(Press-News.org) Pilots are trained to guard against vertigo: a sudden loss of the sense of vertical direction that renders them unable to tell "up" from "down" and sometimes even leads to crashes. Coming up out of a subway station can produce similar confusion: For a few moments, you are unsure which way to go, until regaining your sense of direction. In both cases, the disorientation is thought to be caused by a temporary malfunction of a brain circuit that operates as a three-dimensional (3D) compass.
Weizmann Institute scientists have now for the first time demonstrated the existence of such a 3D compass in the mammalian brain. The study was performed by graduate student Arseny Finkelstein in the laboratory of Prof. Nachum Ulanovsky of the Neurobiology Department, together with Dr. Dori Derdikman, Dr. Alon Rubin, Jakob N. Foerster and Dr. Liora Las. As reported in Nature on December 3, the researchers have shown that the brains of bats contain neurons that sense which way the bat's head is pointed and could therefore support the animal's navigation in 3D space.
Navigation relies on spatial memory: past experience of different locations. This memory is formed primarily in a deep-seated brain structure called the hippocampal formation. In mammals, three types of brain cells, located in different areas of the hippocampal formation, form key components of the navigation system: "place" and "grid" cells, which work like a GPS, allowing animals to keep track of their position; and "head-direction" cells, which respond whenever the animal's head points in a specific direction, acting like a compass. Much research has been conducted on place and grid cells, whose discoverers were awarded the 2014 Nobel Prize in Physiology or Medicine, but until recently, head-direction cells have been studied only in two-dimensional (2D) settings, in rats, and very little was known about the encoding of 3D head direction in the brain.
To study the functioning of head-direction cells in three dimensions, Weizmann Institute scientists developed a tracking apparatus that allowed them to video-monitor all the three angles of head rotation - in flight terminology, yaw, pitch and roll - and to observe the movements of freely-behaving Egyptian fruit bats. At the same time, the bats' neuronal activity was monitored via implanted microelectrodes. Recordings made with the help of these microelectrodes revealed that in a specific sub-region of the hippocampal formation, neurons are tuned to a particular 3D angle of the head: Certain neurons became activated only when the animal's head was pointed at that 3D angle.
The study also revealed for the first time how the brain computes a sense of the vertical direction, integrating it with the horizontal. It turns out that in the neural compass, these directions are computed separately, at different levels of complexity: The scientists found that head-direction cells in one region of the hippocampal formation became activated in response to the bat's orientation relative to the horizontal surface, that is, facilitating the animal's orientation in two dimensions, whereas cells responding to the vertical component of the bat's movement - that is, a 3D orientation - were located in another region. The researchers believe that the 2D head-direction cells could serve for locomotion along surfaces, as happens in humans when driving a car, whereas the 3D cells could be important for complex maneuvers in space, such as climbing tree branches or, in the case of humans, moving through multi-story buildings or piloting an aircraft.
By further experimenting on inverted bats, those hanging head-down, the scientists were able to clarify how exactly the head-direction signals are computed in the bat brain. It turned out that these computations are performed in a way that can be described by an exceptionally efficient system of mathematical coordinates (the technical term is "toroidal"). Thanks to this computational approach used by their brain, the bats can efficiently orient themselves in space whether they are moving head up or down.
This research supports the idea that head-direction cells in the hippocampal formation serve as a 3D neural compass. Though the study was conducted in bats, the scientists believe their findings should also apply to non-flying mammals, including squirrels and monkeys that jump between tree branches, as well as humans. "Now this blueprint can be applied to other species that experience 3D in a more limited sense," Prof. May-Britt Moser, one of the 2014 Nobel laureates, writes in the "News and Views" opinion piece that accompanies the Weizmann study in Nature.
INFORMATION:
The research of Prof. Ulanovsky is supported by the Rowland & Sylvia Schaefer Family Foundation; Mike and Valeria Rosenbloom through the Mike Rosenbloom Foundation; the Irving B. Harris Foundation; Mr. and Mrs. Steven Harowitz, San Francisco, CA; and the European Research Council.
The Weizmann Institute of Science in Rehovot, Israel, is one of the world's top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.
Weizmann Institute news releases are posted on the World Wide Web at http://wis-wander.weizmann.ac.il/, and are also available at http://www.eurekalert.org/
Extensive areas of the world's deltas -- which accommodate major cities such as Shanghai, Dhaka and Bangkok -- will be drowned in the next century by rising sea levels, according to a Comment piece in this week's Nature. In the article, Dr. Liviu Giosan, a geologist with the Woods Hole Oceanographic Institution (WHOI), and colleagues call for maintenance efforts to be started now to avert the loss of vast expanses of coastline, and the consequent losses of ecological services, economic and social crises, and large-scale migrations.
