Saturday, March 20, 2010

SMELLING THE SCENERY IN STEREO

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Scientists of the Max Planck Institute for Chemical Ecology in Jena have investigated another navigational skill of desert ants. These ants are already well-known for their remarkable visual orientation: they use a sun compass along with a step counter and visible landmarks to locate their nest after foraging for food. After the research team from Jena recently discovered that these ants also use olfactory cues to pinpoint their nests, they conducted new experiments: they revealed that the animals can not only locate an odour source, but also use the distribution of different odours in the vicinity of their nests in a map-like manner. The scientists found that the ants need both their antennae for this odour-guided navigation: they smell the scenery in stereo.

The desert ant Cataglyphis fortis is an insect native to the inhospitable salt-pans of Tunisia. To pinpoint the nest – a tiny hole in the desert ground - after foraging for food, Cataglyphis combines several navigation systems: a sun compass, a path integrator (the ant literally counts its steps), and visual recognition of landmarks. Recently, Kathrin Steck, Bill Hansson and Markus Knaden, neuroethologists at the Max Planck Institute for Chemical Ecology in Jena, discovered that local odours also play an important role in the insect's orientation (Frontiers in Zoology, 2009, Vol. 6 No. 5): ants learn to associate a smell with their nest and distinguish this smell from others. But the researchers wanted to know if the insects are also able to recognize odour patterns that emerge, when several odour sources are located at different positions around the nest. And if so, they asked, do ants need both their antennae like stereo receivers just as we employ two eyes and two ears for spatial perception?

"We conducted two key experiments," says Kathrin Steck, PhD student at the institute. "First we marked four odour sources surrounding the nest entrance with the substances methyl salicylate, decanal, nonanal, and indole, and got the ants trained on them. If these four odour points were shifted away from the nest in the original arrangement, the ants repeatedly headed for the odours, even though the nest wasn't there anymore. If we rearranged the odour sources relative to each other, the ants were completely confused." Therefore the researchers assumed that ants do not "think" one-dimensionally – i.e. they do not associate the nest with only one smell – but multi-dimensionally, i.e., they relate an odour landscape to their nest. The odour landscape comprising the four substances was monitored with the help of a special measuring technique: the scientists used a specific photoionisation detector to determine the distribution of the odour substances in space and time.

Spatial perception can easily be acquired if two separate sensory organs are available, such as two eyes for visual orientation. In the case of the ants, this would be their two antennae. "With this assumption, the second key experiment seemed obvious: We tested ants that only had one antenna," Markus Knaden, the leader of the study, explains. In fact, ants with only one sensory device were unable to make use of the odour landscape for navigation.

Stereo smelling in animals is not new – rats and humans are thought to have this ability as well. This new study shows that ants smell in stereo, but not only that: "In our experiments we demonstrated that ants successfully use stereo smelling for navigation in the desert," says Bill Hansson, director at the institute.

(Photo: MPI for Chemical Ecology, Markus Knaden)

Max Planck Institute

MASSAGE EASES ANXIETY, BUT NO BETTER THAN SIMPLE RELAXATION DOES

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A new randomized trial shows that on average, three months after receiving a series of 10 massage sessions, patients had half the symptoms of anxiety. This improvement resembles that previously reported with psychotherapy, medications, or both. But the trial, published in the journal Depression and Anxiety, also found massage to be no more effective than simple relaxation in a room alone with soft, soothing music.

"We were surprised to find that the benefits of massage were no greater than those of the same number of sessions of 'thermotherapy' or listening to relaxing music," said Karen J. Sherman, PhD, MPH, a senior investigator at Group Health Research Institute. "This suggests that the benefits of massage may be due to a generalized relaxation response."

Massage therapy is among the most popular complementary and alternative medical (CAM) treatments for anxiety, she added. But this is the first rigorous trial to assess how effective massage is for patients with generalized anxiety disorder.

