Chapter 2. Cells and Structures: The Anatomy of the Nervous System
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Daniel Cressey Rappers making up rhymes on the fly while in a brain scanner have provided an insight into the creative process. Freestyle rapping — in which a performer improvises a song by stringing together unrehearsed lyrics — is a highly prized skill in hip hop. But instead of watching a performance in a club, Siyuan Liu and Allen Braun, neuroscientists at the US National Institute on Deafness and Other Communication Disorders in Bethesda, Maryland, and their colleagues had 12 rappers freestyle in a functional magnetic resonance imaging (fMRI) machine. The artists also recited a set of memorized lyrics chosen by the researchers. By comparing the brain scans from rappers taken during freestyling to those taken during the rote recitation, they were able to see which areas of the brain are used during improvisation. The study is published today in Scientific Reports1. The results parallel previous imaging studies in which Braun and Charles Limb, a doctor and musician at Johns Hopkins University in Baltimore, Maryland, looked at fMRI scans from jazz musicians2. Both sets of artists showed lower activity in part of their frontal lobes called the dorsolateral prefrontal cortex during improvisation, and increased activity in another area, called the medial prefrontal cortex. The areas that were found to be ‘deactivated’ are associated with regulating other brain functions. © 2012 Nature Publishing Group
Mo Costandi Albert Einstein is considered to be one of the most intelligent people that ever lived, so researchers are naturally curious about what made his brain tick. Photographs taken shortly after his death, but never before analysed in detail, have now revealed that Einstein’s brain had several unusual features, providing tantalizing clues about the neural basis of his extraordinary mental abilities1. While doing Einstein's autopsy, the pathologist Thomas Harvey removed the physicist's brain and preserved it in formalin. He then took dozens of black and white photographs of it before it was cut up into 240 blocks. He then took tissue samples from each block, mounted them onto microscope slides and distributed the slides to some of the world’s best neuropathologists. The autopsy revealed that Einstein’s brain was smaller than average and subsequent analyses showed all the changes that normally occur with ageing. Nothing more was analysed, however. Harvey stored the brain fragments in a formalin-filled jar in a cider box kept under a beer cooler in his office. Decades later, several researchers asked Harvey for some samples, and noticed some unusual features when analysing them. A study done in 1985 showed that two parts of his brain contained an unusually large number of non-neuronal cells called glia for every neuron2. And one published more than a decade later showed that the parietal lobe lacks a furrow and a structure called the operculum3. The missing furrow may have enhanced the connections in this region, which is thought to be involved in visuo-spatial functions and mathematical skills such as arithmetic. © 2012 Nature Publishing Group
By Noah Hutton and Ferris Jabr "Nothing quite like it exists yet, but we have begun building it," Henry Markram wrote in the June 2012 issue of Scientific American. He was referring to a "fantastic new scientific instrument"—a biologically realistic and detailed model of a working human brain hosted on supercomputers. Markram, who directs the Brain Mind Institute at the École Polytechnique Fédérale de Lausanne in Switzerland, has been working on the Blue Brain Project, more recently known as the Human Brain Project, since 2005. "A digital brain will be a resource for the entire scientific community: researchers will reserve time on it, as they do on the biggest telescopes, to conduct their experiments," Markram wrote in SA. "They will use it to test theories of how the human brain works in health and in disease. They will recruit it to help them develop not only new diagnostic tests for autism or schizophrenia but also new therapies for depression and Alzheimer's disease. The wiring plan for tens of trillions of neural circuits will inspire the design of brainlike computers and intelligent robots. In short, it will transform neuroscience, medicine and information technology." Markram has claimed, at various times, that he can complete this ambitious project within 10 years. His critics argue that his ultimate goal is unachievable because the human brain is too complex to simultaneously simulate at every level, from the molecule to the cortex. Say one wanted to build an exact replica of a large and intricate circuit board. One would first need to map every wire linking every component and then re-create these links. In the same way, making a model of the human brain requires knowing the trillions of connections between its neurons. A map of all the connections between neurons in a brain is called a connectome, and no such map exists for the human brain. In fact, the only organism with a complete connectome is the tiny nematode C. elegans, which has 302 neurons total. The human brain has more than 80 billion neurons and 100 trillion connections between those cells. © 2012 Scientific American
