DALLAS, TX--Mothers who drink alcohol risk harming their baby's development. What is not known is how much, if any, alcohol is acceptable during pregnancy. Also not known, relative to brain development, is exactly how toxic alcohol may be at different stages of the pregnancy. Scientists may be one step closer to understanding how alcohol hampers brain development of exposed fetuses during the third trimester. "Alcohol is a 'dirty drug' as it affects a variety of systems in the brain," said James R. West, Professor of Anatomy and Neuroscience at the Texas A&M University Health Science Center. "It's important to understand that alcohol damages the developing brain in a number of ways," he said, noting that alcohol does different things at different times in different parts of the brain. During the third trimester, for example, alcohol kills some kinds of brain cells, but earlier in development, alcohol interferes with cell division. Alcohol's itinerant nature makes it a challenge to track whereas a drug like cocaine, said West, is much easier to study because it specifically affects the absorption of a neurotransmitter called dopamine. Researchers discovered that high levels of alcohol during late fetal development kill an important group of neurons called Purkinje cells, which act to filter and synthesize information leaving the cerebellum for other brain regions.