Chronic stress affects attention by altering neuronal growth(sic!) in the brain

Life experiences actually appear to change the length and complexity of individual brain cells.
Chronic daily stress affected neurons in two different areas of the rat 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.

Stressed rats need more time to catch on to a new pattern in an experimental task.
the researchers looked at neurons in two parts of the rats� brains � the medial prefrontal cortex (mPFC) and the orbital frontal cortex (OFC) � and saw a correlation. The prefrontal cortex is typically involved in working memory: paying attention to one thing at the expense of another, and shifting that attention from one focus to another. And sure enough, neurons in the stressed rats� mPFC were shorter and had less branching or �arborization� than those in the control rats. Prior experiments had shown that lesions in this area of the brain could cause this effect. �But it was remarkable that stress produced almost as large a deficit in attention-shifting tasks as lesions,� McEwen says.

The OFC, on the other hand, is involved more in what scientists call reward processing: modifying behavior to get the most reward possible from the surrounding environs. What McEwen and Liston found when they looked at OFC neurons surprised them: Rather than shrinking, neurons in the stressed rats� OFC were longer and more branched than those of the control rats !

Read more:
http://newswire.rockefeller.edu/index.php?page=engine&id=545