By Laura Sanders In the fraught, emotional world of speed dating, scientific calculations don’t usually hold much sway. But the brain runs a complex series of computations to tally the allure of a prospective partner in just seconds, a new study finds. And the strength of these brain signals predicted which speed daters would go on to score a match. The results help explain how people evaluate others — a process that happens at lightning speed, says neuroscientist Daniela Schiller of Mount Sinai School of Medicine in New York City. “It’s a gut feeling, but here, the paper dissects it for us and tells us, ‘This is what we calculate.’” Scientists led by Jeffrey Cooper, who conducted the work at Trinity College Dublin and Caltech, scanned the brains of single volunteers as they looked at pictures of potential dating partners. Although it’s hard to put a number on people by a photo alone, researchers made volunteers rate on a scale of 1 to 4 how much they’d like to go on a date with the person in the photograph. In contrast to many other lab-based experiments on decision making, this exercise wasn’t just academic: Later, the participants attended three real speed-dating events loaded with many of the potential partners seen in the photos. Like a normal speed-dating scenario, volunteers’ contact information was exchanged if both of the people wanted to follow up. (Also like a typical scenario, there weren’t many love connections, says Cooper. When the scientists checked in six weeks later, only a few couples had gone on real dates.) © Society for Science & the Public 2000 - 2012
Neuroscientists at the University of Ingberg have found a brain region that does absolutely nothing. Their research, presented at the annual Society for Neuroscience meeting, showed that a small region of the cortex located near the posterior section of the cingulate gyrus responded to ‘not one of our 46 experimental manipulations’. Dr. Ahlquist was rather surprised at the finding. “During a pilot study we noticed that this small section of the cortex did not show differential activity in any of our manipulations. Out of curiosity, we wanted to see whether it actually did anything at all. Over the months that followed we tried every we knew, with over 20 different participants. IQ tests, memory tasks, flashing lights, talking, listening, imagining juggling, but there was no response. Nothing. We got more desperate, so we tried pictures of faces, TMS, pictures of cats, pictures of sex, pictures of violence and even sexy violence, but nothing happened! Not even a decrease. No connectivity to anywhere else, not even a voodoo correlation. 46 voxels of wasted space. I know dead salmons that are more responsive. It’s an evolutionary disgrace, that’s what it is.” Some neuroscientists are disappointed by the regions’ lack of response: ‘This is exactly the type of cortical behavior that leads to this popular science nonsense about using only 10% of our brain. Frankly, I am outraged by this lazy piece of brain. It’s the cortical equivalent of a spare tyre. If anyone wants to have it lobotomized, I am happy to break out the orbitoclast and help them out. That’ll teach it.”
Keyword: Brain imaging
Link ID: 17464 - Posted: 11.07.2012
By DENISE GRADY Just when they might have thought they were in the clear, people recovering from meningitis in an outbreak caused by a contaminated steroid drug have been struck by a second illness. The new problem, called an epidural abscess, is an infection near the spine at the site where the drug — contaminated by a fungus — was injected to treat back or neck pain. The abscesses are a localized infection, different from meningitis, which affects the membranes covering the brain and spinal cord. But in some cases, an untreated abscess can cause meningitis. The abscesses have formed even while patients were taking powerful antifungal medicines, putting them back in the hospital for more treatment, often with surgery. The problem has just begun to emerge, so far mostly in Michigan, which has had more people sickened by the drug — 112 out of 404 nationwide — than any other state. “We’re hearing about it in Michigan and other locations as well,” said Dr. Tom M. Chiller, the deputy chief of the mycotic diseases branch of the Centers for Disease Control and Prevention. “We don’t have a good handle on how many people are coming back.” He added, “We are just learning about this and trying to assess how best to manage these patients. They’re very complicated.” In the last few days, about a third of the 53 patients treated for meningitis at St. Joseph Mercy Hospital in Ann Arbor, Mich., have returned with abscesses, said Dr. Lakshmi K. Halasyamani, the chief medical officer. © 2012 The New York Times Company
Link ID: 17449 - Posted: 11.03.2012
By Laura Sanders A genetic tweak makes it easier to see neurons at work in living, breathing animals. The method, described in the Oct. 18 Neuron, capitalizes on a property of a busy neuron: When the cell fires, calcium ions flood in. Using an altered version of the protein GFP that lights up when calcium is present in a mouse’s brain, neuroscientist Guoping Feng of MIT and colleagues could see smell-sensing neurons respond to an odor, and movement neurons light up during walking. Q. Chen et al. Imaging Neural Activity Using Thy1-GCaMP Transgenic Mice. Neuron. Vol. 76, October 18,2012, p. 297. doi: 10.1016/j.neuron.2012.07.011. [Go to] © Society for Science & the Public 2000 - 2012
Keyword: Brain imaging
Link ID: 17435 - Posted: 10.30.2012
