Sunday, October 16, 2016

Highlights and new discoveries in Neuroscience (September 2016)

In the latest issue of this monthly digest series you can find out what our eyes and coloring books have in common, why you shouldn't Pokémon Go and drive, where the brain stores social memories, and much more.


Color vision strategy defies textbook picture

Turns out human color vision may actually work like a colorized version of a black-and-white movie, a new study suggests.

Cone cells, which sense red, green or blue light, detect white more often than colors, researchers reported in Science Advances. The textbook-rewriting discovery could change scientists’ thinking about how color vision works. For decades, researchers have known that three types of cone cells in the retina are responsible for color vision. Those cone cells were thought to send “red,” “green” and “blue” signals to the brain. The brain supposedly combines the colors, much the way a color printer does, to create a rainbow-hued picture of the world (including black and white). But the new findings indicate that “the retina is doing more of the work, and it’s doing it in a more simpleminded way,” says Jay Neitz, a color vision scientist at the University of Washington in Seattle who was not involved in the study.

Red and green cone cells each come in two types: One type signals “white”; another signals color, vision researcher Ramkumar Sabesan and colleagues at the University of California, Berkeley, discovered. The large number of cells that detect white (and black—the absence of white) create a high-resolution black-and-white picture of a person’s surroundings, picking out edges and fine details. Red- and green-signaling cells fill in low-resolution color information. The process works much like filling in a coloring book or adding color to a black-and-white film, says Sabesan, who is now at the University of Washington.

Sabesan and colleagues discerned this color vision strategy by stimulating about 273 individual cone cells in the eyes of two men from the lab. Because the eye is constantly jiggling, the researchers had to determine the pattern of the eye movements to predict where cone cells would be several milliseconds in the future. Sabesan’s team first used a microscope that could peer into living human eyes to map hundreds of light-detecting cone cells in the two volunteers. In order to get a clear picture of the cells through the distortion of the lens and cornea, the researchers borrowed techniques that astronomers use to compensate for disturbances in the atmosphere.

Of the red cones the researchers stimulated, 119 made the men see white, while only 48 flashed red. Similarly, only 21 of the green cones tested actually signaled green, while 77 registered white. Each individual cone probably signals only white or color, the researchers say. Cells surrounded by cones that detect a different color were more likely to send white signals, the researchers found. That finding is unexpected and runs counter to a popular idea that cones ringed by cells detecting other colors would be better at color detection, MacLeod says.

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Pokémons and driving don't mix

Turns out that catching Pokémon while behind the wheel isn't the best of ideas. Who would have thought. There's reason to believe that playing an immersive video game such as Pokémon Go while driving may be even more dangerous than reading a text message while driving, because it pulls attention away from the road longer and with more lasting effects.

Yet alarming numbers of people are doing just that, researchers reported online in JAMA Internal Medicine. A search of Twitter posts that contained “Pokémon” and “driving,” “drives,” “drive” or “car” turned up more than 345,000 tweets during a 10-day period in July. Of those, 113,993 tweets indicated that a driver, passenger or pedestrian was distracted by the augmented-reality game. “This is an incredibly large number,” says study co-author John Ayers of San Diego State University, and likely an underestimate of the number actually playing the game while driving.

Some 18 percent of those tweets indicated a driver was playing the game; 11 percent came from distracted passengers and 4 percent from pedestrians, Ayers and colleagues found. News reports during that same time period showed that drivers playing Pokémon Go caused 14 car crashes.

Pokémon Go was designed to encourage people to explore their neighborhoods. Scattered PokéStops dispense Pokémon-catching tools, and the virtual creatures pop into existence as a player moves. Players incubate and hatch eggs containing the creatures by covering more ground. Rewards for playing in motion are unique to the game, Ayers says. “When you text, the more you drive or the more you walk you don't get more messages, but with Pokémon Go, the feedback mechanism fosters dangerous behaviors.”

The game does ask players to confirm they are passengers if it senses too-fast motion. But game makers could build more safety restrictions into the game such as freezing it at driving speeds and keeping it inaccessible for a short while after a car comes to a stop to discourage stoplight play breaks, Ayers suggests.

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"Sixth sense" might be more than just a feeling

With the help of two young patients with a unique neurological disorder, an initial study by scientists at the National Institutes of Health suggests that a gene called PIEZO2 controls specific aspects of human touch and proprioception, a "sixth sense" describing awareness of one's body in space.

