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feature | wonder, anybody home?

To prevent Shania the octopus from becom- Humans wonder, ing bored, keepers at the National Aquarium in Washington, D.C., gave her a Mr. Potato Head filled with fish to snuggle. Researchers anybody are now looking beyond behavior into the brain for signs of awareness in and invertebrates. home? Brain structure and circuitry offer clues to consciousness in nonmammals By Susan Gaidos

ne afternoon while participat­ except for the fact that Betty was a New ing in studies in a University Caledonian crow. of Oxford lab, Abel snatched Betty isn’t the only crow with such a hook away from Betty, leav­ conceptual ingenuity. Nor are crows the Oing her without a tool to complete a task. only members of the animal kingdom to Spying a piece of straight wire nearby, exhibit similar mental powers. Animals she picked it up, bent one end into a can do all sorts of clever things: Studies hook and used it to finish the job. Noth­ of , gorillas, and

ing about this story was remarkable, birds have found that some can add, post washington the B ill O ’ L eary/

22 | science news | December 19, 2009 www.sciencenews.org feature | humans wonder, anybody home?

subtract, create sentences, plan ahead objects in their visual field. “This raises or deceive others. the intriguing question whether con­ Brain-on-brain comparisons To carry out such tasks, these animals scious experience requires the specific In an effort to find signs of conscious- ness, scientists are identifying analo- must be drawing on past experiences and structure of or brains,” gous structures (same coloring) among then using them along with immediate biologist Donald Griffin wrote inAnimal the brains of humans, birds, octopuses perceptions to make sense of it all. In Minds: Beyond Cognition to Conscious- and other animals. The cortex, hippocam- pus and are believed to be other words, some scientists would say, ness in 2001. involved in generating awareness. Once these animals are thinking consciously. But today, Edelman says, most neuro­ such structures are identified, research- Many people (some scientists among scientists agree that consciousness ers can look for similarities in neural circuitry (yellow arrows represent a vocal them) would like to believe that con­ probably correlates with the degree of learning pathway in the ). sciousness sets the human mind apart complexity of the nervous system, not just from the rest of the animal kingdom. But a specific brain architecture. And studies Human whether in humans or other creatures, are exploring self-awareness beyond mon­ behavioral signs of cognizance all arise keys and apes, even beyond mammals. from the tangled interactions of neu­ Recent studies of brains reveal rons in the brain. So a growing number that avian gray matter is more similar to of scientists contend that animals with mammalian brains than not — a fact that brain structures and neural circuitry might explain why many kinds of birds are Eye similar to humans’ might experience able to manufacture tools (SN: 8/29/09, something like human awareness, even p. 5), solve mathematical problems (SN: 10mm if a bit less sophisticated. 4/25/09, p. 15) and communicate in ways Still, everyone agrees that conscious­ that even some can’t. And new ness is one of science’s great unsolved work suggests that some invertebrates Zebra finch mysteries. Something goes on in the heads with wildly different brain structures, of people when they are seeing, think­ such as octopuses, have elaborate ner­ ing or feeling that does not occur during vous systems and show high intelligence. dreamless sleep. For two decades or so, They use tools, exhibit play behavior and researchers have been conducting studies have distinct personalities. to see what kinds of brain activity match Studies designed to probe the con­ Eye up with those specific experiences. scious states of animals with various Drawing on this information, sci­ brain architectures may help scientists 10mm entists are now poised to explore the better understand the mechanisms possible presence of consciousness in underlying consciousnesses and how animals. Neurobiological information such levels of awareness evolved. John Octopus gleaned from studies of brain activity, David Smith, a psychologist at the Uni­ together with studies of animal behav­ versity at Buffalo of the State University ior, may help scientists identify various of New York, says it’s important to keep types of conscious states in animals, says in mind that consciousness is not an all- neurobiologist David Edelman of the or-nothing event. “It didn’t just wink on Neurosciences Institute in San Diego. like a fuse box in a house getting switched He and collaborator Anil K. Seth out­ on,” he says. “There are levels and grada­ lined a framework for probing animal tions of the capacity, and I think we have consciousness in the September Trends to bear that in mind.” in Neurosciences. 10mm “In many cases, we still know nothing A consciousness loop Cerebral cortex (human), pallium (bird) about the brain areas that would control Everyone has an idea of what being Thalamus consciousness in a particular animal,” conscious means, but nobody seems to Hippocampus Vertical & median superior frontal lobes Edelman says. “But we now have data in be able to define it. In the 17th century, the human domain that suggests where French philosopher and mathematician Midbrain and hindbrain to look and what to look for.” René Descartes declared that mind and Cerebellum (human, bird), Past studies have shown that specific body are separate, leaving the debate peduncle (octopus) Retina and retina-like optic lobe monkey brain structures do what they over the nature of consciousness to Lateral ventricle do in humans when the animals engage philosophers and theologians. Today Pallidum

