Saturday, August 21, 2010

NEW STUDY EXAMINES THE BRAIN’S WIRING

0 comentarios

The brain has been mapped to the smallest fold for at least a century, but still no one knows how all the parts talk to each other.

A study in Proceedings of the National Academy of Sciences answers that question for a small area of the rat brain and in so doing takes a big step toward revealing the brain’s wiring.

The network of brain connections was thought too complex to describe, but molecular biology and computing methods have improved to the point that the National Institutes of Health have announced a $30 million plan to map the human “connectome.”

The study shows the power of a new method for tracing brain circuits.

USC College neuroscientists Richard H. Thompson and Larry W. Swanson used the method to trace circuits running through a “hedonic hot spot” related to food enjoyment.

The circuits showed up as patterns of circular loops, suggesting that at least in this part of the rat brain, the wiring diagram looks like a distributed network.

Neuroscientists are split between a traditional view that the brain is organized as a hierarchy, with most regions feeding into the “higher” centers of conscious thought, and a more recent model of the brain as a flat network similar to the Internet.

“We started in one place and looked at the connections. It led into a very complicated series of loops and circuits. It’s not an organizational chart. There’s no top and bottom to it,” said Swanson, a member of the National Academy of Sciences and the Milo Don and Lucille Appleman Professor of Biological Sciences at USC College.

The circuit tracing method allows the study of incoming and outgoing signals from any two brain centers. It was invented and refined by Thompson over eight years. Thompson is a research assistant professor of biological sciences at the College.

Most other tracing studies at present focus only on one signal, in one direction, at one location.

“[We] can look at up to four links in a circuit, in the same animal at the same time. That was our technical innovation,” Swanson said.

The Internet model would explain the brain’s ability to overcome much local damage, Swanson said.

“You can knock out almost any single part of the Internet and the rest of it works.”

Likewise, Swanson said, “There are usually alternate pathways through the nervous system. It’s very hard to say that any one part is absolutely essential.”

Swanson first argued for the distributed model of the brain in his acclaimed book Brain Architecture: Understanding the Basic Plan (Oxford University Press, 2003).

The PNAS study appears to support his view.

“There is an alternate model. It’s not proven, but let’s rethink the traditional way of regarding how the brain works,” he said.

“The part of the brain you think with, the cortex, is very important, but it’s certainly not the only part of the nervous system that determines our behavior.”

(Photo: USC)

University of Southern California

INSECTS SENSE DANGER ON MAMMALS' BREATH

0 comentarios
When plant-eating mammals such as goats chomp on a sprig of alfalfa, they could easily gobble up some extra protein in the form of insects that happen to get in their way. But a new report in the August 10th issue of Current Biology, a Cell Press publication, shows that plant-dwelling pea aphids have a strategy designed to help them avoid that dismal fate: The insects sense mammalian breath and simply drop to the ground.

"Tiny insects like aphids are not helpless when facing large animals that rapidly consume the plants they live on," said Moshe Inbar of the University of Haifa in Israel. "They reliably detect the danger and escape on time."

Inbar said he had always wondered about accidental predation of small plant-dwellers based on his observations of insects that don't really move around. "As soon as we started to work on this problem, we suspected that the aphids responded to our own breath," he said. (The researchers later used snorkels to keep their own breath from mucking up their experiments).

The researchers allowed a goat to feed on potted alfalfa plants infested with aphids. "Strikingly, 65 percent of the aphids in the colonies dropped to the ground right before they would have been eaten along with the plant," the researchers write.

That mass dropping might have been triggered by many cues: plant shaking, sudden shadowing, or the plant-eater's breath. While a quarter of the aphids dropped when plants were shaken, more than half fell to the ground in response to a lamb's breath, the researchers report.

Shadows had no effect on the aphids' dropping behavior. Ladybugs, an insect enemy of aphids, didn't inspire that kind of synchronous response either.

Further studies with an artificial breath apparatus allowed the researchers to test what it was about the breath that tipped the aphids off. It turned out it wasn't carbon dioxide or other known chemical ingredients found on mammalian breath. Only when the controlled airstream was both warm and humid did it lead to impressive dropping rates of 87 percent in a room with otherwise low humidity.

Inbar said that the aphids' "elegant solution" to the problem of incidental predation is likely practiced by other species as well.

"This remarkable response to mammalian-specific cues, in spite of the inherent cost of an aphid's dropping off the plant, points to the significance of mammalian herbivory to plant-dwelling insects," the researchers concluded. "We predict that this sort of escape behavior in response to mammalian breath may be found among other invertebrates that live on plants and face the same threat."

Cell Press

WHY SOME PEOPLE CAN SLEEP THROUGH ANYTHING

0 comentarios
Ever wonder why some people can sleep through just about anything, while others get startled awake at each and every bump in the night? A new report in the August 10th issue of Current Biology, a Cell Press publication, offers some insight: sound sleepers show a distinct pattern of spontaneous brain rhythms.

"We found that by measuring brain waves during sleep, we could learn a lot about how well a person's brain can block the negative effects of sounds; the more sleep spindles your brain produces, the more likely you'll stay asleep, even when confronted with noise," said Jeffrey Ellenbogen of Harvard Medical School.

During sleep, brain waves become slow and organized, Ellenbogen explained. Sleep spindles refer to brief bursts of faster-frequency waves. Those bursts of activity are generated by a portion of the brain called the thalamus, which serves as a way station for most types of sensory information (everything except smell).

"The thalamus is likely preventing sensory information from getting to areas of the brain that perceive and react to sound," Ellenbogen said. "And our data provide evidence that the sleep spindle is a marker of this blockade. More spindles means more stable sleep, even when confronted with noise."

Ellenbogen said he and his colleagues were surprised at the magnitude of the sleep spindle effect. They observed brain patterns of study participants as they slept in the lab for three nights. The first night was quiet and the second and third nights were noisy, as the researchers introduced a variety of sounds—a telephone ringing, people talking, hospital-based mechanical sounds, and so on. "The effect of sleep spindles was so pronounced that we could see it even after just a single night," he said.

The researchers say they hope to devise ways to enhance sleep spindles via behavioral techniques, drugs, or devices, but it's not yet clear how to do that.

Ellenbogen said such advances would be particularly welcome today, as "our sleeping environments have gotten increasingly complex and problematic, with all the beeps and boops of our 24/7 modern, crowded lives. And there are particular challenges in a hospital setting where some of the sounds are necessary (e.g., heart monitors need to send an alarm if there's a problem). Our goal is to find brain-based solutions that integrate a sleeping person into their modern environment, such that sleep is maintained even in the face of noises. This finding gets us one important step closer to realizing that goal."

Ellenbogen ultimately envisions a future in which we'll have access to multiple strategies, based on sound sleep science and technologies, to help keep us asleep when we want to sleep and awaken us when it's time to get up. "In the meantime," he said, "it still doesn't hurt to put up a sign that says 'Shhh!'"

Another piece of advice for those who really must go to sleep with the radio or TV on: use a timer. The researchers' evidence shows that such noises do disrupt sleep, whether the sleeping person realizes it or not.

Cell Press

Followers

Archive

 

Selected Science News. Copyright 2008 All Rights Reserved Revolution Two Church theme by Brian Gardner Converted into Blogger Template by Bloganol dot com