"Our study highlights the critical importance of PIEZO2 and the senses it controls in our daily lives," said Carsten G. Bönnemann, M.D., senior investigator at the NIH's National Institute of Neurological Disorders and Stroke (NINDS) and a co-leader of the study published in the New England Journal of Medicine. "The results establish that PIEZO2 is a touch and proprioception gene in humans. Understanding its role in these senses may provide clues to a variety of neurological disorders."

Mutations in the gene caused the two patients to have movement and balance problems. The patients were also less sensitive to certain forms of touch. They could not feel vibrations from a buzzing tuning fork as well as the control subjects could. Nor could they tell the difference between one or two small ends of a caliper pressed firmly against their palms. Brain scans of one patient showed no response when the palm of her hand was brushed. Despite these differences, the patients' nervous systems appeared to be developing normally. They were able to feel pain, itch, and temperature normally; the nerves in their limbs conducted electricity rapidly; and their brains and cognitive abilities were similar to the control subjects of their age.

"What's remarkable about these patients is how much their nervous systems compensate for their lack of touch and body awareness," said Dr. Bönnemann. "It suggests the nervous system may have several alternate pathways that we can tap into when designing new therapies."

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Miscellaneous

In this new era of legalized marijuana, far too little research has been conducted on the effect of cannabis on the development of human embryos, say researchers at Georgetown University Medical Center who scoured medical literature on the topic and found what they say is worrisome animal research. Their study, in the journal BioMed Central (BMC) Pharmacology and Toxicology, suggests an urgent need for human epidemiological and basic research that examines the link between maternal cannabinoid use, either smoked or eaten in candy bars, and the health of newborns. We know from limited human studies that use of marijuana in early pregnancy is associated with many of the same risks as tobacco, including miscarriage, birth defects, developmental delays and learning disabilities, but animal research suggests the potential for many more developmental issues linked with the drug,” says the study’s senior investigator, G. Ian Gallicano, PhD, associate professor of biochemistry and molecular & cellular biology at Georgetown. Gallicano says one reason for limited research is that the classification of marijuana as a Schedule I drug creates challenges to conducting research. (BiomedCentral via NeuroscienceNews)

Researchers from the Instituto de Medicina Molecular (iMM) in Lisboa, Portugal found that caffeine can counteract age-related cognitive deficits—at least in rats. Together with their colleagues they showed that the abnormal expression of the adenosine A2A receptor induces an aging-like profile, which includes memory loss and an increase in stress hormones such as cortisol. (Nature Scientific Reports via NeuroscienceNews)


The Allen Institute for Brain Science has published the highest resolution atlas of the human brain to date in a stand-alone issue of the Journal of Comparative Neurology. To create this modern atlas, the team at the Allen Institute partnered with Bruce Fischl, Ph.D. at Massachusetts General Hospital to perform magnetic resonance and diffusion tensor imaging on an intact brain before it was cut into slabs and serially sectioned to allow histological staining of individual sections. This imaging on the same brain created opportunities for linking fine molecular and cellular studies of the brain in health and disease with non-invasive neuroimaging studies. (Allen Institute)

A study at MIT suggests that ventral CA1 neurons in the hippocampus of the mouse store "social memories" that help shape the mice's behavior toward each other. The researchers also showed that they can suppress or stimulate these memories by using optogenetics to manipulate the cells that carry these memory traces, or engrams. The MIT researchers are now investigating a possible link between social memory and autism. (via NeuroscienceNews)

Researchers around the globe united against a workshop organized by US animal rights organization PETA, which was orchestrated as a protest against the use of primates in research. Over twenty organisations, including Speaking of Research, the Society for Neuroscience (SFN), and the American Psychological Association (APA) signed a public letter arguing for the necessity of animal models in neuroscience. "The biological similarities between humans and other primates means that they are sometimes the only effective model for complex neurodegenerative diseases such as Parkinson’s. More than ten million people suffer from Parkinson’s worldwide, and a recent study estimated that one in three people born in 2015 will develop dementia in their lifetime. Primate research offers treatments, and hope for future treatments, to patients and their families." (via speakingofresearch.com)

A new study from Concordia University suggests that estrogen and progesterone levels can affect memory and problem solving in women. Rather than impairing memory in general, these hormones may instead cause the brain to favor one memory system or strategy over another, depending on where the women are in their menstrual cycle. As a result, women women who were ovulating performed better on verbal memory tasks, and women tested in their pre-menstrual phase were better at solving spatial navigation tasks. (via NeuroscienceNews)