Nicotine may cause the teenage brain to develop abnormally, resulting in changes to the structure of white matter -- the neural tissue through which signals are relayed, a study shows.

Teenagers who smoke, or whose mothers smoked during pregnancy, are also more likely to suffer from auditory attention deficits, meaning they find it harder to concentrate on what is being said when other things are happening at the same time, the study by U.S. researchers published Thursday in New Scientist said.

The American researchers reported in the latest issue of the science magazine that they used diffusion tensor imaging, which measures how water diffuses through brain tissue, to study the brains of 33 teenagers whose mothers had smoked during pregnancy. Twenty-five of the teens were daily smokers. The researchers also studied 34 teens whose mothers had not smoked, of whom 14 were daily smokers.

The researchers found that both prenatal and adolescent exposure to tobacco smoke were associated with changes in white matter in brain pathways that relay signals to the ear and the changes were greatest in teenagers who smoked, suggesting the brain is particularly vulnerable to the effects of nicotine during adolescence, when many neural pathways are maturing.

"The changes suggest the brain is particularly vulnerable to the effects of nicotine during adolescence," research leader Leslie Jacobsen of Yale University School of Medicine said.

Nicotine binds to receptors in the brain that regulate neural development. Inappropriate stimulation could cause abnormal connections to form, according to Jacobsen.

The researchers now hope to test whether the changes are reversible, by scanning the brains of teenagers who give up smoking.

 
"The findings are interesting because the key brain pathway affected by nicotine helps determine how we process auditory information when distracted by other tasks. The fact that smokers show changes in this pathway means they may be less able to hear what's being said," David McAlpine, director of the Ear Institute at University College London, commented.

(Xinhua News Agency January 4, 2008)