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Nobel goes for finding brain’s ‘GPS’

The award covered research on how the brain keeps track of where we are by mapping our place within our environment

The science behind it all

A brain region known as the hippocampus is central to memory. In 1971, O’Keefe found that certain cells in a rat’s brain become active only when the animal is in a particular spot. These place cells allow an animal to form an internal map of its surroundings. O’Keefe used implanted electrodes to record the behavior of these neurons (nerve cells) as the rats moved freely about an area.

Decades later, the Mosers discovered grid cells in a nearby brain area. It’s called the entorhinal cortex. Its grid cells fired off signals when a rat passed through certain locations spaced at regular intervals.

These grid cells become active as an animal moves within its in the environment, pacing off the distances. The turned-on cells fire, mapping out a pattern that resembles a Chinese checkers board or the hexagonal cells of a honeycomb.

Other cells take note of borders and the position of the animal’s head. Together with grid cells, these others send messages to place cells in the hippocampus, the Mosers found. The resulting elaborate network of neurons allows an animal to know where it is in the world.With implanted electrodes, scientists uncovered place cells in the brains of people in 2003 and grid cells in 2013.But understanding how the brain navigates doesn’t stop at navigation. Getting a sense of where the body is in space seems an important step for developing babies, says Michael Kahana. A neuroscientist, he too works at the University of Pennsylvania. The hippocampus and the entorhinal cortex have important roles in memory. People build many memories on a scaffold of space, he says. One example: If someone eats a superb meal out at a restaurant, she will often, for instance, recall exactly which table she sat at.

These same brain regions are some of the first affected by Alzheimer’s disease. In the early stages of brain degeneration in this disorder, the ability to figure out how to get somewhere can slip away. That may be due to a loss of these navigational cells.

Interactive map tracks obesity in the United States

Mississippi, West Virginia top list of fattest states

While a rise in obesity is evident in all states, the graphics make clear that some regions have more work cut out for them. West Virginia and Mississippi fare the worst, with obesity prevalence now at 35.1 percent; Colorado gets a gold star for coming in at 21.3 percent. Switching to maps from past years reveals that the weightiest states have jostled for the dubious honor of being at or near the top.

Urine of tiny migrating marine animals affects ocean chemistry

University of Washington

Thee largest migration on the planet is the movement of small animals from the surface of the open ocean, where they feed on plants under cover of darkness, to the sunless depths where they hide from predators during the day.

University of Washington researchers have found that this regular migration helps shape our oceans. During the daylight hours below the surface the animals release ammonia, the equivalent of our urine, that turns out to play a significant role in marine chemistry, particularly in low-oxygen zones. Results are published online this week in the Proceedings of the National Academy of Sciences.

"I’m very fascinated by these massive migrations," said lead author Daniele Bianchi, a postdoctoral researcher in the UW School of Oceanography. "To me, it’s exciting to think about the effects of animal behavior on a large scale in the ocean."

One might not think that peeing into the vastness of the oceans could have an effect. But the animals — which include tiny zooplankton, crustaceans such as krill, and fish such as lanternfish up to a few inches long — compensate for their small size with huge abundance throughout the world’s oceans.

After a nighttime feast near the surface, these small creatures take a couple of hours to swim about 650 to 2,000 feet (200 to 600 meters) deep. Solid waste falls as pellets. The liquid waste is emitted more gradually.

In earlier work, Bianchi made the surprising finding that the animals spend most of their day in low-oxygen water. Marine bacteria consume oxygen as they decompose sinking dead material, creating low-oxygen zones a few hundred feet below the surface.

"The animals really seem to stop in low-oxygen regions, which is sort of puzzling," Bianchi said. Some speculated these zones might protect them from larger predators.

The earlier study also showed that animals actually contribute to these low-oxygen zones by using the little remaining oxygen to breathe.

Researchers next wondered about their other bodily functions.

For the new study, authors mined data from underwater sonar surveys to calculate how many animals are migrating to which depths, and where. Next they gauged the combined effect of their daytime digestion.

Results show that in certain parts of the ocean, ammonia released from animals drives a big part of the oxygen-free conversion of ammonium and other molecules to nitrogen gas, a key chemical transition.


Fish moving poleward at rate of 26 kilometres per decade

University of Faculty of Science British Columbia

Large numbers of fish will disappear from the tropics by 2050, finds a new University of Britsh Columbia study that examined the impact of climate change on fish stocks. The study identified ocean hotspots for local fish extinction but also found that changing temperatures will drive more fish into the Arctic and Antarctic waters.

Using the same climate change scenarios as the Intergovernmental Panel on Climate Change, researchers projected a large-scale shift of marine fish and invertebrates. In the worst-case scenario, where the Earth’s oceans warm by three degrees Celsius by 2100, fish could move away from their current habitats at a rate of 26 kilometres per decade. Under the best-case scenario, where the Earth warms by one degree Celsius, fish would move 15 kilometres every decade. This is consistent with changes in the last few decades.

“The tropics will be the overall losers,” says William Cheung, associate professor at the UBC Fisheries Centre and co-author of this study, published today in ICES Journal of Marine Science.  “This area has a high dependence on fish for food, diet and nutrition. We’ll see a loss of fish populations that are important to the fisheries and communities in these regions.”

Cheung and his colleague used modeling to predict how 802 commercially important species of fish and invertebrates react to warming water temperatures, other changing ocean properties, and new habitats opening up at the poles.

“As fish move to cooler waters, this generates new opportunities for fisheries in the Arctic,” says Miranda Jones, a UBC Nereus Fellow and lead author of this study. “On the other hand it means it could disrupt the species that live there now and increase competition for resources.”

Image: Caribbean islands (stock image). “The tropics will be the overall losers,” says William Cheung, associate professor at the UBC Fisheries Centre and co-author of this study. “This area has a high dependence on fish for food, diet and nutrition. We’ll see a loss of fish populations that are important to the fisheries and communities in these regions.”
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