A Neural Field Theory for Loss of Consciousness
Wassim Haddad2016, Elsevier eBooks
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Abstract
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This research presents a novel mechanistic mean field model for analyzing how anesthetic agents affect neural activity and transition from consciousness to unconsciousness. By employing dynamical system theory, the model captures the influence of synaptic drive on neuronal population activity and predicts that as anesthetic concentration increases, brain activity diminishes, ultimately leading to a transition from a limit cycle of excitatory activity to a stable equilibrium indicative of the anesthetized state. The findings suggest that the transition to unconsciousness may exhibit probabilistic characteristics tied to neural dynamics.
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Science, 2008
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Anesthetic techniques using different substances with anesthetic properties have been used since antiquity. However, even today, it is not known exactly how these anesthetics work, if there is a common site or if their action is multi-level. In this article we present the latest theories regarding the mechanism of anesthetics' action. Thus we will refer to the action of anesthetics on neural networks, we will discuss the fractal theory of consciousness as well as the soliton model and the theory of the action of anesthetics on the cellular cytoskeleton.
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Journal of mathematical neuroscience, 2015
With the advances in biochemistry, molecular biology, and neurochemistry there has been impressive progress in understanding the molecular properties of anesthetic agents. However, there has been little focus on how the molecular properties of anesthetic agents lead to the observed macroscopic property that defines the anesthetic state, that is, lack of responsiveness to noxious stimuli. In this paper, we use dynamical system theory to develop a mechanistic mean field model for neural activity to study the abrupt transition from consciousness to unconsciousness as the concentration of the anesthetic agent increases. The proposed synaptic drive firing-rate model predicts the conscious-unconscious transition as the applied anesthetic concentration increases, where excitatory neural activity is characterized by a Poincaré-Andronov-Hopf bifurcation with the awake state transitioning to a stable limit cycle and then subsequently to an asymptotically stable unconscious equilibrium state. ...
A model of the electrocortical effects of general anaesthesia
British Journal of Anaesthesia, 1997
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Basic Sciences in Anesthesia
Basic Sciences in Anesthesia, 2018
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Anesthesia, Neural Information Processing, and Conscious Awareness* 1
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MORPhA Scale: behavioral and electroencephalographic validation of a rodent anesthesia scale
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PhD Thesis, 2008
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Implications for Anesthesia and Beyond
Journal of neuroanaesthesiology and critical care, 2023
Gamma-aminobutyric acid (GABA), a nonpeptide amino acid transmitter, is a major component of modern neuropharmacology and one of the most crucial target sites for general anesthetics and therapeutic drugs. GABA type A receptors (GABA A Rs) are the most abundant inhibitory neurotransmitter receptors in the central nervous system. They are part of the rapid-acting, ligand-gated ion channel (LGIC) receptor category, a pentameric Cys-loop superfamily member that mediates inhibitory neurotransmission in the mature brain. GABA A Rs mainly consist of two α subunits, two β subunits, and one additional subunit from either γ or d arranged around a central chloride (Cl -) selective channel. Multiple GABA A R subunit subtypes and splice variants have been identified. Each variant of GABA A R exhibits distinct biophysical and pharmacologic properties. Several compounds allosterically modulate the GABA A R positively or negatively. The widely used positive GABA A R modulators include benzodiazepines (anxiolytic and anticonvulsant), general anesthetics (volatile agents like isoflurane, and intravenous agents like barbiturates, etomidate, and propofol), long-chain alcohols, some anticonvulsants, and neuroactive steroids. The binding sites for each drug are distinctly different. The anesthetic drugs enhance receptor-mediated synaptic transmission and thus interrupt the thalamocortical transmission, which controls the sleep-wake patterns. Abnormality in the GABA A R function has been implicated in several neurological conditions, such as sleep disorders, seizures, depression, cognitive function, neurological recovery after injury, and neuroplasticity. Understanding the GABA A R lays the foundation for the development of highly specific drugs in the treatment of neurological disorders and general anesthesia.
Consciousness, EEG and depth of anaesthesia monitoring
Australasian Physical & Engineering Sciences in Medicine, 2012
30 Years Lost in Anesthesia Theory
The recent discovery of the " Stress Repair Mechanism " (SRM) enables the Unified Theory of Medicine postulated by Hans Selye. It confers cohesive theories of anesthesia, analgesia, and allostasis that enable the alteration of anesthetic technique to optimize surgical outcome. The SRM continuously maintains and repairs the vertebrate body in accord with stressful forces and stimuli. Three synergistic pathways activate the SRM: the spinal pathway, the cognitive pathway, and the tissue pathway. Emotional mechanisms modulate the cognitive pathway, which explains allostasis. Surgery simultaneously stimulates all three synergistic pathways, causing harmful SRM hyperactivity that manifests as the Surgical Stress Syndrome. Anesthesia inhibits the cognitive pathway. Analgesia inhibits the spinal pathway. Synergistic combinations of anesthesia and analgesia minimize SRM hyperactivity better than either alone. This principle improves outcome, simplifies anesthetic technique, and minimizes polypharmacy and drug toxicity. Once verified, stress theory will advance surgical safety, accelerate recovery, minimize complications, reduce costs, enhance patient comfort, and guide pharmaceutical development to discover treatments that inhibit the tissue pathway, and thereby eliminate surgical stress altogether.
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