By Ferris Jabr Scientists have mapped, charted, modeled and visualized the human brain in many different ways. They have marked the boundaries of the organ’s four major lobes: the frontal, parietal, temporal and occipital lobes. They have divvied up the cortex into more than 50 Broadmann areas—small regions characterized by particular cell types and specific cognitive functions, such as processing speech and recognizing faces. Researchers have tagged individual neurons with fluorescent proteins, transforming gray tissue into stunning brainbows, and followed water molecules as they move through the nervous system to trace ribbons of neural tissue linking one brain region to another. More recently, some scientists have championed the importance of connectomes—detailed wiring diagrams of all the connections between neurons in a given nervous system or brain. Thoroughly understanding the brain, proponents of connectomics argue, requires precise maps of its neural circuits. The standard way of making a connectome is serial electron microscopy—chopping up an animal’s brain into thin sheets, taking photos of all the resident neurons through an electron microscope and using those photos to painstakingly reconstruct the connections between neurons. In the 1970s biologist Sydney Brenner and his colleagues began using this technique to map the 302 neurons and 7,000 neural connections, or synapses, in the nervous system of a tiny worm known as Caenorhabditis elegans. It took them more than 12 years to finish the map. So far, C. elegans is the only animal with such a thorough connectome. Since mammalian brains contain millions or billions of neurons and billions or trillions of synapses, depending on the species, researchers are searching for faster and cheaper ways to create connectomes. At Harvard University, for example, Jeff Lichtman and his colleagues have constructed an Automatic Tape-Collecting Lathe Ultramicrotome (ATLUM)—a machine that speeds up the business of slicing up brain tissue into thin sheets with conveyor-belt efficiency. © 2012 Scientific American
Keyword: Brain imaging
Link ID: 17417 - Posted: 10.24.2012
Mo Costandi Scientists have learned how to discover what you are dreaming about while you sleep. A team of researchers led by Yukiyasu Kamitani of the ATR Computational Neuroscience Laboratories in Kyoto, Japan, used functional neuroimaging to scan the brains of three people as they slept, simultaneously recording their brain waves using electroencephalography (EEG). The researchers woke the participants whenever they detected the pattern of brain waves associated with sleep onset, asked them what they had just dreamed about, and then asked them to go back to sleep. This was done in three-hour blocks, and repeated between seven and ten times, on different days, for each participant. During each block, participants were woken up ten times per hour. Each volunteer reported having visual dreams six or seven times every hour, giving the researchers a total of around 200 dream reports. Most of the dreams reflected everyday experiences, but some contained unusual content, such as talking to a famous actor. The researchers extracted key words from the participants’ verbal reports, and picked 20 categories — such as 'car', 'male', 'female', and 'computer' — that appeared most frequently in their dream reports. Kamitani and his colleagues then selected photos representing each category, scanned the participants’ brains again while they viewed the images, and compared brain activity patterns with those recorded just before the participants were woken up. © 2012 Nature Publishing Group
By David DiSalvo Neuroscientists aren’t usually thought of as advocates for special interests. They’re a generally objective bunch, dedicated to their discipline and concerned above all with making solid contributions to understanding how our brains work. Advances in understanding and treating Alzheimer’s, Parkinson’s, multiple sclerosis, and a host of other diseases and conditions are largely attributable to the commitment of neuroscientists focused on solving some of the most difficult problems in medicine. But, over the past decade, as neuroscience—and brain imaging in particular—has become a star science attraction, the role of the impartial neuroscientist has been redefined. When the forces of marketing realized that neuroscience could assist in predicting consumer behavior, neuroscientists became a hot commodity as “consultants” to some of the biggest brands on the planet. Soon “neuromarketing” was born, and firms armed with fMRI machines started becoming mainstays at consumer focus groups for Fortune 500 companies. A similar story is playing out in the legal arena—but the stakes are much higher. When neuroscientists are recruited to weigh in on critical issues like lie detection and the alleged mental state of a defendant, people’s lives, and not just their wallets, are directly affected. But much of this technology is too new to be reliable. Furthermore, neuroscience experts aren’t just being used on the stand—they are also being paid to help select, even sway, juries, and that poses an entirely new ethical dilemma. © 2012 The Slate Group, LLC
The Crack Team That Removes & Preserves People's Brains Just Hours After They Die by Jeff Wheelwright On average, the residents of Sun City, Arizona, occupy their domiciles for a dozen years. When they depart—almost always by dying—they often leave their brains behind. The stages of physical and mental decline take them from their dream house to a hospital off Del Webb Boulevard, then to a nursing home, and finally back to the medical complex, where researchers harvest their most important organ. Hoping to do good for science, they have enrolled in the Brain and Body Donation Program of the Banner Sun Health Research Institute—widely considered the world’s preeminent brain bank. A large base of well- documented donors in close proximity sets the Sun City program apart from other repositories, which often have scant information about patients who may be scattered and diverse. Here, healthy, active seniors who eventually die of, say, heart disease, can be compared with others who develop neurodegenerative disorders. Because the two sets of subjects have similar backgrounds, lifestyles, and ethnic traits, changes relating to a brain disease should be easier to detect. The institute is also famed for its crack autopsy team, which responds so quickly that no more than three hours elapse from the time a donor expires to the time that the brain is removed and preserved. “We’re not the biggest brain bank in the world, but we have the highest-quality tissue,” says pathologist Thomas Beach, the program director, who notes that donors must live within a 50-mile radius of the morgue. © 2012, Kalmbach Publishing Co.
