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Why people lose hearing as they age

Researchers from Johns Hopkins and the National Institute on Aging have found that as the brain becomes smaller with age, the shrinkage seems to be fast-tracked in older adults with hearing loss.

The findings add to a growing list of health consequences associated with hearing loss, including increased risk of dementia, falls, hospitalizations, and diminished physical and mental health overall. For the study, Frank Lin, MD, PhD, and his colleagues used information from the ongoing Baltimore Longitudinal Study of Aging to compare brain changes over time between adults with normal hearing and adults with impaired hearing.

Previous research from other studies had linked hearing loss with marked differences in brain structure compared to those with normal hearing, both in humans and animals.

As part of the Baltimore Longitudinal Study of Aging, 126 participants underwent yearly magnetic resonance imaging (MRI) to track brain changes for up to 10 years. Each also had complete physicals at the time of the first MRI in 1994, including hearing tests. At the starting point, 75 had normal hearing, and 51 had impaired hearing, with at least a 25-decibel loss.

Analysing their MRIs over the following years, Lin and his colleagues, reported that those participants whose hearing was already impaired at the start of the sub-study had accelerated rates of brain atrophy compared to those with normal hearing.
Overall, the scientists report, those with impaired hearing lost more than an additional cubic centimeter of brain tissue each year compared with those with normal hearing. Those with impaired hearing also had significantly more shrinkage in particular regions, including the superior, middle and inferior temporal gyri, brain structures responsible for processing sound and speech.

Too much oxytocin can make healthy people oversensitive

Researchers at Concordia’s Centre for Research in Human Development have shown that too much oxytocin or “love hormone” in healthy young adults can actually result in oversensitivity to the emotions of others.

With the help of psychology professor Mark Ellenbogen, PhD candidates Christopher Cardoso and Anne-Marie Linnen recruited 82 healthy young adults who showed no signs of schizophrenia, autism or related disorders. Half of the participants were given measured doses of oxytocin, while the rest were offered a placebo.

The participants then completed an emotion identification accuracy test in which they compared different facial expressions showing various emotional states. As expected, the test subjects who had taken oxytocin saw greater emotional intensity in the faces they were rating.

“Many psychologists initially thought that oxytocin could be an easy fix in overcoming these worries. Our study proves that the hormone ramps up innate social reasoning skills, resulting in an emotional oversensitivity that can be detrimental in those who don’t have any serious social deficiencies,” Cardoso, the study’s lead author, said.
Ultimately, however, oxytocin does have the potential to help people with diagnosed disorders like autism to overcome social deficits.

Baby sense prevails in adults on number counting

Even education does not completely wipe out innate number sense, common in children and uneducated adults, a study has found.

Educated adults generally understand numbers ‘linearly’ based on the familiar number line from 0 to infinity.  On the other hand, children and uneducated adults understand numbers ‘logarithmically’ - in terms of what percentage one number is of another. Now a team of researchers from France and Israel have discovered that educated adults continue to retain traces of their childhood, or innate number sense.

“We were surprised when we saw that people never completely stop thinking about numbers as they did when they were children,” said Dror Dotan, a doctoral student at Tel Aviv University in Israel.

“The innate human number sense has an impact, even on thinking about double-digit numbers,” he said. The research showed that the innate number sense is capable of handling the complexity of two-digit numbers as well.

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