jueves, noviembre 09, 2006

Efecto del estres cronico sobre la atencion

Chronic stress affects attention by altering neuronal growth in the brain (ver completo)

Anxiety and depression can make a person feel as if he’s battling his own brain, complete with wounds and scars. Traumatic events ­ war, divorce, the death of a loved one ­ can trigger these disorders, and scientists are just beginning to clarify the biological connection. Now, working neuron by neuron, researchers have found that life experiences actually appear to change the length and complexity of individual brain cells. In a recent study published in The Journal of Neuroscience, Rockefeller University scientists show that chronic daily stress affected neurons in two different areas of the rat brain, showing for the first time a link between anxiety symptoms and the dynamic anatomy of the brain.

One of the characteristic manifestations of prolonged stress is decreased performance in tasks that require attention, including the ability to shift focus as well as to learn and unlearn information. Bruce McEwen, Rockefeller’s Alfred E. Mirsky Professor and head of the Harold and Margaret Milliken Hatch Laboratory of Neuroendocrinology, was interested in finding out how this translates to changes in the brain itself. So he and Conor Liston, a graduate student in McEwen’s lab, compared neuronal change in stressed and unstressed rats.

The researchers stressed out a dozen rats by keeping them in painless restraints for six hours a day. Then, after 21 days, they used a complex progression of trials to test how quickly the rats learned to make associations between different cues and the location of hidden food. First, Liston provided two different materials for the rats to dig in, such as sand and sawdust, and buried food consistently under only one. Next, he left the food in the same material but scented it with strong spices (like cumin or nutmeg) that were unrelated to the food’s location.

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