Fading whispers down the lane: signal propagation in anaesthetized cortical networks

An active area of enquiry in the neuroscientific investigation of general anaesthesia is the question of whether anaesthetic-induced unconsciousness is mediated by bottom-up or top-down mechanisms in the brain. Candidates for the bottom-up approach include suppression of arousal centres in the brainstem and diencephalon,12 activation of sleep-promoting neurones or nuclei in similar locations,13 blockade of sensory informationen route from the thalamus to the cortex,4 and a disabled thalamic conductor for the neuronal orchestra of the cortex.5 Candidates for the top-down approach include direct effects on long-latency activity in cortical networks,6 with a consequent disruption of higher-order information synthesis that occurs beyond the level of the primary sensory cortex.7 –9 This bottom-upvs top-down distinction is almost surely artificial given the integrated circuits required for the normal function of neural systems and the widespread effects of general anaesthetics on the brain. We recently proposed that anaesthetics alter the level of consciousness (e.g. awakevs somnolent) through bottom-up mechanisms while degrading the contents of consciousness (e.g. the particular qualities of experience) through top-down mechanisms.10 Developing a clearer understanding of these processes is important because it can inform (i) the neurobiology of consciousness, a fundamental question in science, and (ii) our approach to brain monitoring, a fundamental and unmet challenge in clinic...
Source: British Journal of Anaesthesia - Category: Anesthesiology Source Type: research