Cognitive unbinding: a neuroscientific paradigm of general anesthesia and related states of unconsciousness

Abstract

"Cognitive unbinding" refers to the impaired synthesis of specialized cognitive activities in the brain and has been proposed as a mechanistic paradigm of unconsciousness. This article draws on recent neuroscientific data to revisit the tenets and predictions of cognitive unbinding, using general anesthesia as a representative state of unconsciousness. Current evidence from neuroimaging and neurophysiology supports the proposition that cognitive unbinding is a parsimonious explanation for the direct mechanism (or "proximate cause") of anesthetic-induced unconsciousness across multiple drug classes. The relevance of cognitive unbinding to sleep, disorders of consciousness, and psychological processes is also explored. It is concluded that cognitive unbinding is a viable neuroscientific framework for unconscious processes across the fields of anesthesiology, sleep neurobiology, neurology and psychoanalysis.

Keywords: Anesthesia; Cognitive binding; Cognitive unbinding; Consciousness; Information integration; Psychoanalysis; Sleep; Unconsciousness; Unresponsive wakefulness syndrome.

Copyright © 2013 Elsevier Ltd. All rights reserved.

Figures

Figure 1. Primary sensory networks are preserved after propofol-induced unconsciousness

Data from functional magnetic resonance imaging was gathered in healthy volunteers exposed to propofol. Panels A and C show primary visual cortex, whereas panels B and D show primary auditory cortex, during consciousness and unconsciousness. Reproduced from Boveroux et al, 2010, with permission.

Figure 2. Schematic of temporal unbinding after propofol-induced unconsciousness

Data gathered from electrocorticography in human epilepsy patients shows temporal unbinding after administration of propofol, based on the relationship of single-unit activity and local field potentials. Reproduced from Lewis et al, 2012, with permission.

Figure 3. Theoretical relevance of impaired feedback and preserved feedforward processing to cognitive binding

These modeling data demonstrate the effects of neural inhibition, feedback processing and feedforward processing on error rate and signal-to-noise ratio during cognitive binding of multiple objects. Importantly, feedforward processing alone results in the highest error rate and lowest signal-to-noise (relevant/irrelevant) ratio. Reproduced from Wyatte et al, 2012, with permission (open access journal).

Figure 4. Empirical demonstration of impaired feedback and preserved feedforward connectivity after anesthetic-induced unconsciousness

This figure demonstrates feedback and feedforward connectivity in frontal-parietal networks during and after anesthetic-induced unconsciousness in surgical patients (A–C). Lower panels (D–F) show asymmetry of directional connectivity, with positive values representing feedback dominance and negative values representing feedforward dominance. Connectivity was measured using electroencephalography and symbolic transfer entropy, which is rooted in information theory. Blue shaded area represents induction of anesthesia; the period before induction is baseline consciousness and the period after is anesthetic-induced unconsciousness. Each state is separated into three substates of Baseline (B1, B2, B3) and Anesthetized (A1, A2, A3) conditions; the timescale is different because patients receiving ketamine were studied using a different protocol than patients receiving propofol and sevoflurane. FB=Feedback, FF= Feedforward. Reproduced from Lee et al, 2013a, with permission.