General anesthesia can be tolerated by patients older than 65

Contrary to conventional medical wisdom, a new study by NYU Langone Medical Center researchers shows that healthy elderly patients with severe to profound hearing loss can undergo a surgical procedure to receive cochlear implants with minimal risk. "Due to concerns about the effects of general anesthesia, many elderly people with hearing loss are not receiving the implants which can significantly improve their hearing and quality of life," according to Anil Lalwani, M.D., Mendik Foundation Professor of Otolaryngology and Chairman of the Department of Otolaryngology at NYU School of Medicine and a study co-author. "The elderly are often incorrectly considered too fragile for this life transforming technology that can deliver them from a world of silence and loneliness to a world of hearing and engagement," says Dr. Lalwani. The new study is published in the February issue of the journal The Laryngoscope.

The National Institute on Aging estimates that about one-third of Americans between ages 65 and 74 have hearing difficulty – and that number increases to 50 percent in people 85 and older. In about 10% of the elderly, the impairment is so severe that conventional hearing aids provide little benefit. The inability to communicate interferes greatly with daily living and can lead to cognitive impairment, personality changes, depression, reduced functional status and social isolation.

The researchers conducted a retrospective chart review of 70 patients over 70 years of age who received cochlear implants under general anesthesia at NYU Langone Medical Center between 1984 and 2007. The patients were divided into risk groups and intraoperative and postoperative anesthesia-related complications were identified. Most patients tolerated the procedure and there was no long-term morbidity or mortality related to the surgery or anesthesia.

The researchers concluded that general anesthesia is well tolerated by elderly patients undergoing cochlear implantation. Any pre - existing medical condition is a better predictor of intraoperative and postoperative complication than age alone, they observed. Jung T. Kim, M.D. Vice chairman of the Department of Anesthesiology at NYU School of Medicine and a study co-author said "As seniors embrace a healthy and active lifestyle, it is important that age alone should not deter a person from having surgery that could potentially improve their quality of life."

Arrangement of receptors appears uniformly random across individuals and species

Despite the striking aromatic differences between coffee, peppermint, and pine, a new mapping of the nose's neural circuitry suggests a haphazard patchwork where the receptors for such disparate scents are as likely as not to be neighbors. Inexplicably, this seemingly random arrangement is faithfully preserved across individuals and even species, with cells that process the same scent located in precisely the same location on the olfactory bulb, the brain's first processing station for odors. The crazy-quilt map of odor-processing neurons on the front lines of the olfactory system is described by Harvard University neuroscientists in the February issue of the journal Nature Neuroscience.

"It had been thought that the layout of the olfactory bulb was variable from individual to individual, but followed a chemotopic order where cells handling similar odor responses are near each other," says Markus Meister, the Jeff C. Tarr Professor of Molecular and Cellular Biology in Harvard's Faculty of Arts and Sciences. "Here we show that the layout is actually very precise -- the same from animal to animal -- but doesn't appear to follow any chemotopic order whatsoever."

Working with mice and rats, Meister and colleague Venkatesh N. Murthy recorded neural responses to several hundred distinct odors, including anise, beer, cloves, coffee, ginger, lemon, orange, peppermint, pine, rose, and even fox pheromones. The neuroscientists found that across individuals and even across the two species, bundles of neurons from a given type of odor receptor -- known as glomeruli -- were found in almost exactly the same spot on the olfactory bulb, a sensory structure measuring some four to five millimeters across and located at the very front of the brain.

"Glomeruli from different receptors line the surface of the olfactory bulb like an array of close-packed marbles," says Murthy, professor of molecular and cellular biology at Harvard. "Across individuals the location of a given glomerulus varies by only one array position. Compared to the size of the map, this represents a remarkable developmental precision of one part in 1,000." Meister and Murthy then analyzed whether nearby glomeruli detect similar odors, such as those with similar chemical structures. Neuroscientists have previously hypothesized axes of similarities along which odors might be classified. "One might expect that nearby glomeruli should have similar odor sensitivities," Meister says, "but we were surprised to find this was not the case. The odor response spectra of two neighboring glomeruli were as dissimilar as those of distant glomeruli."

