Author: Jordan Hall
Institution: Duke University
Date: November 2011
Ever had an annoying yet catchy song stuck in your head? Blame your right anterior temporal lobe. A study investigating the physical and cognitive changes to the brain resulting from different forms of dementia has pinpointed this thumb-shaped region of the brain as the location of well-known songs and melodies.
In August, Dr. Oliver Piguet and his research team from Neuroscience Research Australia in Sydney published the results of their study that investigated how and why people with dementia are unable to recognize famous melodies. Published online in the journal Brain, the study provides a unique window into the structure of memory, and a specific example of how deficits in this system affect our lives.
The researchers examined two specific forms of dementia: Alzheimer's disease and semantic dementia. Interestingly, patients with Alzheimer's can remember information when it is sung to them, despite their deficits in memory. Patients with semantic dementia are known to lose the meaning of sounds, objects, and people, and their memory of musical recognition has not been previously investigated: might they remember classic, timeless, commonplace melodies? The researchers sought to characterize these patients' musical memory.
"Every day, we are building a more detailed map of the human brain, [and] as our map improves, we will be better able to understand how we can repair the damage that occurs in dementia," explained Piguet.
Piguet recruited 47 volunteers to listen to 30 pairs of tunes. Fourteen of the volunteers had Alzheimer's, thirteen had semantic dementia, and twenty healthy participants served as controls. Each pair of melodies had one that is very well known (e.g. Jingle Bells, the Pink Panther theme, the Happy Birthday song) and another that was fabricated, played in the same key and tempo as its famous counterpart. The melodies were played in a random order, and after each one, the volunteers were asked whether it was famous.
Those with Alzheimer's and the healthy participants were able to correctly identify the famous melody about nine times out of ten. But the participants with semantic dementia could only identify the famous tunes with a success rate of around 60 percent.
MRI scans revealed that the right anterior temporal lobe was severely shrunken in most patients with semantic dementia. On average, those with more damage in this area were worse at identifying famous tunes. On the contrary, patients with Alzheimer's did not show significant damage to this brain region, possibly explaining why they were able to recognize music and identify the melodies.
"Different nerve cells in these particular brain regions may be more vulnerable to different proteins," said Piguet. He suspects that the right anterior temporal lobe is attacked in semantic dementia but not in Alzheimer's disease. The very different sets of proteins active in the two diseases may explain why musical memory of patients with Alzheimer's is preserved and is lost in those with semantic dementia.
Piguet advises that because this musical ability is preserved in patients with Alzheimer's, caregivers and family members should "use music as a means of communication and enjoyment." For those with Alzheimer's, the ability to retain a catchy phrase is certainly not annoying. It is a lifesaver.