Sing-a-long… if you know the words

Many of us recognise ‘Waltzing Matilda’ as a favourite Australian song and also know the words to traditional special occasion songs such as ‘Happy Birthday’. But how and why do we memorise these popular melodies? Australian scientists may have discovered the answer.

Scientists from Neuroscience Research Australia at the University of New South Wales have pinpointed a region of the brain that is important for recognising well-known melodies, and to their surprise, it seems to be essential for recognising famous faces too.

The study, led by Professor John Hodges and Dr Sharpley Hsieh, compared 27 dementia patients with 20 healthy people. The results, reported this week in the journal Brain, showed dementia patients fell into two categories: half had Alzheimer’s disease and half had a rare form of dementia called Semantic Dementia (SD); which is when patients lose their ability to understand the meaning of words, objects and sounds.

MRI scans found the brains of patients with SD showed significant shrinking and damage (atrophy) in their temporal lobes.

Member of the research team, Dr Oliver Pigut, told DPS eNews “it has been known for some time patients with SD have difficulty with everyday sounds”.

“For example, if they hear a frog croaking, they have no idea what it is. However, very little work has been done on music in these patients. There are reports of patients with Alzheimer’s disease being able to enjoy music even in the later stages of the disease,” Dr Pigut said.

The team presented their subjects with familiar tunes, such as ‘Waltzing Matilda’, ‘Happy Birthday’ or the ‘Pink Panther theme’, paired with an artificial tune constructed from the same notes in a different order. Participants were asked which of the two tunes they recognised as a ‘famous’ one.

The control group recognised the famous tune about 90% of the time and Alzheimer’s patients were almost as successful. Most of the patients with SD recognised the tune less than 60% of the time; however three of the SD sufferers reportedly performed very well.

When these three successful SD participants were put in the MRI scanner, their brains showed considerably less damage in a part of the right temporal lobe, called the temporal pole, than the patients whose melody recognition was poor.

The team also asked the participants to point out famous faces from groups of four photos, where three were of unknown individuals and one photo was a well-known person. There was a strong correlation between people’s performance on the famous tunes and famous faces tests. Those who were poor at recognising tunes were poor with identifying famous faces too.

Rather than finding a brain region where these famous faces and tunes are stored, Dr Pigut said the team may have discovered a brain region involved in “uniqueness”. He questioned whether the right temporal pole might also be important for recognising famous buildings, such as the Sydney Opera House.

According to Dr Pigut, SD is a rarer form of dementia compared to the most common being Alzheimer’s disease. He said SD patients, who are generally diagnosed in their 50s or 60s, often present “progressive loss and knowledge about the world”.

“Clinically, SD is very different to Alzheimer’s. Patients will complain they can’t remember the meaning of things… they begin to lose more and more information,” Dr Pigut said.

While researchers still do not understand what triggers SD, Dr Pigut said the study group’s interpretation of the latest results was pivotal to future research.

“We’re trying to understand what is happening to these patients and what is also happening to that part of the brain,” Dr Pigut said. “We can then clinically inform families and clinicians,” he added.

Dr Bruce Barber, a deputy director at the National Ageing Research Institute at the University of Melbourne, said the study was “unusual in linking the loss of visual and auditory recognition” – two functions normally regarded as very distinct.

He added the research emphasised that different types of dementias “have different underlying neuropathies”; therefore requiring “quite different” treatment and management.

“Research is light years ahead of what typically happens in a hospital or residential aged care facility; and sadly, all dementias can tend to be lumped together and managed in much the same way,” Dr Barber said.

“SD is a breathtakingly complex thing. This study has made some of that complexity clearer to us,” he added.

Do you know much about Semantic Dementia? Share your thoughts on this latest Australian study by commenting in the box below.