Participants Needed
We need research participants with Parkinson's disease and
healthy adults who are willing to volunteer to perform some
language, cognitive and mood tests and a series of computer
tasks during MRI scanning. Three sessions totaling six
hours required. If interested please call Tossi Ikuta at
(812) 856-1776.
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Language and Motor
Interactions in Parkinson's Disease
as presented by Bridget Walsh, Ph.D. at the 2007 Symposium
The
central pathology of Parkinson's Disease results in a loss of
nuclei affecting motor characteristics of speech production. We
know there are loops between the basal ganglia and the cortex of the
brain which affects many aspects of behavior including speech,
language, cognition and mood. Dysarthria is the term we use to
describe speech disturbances in PD. It is a common part of PD:
voice disorders in 89%, articulation deficits in 45%, and voices may
be monotone.
Most previous studies of speech with PD have been subjective,
describing how speech sounds. There have been few scientific
studies of the physiology or movement studies.
The articulators are the structures
you use to talk: the lips, tongue, jaw, and velum.
Some studies
have shown reduced amplitude (volume), and other studies have shown
these were normal. Studies had small numbers of subjects and some
studies did not use longer utterances. Studies of rate and
intensity have not had consistent findings.
The objective of Ms.Walsh’s study was
to include multiple measures of speech production and a larger
number of subjects. Sixteen subjects with idiopathic PD, and 16
normal adults matched with regard to age and gender were tested.
The mean age of the group was 73 years. Those with PD had to have a
mild to moderate disorder of speech and voice based on a speech
evaluation. She showed a picture of the equipment used (IREDS).
Each subject produced six sentences, some short and some longer;
some simple and some with more complex grammar. The subjects saw
the sentences they needed to say. She took measurements of the
coordination of the upper and lower jaw, how fast the jaw and lips
moved, and the duration of movement, intensity (loudness), the rate
of speech; and analyzed the F-2 format (an important frequency to
understand speech).
For all sentences involved, all
subjects with PD had higher lip aperture variability than the
control subjects. There was less speech and less displacement. PD
subjects spoke at lower intensity than normal adults did by 4.79 dB
SPL. There was no group effect for speech rate. F-2 slopes were
significantly reduced by the PD group as compared with normal
controls.
Lip Aperture Index: this was
designed to capture the coordination of the articulators. Although
there was some degree of overlap on the average, the individuals
with PD had higher Lip Aperture Index as compared to the controls.
The results support a possible role of the basal ganglia in the
programming and coordination of speech movement sequences.
Other
Kinemotoric and Acoustic Variables:
The individuals with PD produced speech with reduced displacement
amplitudes and velocities. Acoustic data showed that they spoke at
lower intensities and presumably had decreased lingual excursion as
indicated by reduced F-2 slopes.
Interpretations: Results
suggest a "down scaling" of speech production with PD. These
deficits presumably are from dopamine loss, which reduces neuronal
discharge abnormalities within the entire motor circuit.
Discussion:
There was no difference between those with PD and normal adults for
prolonged speaking rate. However, those with PD had either the
fastest or the slowest rates of speech. The participants had
similar syllable duration. Varying the duration of components of
the speech signal affects the perception of consonant sounds. It is
possible that a greater importance is placed on the preservation of
timing mechanisms, which are essential for intelligible speech.
This study was the most comprehensive to date. The heterogeneity of
individuals with PD is likely the explanation for the mixed results
of early studies. Additional studies need to be done with a larger
number of subjects.