This seemingly haphazard layout of sensory properties stands in marked contrast to other brain maps, such as those governing vision, touch, and hearing. In these three cases, our brains represent the outside world using ordered maps -- such as when neighboring points in visual space activate neighboring points on the retina. "That sort of arrangement makes sense, since most brain computation is local, relying on short connections between nearby cells," Murthy says. "This is necessary because the connections between neurons occupy most of the volume available to the brain, and long-distance connections require more of this volume."

Meister and Murthy suspect that the deliberate randomness in rodents' odor maps is likely also found in humans, which have only one-third as many receptors but are capable, in some extreme cases, of discerning tens of thousands of distinct smells.

Meister and Murthy's co-authors on the Nature Neuroscience paper are Edward R. Soucy, Dinu F. Albeanu, and Antoniu L. Fantana, all of Harvard's Department of Molecular and Cellular Biology and Center for Brain Science. Their work was funded by Harvard University.

Observers of Walking Figures See Men Advancing, Women in Retreat

When viewing figures walking, a curious illusion appears. People perceive male strollers as moving toward them, whereas the female walkers appear to be moving away, regardless of the figure's actual direction.

60-Second Psych from Scientific American podcasts
8 September 2008

Cochlear implant recipients experience a significant improvement in their quality of life, and have improved speech recognition, according to new research published in the March 2008 issue of Otolaryngology – Head and Neck Surgery.

The German study evaluated the quality of life of 56 cochlear implant recipients using the Nijmegen Cochlear Implant Questionnaire (NCIQ), a self-administered assessment that asks responders about sound perception, speech, self-esteem, and social interaction. Responders reported significant improvements in all areas, with especially large gains observed in the areas of sound perception and social interaction. The study also gauged participants using the Medical Outcome Study Short Form 36 (SF36). While the results provided by this tool are not specific to hearing loss or cochlear implants, they nonetheless indicated significant improvements in the areas of social functioning and mental health.

A cochlear implant is an electronic device that restores partial hearing to the deaf. It is surgically implanted in the inner ear and activated by a device worn outside the ear. Unlike a hearing aid, it does not make sound louder or clearer. Instead, the device bypasses damaged parts of the auditory system and directly stimulates the hearing nerve, allowing individuals who are profoundly hearing-impaired to receive sound.

Primer describes current understanding of human taste perception and biology

Despite the significance of taste to both human gratification and survival, a basic understanding of this primal sense is still unfolding. Taste provides both pleasure and protection. Often taken for granted, the sense of taste evaluates everything humans put into their mouths. Taste mediates recognition of a substance and the final decision process before it is either swallowed and taken into the body, or rejected as inappropriate.

A new primer written by scientists at the Monell Center and Florida State University and published in the February 26 issue of Current Biology, provides a clear and accessible overview of recent advances in understanding human taste perception and its underlying biology.

Within the past few years, identification of receptors for sweet, bitter and umami (savory) taste has led to new insights regarding how taste functions, but many questions remain to be answered. The Current Biology primer reviews the current state of knowledge regarding how taste stimuli are detected and ultimately translated by the nervous system into the perceptual experiences of sweet, sour, salty, bitter, and umami.

Such perceptual evaluations are related to the function and ultimately, the consequences, of taste evaluation. These can range from pleasurable emotional reactions, for example the delight a child receives from a sweet candy, to the critical life-dependent response that causes a person to spit out a bitter potential toxin.

Author Paul A.S. Breslin, PhD, a sensory scientist at the Monell Center, observes, “For all mammals, the collective influence of taste over a lifetime has a huge impact on pleasure, health, well being, and disease. Taste’s importance to our daily lives is self-evident in its metaphors – for example: the ‘sweetness’ of welcoming a newborn child, the ‘bitterness’ of defeat, the ‘souring’ of a relationship, and describing a truly good human as the ‘salt’ of the earth.”

25 February 2008

In the first study to use imaging technology to see what goes on in the brain when we scratch, researchers at Wake Forest University Baptist Medical Center have uncovered new clues about why scratching may be so relieving – and why it can be hard to stop. The work is reported online in the Journal of Investigative Dermatology and will appear in a future print issue.

