Estrogen helps form memories in mice

AGING
Menopausal women often complain of memory problems. Since estrogen levels plummet following menopause, one theory holds that estrogen normally helps with memory formation. Mice injected with estrogen, for example, perform better at memory-related tasks, like navigating through a maze or recognizing objects. But so far, its been unclear how estrogen acts chemically in the brain. Now, research from the Department of Psychology at Yale University provides the first hard evidence suggesting that estrogen helps to chemically fine-tune the molecules in the brain responsible for generating a memory. Researchers found that mice that received injections of estrogen in the hippocampus, one of the memory centers of the brain, were better at recall tasks. The injected mice also had changes in a certain molecule in the brain, called ERK, that is associated with memory formation. "Clinically, we might be able to develop drugs that target ERK to help menopausal women with memory loss, without having to risk the side effects of estrogen replacement," said principal investigator Karyn Frick. Estrogen-replacement therapy has come into question because of its association with increased cardiovascular and breast cancer risk. BOTTOM LINE: Estrogen has been shown to have a direct chemical effect on the signaling molecules implicated in memory formation in the brain. CAUTIONS: The experiments were done in mice, not in humans. WHAT'S NEXT: The mice used in these experiments were young - so researchers plan on repeating the studies in aging female mice to more accurately represent the menopausal population. WHERE TO FIND IT: The Journal of Neuroscience, Aug. 27 SUSHRUT JANGI

NEUROSCIENCE

In blind people, the brain's visual cortex processes touch and sound stimuli, but how this happens is not clear. Recently, a group of researchers led by Dr. Alvaro Pascual-Leone of Harvard Medical School conducted a study that helps explain the mechanism by which tactile abilities are enhanced in a blind person, and they found that the brain is surprisingly flexible. The researchers did brain scans of 47 participants, half of whom were then blindfolded 24 hours a day for the next five days. All the participants then took a test, blindfolded, to observe their tactile abilities. The group that had been blindfolded for five days was better at learning Braille, their ability to process touch was enhanced, and brain scans showed that their visual cortices were activated by touch. Further, when the visual cortex was blocked using a method called transcranial magnetic stimulation, the improvement in their tactile abilities was lost. A day after the blindfolds were removed and normal vision restored, the enhancement in tactile ability was lost and the visual cortex began responding, once again, to visual stimuli and not touch.

BOTTOM LINE: "The brain is far more plastic than we previously believed," said Pascual-Leone. "Understanding these rapid changes in the brain can help devise strategies for treating blindness."

CAUTIONS: The brain "plasticity" observed in blindfolded participants may not be the only change taking place in blind people to account for their enhanced tactile abilities.

WHAT'S NEXT: The researchers want to find out how blindness affects the visual cortex's ability to process sound and memory, and the mechanism of suppression and unmasking of these abilities.

WHERE TO FIND IT: Public Library of Science ONE online, Aug. 27

SENA DESAI GOPAL