Tuesday, October 12, 2010

Estrogen, Hearing and More

SMI32-stained pyramidal neurons in cerebral co...Image via WikipediaHave you ever thought that you weren't as sharp as you used to be?  Are you not hearing as well as you used to?  Many women find this dip at midlife.  Researchers have found a link between Estrogen, Hearing and possibly Sensory Integration.

“We’ve discovered estrogen doing something totally unexpected,” says Raphael Pinaud, assistant professor of brain and cognitive sciences at the University of Rochester and lead author of the study. “We show that estrogen plays a central role in how the brain extracts and interprets auditory information. It does this on a scale of milliseconds in neurons, as opposed to days, months, or even years in which estrogen is more commonly known to affect an organism.”

Previous studies have hinted at a connection between estrogen and hearing in women who have low estrogen, such as often occurs after menopause, says Pinaud. No one understood, however, that estrogen was playing such a direct role in determining auditory functions in the brain, he says. “Now it is clear that estrogen is a key molecule carrying brain signals, and that the right balance of hormone levels in men and women is important for reasons beyond its role as a sex hormone.”

Pinaud, along with Lisa Tremere, a research assistant professor of brain and cognitive sciences, and Jin Jeong, a postdoctoral fellow in Pinaud’s laboratory, demonstrated that increasing estrogen levels in brain regions that process auditory information caused heightened sensitivity of sound-processing neurons, which encoded more complex and subtle features of the sound stimulus. Perhaps more surprising, says Pinaud, is that by blocking either the actions of estrogen directly, or preventing brain cells from producing estrogen within auditory centers, the signaling that is necessary for the brain to process sounds essentially shuts down. Pinaud’s team also shows that estrogen is required to activate genes that instruct the brain to lay down memories of those sounds.
“It turns out that estrogen plays a dual role,” says Pinaud. “It modulates the gain of auditory neurons instantaneously, and it initiates cellular processes that activate genes that are involved in learning and memory formation.”

Pinaud wants to look at the effect of estrogen in a much larger sense of how estrogen impacts sensory integration with other senses than just hearing.

However, estrogen is not the bee-all and end all towards improved cognition.   There is another study on estrogen and   thinking abilities.

One recent study of women in surgical menopause - when the uterus and ovaries are removed - suggested that estrogen might provide a memory benefit, but that testosterone canceled out some of that benefit when women took both hormones (see Reuters Health story of July 2, 2010: Testosterone may not help memory after menopause).

"Since many women during the time of menopausal transition complain about cognitive impairment it has been suggested that estrogen may have a beneficial effect on memory and cognitive abilities," while "testosterone is suggested to improve spatial ability but impair verbal memory," Dr. Angelica Linden Hirschberg, one of the current study's authors from the Karolinska Institutet in Stockholm, Sweden, told Reuters Health by email.

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