Abstract: Among all invertebrates, the coleoid cephalopods—that group of molluscs which includes octopuses, squid, and cuttlefish—have by far the largest and most elaborate nervous systems. In addition, these animals have eyes that in many ways resemble those of vertebrates, albeit with some notable differences (e.g., one type of photoreceptor, no retinal ganglia). Moreover, the coleoid cephalopods—particularly the octopus—appear to be capable of both seeing moving objects such as predators and prey at reasonably great distances and executing a variety of adaptive behaviors in response to what they see. Such observations suggest: 1) the presence of relatively sophisticated visual processing, i.e., neural circuitry that can support dense visual input; 2) the possible specialization of sub-modal visual areas in the central brain, perhaps analogous to the vertebrate case; and 3) spatiotemporal properties of memory that would necessarily involve rapid integration of visual information into a dynamic 'scene.'
Here, I will argue that, on neuroanatomical, neurophysiological, and behavioral grounds, the octopus in particular represents an excellent model for investigating the possibility of conscious states in an invertebrate. In making this argument, I will: 1) lay out a working definition for consciousness that may be extended beyond the vertebrate case; 2) describe structural and functional properties which may be the sine qua non of sensory consciousness; 3) suggest evolutionary trends (e.g., the emergence of complex vision) that may have set the stage for the advent of conscious states in a variety of phyla; and 4) discuss my ongoing work and offer a 'roadmap' for additional experiments that could lead to a robust methodology for the explicit investigation of sensory consciousness in these, and perhaps other, invertebrates
Identifying Hallmarks of Consciousness in Non-Mammalian Species
Criteria for consciousness in humans and other mammals
Animal consciousness: a synthetic approach
Gerald Edelman "Wider than the Sky: The Phenomenal Gift of Consciousness"
Hochner, Shomrat & Fiorito (2006) The Octopus: A Model for a Comparative Analysis of the Evolution of Learning and Memory Mechanisms Biol. Bull. 210: 308–317
Borrelli L, Fiorito G (2008) Behavioral analysis of learning and memory in Cephalopods. In: Menzel R, Byrne J, editors. Learning and Memory: A Comprehensive Reference. UK: Elsevier. pp. 605–627. (PDF will be provided)