David Edelman, PhD: Neural Correlates of Consciousness in Non-human Animals
David Edelman, PhD is an Associate Fellow in Experimental Neurobiology at The Neurosciences Institute in San Diego, California and an Assistant Professor of Neurobiology at The Scripps Research Institute in La Jolla.
One of his main areas of study is the neural correlates of consciousness in non-human animals.
With his colleague, Dr. Anil Seth of the University of Sussex, Dr. Edelman recently laid out a framework for the study of animal consciousness that suggests that certain fundamental properties of conscious states are amenable to study and may in fact be present in widely different phyla, from cephalopod mollusks to humans.
Dr. Edelman earned his B.A. in Sociology and Anthropology from Swarthmore College and his Ph.D. in Physical Anthropology, with a specialization in paleoanthropology, from the University of Pennsylvania. From 1997 to 2005, he was a postdoctoral fellow at both the Scripps Research Institute and the Neurosciences Institute.
Endowed with a nervous system containing up to half-a-billion neurons, as well as eyes that are similar in structure and function to those of vertebrates, the octopus is a fascinating invertebrate. With its complex nervous system and rich behavioral repertoire, this creature offers an extraordinary opportunity to explore aspects of brain function and behavior in an invertebrate that is radically different from the animal models that are so familiar to contemporary neuroscientists. In overall size and number of constituent neurons, the central brain of the common octopus dwarfs those of all other invertebrates, including the fruit fly and honeybee, and indeed rivals those of mammals such as the rat and mouse. Despite the alien appearance of the octopus nervous system, there’s something strikingly familiar about the learning, memory, and overall cognitive capabilities of these animals. As we learn more about them, the brain and behavior of the octopus may challenge our assumptions about how complex nervous systems function, regardless of major anatomical differences.
Vision figures prominently in the way in which cephalopods, including the octopus, process and negotiate their world. In my laboratory, we are investigating the major features of octopus vision, from the various properties that are most salient to the behaving animal to the electrophysiological signatures of those properties and their associated functional anatomies. In order to characterize the octopus visual system, we are using a variety of techniques, including: 1) high-definition video presentation of stimuli; 2) electrophysiological recording in live animals during presentation of video stimuli; and 3) molecular labeling to define the anatomy of visual pathways in the central octopus brain.
Such a picture would have major significance, not only for understanding the fundamental principles of complex animal vision generally, but also for addressing the question of how complex vision evolved in the first place.
Vertebrate Brain Energetics
The brain is a metabolically expensive organ, accounting for as much as 20% of an animal’s day-to-day energy consumption. Most of the brain’s energy requirements are met through aerobic respiration, specifically through mitochondrial production of adenosine triphosphate, or ATP. We are investigating mitochondrial dynamics in the brain at both the cellular and organismal levels by exploring the signaling pathways that induce mitochondrial movement in neurons. We are also investigating the functional properties and regional distribution of mitochondria in different brain states, for example those induced by sleep and learning.
Mitochondria are critical components of eukaryotic cellular metabolism. This is particularly true in the case of neurons, which, in their morphology and function, are among the most complex and specialized of all animal cells. Yet we still do not fully understand the relationship between mitochondria and neuronal function in the context of specific brain states, such as sleep. Impairment of mitochondrial function has been implicated in a number of brain pathologies, including Alzheimer’s and Parkinson’s diseases. It is hoped that our studies will lead to a better understanding of the role of mitochondrial dynamics in the onset of these pathologies, as well as help us to gain broader insights into the relationship between mitochondria and normal brain function.
- David Edelman: The Octopus as a Possible Invertebrate Model for Consciousness Studies
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.’(Part 1 of 2)
David Edelman: The Octopus as a Possible Invertebrate Model for Consciousness Studies (Part 2 of 2)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.
Several Abstract References:Identifying Hallmarks of Consciousness in Non-Mammalian SpeciesCriteria for consciousness in humans and other mammalsAnimal consciousness: a synthetic approachGerald Edelman “Wider than the Sky: The Phenomenal Gift of Consciousness”
Baars, B.J., and Edelman, D.B. In Press. Consciousness, Biology, and Quantum Hypotheses. Phys. Life Rev.
Edelman, D.B. (2012). How uniquely irreducible is consciousness? Defining the limits of biological reductionism, Commentary of Feinberg, T.E., Neuroontology, neurobiological naturalism, and consciousness: Achallenge to scientific reduction and a solution, Phys. Life Rev., 9(1), http://dx.doi.org/10.1016/j.plrev.2012.01.001.
Edelman, D.B., Owens, G.C., and Chen, S. (2011). Neuromodulation and mitochondrial transport: live imaging in hippocampal neurons. J. Visual. Exp., 52, http://jove.com/details.php?id=2599, doi: 10.3791/2599.
Chen, S., Owens, G.C., Makarenkova, H., and Edelman, D.B. (2010). HDAC6 regulates mitochondrial transport in hippocampal neurons, Plos One, 5(5):e10848, doi: 10.1371/journal.pone.0010848.
Chen, S., Owens, G.C. and Edelman, D.B. (2008). Dopamine inhibits mitochondrial motility in hippocampal neurons. Plos One, 3(7):e2804, doi:10.1371/journal.pone.0002804.
FOR A FULL LIST, CLICK HERE
“Fossil evidence of the humble Cambrian origins of the Cephalopoda gives little indication of the elaborate life-ways and behaviors that would come to define the surviving genera of this class, which today are the most complex of all known invertebrates. Of the four living groups of cephalopod molluscs, the octopus may be the most elaborate in its cognitive and behavioral adaptations. But the facts—nervous systems in some species that contain more cells than those of many rodents, eyes that are in many ways convergent with the vertebrate eye, the ability to change skin color and texture rapidly to match background, boneless arms that can form elbows to solve biomechanical problems in much the same fashion that the vertebrate arm does—are poor preparation for one’s first ‘up close and personal’ encounter with an octopus.Octopuses look and move like nothing else we’re accustomed to observing on land or in the ocean. Yet, despite a truly alien countenance—which, by the way, can hit one like a ‘ton of bricks’—there’s something strangely familiar—a reassuring presence—in the way these animals comport themselves; the presence, perhaps, of thought, albeit an inscrutable, otherworldly flavor of thought that’s well beyond our grasp.”