Older adults may have difficulty understanding speech because of age-related changes in brain tissue, according to new research in the May 13 issue of The Journal of Neuroscience. The study shows that older adults with the most difficulty understanding spoken words had less brain tissue in a region important for speech recognition. The findings may help explain why hearing aids do not benefit all people with age-related hearing difficulties.
Although some hearing loss can be a normal part of aging, many older adults complain about difficulty understanding speech, especially in challenging listening conditions like crowded restaurants. Research has suggested that this decline in speech recognition is independent of hearing loss.
Harris and her colleagues found that structural differences in the brain's auditory cortex predicted performance on the task, even when they controlled for hearing loss. The older adults who had the most difficulty recognizing words also had the least brain volume in a region of auditory cortex called Heschl's gyrus/superior temporal gyrus. However, the relationship between the ability to identify words and the volume of auditory cortex was also present in younger adults.