Link ID: 17376 - Posted: 10.17.2012
By Ferris Jabr In the 1970s biologist Sydney Brenner and his colleagues began preserving tiny hermaphroditic roundworms known as Caenorhabditis elegans in agar and osmium fixative, slicing up their bodies like pepperoni and photographing their cells through a powerful electron microscope. The goal was to create a wiring diagram—a map of all 302 neurons in the C. elegans nervous system as well as all the 7,000 connections, or synapses, between those neurons. In 1986 the scientists published a near complete draft of the diagram. More than 20 years later, Dmitri Chklovskii of Janelia Farm Research Campus and his collaborators published an even more comprehensive version. Today, scientists call such diagrams "connectomes." So far, C. elegans is the only organism that boasts a complete connectome. Researchers are also working on connectomes for the fruit fly nervous system and the mouse brain. In recent years some neuroscientists have proposed creating a connectome for the entire human brain—or at least big chunks of it. Perhaps the most famous proponent of connectomics is Sebastian Seung of the Massachusetts Institute of Technology, whose impressive credentials, TED talk, popular book, charisma and distinctive fashion sense (he is known to wear gold sneakers) have made him a veritable neuroscience rock star. Other neuroscientists think that connectomics at such a large scale—the human brain contains around 86 billion neurons and 100 trillion synapses—is not the best use of limited resources. It would take far too long to produce such a massive map, they argue, and, even if we had one, we would not really know how to interpret it. To bolster their argument, some critics point out that the C. elegans connectome has not provided many insights into the worm's behavior. In a debate* with Seung at Columbia University earlier this year, Anthony Movshon of New York University said, "I think it's fair to say…that our understanding of the worm has not been materially enhanced by having that connectome available to us. We don't have a comprehensive model of how the worm's nervous system actually produces the behaviors. What we have is a sort of a bed on which we can build experiments—and many people have built many elegant experiments on that bed. But that connectome by itself has not explained anything." © 2012 Scientific American
Keyword: Development of the Brain
Link ID: 17325 - Posted: 10.03.2012
The brain that revolutionized physics now can be downloaded as an app for $9.99. But it won't help you win at Angry Birds. While Albert Einstein's genius isn't included, an exclusive iPad application launched Tuesday promises to make detailed images of his brain more accessible to scientists than ever before. Teachers, students and anyone who's curious also can get a look. A medical museum under development in Chicago obtained funding to scan and digitize nearly 350 fragile and priceless slides made from slices of Einstein's brain after his death in 1955. The application will allow researchers and novices to peer into the eccentric Nobel winner's brain as if they were looking through a microscope. "I can't wait to find out what they'll discover," said Steve Landers, a consultant for the National Museum of Health and Medicine Chicago who designed the app. "I'd like to think Einstein would have been excited." After Einstein died, a pathologist named Thomas Harvey performed an autopsy, removing the great man's brain in hopes that future researchers could discover the secrets behind his genius. Harvey gave samples to researchers and collaborated on a 1999 study published in the Lancet. That study showed a region of Einstein's brain - the parietal lobe - was 15 percent wider than normal. The parietal lobe is important to the understanding of math, language and spatial relationships. © 2012 Hearst Communications Inc
Link ID: 17302 - Posted: 09.26.2012
The human brain is big and complicated. There has been a map for gene expression in mice brains available for a number of years but human brains are a thousand times bigger and a little harder to come by for post-mortem research. But published today is a high-resolution 3D atlas of the human brain created by an international team led by Michael Hawrylycz of the Allen Institute for Brain Science in Seattle. The project was launched in March 2008 with a budget of $55 million. Working with just two whole male brains and a single hemisphere from a third, the team used around 900 precise subdivisions and 60,000 gene expression probes to create the atlas. This image is a 3D rendering of just one of the genes in internal brain structures overlaid onto an MRI scan. The level of gene expression at the different points on the map is indicated on a colour scale, with blue dots reflecting relatively low expression and red dots reflecting high expression. The aim of the project is to provide a platform for further study into gene expression in the brain and how it is involved in normal and abnormal brain function. The Allen Brain Atlas is freely accessible online. Journal reference: Nature, DOI: 10.1038/nature11405 © Copyright Reed Business Information Ltd.
