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Front Neural Circuits. 2017 Jun 20;11:44. doi: 10.3389/fncir.2017.00044. eCollection 2017.

Bottom-Up and Top-Down Mechanisms of General Anesthetics Modulate Different Dimensions of Consciousness.

Mashour GA1,2,3, Hudetz AG1,2,3.

Author information

1
Department of Anesthesiology, University of MichiganAnn Arbor, MI, United States.
2
Center of Consciousness Science, University of MichiganAnn Arbor, MI, United States.
3
Neuroscience Graduate Program, University of MichiganAnn Arbor, MI, United States.

Abstract

There has been controversy regarding the precise mechanisms of anesthetic-induced unconsciousness, with two salient approaches that have emerged within systems neuroscience. One prominent approach is the "bottom up" paradigm, which argues that anesthetics suppress consciousness by modulating sleep-wake nuclei and neural circuits in the brainstem and diencephalon that have evolved to control arousal states. Another approach is the "top-down" paradigm, which argues that anesthetics suppress consciousness by modulating the cortical and thalamocortical circuits involved in the integration of neural information. In this article, we synthesize these approaches by mapping bottom-up and top-down mechanisms of general anesthetics to two distinct but inter-related dimensions of consciousness: level and content. We show how this explains certain empirical observations regarding the diversity of anesthetic drug effects. We conclude with a more nuanced discussion of how levels and contents of consciousness interact to generate subjective experience and what this implies for the mechanisms of anesthetic-induced unconsciousness.

KEYWORDS:

anesthesia; anesthetic mechanisms; awareness; connectivity; sleep; unconsciousness; wakefulness

PMID:
28676745
PMCID:
PMC5476707
DOI:
10.3389/fncir.2017.00044
[Indexed for MEDLINE]
Free PMC Article

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