"Our study shows for the first time how scratching may relieve itch,” said lead author Gil Yosipovitch, M.D., a dermatologist who specializes in itch. “It’s important to understand the mechanism of relief so we can develop more effective treatments. For some people, itch is a chronic condition that affects overall health.” The study involved 13 healthy participants who underwent testing with functional magnetic resonance imaging (MRI) technology that highlights areas of the brain activated during an activity. Participants were scratched on the lower leg with a small brush. The scratching went on for 30 seconds and was then stopped for 30 seconds – for a total of about five minutes.

“To our surprise, we found that areas of the brain associated with unpleasant or aversive emotions and memories became significantly less active during the scratching,” said Yosipovitch. “We know scratching is pleasurable, but we haven’t known why. It’s possible that scratching may suppress the emotional components of itch and bring about its relief.” The reduced brain activity occurred in the anterior cingulate cortex, an area associated with aversion to unpleasant sensory experiences, and the posterior cingulate cortex, which is associated with memory. When participants reported that the scratching felt most intense, activation in these areas was lowest.

Yosipovitch said patients occasionally report that intense scratching – to the point of drawing blood – is the only thing that relieves chronic itch. “This is the first real scientific evidence showing that itch may be inhibited by scratching,” he said. “Of course, scratching is not recommended because it can damage the skin. But understanding how the process works could lead to new treatments. For example, drugs that deactivate this part of the brain might be effective.”

The imaging studies also showed that some areas of the brain were made more active by the scratching, including the secondary somatosensory cortex, a sensory area involved in pain, and the prefrontal cortex, which is associated with compulsive behavior. “This could explain the compulsion to continue scratching,” said Yosipovitch.

One drawback to the study is that the scratching occurred in the absence of itch. Yosipovitch’s team is continuing the research by evaluating whether the findings will apply to chronic itch. Understanding more about chronic itch is important, Yosipovitch said, noting that more than 30 million Americans suffer from eczema and that almost half (42 percent) of kidney dialysis patients are bothered by moderate to severe itch. In fact, those kidney dialysis patients with itch have a 17 percent higher mortality rate, likely from a loss of sleep, according to a report in Nephrology Dialysis Transplantation.


Wake Forest University Baptist Medical Center News
31 January 2008

FDA approves study to evaluate an artificial retina intended to help subjects blinded by retinitis pigmentosa. Patients who have gone blind are a step closer to perhaps one day regaining some of their sight.

Researchers at the USC Doheny Eye Institute announced today the next step in their efforts to advance technology that hopefully will help patients with retinitis pigmentosa and macular degeneration regain some vision using an implanted artificial retina. The announcement by Mark Humayun, professor of ophthalmology at the Keck School of Medicine of USC and associate director of research at the Doheny Retina Institute, came at a press conference at the annual meeting of the American Association for the Advancement of Science in San Francisco.

The Food and Drug Administration recently approved an Investigational Device Exemption to conduct a clinical study of the new device – dubbed the Argus II Retinal Prosthesis System. The implantable technology is a collaborative effort between USC and Second Sight Medical Products, which manufactures the implant.

The Argus II is the second generation of an electronic retinal implant designed for the treatment of blindness due to retinitis pigmentosa, a group of inherited eye diseases that affect the retina. RP causes the degeneration of photoreceptor cells in the retina, which capture and process light, helping individuals to see. As these cells degenerate, patients experience progressive vision loss. The Argus device is essentially designed to take the place of the photoreceptors.

“The first phase of our implant work began in 2002,” Humayun said. “We have successfully implanted six patients in the trial, and we have found that the devices are indeed electrically conducting and can be used by patients to detect light or even to distinguish between objects such as a cup or plate.”

While the first generation of implants contained 16 electrodes laid out on an array, the Argus II is designed with 60 electrodes, which is intended to allow for higher-resolution images. The new device is also approximately one quarter the size of the original, reducing surgery and recovery times. The array is attached to the retina and used in conjunction with an external camera and video processing system to provide a rudimentary form of sight to implanted subjects.

