Correlation between acoustic speech characteristics and non-speech motor performance in Parkinson Disease

Research has found that non-speech motor deficits in Parkinson Disease (PD) can be consistently improved by levodopa medications and surgical treatment, but that speech and voice are only partially responsive to treatment. This has led to the assertion that speech is an axial (non-peripheral) feature of PD, along with other features that are only partially responsive to treatment (e.g., postural stability and gait). The current study tested this assertion via examination of the relationship between multiple measures of speech production and multiple measures of non-speech movement in individuals with PD.

Nine individuals with idiopathic PD were studied, and all participants were taking levodopa-carbidopa medication. Motor performance was examined using the motor portion of the Unified Parkinson's Disease Rating Scale, and speech was examined via acoustic analysis of phonation, articulation, and prosody.

Seven of sixteen speech acoustic measures (FoSD in vowels, F2 slope for /u/ and /ae/, FoSD in reading, articulation rate in monologue, and percent pause in reading and monologue) were significantly correlated with non-speech movements. Results suggested that speech measures are correlated with both axial motor symptoms (e.g., gait, facial expression, posture, postural stability) and non-axial motor symptoms (e.g., rest tremor, left and right bradykinesia, postural tremor).

It has been hypothesized that axial symptoms of PD are more purely dopaminergic, and non-axial symptoms are related to non-dopaminergic lesions. Therefore, the current results indicate that certain speech deficits in PD may result from dopaminergic lesions, while others appear to result from non-dopaminergic lesions.