2012 by Graham Lawton My usual pick-me-up on a Monday morning is a cup of coffee. Today it's going to be something very different. I've been up since 6 am. I've had a breath test for alcohol, a urine test for drugs and a psychological test for mental health. Then I'm handed a red pill and a glass of water. I swallow it… and I'm told to relax. Which is easier said than done when you don't know if you've just taken vitamin C or 83 milligrams of pure MDMA. Half an hour later I'm inside an fMRI brain scanner, my head clamped in place and a visor over my face. It's noisy and claustrophobic but I'm reassured by the panic button in my hand and a voice from the control room. And then I start to feel it. A tingle of energy, like pins and needles, starts in the pit of my stomach and rises slowly, not unpleasant but not exactly pleasurable either. It builds in intensity, then breaks into a wave of bliss. The placebo effect can be powerful but when it happens again, I'm in no doubt. I'm coming up. I'm taking part in a groundbreaking study on MDMA, the drug commonly known as ecstasy. The research is run by David Nutt of Imperial College London, a former government adviser and one of the few UK researchers licensed to study class-A drugsMovie Camera. His main aim is to discover what MDMA does to the human brain, something that, remarkably, has never been done before. A second goal is to study MDMA as a therapy for post-traumatic stress disorder. © Copyright Reed Business Information Ltd
by Douglas Heaven Nanoparticles often meet a sticky end in the brain. In theory, the tiny structures could deliver therapeutic drugs to a brain tumour, but navigating the narrow, syrupy spaces between brain cells is difficult. A spot of lubrication could help. Justin Hanes at Johns Hopkins University in Baltimore, Maryland, was surprised to discover just how impermeable brain tissue is to nanoparticles. "It's very sticky stuff," he says, similar in adhesiveness to mucus, which protects parts of the body – such as the respiratory system – by trapping foreign particles. It was thought that the adhesiveness of brain tissue limited the size of particles that can smoothly spread through the brain. Signalling molecules, nutrients and waste products below 64 nanometres in diameter can pass through the tissue with relative ease, but larger nanoparticles – suitable for delivering a payload of drugs to a specific location in the brain – quickly get stuck. Now Hanes and his colleagues have doubled that size limit. They coated their nanoparticles with a densely-packed polymer shield, which lubricates their surface by preventing electrostatic and hydrophobic interactions with the surrounding tissue. "A nice hydrated shell around the particle prevents it from adhering to cells," says Hanes. Using this approach, they were able to observe the diffusion of nanoparticles 114 nanometres in diameter through live mouse brains and dissected human and rat brain tissue. Hanes believes the true upper size limit now lies somewhere between 114 nm and 200 nm. "Things were starting to slow down at 114," he says. © Copyright Reed Business Information Ltd.