The clinical trial of the first generation of implants continues at the Doheny Eye Institute at USC. All six previously blind patients in the first trial have been able to detect light, identify objects in their environment and even perceive motion after implantation with the first generation device.

The device ultimately may be used for the millions of people suffering from age-related macular degeneration, or AMD. In fact, Humayun said, there are 25 million people around the world, including 6 million in the United States, who have been blinded or are severely visually impaired due to diseases like RP and AMD. By 2020, that figure is expected to double, creating a virtual vision-loss epidemic. Both AMD and RP destroy vision by annihilating the retinal cells that allow light to be translated into recognizable images.

“Perhaps what we’re most excited about in this next study,” Humayun said, “is, similar to the first generation Second Sight device, we will be able to test the new device with patients at their homes, churches, schools and similar locations. The importance of this work is going to be reflected in how well this helps them regain some of their lost vision.”

The current study will include patients over 50 years of age who have RP or AMD and who have had previous functional vision.

This study is supported by the Department of Energy, the National Science Foundation, National Eye Institute/NIH, Research to Prevent Blindness, the W. M. Keck Foundation and the Albaugh Family Trust.

The color of a drink can fool the taste buds into thinking it is sweeter

Does orange juice taste sweeter if it's a brighter orange? A new study in the March issue of the Journal of Consumer Research finds that the color of a drink can influence how we think it tastes. In fact, the researchers found that color was more of an influence on how taste was perceived than quality or price information.

"Perceptual discrimination is fundamental to rational choice in many product categories yet rarely examined in consumer research," write JoAndrea Hoegg (University of British Columbia) and Joseph W. Alba (University of Florida). "The present research investigates discrimination as it pertains to consumers' ability to identify difference—or the lack thereof—among gustatory stimuli."

Hoegg and Alba are the first to look at how individual attributes -- such as color, price, or brand -- can affect which products we prefer. The researchers manipulated orange juice by changing color (with food coloring), sweetness (with sugar), or by labeling the cups with brand and quality information. They found that though brand name influenced people's preferences for one cup of juice over another, labeling one cup a premium brand and the other an inexpensive store brand had no effect on perceptions of taste.

In contrast, the tint of the orange juice had a huge effect on the taster's perceptions of taste. As the authors put it: "Color dominated taste."

Given two cups of the same Tropicana orange juice, with one cup darkened with food coloring, the members of the researcher's sample group perceived differences in taste that did not exist. However, when given two cups of orange juice that were the same color, with one cup sweetened with sugar, the same people failed to perceive taste differences.

"It seems unlikely that our consumers deliberately eschewed taste for color as a basis for discrimination," write the authors. "Moreover, our consumers succumbed to the influence of color but were less influenced by the powerful lure of brand and price information."

---

Hoegg, J. and J.W. Alba. "Taste Perception: More Than Meets the Tongue," Journal of Consumer Research: March 2007.

Berkeley -- University of California, Berkeley, graduate student Allen Liu last Friday donned coveralls, a blindfold, earplugs and gloves, then got down on all fours and sniffed out a 33-foot chocolate trail through the grass. This was no fraternity initiation, but part of an experiment to find out whether mammals compare information coming from their two nostrils in order to aid scent-tracking performance, much like they compare information from their ears in order to locate a sound.

In a paper appearing this week in the advance online edition of Nature Neuroscience, UC Berkeley researchers report conclusive evidence from these experiments that humans do indeed gain a performance advantage from cross-nostril comparisons. They also found that humans can scent-track, and that, with training, they can improve their accuracy significantly while nearly doubling their speed along the scent trail.

In one experiment, the authors found that while volunteers with one nostril blocked could still track a scent - in this experiment, essence of chocolate - volunteers with two open nostrils tracked a scent quicker and with fewer deviations from the trail. "We were asking the question, 'Are two nostrils better than one"'" said lead author Jess Porter, a graduate student in biophysics at UC Berkeley. "The answer is yes."

