Fundamental Frequency and Diadochokinetic Jitter in Multiple Sclerosis
Kimberlee Wassink and J. Anthony Seikel Ph.D.
Idaho State University
The analysis of the mean fundamental frequency comparing MS participants with control participants revealed results
that strikingly contradict the study completed by Hartelius, et al. (1995), in which she found that no significant
differences exist in fundamental frequency between five MS participants and two control participants. These results
also contradict results found in a study by Feijo, et al. (2004) regarding fundamental frequency in MS. The study
reported that fundamental frequency was higher among MS individuals versus controls. However, this study was
greatly skewed by gender within the groups.
Background
Diadochokinetic Jitter
The site of lesion is a strong predictor of type of dysarthria. Hartelius, et al. (1995) reported
that several of the perceptual speech symptoms of MS are attributable to respiratory
insufficiency or dysfunction. Indeed, a majority of the subjects in the study by Murdoch,
Cherery, Stokes, and Hardcastle (1991) exhibited discoordinated irregular chest wall
movements and jerkiness in performing sustained vowels and syllable repetition tasks, as
well as during reading and conversation. Darley, et al. (1975) describe MS patients as
having scanning speech, a term used to describe impaired emphasis. Hartelius et al.
(1995) did not find difference between MS patients and controls on mean fundamental
frequency.
This study calculated cycle-by-cycle variability in DDK (or DDK jitter) utilizing a modified
version of this formula. In the case of this study, diadochokinetic jitter, which is defined as
the syllable-by-syllable variability in DDK production, was derived by summing the absolute
differences between adjacent syllable duration and also deriving the mean syllable
duration. This sum was then divided by the mean duration and multiplied by one hundred
to be expressed as a percentage.
The two research questions addressed in this study were: 1) Is there a significant
difference in the mean fundamental frequency between MS participants and control
participants? And 2) Is there a significant difference in the mean diadochokinetic jitter
between MS participants and control participants?
Method
Participants
Twenty individuals with definite diagnosis of multiple sclerosis (MS) as confirmed by MRI
and the Expanded Disability Status Scale (EDSS)(Kurtzke, 1983) served as subjects for
this study. Twenty control participants were matched for age, gender, and educational level.
All twenty pairs were used in the determination of difference in fundamental frequency for
/i/ and /a/ vowels, while 12 of these were used for determination of DDK jitter. Data
collection was completed in Greece, the participants were all from the Athens region, and
all participants spoke Greek.
Materials
Audio and electrolaryngography recordings were made using a laryngograph, a Sony
digital audio tape (DAT) recorder, and an oscilloscope. Subjects were recorded in a sound
attenuated audiology booth. Acoustical analysis was performed using the Kay
Computerized Speech Lab and the Sony Sound Forge Audio 7.0 software.
Participants were asked to perform four tasks:
1. Sustained vowels /a/ and /i/.
2. Reading of a paragraph in Greek.
3. Monologue
4. Rapid repetition of consonant vowel pairs (diadochokinesis).
Procedure
•The fundamental frequency was calculated using a two-second time period beginning one
second following the onset of the sustained vowels /a/ and /i/.
•DDK jitter was calculated for the durations of the initial burst and consonant, the vowel
and the silent periods individually.
Department of Communication Sciences & Disorders, and Education of the Deaf
http://www.isu.edu/departments/spchpath/
Poster formatted by Jackie Stokes
The DDK task may be viewed as revealing the ataxic component of the mixed dysarthria. This is apparent in that
there are variations in the duration of each component during the production of DDK tasks, demonstrating difficulty
with coordination of muscle movements. It is hypothesized that these difficulties are a direct result of ataxic dysarthria
and cerebellar disorder. The cerebellum controls coordination, timing, and initiation and termination of individual
muscle movements (Hartelius, et al., 2000). These results are in agreement with Kent, et al. (1997) which indicated
that the participants with ataxic dysarthria demonstrated increased variability of segments during syllable repetition.
