A new study published in the Journal of Neuroscience suggests that problems interpreting speech sounds may be a diagnostic marker for early dementia. The study, which was conducted by researchers at Toronto's Baycrest Centre for Geriatric Care and the University of Memphis, used EEG measurement in older adults to show that abnormal functioning in regions of the brain that process speech predicted mild cognitive impairment (MCI) with over 80 percent accuracy. Since MCI can be an early sign of developing dementia, testing for early communication problems may allow for doctors to diagnose potential dementia much earlier than is currently possible.
While brain regions such as the brainstem and auditory cortex are not usually considered to be strongly affected by Alzheimer's disease and other dementias, the new study shows that the brainstems of vulnerable older adults show abnormally large activity within seven to ten milliseconds after speech sound first hit the ear. This was tested by measuring brain activity while research subjects were watching a video as well as identifying vowel sounds. Statistical analysis was then used to determine how changes to the brain can predict MCI.
“When we hear a sound, the normal aging brain keeps the sound in check during processing, but those with MCI have lost this inhibition and it was as if the flood gates were open since their neural response to the same sounds were over-exaggerated,” says Dr. Gavin Bidelman, first author on the study, a former RRI post-doctoral fellow and assistant professor at the University of Memphis. “This functional biomarker could help identify people who should be monitored more closely for their risk of developing dementia.”
“This opens a new door in identifying biological markers for dementia since we might consider using the brain’s processing of speech sounds as a new way to detect the disease earlier,” says Dr. Claude Alain, the study’s senior author and senior scientist at Baycrest’s Rotman Research Institute (RRI) and professor at the University of Toronto’s psychology department. “Losing the ability to communicate is devastating and this finding could lead to the development of targeted treatments or interventions to maintain this capability and slow progression of the disease.”
Even for adults who score below the normal cutoff score for dementia screening tests, potential communication problems can alert doctors that certain patients need to be monitored more frequently. Researchers also hope to develop a portable test that can measure different senses quickly and inexpensively. “MCI is known to cause changes in different senses, such as vision or touch,” says Dr. Alain. “If we could incorporate these changes into a wireless EEG test, we could combine all this information and develop a better biomarker. One day, doctors could administer a short, 10-minute assessment and instantly provide results.”
More research is still needed measuring communication problems in patients with dementia or who convert early from MCI to full-blown dementia. An early test for dementia risk can be especially valuable giving the rising number of Baby Boomers who are entering into their senior years.