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Trends in Cell & Molecular Biology   Volumes    Volume 15 
Testing for consciousness in cerebral organoids
Stuart Hameroff, Alysson R. Muotri
Pages: 43 - 57
Number of pages: 15
Trends in Cell & Molecular Biology
Volume 15 

Copyright © 2020 Research Trends. All rights reserved

Consciousness cannot be directly measured, but there exist in the brain putative ‘neural correlates of consciousness’ (‘pNCCs’). We describe four novel electrophysiological pNCCs found in humans and animals. pNCC1 is ‘high gamma’ frequency (~85-165 Hz) electro-encephalography (‘EEG’), selectively abolished by anesthesia, and enhanced in meditation. The second, pNCC2, is related to ‘phase-amplitude coupling’, or ‘nesting’ between different EEG frequencies, e.g. between delta/theta waves (1-10 Hz), and ‘low gamma’ EEG waves (25-65 Hz). EEG nesting correlates with cognitive short-term memory and perception, but paradoxically is enhanced by anesthesia, suggesting that deviation from nested EEG correlates with consciousness (pNCC2). Similarly, pNCC3 involves ‘non-computable’ deviation from ‘integrate-and-fire’, Hodgkin-Huxley neuron behavior, as found in brain pyramidal neurons in awake animals. pNCC4 is a generalized reverberation, or EEG ‘chiming’ in response to a focused stimulus. pNCC2 and pNCC3 suggest consciousness supervenes on non-conscious cognitive (‘autopilot’) mechanisms, seen as deviation from algorithmic processing as an observable ‘shadow’ of consciousness. Invasive pNCC testing in humans and animals is limited for ethical reasons, but simpler biological systems with pNCCs are potentially conscious, with fewer ethical concerns. Recently, ‘high gamma’ and nested EEG were observed in cerebral organoids, stem cell-derived cooperative assemblies of ~2.5 million cortical neurons. We propose to perturb cerebral organoids in ways known to affect consciousness, and evaluate perturbing effects on pNCCs1-4 in the context of various theories of consciousness. Organoids will be perturbed by 1) anesthesia, 2) psychedelics, 3) electromagnetic and ultrasound energy, 4) drugs which impair membrane receptors and ion channels, and 5) drugs which impair cytoskeletal microtubules inside neurons. We hope to establish criteria for assessing consciousness in biology, evaluate contributions from membrane/synaptic and intra-neuronal cytoskeletal processes to consciousness, find support for one or more theories of consciousness, and reach an informed opinion on whether cerebral organoids are conscious.
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