Evolution of consciousness: Phylogeny, ontogeny, and emergence from general anesthesia

Abstract

Are animals conscious? If so, when did consciousness evolve? We address these long-standing and essential questions using a modern neuroscientific approach that draws on diverse fields such as consciousness studies, evolutionary neurobiology, animal psychology, and anesthesiology. We propose that the stepwise emergence from general anesthesia can serve as a reproducible model to study the evolution of consciousness across various species and use current data from anesthesiology to shed light on the phylogeny of consciousness. Ultimately, we conclude that the neurobiological structure of the vertebrate central nervous system is evolutionarily ancient and highly conserved across species and that the basic neurophysiologic mechanisms supporting consciousness in humans are found at the earliest points of vertebrate brain evolution. Thus, in agreement with Darwin's insight and the recent "Cambridge Declaration on Consciousness in Non-Human Animals," a review of modern scientific data suggests that the differences between species in terms of the ability to experience the world is one of degree and not kind.

What insects can tell us about the origins of consciousness

“…Midbrain structures, rather than cortex, seem to be especially important. Merker (8,9), Parvisi and Damasio (11), Damasio and Carvalho (15), and Mashour and Alkire (16) have all argued that the integrated structures of the vertebrate midbrain are sufficient to support the capacity for subjective experience.…”

“…Anesthetics (28) or electrical stimulation (19), which affect cortical midline structures without affecting subcortical structures, do not abolish consciousness; they instead produce unresponsive but conscious dreamlike states. Conversely, emergence from anesthesia (16,29) and coma/vegetative state (30) are predicted by the reengagement of subcortical structures and reintegration of those structures with cortical circuits. Other authors have noted the powerful subcortical effect of drugs, endogenous peptides, and direct stimulation on primitive motivational states (12,16,31).…”

“…Conversely, emergence from anesthesia (16,29) and coma/vegetative state (30) are predicted by the reengagement of subcortical structures and reintegration of those structures with cortical circuits. Other authors have noted the powerful subcortical effect of drugs, endogenous peptides, and direct stimulation on primitive motivational states (12,16,31).…”

Animal Consciousness

“…Taking this line, Mashour and Alkire (2013), for example, proposed a global picture of current knowledge and called for experimental models in which: (i) consciousness emerges from unconsciousness at a discrete and measurable point in evolutionary time, (ii) phenomenal consciousness and access consciousness (cf. Chap 2, section 2.2.1) are closely juxtaposed or mixed, and (iii) it is possible to assess neural structures and functions linked to consciousness.…”

Senomic view of the cell: SenomeversusGenome

“…Here we suggest that in order to succeed in resolving the biological basis of these fundamental aspects of living organisms, we need to add a new science to our biological agenda that focuses on sensory biology linked to cellular cognition and behavior. This new science of feelings, emotions, qualia and consciousness must be able to tackle these issues from an evolutionary perspective [4–7,16,18–22]. Its further requirement is an explanation of the emergence of a variety of elusive biological phenomena in their hypothetical ancient proto-states at the level of the simplest unicellular organisms [7,14,16,22,23], such as proto-feelings, proto-emotions, proto-qualia, proto-consciousness [7,24] which could then be further engaged as complexation in multicellular organisms.…”