Apical amplification-a cellular mechanism of conscious perception?

A theoretical account proposes that conscious perceptual experience depends on a specific cellular mechanism in the neocortex: apical amplification. Inputs to apical dendrites in layer 1 of many neocortical neurons integrate diverse contextual signals, which then amplify the transmission of sensory information arriving at the cell's basal synapses. This context-sensitive amplification makes perception more flexible and adaptive. The mechanism offers a way to implement recurrent processing without strong loops, supports global broadcasting while preserving individual cell contributions, and contributes to integrated information theory's holistic aspects. Because apical amplification relies on neuromodulators like acetylcholine and amines, it links specific conscious contents to global mental states and arousal fluctuations. The authors conclude that apical dendrites provide a cellular basis for the context-sensitive selective amplification necessary for conscious perception.

Study at a glance

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.