Apparently, according to Porter and her colleagues, the mammalian brain compares smells between nostrils to tell where an odor is coming from in the same way that the brain compares the sounds entering a person's two ears to locate a source. Until now, many researchers thought this was unlikely because a mammal's nostrils, in a mouse, for example, are too close together to receive distinctly different smells.

"The human brain compares information from two 'noses' to turn smell information into spatial information," said Noam Sobel, associate professor of neuroscience and psychology and member of the program in biophysics at UC Berkeley. Sobel hopes to use information from these experiments to design scent-tracking robots equipped with his eNose, an electronic nose that one day could detect odors such as that from an explosive mine.

To test Sobel and Porter's smell hypothesis, the UC Berkeley researchers soaked a 33-foot (10-meter) string in chocolate essence and laid it in the grass outside Barker Hall, located at the northwest corner of the UC Berkeley campus. They then garbed volunteers to block their senses of sight, hearing and touch, eliminating all clues other than smell to guide them along the trail. Sniffing like bloodhounds, two-thirds of 32 subjects were able to follow the chocolate scent to the end of the trail within three attempts. All volunteers zigzagged along the trail in the same way that tracking dogs follow a scent.

The researchers then trained four of these volunteers to see if they could improve. All were able to double their speed along the track within just a few days and deviated much less from the scent trail than on their first attempts. The researchers measured subjects' sniffs and noticed that the faster the subjects moved along the trail, the more rapid their sniffing - just as with dogs, though not as fast as the six sniffs per second rate exhibited by dogs. The big question, however, was whether two nostrils allow scent localization in the same way that a human's two ears and eyes help locate sounds and sights.

To further test this, the researchers devised an ingenious nasal "prism" that mixed scents from the outside world and then presented this to both nostrils, so that there was no difference between what the nostrils smelled. The four subjects were half as accurate at tracking smells under these conditions.

Independent measurements showed that a human's two nostrils sample odors from distinct areas separated by approximately 1.5 inches (3.5 centimeters), more than enough distance to distinguish the edge of a scent plume. All of these experiments put the lie to a common assumption that humans are lousy smellers compared to all other mammals. While it's true that humans are predominantly visual creatures, Sobel said, their olfactory sense can be compared to that of dogs and other mammals.

"Our sense of smell is less keen partly because we put less demand on it," Porter said. "But if people practice sniffing smells, they can get really good at it."

Do you hate Brussels sprouts because your mother did" Does the size of your plate determine how hungry you feel" Why do you actually overeat at healthy restaurants"

"You can ask your smartest friend why he or she just ate what they ate, and you won’t get an answer any deeper than, 'It sounded good,'" says Brian Wansink, Ph.D.), author of "Mindless Eating: Why We Eat More Than We Think," and Professor and Director of the Cornell Food and Brand Lab.

Dubbed the "Freakonomics of food" by the Canadian Broadcasting Commission, Mindless Eating, uses hidden cameras, two-way mirrors, and hundreds of studies to show why we eat what and how much we eat. "The unique thing about his work is that it cleverly answers everyday questions about food and shows translates them into Good News – how we can improve it," said Seth Roberts, Ph.D., a psychology professor at the University of California at Berkeley.

Take how much we eat. Wansink claims we typically don’t overeat because we are hungry or because the food tastes good. Instead we overeat because of the cues around us – family and friends, packages and plates, shapes and smells, distractions and distances, cupboards and containers.

Consider your holiday ice cream bowl. If you spoon 3 ounces of ice cream onto a small bowl, it will look like a lot more than if you had spooned it into a large bowl. Even if you intended to carefully follow your diet, the larger bowl would likely influence you to serve more. This tricks even the pros.

During one holiday party, Wansink and his Lab put this to the test by inviting 63 distinguished nutritional science professors at a leading university to an holiday ice cream social. When they arrived, they were given either medium-size 17-ounce bowls or large-size 34-ounce bowls. "Even though these people think, sleep, lecture and study nutrition," Wansink said, "They still served themselves and ate 31 percent more ice cream (106 more calories) if they had been given a big bowl."

