Researchers have found a link between a Parkinson’s disease gene and vocal issues which could lead to earlier diagnoses, a new study reports.
One little-known symptom of Parkinson’s is a soft monotonous voice.
Research has suggested these vocal symptoms often appear much earlier – sometimes decades – before movement-related issues.
The condition’s physical symptoms, including tremors and stiffness, are perhaps the best known signs, but Parkinson’s also causes vocal issues.
The study was conducted by neuroscientists in the lab of Julie E Miller, assistant professor at the University of Arizona.
Miller said: “We have this big gap here – we don’t know how this disease impacts the brain regions for vocal production, and this is really an opportunity to intervene early and come up with better treatments.”
Researchers turned to the zebra finch, a songbird native to Australia, to investigate any link between vocal changes and the Parkinson’s-related gene called alpha-synuclein.
Birds are an ideal model for human speech and voice pathways for several reasons, said the study’s lead author, César A. Medina.
Scientists explained that young finches learn their songs from older, father-like male birds, much in the same way babies learn to speak by listening to their parents.
The part of a finch’s brain that deals with speech and language is also organized very similarly to the human brain.
Medina said: “These similarities across behaviour, anatomy and genetics allow us to use the zebra finches as a model for human speech and voice.”
To see how alpha-synuclein might affect vocal production in the birds, researchers first took baseline recordings of their songs.
They then introduced a copy of the gene into some birds whilst other birds were not given the gene in order to compare the results.
All the birds’ songs were recorded again immediately after introducing the gene, and then one, two and three months later.
The researchers used computer software to analyze and compare the acoustic features of the songs over time, studying pitch, amplitude and duration of the songs to determine whether and when the birds’ vocal production changed.
Initial findings showed that the Parkinson’s gene did affect song production.
The birds with the gene sang less after two months, and they sang less at the start of a song session three months after receiving the gene.
Their vocalisations were also softer and shorter – findings similar to what is seen in Parkinson’s disease.
To determine whether the effects on speech were connected to changes in the brain, the researchers zeroed in on a section of the brain called Area X.
They found that there were higher levels of the alpha-synuclein protein in Area X, helping them establish that the gene did, in fact, cause the changes in the brain that led to changes in vocal production, Medina said.
He said this connection had been predicted in previous Parkinson’s research, but it was not conclusive.
Miller added that the next step is figuring out how to apply these findings to human data, which could provide more answers that lead to better Parkinson’s diagnoses and treatments – ones that come long before movement-related symptoms tell a patient to visit a neurologist.
She said the long-term goal of the Miller Lab is to partner with other researchers and private companies to develop drugs that target alpha-synuclein and other genes associated with Parkinson’s.
Doing so, Medina said, would mean “we could stop the progression of Parkinson’s disease before it becomes a detrimental impediment to the quality of life for the patient.”
The study was published in the scientific journal PLOS ONE.
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