These results also are consistent with Hartelius, et al. (2000) who determined that the MS group demonstrated
significantly longer syllables and increased inter-utterance variation in the duration of multi-syllabic productions.
Figure 3: Measurement of silent post-vocalic period.
Note that the marked region indicates the silent interval;
a) marks the onset and b) the termination point.
Results
A two (group) by two (gender) ANOVA was calculated to identify differences in fundamental frequency between MS
and Control. Results revealed the predicted significance based on gender [F(1,18) = 19.684], as well as a main effect
for group [F(1,18) = 9.151]. The fundamental frequency for MS was significantly lower (MN = 154.8) than that of the
control participants (MN = 183.9) for /a/, but not for /i/.
Frequency
The temporal domain extends into the suprasegmental arena, which involves duration of
elements that extend beyond phoneme (or even word) boundaries. Diadochokinesis
(DDK), or the ability to rapidly repeat relatively simple patterns of vowels and consonants,
is a task that examines, among other things, temporal aspects of speech that span single
phoneme boundaries (Baken, 1987). Vocal jitter is defined by, Blomgren, Chen, Ng, and
Gilbert (1998) as a percentage of frequency that can be calculated by taking the absolute
difference between consecutive fundamental frequencies (in Hz), and dividing it by the
mean fundamental frequency (Blomgren, et al., 1998).
The present study used analysis that compared the fundamental frequencies separately between the genders and
used the same number of females and males in both groups. This study found a significant difference during the
production of /a/, however not for the production of /i/.
Figure 2: Measurement criteria for vowel duration.
Note that the marked area indicates that which
was considered vowel in the present study; a)
marks the onset and b) the termination point.
Figure 1: Measurement of Consonant Duration.
Note that the area marked represents the region
defined by the study criteria as being the consonant;
a) marks the onset and b) the termination point.
250
250
200
200
150
Males
Females
100
Frequency
Dysarthria is characterized by disturbed movements of the speech musculature, which
may be slow, weak, imprecise, or uncoordinated (Hartelius, Svensson, & Bubach, 1993).
The difficulties experienced with dysarthria cause a degeneration in speech quality,
resulting from the alterations of muscle function in each of the systems of speech.
Degenerative diseases can cause either global deterioration or focus upon one or more
systems of the speech mechanisms.
150
Males
100
50
50
0
0
MS
Females
Control
MS
Groups
Control
Groups
Mean Fundamental Frequency for the vowel /i/
Mean Fundamental Frequency for the vowel /a/
The mean percent of total diadochokinetic jitter, consonant diadochokinetic jitter, vowel diadochokinetic jitter, and silent
period diadochokinetic jitter was calculated for each consonant vowel pair, and were subsequently subjected to a 2
(gender) by 2 (group) ANOVA.
Results revealed that, for the vowel in the /p4/ syllable, the MS group (MN =21.20) showed significantly greater DDK
jitter than the controls (MN =14.87, p = .026). Similarly, the DDK jitter for the entire /t4/ syllable was significant (MN =
20.58 for MS; MN = 13.69 for control; p = .031).
Discussion
Results are discussed in terms of the effects of the mixed spastic-ataxic dysarthria on the two tasks of the study, as
well as comparison with the Hartelius et al. (1995) study.
Mean Fundamental Frequency
This study revealed a way to differentiate the effects of spastic and ataxic dysarthria separately by using different
tasks. In this sample it appears that spastic dysarthria was the dominant dysarthria component during production of
the sustained vowel /a/, as verified by the significant statistical difference in the mean fundamental frequency between
the MS and control groups. Indeed, individuals with spastic dysarthria tend to have lower perceived pitch as well as
harsh voice. For example, Darley, et al. (1975) described the phonation in a person with spastic dysarthria as one who
sounds as if he or she is forcing a breath stream through a narrowed airway. Darley, et al. also describe the tone of
voice as having a harsh quality, which may likely to lead to the perception of a lower pitch. In addition, Darley et al.