If experts can’t control mindless eating, what help is there for the rest of us" Here’s the good news reassures Wansink, "As Mindless Eating shows, what we eat and how much we eat – is so automatic, the easiest changes are those that are smallest."

At a holiday buffet" Use a smaller plate, or put only two items on your plate during any given trip to the table. Return as many times as you like, but only take two items each time.

Meticulous studies outline why we are consistently influenced, but they also provide the silver lining. If we know that we tend to pour 28% more into short wide glasses than in tall thin ones, the secret is simply getting rid of the short glasses.

###

More on the topic can be found at www.MindlessEating.org, which also shows photos of studies and top tips for the holidays – and beyond.

ANN ARBOR, Mich.—A ribbon-like cochlear implant
developed at the University of Michigan could greatly
improve hearing for profoundly deaf patients, and simplify insertion to help surgeons minimize damage to healthy ear tissue.

A team led by U-M's Kensall D. Wise, director of the NSF Engineering Research Center for Wireless Integrated Microsystems (WIMS), made the implant using thin-film electrode sites that directly stimulate the auditory nerve.

The implant is currently being tested in guinea pigs and cats, said Wise, who has appointments in the departments of Biomedical Engineering and Electrical Engineering and Computer Science. The device may be available in four to five years for use in humans, Wise said, and could be used in current cochlear patients—removing the old device first—to improve their hearing. Additionally, the FDA approves implants for wider use as the technology improves.

Approximately 100,000 patients today have received cochlear implants worldwide. The current technology, Wise said, is bulky, difficult for surgeons to insert, and doesn't allow a great range of perceived frequencies. The present implants use electrodes formed from a bundle of wires fed into the snail-shaped cochlea of the inner ear, but difficulties in inserting such devices make it tough to achieve the deep insertion needed to stimulate lower-frequency sounds, and collisions with the cochlear wall can damage any residual hearing that still exists.  

"The range of frequencies that can be stimulated depends on how far into the cochlea the implant can go, with the lower frequencies located further up toward the apex of the spiral canal," Wise said. In current technology, each implant has anywhere from 16 to 22 stimulating sites along its length. By contrast, the U-M implant will host up to 128 stimulating sites.

"More sites mean greater tonal range and better frequency perception," Wise said, "and the implant's flexibility will minimize damage to existing hearing."

The ribbon film technology lets researchers embed other functions in the implant, such as position sensors that allow surgeons to watch the implant's progress on a monitor as they're feeding it into the cochlea.

"With the position sensors, doctors can see, on a screen, a silhouette of the ribbon against the shape of the cochlea," Wise said. "Eventually the idea is to be able take the signals from the position sensors and use them to control actuators in an insertion tool, so that the electrode array can achieve deep insertion and navigate around any obstacles in its path.

"The idea is to use a pneumatic insertion tool that can be inflated or deflated, similar to a spiral party favor, and is pre-stressed to hug the inner wall of the cochlea," Wise said. "The position sensors set the stage for doing that because they give you feedback on what's happening when you insert these devices."

Researchers make the implant with the same processes used to make integrated circuits, which means they can be made in batch. The research is funded by the National Science Foundation and was to be presented on Feb. 6 at the International Solid-State Circuits Conference (ISSCC) in San Francisco. Doctoral student Pamela Bhatti was to present the paper, which is co-authored by Wise and by research fellow Sangwoo Lee.

Univeristy of Michigan News Service
6 February 2006

Visual information can be processed unconsciously when the area of the brain that records what the eye sees is temporarily shut down, according to research at Rice University in Houston.

The research, published the week of Oct. 31 in the Proceedings of the National Academy of Sciences' (PNAS) online Early Edition, suggests the brain has more than one pathway along which visual information can be sent.

For the study, the researchers induced temporary, reversible blindness lasting only a fraction of a second in nine volunteers with normal vision. Transcranial magnetic stimulation (TMS), a harmless noninvasive technique using brief magnetic pulses, was applied to the volunteers' visual cortex -- the area at the back of the brain that processes what the eye sees - to interrupt the normal visual pathway. The volunteers looked at a computer screen, and during their momentary blindness, either a horizontal or a vertical line or a red or a green dot flashed on the screen.

