David Edelman, Department of Psychological and Brain Sciences, Dartmouth College, Hanover
The ability to resolve distant objects within a complex visual scene may have emerged more than 500 million years ago during the Cambrian explosion: a period characterized by the appearance of diverse new sensory innovations, including every major type of eye found in living vertebrates and invertebrates today. Here, I argue that distance vision and its underlying neural circuitry provided the first critical substrates for sensory consciousness. The ability to see distant objects entailed a new sort of neural faculty that adaptively linked space and time in high-resolution sensory percepts. Animals equipped with this faculty were able to not only monitor their environment for salience (e.g., identify and track predators or prey), but also make predictions about future outcomes upon which their survival would depend. Making such predictions must necessarily have relied on a continuous and recurrent linkage between perception and memory: a connection that, some suggest, is a critical requisite for conscious experience. As a capable predator with acute vision comparable to that of many higher vertebrates, the octopus provides a plausible window into the evolutionary history of sensory awareness, as well as a striking test case for subjective experience in an animal quite distant from the vertebrate line. Indeed, probing the octopus visual system could conceivably help identify neuroanatomical and neurophysiological properties of conscious states that are universal among animals with sophisticated sensory faculties and complex nervous systems, regardless of profound morphological differences and divergent evolutionary histories.