The trial randomly assigned 68 Group Health patients with generalized anxiety disorder to 10 one-hour sessions in pleasant, relaxing environments, each presided over by a licensed massage therapists who delivered either massage or one of two control treatments:

-Relaxation therapy: breathing deeply while lying down
-Thermotherapy: having arms and legs wrapped intermittently with heating pads and warm towels

All three treatments were provided while lying down on a massage table in a softly lighted room with quiet music. All participants received a handout on practicing deep breathing daily at home. Unlike the two control treatments, massage was specifically designed to enhance the function of the parasympathetic nervous system and relieve symptoms of anxiety including muscle tension.

Using a standard rating scale in interviews, the researchers asked the patients about the psychological and physical effects of their anxiety right after the 12-week treatment period ended and three months later, Dr. Sherman said.

All three of the groups reported that their symptoms of anxiety had decreased by about 40 percent by the end of treatment—and by about 50 percent three months later. In addition to the decline in anxiety, the patients also reported fewer symptoms of depression and less worry and disability. The research team detected no differences among the three groups; but the trial did not include a control group that got no treatment at all.

"Treatment in a relaxing room is much less expensive than the other treatments (massage or thermotherapy), so it might be the most cost-effective option for people with generalized anxiety disorder who want to try a relaxation-oriented complementary medicine therapy," Dr. Sherman said.

Group Health Research Institute

EARTHQUAKE IN CHILE -- A COMPLICATED FRACTURE

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The extremely strong earthquake in Chile on 27 February this year was a complicated rupture process, as scientists from the GFZ German Research Centre for Geosciences found out. Quakes with such magnitude virtually penetrate the entire Earth's crust.

After closer analysis of the seismic waves radiated by this earthquake during the first 134 seconds after start of the rupture, the researchers came to the conclusion that only the region around the actual epicentre was active during the first minutes. In the second minute the active zone moved north towards Santiago. After that the region south of Concepción became active for a short time. This rupturing trend agrees well with the distribution of the aftershocks during the following three days, as observed by the GEOFON-measuring network of the GFZ up to 03.03.2010.

In the year 1960, the strongest earthquake measured at all to date, with a magnitude of M=9.5, had its origin at Valdivia, south of the region affected now. "The quake of 27 February connects directly to the rupture process of Valdivia", explains Professor Jochen Zschau, Director of the Section "Earthquake Risk and Early Warning" at the GFZ. "With this, one of the last two seismic gaps along the west coast of South America might now be closed. With the exception of one last section, found in North Chile, the entire earth crust before the west coast of South America has been ruptured within the last 150 years."

The underlying plate tectonic procedure is such that the Nazca-Plate as part of the Pacific Ocean Floor moves eastwards with approximately seventy millimetres per year, collides with South America and thereby pushes under the continent. The hereby developing earthquakes belong to the strongest world-wide. In the course of about one century, the Earth's ruptures completely in a number of strong quakes from Patagonia in the South to Panama in the North. Even Darwin reported, in his diary, of the strong earthquake in Concepción on 20 February 1835 and the resulting Tsunami.

In order to examine the aftershock activity in the now fractured seismic gap, scientists from the GFZ are travelling to Chile on March 13, 2010 where, together with the Chilean Seismological Service, they will set-up a seismological-geodetic network in the area of Concepción-Santiago. Partners from Germany (IFM Geomar, Kiel; Free University of Berlin) and from abroad (Institut de Physique du Globe, Paris; University of Liverpool; United States Geological Survey; IRIS) are also taking part in this measuring campaign. The mission will last about three months. The results, one expects, will be able to provide an insight into the mechanisms of the fracture in the Earth's crust. This activity is financed on the German side by the GFZ.

Scientists from the GFZ have been examining the collision of the Nazca plate and the South American continent since 1994. As a result of numerous expeditions and measuring campaigns in this area this Potsdam Helmholtz Centre avails of the probably the most dense data record on such a subduction zone. "Within the framework of the DFG Priority Programme "Deformation processes in the Andes", and with the Geotechnology Project TIPTEQ we have just been able to collect a unique data record for the southern part of the Andes" says Professor Onno Oncken, Director of the Department Geodynamics and Geomaterials at the GFZ, and leader of these studies. The current quake puts us in the position to precisely compare the tectonics before and afterwards, a unique situation both internationally and in Earth science.

(Photo: © GFZ)

The Helmholtz Association

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