Newswise — Along with left- or right-handedness, the hemisphere of the brain where language capacity resides is likely predetermined. Researchers have now shown that with age, language capacity in the brain becomes more evenly distributed between hemispheres. These study outcomes may offer promising therapeutic implications for adults who have experienced an injury, illness or other trauma to the brain. Details of this study will be presented at the American Academy of Neurology 56th Annual Meeting in San Francisco, Calif., April 24 — May 1, 2004.
From childhood until about age 25, language capacity in right-handers grows stronger in the left hemisphere of the brain. This phenomenon is usually converse to a person's "handedness" , where a right-handed person holds language in the left hemisphere, and vice versa. Using functional magnetic resonance imaging (fMRI) researchers have now shown that after about age 25, language capacity "evens out" somewhat, with older adults using more of both hemispheres relative to language skills.
"We are most interested in why this occurs, and the age at which the hemispheric language dominance begins to decrease," notes study author Jerzy P. Szaflarski, MD, PhD, of the University of Cincinnati Medical Center in Ohio.
Szaflarski and colleagues used fMRI to study the brain activity of 155 healthy right-handed subjects (103 aged five to 17, and 52 aged 18 to 67) while they performed language tasks. "We observed changes in language lateralization with age that followed a progressive curve," says Szaflarski. He concludes, "The increase in hemisphere dominance as children age is probably related to improving linguistic skills, maturation of the central nervous system, and the 'pruning' of synaptic connections; the decrease among older subjects perhaps reflects compensation for age-related loss of functional capacity."
This study was supported by the National Institutes of Health and the Neuroscience Institute of Cincinnati.
The American Academy of Neurology, an association of more than 18,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as stroke, Alzheimer's disease, epilepsy, Parkinson's disease, autism and multiple sclerosis.
For more information about the American Academy of Neurology, visit its website at http://www.aan.com/press/.
Editor's Notes: Dr. Szaflarski will present this research during a scientific session at the 56th Annual Meeting at 2:00 p.m. PT (5:00 p.m. ET) on Tuesday, April 27 in Room 310 of the Moscone Convention Center.