D. Ed elman D. in certain activities, such as tracking scientists reject that notion, viewing

www.sciencenews.org December 19, 2009 | science news | 23 feature | humans wonder, anybody home?

consciousness as arising from the activ­ or minutes — that allows one to interact in ness, rather than a direct measure, ity of neurons in the brain. a meaningful way,” Edelman says. because “it’s hard to know the exact The late Francis Crick, who shared a Scientists are working to identify the instant a person is being conscious,” Nobel Prize for the discovery of DNA’s neurological mechanisms that knit sen­ Edelman says. “Still, 99 percent of the structure, helped pioneer studies on the sory input and memory into a unified time if you’re scanning a person and neural basis of consciousness. Working perception. One possible mechanism is they’re responding to something and with his longtime collaborator, neuro- a curious electrical rhythm in the brains they’re aware of something, that signa­ scientist Christof Koch of Caltech, of animals exposed to sensory stimuli. ture appears reliably.” Crick argued that consciousness is syn­ Known as gamma oscillations, the waves Such EEG patterns and cortical-thal­ onymous with awareness — all forms of reflect the synchronous activity of large amic interactions serve as a convenient awareness — and that only by examining interconnected networks of neurons fir­ reference point to probe for potential neurons and their interactions could sci­ ing together roughly 40 times per sec­ conscious states in other animals, he entists accumulate the kind of empirical ond. This beat spreads across the brain says. Birds, for example, don’t have a cor­ knowledge needed to create a scientific and seems to be especially strong when tex, but recent findings on the structure model of it. animals are concentrating on a single of avian brains do reveal a robust higher- Edelman likens conscious experiences object — such as they might when track­ processing center intricately wired to to “scenes” in which sensations, percep­ ing the scent of their favorite prey. deal with information in a similar way. tions, thoughts and feelings are unified More recent studies of human brain into a picture of the world. Higher-order activity show that consciousness cre­ Singing in the brain consciousness — the kind that humans ates other frequencies of oscillation Bird brains have long had a bad rep, and have — may include context that helps that can be detected using an electroen­ until recently were considered to consist shape the experience, such as inner dia­ cephalograph, or EEG. In 2005, Edelman of one large forebrain and log, implicit expectations and voluntary and colleagues published a paper in a few “primitive” structures. In 2005, control of thought and action. Such high- Consciousness and Cognition outlining a Duke University neuroscientist Erich level cognizance makes people aware series of studies showing that recordings Jarvis showed this isn’t the case at all. that they are aware. Primary conscious­ taken during tasks such as memorization In reviewing the neuroanatomy of birds, ness, on the other hand, requires no self- or problem solving reveal a circuit of neu­ he noted that there is a higher-process­ reflection but does require a neuronal ral activity running in loops between the ing center — similar to humans’ cortical circuit capable of combining attention thalamus, known to help control alert­ area — in the brains of all vertebrates, and short-term memory, Edelman says. ness, and the cerebral cortex, the brain’s including birds, fish, reptiles and mam­ “It’s the ability to take in sensory infor­ outer layer where sensory stimuli enter. mals. This area, critical for reasoning and mation and form memories — whether The presence of such activity is con­ remembering, is organized differently those memories persist for tens of seconds sidered a correlate of human conscious­ in birds and in mammals. In mammals, it appears as layered cells in the cortex, Big brains and small brains Some scientists look to brain-to-body mass ratio as a sign while in birds it is organized as clustered of intelligence. Humans and dolphins have larger ratios, while the hippopotamus and blue cells, Jarvis and colleagues pointed out in have smaller brains than expected for their body size. New Caledonian crows beat out some mammals; octopuses, despite being invertebrates, rival some mammals. Nature Reviews Neuroscience. Ann Butler, a neuroscientist at George Brain-to-body mass ratios Mason University in Fairfax, Va., says

10000 that before Jarvis’ studies, many people African Sperm whale Blue whale thought the layering of cells, such as is Dusky found in the human cortex, was required 1000 Human Hippopotamus to carry out complex behavior. Now scien­ Horse Pig tists think that is not necessarily the case. 100 Rhesus monkey Dog “For some reason, people think that Cat 10 New Caledonian crow because birds are far away from their Squirrel Alligator Pike genetic relationship to humans, that Brain weight (g) Rat Octopus 1 they’re one of the last groups of ani­ Mouse Hedgehog mals in which you should look for con­ sciousness,” says Butler, who is working 0.1 Shrew Frog to identify neural features that may be

0.0001 0.001 0.01 0.1 110 100 1,000 10,000 100,000 capable of rendering consciousness in Body weight (kg) birds. “But I’m going to argue that they’re

Source: Gerhard Roth and Ursula Dicke/Trends in Cognitive Sciences, May 2005 probably one of the first.”