Researchers then asked the study participants whether they had seen a horizontal or a vertical line; because their primary visual pathway had been shut down, the participants reported that they saw nothing. However, when forced to guess which line had appeared on their computer screen, the participants gave the correct answer 75 percent of the time. When the participants had to guess whether a red or a green dot had flashed on the screen, they gave the correct answer with 81 percent accuracy.

"This high degree of accuracy for both the directional orientation and color tasks was significantly above chance," said Tony Ro, associate professor of psychology and principal investigator for the study. "Even though the human primary visual cortex activity was temporarily shut down, it's clear that detailed visual information was still being processed unconsciously."

Because only a certain region of the thalamus - the area of the brain where all sensory information is relayed -- can process color, the study provides evidence that there must be a pathway that goes through this region of the thalamus to the higher visual centers of the brain, Ro said.

"In addition to providing direct evidence that unconscious processing takes place within the brain - a controversial claim that was advanced by the likes of Sigmund Freud and William James - our results suggest that multiple pathways relay visual input into the central nervous system for different types of processing," Ro said. "And our study also begins to shed light on the brain structures that are necessary for consciousness, with the primary visual cortex playing an essential role for visual awareness."

The phenomenon of "blindsight" has been reported in patients with brain damage who report not seeing something but correctly identify the shape and location when forced to guess. Ro noted that his study demonstrates that TMS can be used successfully to induce blindsight in people with normal vision.

Rice University News Release
31 October 2005

First-ever images of living human retinas have yielded a surprise about how we perceive our world. Researchers at the University of Rochester have found that the number of color-sensitive cones in the human retina differs dramatically among people--by up to 40 times--yet people appear to perceive colors the same way. The findings, on the cover of this week's journal Neuroscience, strongly suggest that our perception of color is controlled much more by our brains than by our eyes.

"We were able to precisely image and count the color-receptive cones in a living human eye for the first time, and we were astonished at the results," says David Williams, Allyn Professor of Medical Optics and director of the Center for Visual Science. "We've shown that color perception goes far beyond the hardware of the eye, and that leads to a lot of interesting questions about how and why we perceive color."

Williams and his research team, led by postdoctoral student Heidi Hofer, now an assistant professor at the University of Houston, used a laser-based system developed by Williams that maps out the topography of the inner eye in exquisite detail. The technology, known as adaptive optics, was originally used by astronomers in telescopes to compensate for the blurring of starlight caused by the atmosphere.

Williams turned the technique from the heavens back toward the eye to compensate for common aberrations. The technique allows researchers to study the living retina in ways that were never before possible. The pigment that allows each cone in the human eye to react to different colors is very fragile and normal microscope light bleaches it away. This means that looking at the retina from a cadaver yields almost no information on the arrangement of their cones, and there is certainly no ability to test for color perception. Likewise, the amino acids that make up two of the three different-colored cones are so similar that there are no stains that can bind to some and not others, a process often used by researchers to differentiate cell types under a microscope.

Imaging the living retina allowed Williams to shine light directly into the eye to see what wavelengths each cone reflects and absorbs, and thus to which color each is responsive. In addition, the technique allows scientists to image more than a thousand cones at once, giving an unprecedented look at the composition and distribution of color cones in the eyes of living humans with varied retinal structure.

Each subject was asked to tune the color of a disk of light to produce a pure yellow light that was neither reddish yellow nor greenish yellow. Everyone selected nearly the same wavelength of yellow, showing an obvious consensus over what color they perceived yellow to be. Once Williams looked into their eyes, however, he was surprised to see that the number of long- and middle-wavelength cones--the cones that detect red, green, and yellow--were sometimes profusely scattered throughout the retina, and sometimes barely evident. The discrepancy was more than a 40:1 ratio, yet all the volunteers were apparently seeing the same color yellow.

"Those early experiments showed that everyone we tested has the same color experience despite this really profound difference in the front-end of their visual system," says Hofer. "That points to some kind of normalization or auto-calibration mechanism--some kind of circuit in the brain that balances the colors for you no matter what the hardware is."

