Apical amplification-a cellular mechanism of conscious perception?

Tomáš Marvan,William A Phillips,Michal Polák,Talis Bachmann

doi:10.1093/nc/niab036

Abstract

We present a theoretical view of the cellular foundations for network-level processes involved in producing our conscious experience. Inputs to apical synapses in layer 1 of a large subset of neocortical cells are summed at an integration zone near the top of their apical trunk. These inputs come from diverse sources and provide a context within which the transmission of information abstracted from sensory input to their basal and perisomatic synapses can be amplified when relevant. We argue that apical amplification enables conscious perceptual experience and makes it more flexible, and thus more adaptive, by being sensitive to context. Apical amplification provides a possible mechanism for recurrent processing theory that avoids strong loops. It makes the broadcasting hypothesized by global neuronal workspace theories feasible while preserving the distinct contributions of the individual cells receiving the broadcast. It also provides mechanisms that contribute to the holistic aspects of integrated information theory. As apical amplification is highly dependent on cholinergic, aminergic, and other neuromodulators, it relates the specific contents of conscious experience to global mental states and to fluctuations in arousal when awake. We conclude that apical dendrites provide a cellular mechanism for the context-sensitive selective amplification that is a cardinal prerequisite of conscious perception.

Highlights

More than a decade ago, John Bickle announced the coming era of “molecular and cellular consciousness studies” (Bickle 2007, 291)
We present a theoretical view of the cellular foundations for network-level processes involved in producing our conscious experience
We argue that apical amplification enables conscious perceptual experience and makes it more flexible, and more adaptive, by being sensitive to context

Summary

Introduction

More than a decade ago, John Bickle announced the coming era of “molecular and cellular consciousness studies” (Bickle 2007, 291). Whereas mainstream cognitive neuroscience usually investigates consciousness at network and higher levels, cellular and molecular approaches to consciousness are concerned with processes within individual neurons. This lowlevel approach is not yet common in consciousness science (for notable recent exceptions, Flohr 2000; see Sevush 2016; Laberge and Kasevich 2007; Aru et al 2020b), it has several strengths to recommend it. The theory of conscious perception presented here aims to explain how mechanisms within a particular class of pyramidal neurons, i.e. context-sensitive cells in layer 5B of the neocortex, provide cellular foundations for network-level processes that have long been thought to be neuronal correlates of perceptual experience. The ways in which this article complements and advances beyond previous articles on the perspective that we advocate are listed in the “Concluding remarks” section

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Conclusion