Humans Wonder, Anybody Home? Brain Structure and Circuitry Offer Clues to Consciousness in Nonmammals

Article excerpt


One afternoon while participating in studies in a University of Oxford lab, Abel snatched a hook away from Betty, leaving her without a tool to complete a task. Spying a piece of straight wire nearby, she picked it up, bent one end into a hook and used it to finish the job. Nothing about this story was remarkable, except for the fact that Betty was a New Caledonian crow.

Betty isn't the only crow with such conceptual ingenuity. Nor are crows the only members of the animal kingdom to exhibit similar mental powers. Animals can do all sorts of clever things: Studies of chimpanzees, gorillas, dolphins and birds have found that some can add, subtract, create sentences, plan ahead or deceive others.

To carry out such tasks, these animals must be drawing on past experiences and then using them along with immediate perceptions to make sense of it all. In other words, some scientists would say, these animals are thinking consciously.

Many people (some scientists among them) would like to believe that consciousness sets the human mind apart from the rest of the animal kingdom. But whether in humans or other creatures, behavioral signs of cognizance all arise from the tangled interactions of neurons in the brain. So a growing number of scientists contend that animals with brain structures and neural circuitry similar to humans' might experience something like human awareness, even if a bit less sophisticated.

Still, everyone agrees that consciousness is one of science's great unsolved mysteries. Something goes on in the heads of people when they are seeing, thinking or feeling that does not occur during dreamless sleep. For two decades or so, researchers have been conducting studies to see what kinds of brain activity match up with those specific experiences.

Drawing on this information, scientists are now poised to explore the possible presence of consciousness in animals. Neurobiological information gleaned from studies of brain activity, together with studies of animal behavior, may help scientists identify various types of conscious states in animals, says neurobiologist David Edelman of the Neurosciences Institute in San Diego. He and collaborator Anil K. Seth outlined a framework for probing animal consciousness in the September Trends in Neurosciences.

"In many cases, we still know nothing about the brain areas that would control consciousness in a particular animal," Edelman says. "But we now have data in the human domain that suggests where to look and what to look for."

Past studies have shown that specific monkey brain structures do what they do in humans when the animals engage in certain activities, such as tracking objects in their visual field. "This raises the intriguing question whether conscious experience requires the specific structure of human or primate brains," biologist Donald Griffin wrote in Animal Minds: Beyond Cognition to Consciousness in 2001.

But today, Edelman says, most neuroscientists agree that consciousness probably correlates with the degree of complexity of the nervous system, not just a specific brain architecture. And studies are exploring self-awareness beyond monkeys and apes, even beyond mammals.

Recent studies of bird brains reveal that avian gray matter is more similar to mammalian brains than not--a fact that might explain why many kinds of birds are able to manufacture tools (SN: 8/29/09, p. 5), solve mathematical problems (SN: 4/25/09,p. 15) and communicate in ways that even some primates can't. And new work suggests that some invertebrates with wildly different brain structures, such as octopuses, have elaborate nervous systems and show high intelligence. They use tools, exhibit play behavior and have distinct personalities.

Studies designed to probe the conscious states of animals with various brain architectures may help scientists better understand the mechanisms underlying consciousnesses and how such levels of awareness evolved. …