In a related experiment, Williams and a postdoctoral fellow Yasuki Yamauchi, working with other collaborators from the Medical College of Wisconsin, gave several people colored contacts to wear for four hours a day. While wearing the contacts, people tended to eventually feel as if they were not wearing the contacts, just as people who wear colored sunglasses tend to see colors "correctly" after a few minutes with the sunglasses. The volunteers' normal color vision, however, began to shift after several weeks of contact use. Even when not wearing the contacts, they all began to select a pure yellow that was a different wavelength than they had before wearing the contacts.

"Over time, we were able to shift their natural perception of yellow in one direction, and then the other," says Williams. "This is direct evidence for an internal, automatic calibrator of color perception. These experiments show that color is defined by our experience in the world, and since we all share the same world, we arrive at the same definition of colors."

Williams' team is now looking to identify the genetic basis for this large variation between retinas. Early tests on the original volunteers showed no simple connection among certain genes and the number and diversity of color cones, but Williams is continuing to search for the responsible combination of genes.

University of Rochester Press Release
25 October 2005

The figure is famous: a deceptively simple line drawing that at first glance resembles a vase and, at the next, a pair of human faces in profile. When you look at this figure, your brain must rapidly decide what the various lines denote. Are they the outlines of the vase or the borders of two faces? How does your brain decide?

It does so in a fraction of a second via special nerve circuits in the brain's visual center that automatically organize information into a "whole" even as an individual's gaze and attention are focused on only one part, according to Johns Hopkins researchers writing in a recent issue of the journal Neuron.

"Our paper answers the century-old question of the basis of subconscious processes in visual perception, specifically, the phenomenon of figure-ground organization," said Rudiger von der Heydt, a professor in the Zanvyl Krieger Mind-Brain Institute. "Early in the 20th century, the Gestalt psychologists postulated the existence of mechanisms that process visual information automatically and independently of what we know, think or expect. Since then, there has always been the question as to whether these mechanisms actually exist. They do. Our work suggests that the system continuously organizes the whole scene, even though we usually are attending only to a small part of it."

The report, based on recordings of nerve cells in the visual cortex of macaque monkeys, suggests that this automatic processing of images is repeated each time an individual looks at something new, usually three to four times per second. What's more, the brain provides what von der Heydt calls "a sophisticated program" to select and process the information that is relevant at any given moment.

"The result of this organization is an internal data structure, quite similar to a database, that allows the attention mechanism to work efficiently," von der Heydt said. "An image can be compared with a bag of thousands of little Lego blocks in chaotic order. To pay attention to an object in space, the visual system first has to arrange this bag of blocks into useful 'chunks' and provide threads by which one or the other chunk can be pulled out for further processing."

He noted that the research provides the theoretical foundation that might one day lead to better diagnosis and treatment of human brain disorders.

"The last decades have seen rapid progress in the neurosciences at a very broad front, particularly at the molecular and cellular levels, and this progress makes it increasingly clear that we still lack sufficient understanding of brain function at the 'system level,'" he said. "We need to understand the basis of mental processes. Single cell recording in animals is only one approach to this formidable task. It is complemented by new brain imaging techniques, traditional psychophysics, psychology and computational and theoretical neuroscience. ... Understanding the function of the visual cortex will help to interpret neurological symptoms in diseases that produce disorders of vision."

This work was funded by grants from the National Institutes of Health.

The paper, "Figure and Ground in Visual Cortex: V2 Combines Stereoscopic Cues with Gestalt Rules" appeared in the July 7, 2005, issue of Neuron (Volume 47).

The new study by US psychologists found that people shown erotic or gory images frequently fail to process images they see immediately afterwards. And the researchers say some personality types appear to be affected more than others by the phenomenon, known as “emotion-induced blindness”.

12 August 2005
NewScientist.com news service
Gaia Vince

From Johns Hopkins University
Multitasking: You Can't Pay Full Attention to Sights, Sounds
The reason talking on a cell phone makes drivers less safe may be that the brain can't simultaneously give full attention to both the visual task of driving and the auditory task of listening, a study by a Johns Hopkins University psychologist suggests. (video)