Primary States of Consciousness: A Review of Historical and Contemporary Developments

Primary states of consciousness are phylogenetically older than secondary states, which are governed by sociocultural inhibition. The article reviews the concept's history in psychiatry and neurobiology and its relation to consciousness theories. Primary states involve a temporary breakdown of self-control and a merging of action, communication, and emotion (ACE fusion), normally segregated in adults. The neurobiologic basis includes neural dedifferentiation, loss of modularity during altered states, and increased corticostriatal connectivity. The authors propose a gradient from primary to secondary consciousness, with changes in thalamocortical interactions and arousal function, and offer testable hypotheses for distinct phenomenological and neural signatures.

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Abstract

Primary states of consciousness are conceived as phylogenetically older states of consciousness as compared to secondary states governed by sociocultural inhibition. The historical development of the concept in psychiatry and neurobiology is reviewed, along with its relationship to theories of consciousness. We suggest that primary states of consciousness are characterized by a temporary breakdown of self-control accompanied by a merging of action, communication, and emotion (ACE fusion), ordinarily segregated in human adults. We examine the neurobiologic basis of this model, including its relation to the phenomenon of neural dedifferentiation, the loss of modularity during altered states of consciousness, and increased corticostriatal connectivity. By shedding light on the importance of primary states of consciousness, this article provides a novel perspective on the role of consciousness as a mechanism of differentiation and control. We discuss potential differentiators underlying a gradient from primary to secondary state of consciousness, suggesting changes in thalamocortical interactions and arousal function. We also propose a set of testable, neurobiologically plausible working hypotheses to account for their distinct phenomenological and neural signatures.