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HU researchers: Brain locates sound automatically
Judy Siegel-Itzkovich
10/06/2007
Findings settle controversy in earlier studies that failed to establish auditory region as responsible for perception of auditory space.
While the regions of the brain that enable us to see have been intensively mapped, many areas that make hearing possible remain uncharted. Now, researchers at The Hebrew University of Jerusalem and elsewhere have identified a region responsible for a key auditory process - the perception of "sound space" or the ability to locate sounds even when the listener isn't concentrating on them. The findings settle a controversy in earlier studies that failed to establish the auditory region, called the planum temporale, as responsible for perception of auditory space. The researchers, led by Dr. Leon Deouell of the HU's psychology department and the university's Interdisciplinary Center for Neural Computation, along with colleagues from the University of California at Berkeley and the Weizmann Institute of Science, published their findings in a recent issue of Neuron. Working with Deouell on the project were Aaron Heller of the University of California, Berkeley; Prof. Rafael Malach of the Weizmann and Professors Mark D'Esposito and Robert Knight of UC. Studies by other researchers had shown that the planum temporale is activated when people are asked to perform tasks in which they locate sounds in space. However, many researchers believed the region was responsible only for intentional processing of such information. Previous research done by Deouell and others has shown that some patients with brain damage may be impaired in this function. Understanding how the normal brain machinery for this function is organized may help us understand why it breaks down, and eventually how to mend it. In their work, Deouell and colleagues used an improved experimental design that enabled them to more sensitively determine the brain's auditory spatial location center. For example, they presented their subjects with sounds against a background of silence, used headphones that more accurately reproduced sound location, and used noise with a rich spectrum, which has been shown to be more readily locatable in space. They also used sounds recorded from microphones placed in each subject's ears and then played the same sounds back, thus tailoring the sounds to the subjects' head. In their experiments, they presented bursts of noise to the volunteers wearing the headphones while the subjects' brains were scanned by functional magnetic resonance imaging. In this widely used brain-scanning technique, harmless magnetic fields and radiowaves are used to image blood flow, which reflects brain activity in those locations. The subjects were instructed to ignore the sounds, and to divert their attention they either watched a movie with the sound turned off or were given a simple button-pushing task. When the position of the noise bursts was varied in space, the researchers found that the planum temporale in the subjects' brain was indeed activated. In addition, the greater the number of distinct sound locations subjects heard during test runs, the greater the activity in the planum temporale. The researchers concluded that their experiments "suggest that neurons in this region represent, in a non-intentional or pre-attentive fashion, the location of sound sources in the environment." TEACHING CHINA ABOUT HEALTH Two Israeli physicians from Barzilai Medical Center in Ashkelon and Ben-Gurion University in Beersheba have been lecturing in China on public health and Israel's preparedness for health threats such as bioterror and bird flu, and the decision-making process in coping with them. Dr. Michael Gedalevitz, the Ashkelon district health officer at Barzilai in Ashkelon, and Dr. Itamar Groto of BGU were sent by the Foreign Ministry's Center for International Cooperation (Mashav) to Shanghai and Wu Han. The courses, which were delivered in English with translation into Chinese, were widely attended, with many questions presented. Wu Han has eight million residents, and is a two-hour flight from Shanghai. The two physicians also visited a number of hospitals, community clinics and a medical center that integrates traditional Chinese medicine with conventional medicine. The doctors were impressed by the Chinese people's intense desire to develop Western medicine alongside traditional practices, and noted that the pace of development in China is astounding, with most of the larger cities being already completely Western and modern. Preparations for the 2008 Olympic Games in China are also an engine of development, they said. TWILIGHT ZONE CALLING Do you suffer from "ringziety"? This is not an unmarried woman's worry about finding a husband. It is hearing your cellphone ring or feeling it vibrate when no one has called. A new study has found that two-thirds of cellphone users have experienced this phenomenon. The more frequently a person uses their phone, the more often they report hearing a phantom ring, the foreign study found. These 67 percent of participants had higher monthly charges, sent more text messages and showed higher levels of impulsivity. They were also younger. The study also shows that some people rely on their mobile phone to maintain social connectedness. Those who prefer to use their phones for text messaging rather than talking display higher levels of loneliness, social anxiety and problem phone use.
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