythms (10-13 Hz) in the EEG (1). Recent data analyses (2, 3) suggest that this rhythm, which is spatially distinct from the classic occipital α-rhythm, is highly coherent across electrodes. Moreover, its appearance is well correlated with the anesthetic-induced loss of consciousness. Although much is known about the molecular actions of propofol, an understanding of the network mechanisms that lead to such EEG-level phenomena remains absent. The present work uses computational models to elucidate some of these mechanisms. It builds on the work of McCarthy et al. (4), in which a model of cortical networks was used to reveal dynamic changes that may underlie the paradoxical excitation associated with low doses of propofol. Here, these mechanisms are incorporated into a broader thalamocortical model that accounts for the aforementioned EEG features associated with the administration of higher anesthetic doses.The model suggests that propofol, via its potentiation of the GABA A synaptic current, effectively enhances the strength of projections from the cortex to thalamus, resulting in a wellcoordinated thalamocortical α-oscillation. We consider a network of cortical pyramidal (E) cells and interneurons (INs), coupled with thalamocortical relay (TC) and thalamic reticular (RE) neurons. Reciprocal projections between the E and TC cells form an excitatory thalamocortical loop. Propofol enters the model as an increase in the conductance and decay time of the GABA A inhibitory current. At low levels of the drug, the cortical part of the model produces the expected paradoxical excitation, whereas the thalamic part fires at a slower irregular rate. Increasing the inhibition to a level commensurate with a higher dose of the drug causes cortical cell firing to slow into the α-range. Importantly, this also changes the thalamic substrate by increasing the inhibition delivered by the RE neurons to the TC neurons, producing rebound spiking. Thus, the cortical input to the thalamus is effectively enhanced, enabling the latter to be recruited into the same α-frequency. Because the reticular nucleus innervates widely, it has the capacity to synchronize thalamic oscillations. These oscillations then manifest coherently at the cortex through the thalamocortical loop. Thus, the model produces a coherent propofol-induced α-rhyth...

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“…In what follows, we give a brief overview of applications of ordinal time series analysis to studies of brain (electrical) activity, namely in epilepsy research [63][64][65][66][67][68][69], in anesthesiology [70][71][72][73][74], and cognitive neuroscience [75,76]. All the studies reviewed below investigated brain electrical activity, recorded with electroencephalographic (EEG) techniques.…”

Section: Biomedical Applicationsmentioning

confidence: 99%

“…Electroencephalogram-based parameters typically aim at reducing the complex observed electroencephalographic pattern to a single value associated with the anesthetic drug effect and clinical patient status, e.g., consciousness and unconsciousness. These issues were examined in various studies [70,[72][73][74]79], which consistently showed that permutation entropy can be used to efficiently discriminate between different levels of consciousness during anesthesia, providing an index of the anesthetic drug effect.…”

Section: Anesthesiamentioning

confidence: 99%

Permutation Entropy and Its Main Biomedical and Econophysics Applications: A Review

Zanin

Zunino

Rosso

et al. 2012

Entropy

562

440

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Entropy is a powerful tool for the analysis of time series, as it allows describing the probability distributions of the possible state of a system, and therefore the information encoded in it. Nevertheless, important information may be codified also in the temporal dynamics, an aspect which is not usually taken into account. The idea of calculating entropy based on permutation patterns (that is, permutations defined by the order relations among values of a time series) has received a lot of attention in the last years, especially for the understanding of complex and chaotic systems. Permutation entropy directly accounts for the temporal information contained in the time series; furthermore, it has the quality of simplicity, robustness and very low computational cost. To celebrate the tenth anniversary of the original work, here we analyze the theoretical foundations of the permutation entropy, Entropy 2012, 14 1554 as well as the main recent applications to the analysis of economical markets and to the understanding of biomedical systems.

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Comparison of Anesthetic Depth Indexes Based on Thalamocortical Local Field Potentials in Rats

Abstract: The permutation entropy corrected with the classic burst suppression ratio is a promising alternative to other indexes of anesthetic depth. Furthermore, high coherence level of activity exists between the somatosensory cortical and thalamic regions, even at deep isoflurane stages.

Cited by 61 publications

References 28 publications

Cortical and Subcortical Connectivity Changes during Decreasing Levels of Consciousness in Humans: A Functional Magnetic Resonance Imaging Study using Propofol

Cortical and Subcortical Connectivity Changes during Decreasing Levels of Consciousness in Humans: A Functional Magnetic Resonance Imaging Study using Propofol

Thalamocortical model for a propofol-induced α-rhythm associated with loss of consciousness

Permutation Entropy and Its Main Biomedical and Econophysics Applications: A Review

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