Link ID: 17219 - Posted: 08.30.2012
By Stephani Sutherland Ice cream headache is a familiar summertime sensation, but the pain's source has been mysterious until now. A team led by Jorge Serrador of Harvard Medical School produced brain scans of “second-by-second changes” in blood flow while subjects sipped iced water through a straw pressed against the roof of the mouth, which caused the brain's major artery to widen. “Blood flow changes actually preceded the pain” that subjects reported, Serrador says. As the vessel narrowed again, the discomfort ebbed. He suspects that the influx of blood is meant to protect the brain from extreme cold and that increased pressure inside the skull could cause the pain. Serrador presented the results at Experimental Biology 2012 in April in San Diego. © 2012 Scientific American
Keyword: Pain & Touch
Link ID: 17205 - Posted: 08.27.2012
By Carrie Arnold Like an overwhelmed traffic cop, the depressed brain may transmit signals among regions in a dysfunctional way. Recent brain-imaging studies suggest that areas of the brain involved in mood, concentration and conscious thought are hyperconnected, which scientists believe could lead to the problems with focus, anxiety and memory frequently seen in depression. Using functional MRI and electroencephalography (EEG), psychiatrist Andrew Leuchter of the University of California, Los Angeles, and his colleagues measured the activity of depressed patients' brains at rest. They found that the limbic and cortical areas, which together produce and process our emotions, sent a barrage of neural messages back and forth to one another—much more than in the brains of healthy patients. These signals, Leuchter says, can amplify depressed people's negative thoughts and act like white noise, drowning out the other neural messages telling them to move on. A separate study by psychiatrist Shuqiao Yao of Central South University in Hunan, China, produced a more nuanced view of these two areas' hyperconnectivity. In work published in Biological Psychiatry in April, Yao and his colleagues reported that stronger links among certain corticolimbic circuits are seen in patients more prone to rumination, the act of continuously replaying negative thoughts. Less connectivity in other corticolimbic circuits corresponded to autobiographical memory impairments, which is another common feature that appears in depression. © 2012 Scientific American
Link ID: 17197 - Posted: 08.25.2012
by Sara Reardon The carnival trick of guessing a person's age has just gained a lot more rigour. A new brain imaging technique can predict a child's age to within a year. The technique could be useful for determining whether a child is developing normally, or confirm that a young person is the age they say they are. There is no doubt that children of the same age often have vast differences in their maturity and mental ability, says Timothy Brown of the University of California in San Diego. But what hasn't been clear is how much of that difference is psychological and how much is biological. To simplify the question, Brown and his colleagues looked at brain structure rather than brain activity. Working with 10 hospitals in different parts of the US, they recruited 885 children and young adults between the ages of 3 and 20. They ensured that the participants represented many different races, socioeconomic statuses and education levels. The group performed structural magnetic resonance imaging (MRI) on the young peoples' brains. The images showed features such as the size of each brain region, the level of connectivity between neurons, and how much white matter was insulating the neurons. By putting all these features together in an algorithm, the researchers formed a picture of what the average brain looks like at each year of childhood. Different areas and features of the brain varied between individuals, but the algorithm correctly predicted a child's age to within a year in 92 per cent of cases. © Copyright Reed Business Information Ltd.
By Jason G. Goldman The largest fish in the ocean is the whale shark (Rhincodon typus). This massive, migratory fish can grow up to twelve meters in length, but its enormous mouth is designed to eat the smallest of critters: plankton. While the biggest, the whale shark isn’t the only gigantic filter-feeding shark out there: the basking shark and the megamouth shark also sieve enormous amounts of the tiny organisms from the sea in order to survive. While scientists like Al Dove and Craig McClain (of Deep Sea News) are learning more and more about the basic biology and behavior of these magnificent creatures, other scientists are busy investigating their neuroanatomy. A few years ago, Kara E. Yopak and Lawrence R. Frank from the University of California in San Diego got their hands on two whale shark brains from an aquarium, and put them into an MRI scanner. But they weren’t just interested in imaging the brains of the whale sharks. What they wanted to know was how the organization of whale shark brains compared to the brains of other shark species for which scientists had previously obtained neuroanatomical data. Would the brains of two species be more similar if they shared a recent evolutionary ancestor, and were therefore more genetically related? Or would shark brains be more similar among species that shared a similar lifestyle, such as those that patrol the middle and surface of the water column (pelagic sharks, such as the great white, oceanic whitetip, blue, mako, and whale sharks) versus those that live along the sea floor (benthic sharks, such as the nurse and cat sharks). Or perhaps the brains of sharks would be grouped according to their habitat, such as those that live in coastal waters, around reefs, or in the open ocean. Maybe sharks brains ought to be grouped according to behavioral specialization, such as hunting methods. Answers to these questions could shed some important light on brain evolution, both in sharks as well as more generally. © 2012 Scientific American