Integrating the science of consciousness and anesthesia.
ABSTRACT The nature and mechanism of human consciousness is emerging as one of the most important scientific and philosophical questions of the 21st century. Disregarded as a subject of serious inquiry throughout most of the 20th century, it has now regained legitimacy as a scientific endeavor. The investigation of consciousness and the mechanisms of general anesthesia have begun to converge. In the present article I provide an introduction to the study of consciousness, describe the neural correlates of consciousness that may be targets of general anesthetics, and suggest an integrated approach to the science of consciousness and anesthesia.
- SourceAvailable from: Matthew Banks[Show abstract] [Hide abstract]
ABSTRACT: The mechanism of loss of consciousness (LOC) under anesthesia is unknown. Because consciousness depends on activity in the cortico-thalamic network, anesthetic actions on this network are likely critical for LOC. Competing theories stress the importance of anesthetic actions on bottom-up "core" thalamo-cortical (TC) vs. top-down cortico-cortical (CC) and matrix TC connections. We tested these models using laminar recordings in rat auditory cortex in vivo and murine brain slices. We selectively activated bottom-up vs. top-down afferent pathways using sensory stimuli in vivo and electrical stimulation in brain slices, and compared effects of isoflurane on responses evoked via the two pathways. Auditory stimuli in vivo and core TC afferent stimulation in brain slices evoked short latency current sinks in middle layers, consistent with activation of core TC afferents. By contrast, visual stimuli in vivo and stimulation of CC and matrix TC afferents in brain slices evoked responses mainly in superficial and deep layers, consistent with projection patterns of top-down afferents that carry visual information to auditory cortex. Responses to auditory stimuli in vivo and core TC afferents in brain slices were significantly less affected by isoflurane compared to responses triggered by visual stimuli in vivo and CC/matrix TC afferents in slices. At a just-hypnotic dose in vivo, auditory responses were enhanced by isoflurane, whereas visual responses were dramatically reduced. At a comparable concentration in slices, isoflurane suppressed both core TC and CC/matrix TC responses, but the effect on the latter responses was far greater than on core TC responses, indicating that at least part of the differential effects observed in vivo were due to local actions of isoflurane in auditory cortex. These data support a model in which disruption of top-down connectivity contributes to anesthesia-induced LOC, and have implications for understanding the neural basis of consciousness.Frontiers in Systems Neuroscience 10/2014; 8:191.
- [Show abstract] [Hide abstract]
ABSTRACT: Background / Purpose: Although feed-forward-feed-back imbalance during anesthesia is widely confirmed with diverse anesthetic drugs; the disparity of information processing between left and right brain during unconscious state is not yet probed. Here we study the hemispheric asymmetry of information flow by comparing the change of feed-forward, feed-back and inter-hemispheric information flows computed from electroencephalogram (EEG). Main conclusion: We suggest that the hemispheric asymmetry of feed-forward and feed-back information reflects the qualitatively different unconsciousness. Also, left and right brain hemispheres could have a different role even during unconscious state.20th Annual Meeting of the Organization for Human Brain Mapping (OHBM) 2014; 07/2014
- [Show abstract] [Hide abstract]
ABSTRACT: The Ouroboros Model features a biologically inspired cognitive architecture. At its core lies a self-referential recursive process with alternating phases of data acquisition and evaluation. Memory entries are organized in schemata. The activation at a time of part of a schema biases the whole structure and, in particular, missing features, thus triggering expectations. An iterative recursive monitor process termed \consumption analysis" is then checking how well such expectations ¯t with successive activations. Mismatches between anticipations based on previous experience and actual current data are highlighted and used for controlling the allo-cation of attention. In case no directly ¯tting ¯ller for an open slot is found, activation spreads more widely and includes data relating to the actor, and Higher-Order Personality Activation, HOPA, ensues. It is brie°y outlined how the Ouroboros Model produces many diverse charac-teristics and thus addresses established criteria for consciousness. Coarse-grained relationships to selected previous conceptualizations of consciousness and a sketch of how the Ouroboros Model could shed light on current research themes in arti¯cial general intelligence and con-sciousness conclude this paper.International Journal of Machine Consciousness 06/2011; 03(01).