24 | science news | December 19, 2009 www.sciencenews.org

MARK WILSON/Boston Globe/Landov studies ofconsciousnessinbirds. neurobiological initiate to place logical a be may areas the humans, and birds in these brain areas serve a similar function power limb and body movements. Because ing evolved out of the same pathways that learn­ vocal for used pathways brain the in 2008 March within, areasthatcontrolmovement. even to,and adjacent lie also speech for structures brain Human movement. controlling areas in embedded are sing to learning and singing for structures and with vocal learning abilities birds in that found group His speech. human pathwayinvolvedin a to larities simi­ with pathway brain one least at revealed have studies Jarvis’ humans, in states conscious with associated loops cortical the of birds in evidence be definedasaconsciousbehavior.” can people’sthat mostminds, “In says. processes,”she thought animals’ other bird who was hiding an object is aware of mal sees them hide it, suggesting that the ani­ another when differently objects and make tools. design to ability the or others deceive intentionallythey which in games play to ability the including mammals, with associated generally processes nitive cog­ sophisticated out carry can birds that to showing studies pointed leagues col­ her and Butler Bulletin, Biological birds, published in October 2006 in neuro­ on ture times or places. In a survey of the litera­ distinct from events recalling as such were once thought specific to primates, that things do can Alex, gray can why some birds, such as the famous ­ Afri www.sciencenews.org central brain is connected to a relatively large a where mammals, in Unlike cult. diffi ­ more is octopuses, and cuttlefish as such invertebrates, in states scious con­ assessing features, neurological many share mammals and birds While Invertebrates join big brain club Jarvis says the findings, reported in reported findings, the says Jarvis find to yet have scientists Though hide will birds some show “Studies explain studies Jarvis’ says Butler anatomy and behavior inbehavior anatomyand , suggest that suggest ONE, PLoS — — , the brain the The

distinguish colors andnumbers. distinguish colors 100 wordsbeforehisdeathandcould scientific study. morethan Helearned 2007, was of thesubjectof30years Alex, anAfricangray whodiedin parrot Graziano Fiorito oftheoctopusbehav about how it works, Edelman says. With knowledge limited haveanatomy, they eral knowledge about cephalopod brain thing wehumanshave,” shesays. learning and memory. “That’s the kind of tebrates, butalsohasareasdedicatedto inver most of that than larger just not is brain octopus the that says years, 35 than more for octopuses studied has University of Lethbridge in Canada, who through mazes. sels prey favorite their of adapt shells the opening and for techniques new learn easily can show they that Studies around. invertebrates intelligent most the of one be to seem do octopuses And intelligence. higher mean may mass, body of percentage a as expressed when brain, bigger a that speculated have Scientists ratio. mass brain-tobody high a have They birds: share one brain trait with mammals and sit outsidethecentralbraincapsule. eyes and the nervous system of the arms, the for lobes opticparts, the largest two The parts. three into divided is system nervous octopus the cord, spinal small ­ gen some have scientists Although the of Mather JenniferPsychologist Despite this weird anatomy, octopuses — n cn s cus o navigate to clues use can and — clams and mus­ and clams ­ ­

based inMaine. Susan Gaidos is a freelance science writer are presentacrosstheboard.” s those if see to look then and are, there features neural what see to look found, be might it where places few a identify is do to need we what ior,”“Sosays. she behav complex have don’t you where developed cognitive systems. highly with animals to only sciousness use caution in limiting the study of con­ similar socialandphysical challenges. facing species in emerge to seem states such say,scientistsconsidering prising, sur all at not structures,is brain ferent dif­ with lineages distant in appearing , of course the over times eral in mammalsorthebirds,” hesays. these animals long before they appeared in appeared have may states conscious that sense the in convergence, of case ple of animals where we can show a true a broaderperspective onconsciousness. maygivecreatures researchers these ing mammals and birds, Edelman says study from speaking, evolutionarily are, pods signals.” those into tap to where out figure to be will octopus, the with trick, “The says. have a conscious experience,” Edelman to able is who animal any across posed networks ity, properties of certain kinds of neural properties fundamental are there is, brain the to visualcues. respond creatures the as signals brain other and data EEG collect to system recording a developing is Edelman Zoologica Anton Dohrn in Naples, Italy, ioral biology laboratory at the Stazione Explore more s December 19, 2009 s Yu a’ rl ot consciousness out rule can’t “You to need scientists that adds Butler sev arise could consciousness That exam­ one that “Cephalopodsbe may Considering how far removed cephalo­ “No matter how differently organized September 2009. approach.” “ D.B. : a synthetic Edelman and — — ht r uiesly dis­ universally are that signaling, electrical activ electrical signaling, T rends in

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