Parkinson’s speech issues linked to activity changes in brain region
LIFC, part of frontal cortex, is key part of brain's speech production network
Changes in the electrical activity of a brain region called the left inferior frontal cortex (LIFC) may underlie certain speech difficulties in people with Parkinson’s disease, a study found.
Patients with more severe articulation problems had higher frequency activity in the LIFC, and more limited communication between the LIFC and other brain regions, which scientists believe ultimately could serve as biomarkers for speech problems in Parkinson’s.
An  “intuitive and interactive app” to quantify speech impairments due Parkinson’s, recently developed by members of the Canadian research team, also was found to be reliable and correlate well with a patient’s status.
“We believe our data advance the understanding of basic mechanisms involved in speech production in health and disease,” the scientists wrote.
Changes in speaking abilities among Parkinson’s earlier symptoms
The study, “Aberrant neurophysiological signaling associated with speech impairments in Parkinson’s disease,” was published in npj Parkinson’s Disease.
Speech difficulties, from a hoarse and soft voice, to poor articulation and a monotonous rhythm, are among the earliest and most common symptoms of Parkinson’s disease.
Speech is coordinated by the complex communication between multiple brain regions, and how these networks are affected by Parkinson’s to drive speech problems is not understood fully. This lack hampers the development of treatment approaches to aid articulation.
Researchers, led by those at McGill University’s Montreal Neurological Institute, examined the relationship between electrical changes in certain brain regions and speech impairments among 59 people with Parkinson’s.
Patients, all part of the Quebec Parkinson Network, had mild-to-moderate disease and were on stable disease treatments.
The team began the study by developing a speech scoring system, designed to be used by nonexperts to accurately rate speech via an interactive app.
Using the app, people without expertise as raters could reliably quantify speech quality in ways comparable to gold standard methods. Moreover, ratings of speech were associated with Parkinson’s clinical presentations, with greater speech difficulties linked to more severe motor and cognitive impairments.
Should future studies further validate the approach, such a method of speech quantification could “alleviate the costs of and limited access to movement disorder specialists,” the researchers wrote.
Higher frequency electrical firing in region tied to articulation problems
Next, the scientists generated maps of the brain’s electrical activity in Parkinson’s patients and correlated it with speech performance. To do so, they used magnetoencephalography, which measures the magnetic field generated from the electrical activity of nerve cells. Neuroimaging data from a group of 65 healthy adults were used for comparison.
Higher frequency electrical firing in the LIFC linked with articulation difficulties among the patients.
These changes in the LIFC were normalized among patients taking higher doses of dopamine-replacement therapy, suggesting that “the neurophysiological bases of speech deficits in PD may be, in part, modifiable with levodopa,” the team wrote.
But only 25 of the patients whose data were analyzed had information covering medication use, and no conclusions could be drawn. Further study here is needed, the scientists noted.
The LIFC is a “key” component of the brain’s “speech production network,” where it plays a role in a type of speech planning, the researchers reported. Normally, this higher frequency electrical activity is associated with functional inhibition of brain regions, and this inhibition lowers in the LIFC around the time when a person is preparing to speak.
“Taken together, we interpret our findings as indicative that patients with reduced inhibition of LIFC at rest exhibited the best articulation abilities,” the scientists wrote.
Connectivity between the LIFC and a network of other brain regions, including the premotor cortex, anterior cingulate cortex, and somatomotor cortex, also were found to be related to these articulation difficulties.
Specifically, patients with weaker connectivity between the LIFC and the somatomotor region showed more significant articulation impairments, and this was not affected by the use of dopamine-replacement therapy.
The previously observed relationship between articulation difficulties and poorer cognition also appeared to be mediated by connectivity changes between these brain regions.
“These findings may be of significance to future biomarker research and therapeutic targeting in [Parkinson’s disease],” the researchers wrote.
Scientists noted, however, that more research is needed to better understand how well these brain changes truly predict speech alterations.
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