Problems start upstream: deltas are built ...
HOUSTON - (Dec. 3, 2014) - A novel mechanism - similar to how normal tissue stem cells respond to wounding - might explain why bladder cancer stem cells actively contribute to chemo-resistance after multiple cycles of chemotherapy drug treatment. Targeting this "wound response" of cancer stem cells can potentially provide a novel approach for therapeutic invention, said researchers from the National Cancer Institute-designated Dan L. Duncan Cancer Center at Baylor College of Medicine.
The results of their study appear online in the journal Nature today.
"Treatment ...
LA JOLLA, CA--December 3, 2014--A team led by biologists at The Scripps Research Institute (TSRI) has solved a long-standing mystery in neuroscience by identifying the "mechanoreceptor" protein that mediates the sense of touch in mammals.
Mice that lack the Piezo2 ion-channel protein in their skin cells and nerve endings lose nearly all their sensitivity to ordinary light touch, but retain a mostly normal sensitivity to painful mechanical stimuli.
"We can say with certainty that Piezo2 is the principal touch sensor in mammals," said Ardem Patapoutian, professor at TSRI ...
Researchers from the African Genome Variation Project (AGVP) have published the first attempt to comprehensively characterise genetic diversity across Sub-Saharan Africa. The study of the world's most genetically diverse region will provide an invaluable resource for medical researchers and provides insights into population movements over thousands of years of African history. These findings appear in the journal Nature.
"Although many studies have focused on studying genetic risk factors for disease in European populations, this is an understudied area in Africa," says ...
ROSEMONT, Ill.--Compression fractures in the spine due to osteoporosis, a common condition causing progressive bone loss and increased fracture risk, are especially common in older women. A new study appearing in the December 3rd issue of the Journal of Bone & Joint Surgery (JBJS) found that patients who wore a brace as treatment for a spinal compression fracture had comparable outcomes in terms of pain, function and healing when compared to patients who did not wear a brace.
Nearly 700,000 men and women suffer from a spinal compression fracture each year. These fractures, ...
People who work around the clock could actually be setting themselves back, according to Virginia Tech biologists.
Researchers found that a protein responsible for regulating the body's sleep cycle, or circadian rhythm, also protects the body from developing sporadic forms of cancers.
"The protein, known as human period 2, has impaired function in the cell when environmental factors, including sleep cycle disruption, are altered," said Carla Finkielstein, an associate professor of biological sciences in the College of Science, Fralin Life Science Institute affiliate, ...
The more time you spend getting to and from work, the less likely you are to be satisfied with life, says a new Waterloo study.
Published in World Leisure Journal, the research reveals exactly why commuting is such a contentment killer--and surprisingly, traffic isn't the only reason to blame.
"We found that the longer it takes someone to get to work, the lower their satisfaction with life in general," says Margo Hilbrecht, a professor in Applied Health Sciences and the associate director of research for the Canadian Index of Wellbeing.
While commuting has long been ...
Is your inbox burning you out? Then take heart - research from the University of British Columbia suggests that easing up on email checking can help reduce psychological stress.
Some of the study's 124 adults -- including students, financial analysts medical professionals and others -- were instructed to limit checking email to three times daily for a week. Others were told to check email as often as they could (which turned out to be about the same number of times that they normally checked their email prior to the study).
These instructions were then reversed for ...
RIVERSIDE, Calif. - Geckos, found in places with warm climates, have fascinated people for hundreds of years. Scientists have been especially intrigued by these lizards, and have studied a variety of features such as the adhesive toe pads on the underside of gecko feet with which geckos attach to surfaces with remarkable strength.
One unanswered question that has captivated researchers is: Is the strength of this adhesion determined by the gecko or is it somehow intrinsic to the adhesive system? In other words, is this adhesion a result of the entire animal initiating ...
An efficient method to harvest low-grade waste heat as electricity may be possible using reversible ammonia batteries, according to Penn State engineers.
"The use of waste heat for power production would allow additional electricity generation without any added consumption of fossil fuels," said Bruce E. Logan, Evan Pugh Professor and Kappe Professor of Environmental Engineering. "Thermally regenerative batteries are a carbon-neutral way to store and convert waste heat into electricity with potentially lower cost than solid-state devices."
Low-grade waste heat is an ...