(1969) reported that, in a study completed at the Mayo Clinic, twenty-six of thirty patients presented with excessively
low pitch, which was a joint sign, along with the harsh quality, of dysphonic voice production. With this research in
mind, it is not surprising that this study found the fundamental frequency in participants with MS to be lower than
control participants, as spastic dysarthria is one of the main characteristics of MS.
Factors which may have had an affect of voice production and quality:
1. Emotion
2. Stress
3. Lifestyle
In this study the Mini-Mental Status Exam (MMSE) (Folstein, M., Folstein, S., & McHugh, P. 1975) and the Hamilton
Depression Scale (HAM-D) (Hedlung, & Vieweg, 1979) were used to determine if either emotional state or
depression were playing a part in altering the voice characteristics of the individuals participating in the study. Emotion
and depression were determined not be contributing factors in the voice production of these individuals. It was
determined that in terms of lifestyle that it should be kept in mind that several of the participants were smokers.
In this study, further evaluation of the results of ANOVA testing revealed that it appears that the DDK syllable /t4/ is the
most sensitive production for detecting DDK jitter. It may be that production of /t4/ involves more intricate coordination
among the systems of speech than the other syllables. Indeed the /t4/ syllable involves tongue tip, jaw, larynx and lip
coordination. This information is supportive of the findings in Hartelius and Lillvik (2003), in which they found that
tongue function is more significantly affected than lip function both when compared within the MS group and when
compared with a control group.
In addition the Hartelius and Lillvik study found that tongue function alone was affected (though not as significantly) in
MS participants who were identified as not having dysarthria, implying that the MS in itself can affect tongue
movement regardless of dysarthria.
Because the analysis of the syllable /t4/ was able to identify a significant difference between the MS and control groups
as a whole, it would be assumed that one would not need to measure the durations of the consonant, the vowel, and
the silent period separately. Hartelius and Lillvik (2003) identified that testing tasks that required quick rates of
movement of the tongue were more significantly impaired than tasks which required either force of movement, or
range of motion. With this finding in mind, this single syllable (/t4/) measurement in diadochokinesis may be enough to
determine if there is a large percentage of jitter and may be enough to give a positive indicator of ataxic dysarthria.
Hartelius and Lillvik (2003) agree that before identifying a treatment plan it is critical that you determine which
articulators are more severely affected than others, or in this case, even determining which type of dysarthria would
lead to a narrowed area of affected articulators.
From this study it seems that the combination of determining fundamental frequency and using DDK jitter may prove
to be a useful clinical tool for determining the effects of spastic and ataxic dysarthria on speech, in MS or in any other
disease. These measurements and analyses provide information that it may be possible to identify the dominant form
of dysarthria, therefore providing the clinician with more evidence for a diagnosis and a starting point for a plan of
treatment for these individuals.
References
Baken, R. (1987). Clinical measurement of speech and voice. Austin: Pro-Ed Inc.
Blomgren, M., Chen, Y., Ng, M., & Gilbert, H. (1998). Acoustic, aerodynamic, physiologic, and perceptual properties of modal and vocal fry registers.
Journal of the Acoustical Society of America, 103(5), 2649-2658.
Brown, J., Darley, F., & Aronson, A. (1970). Ataxic dysarthria. International Journal of Neurology, 7(2), 302-318.
Darley, F., Brown, J., & Aronson, A. (1969). Differential diagnostic patterns of dysarthria. Journal of Speech and Hearing Research, 12(2), 246-269.
Darley, F., Brown, J., & Aronson, A. (1969). Clusters of deviant speech dimensions in the dysarthrias. Journal of Speech and Hearing Research,
12(3), 462-496.
Darley, F., Brown, J., & Aronson, A. (1975). Motor speech disorders. Philadelphia: W.B. Saunders Company.
Feijo, A, Parente, M., Behlau, M., Haussen, S., DeVeccino, M., Castellar de Faria Martignago, B. (2004). Acoustic analysis of voice in multiple
sclerosis patients. Journal of Voice, 18 (3) 341-348.
Folstein, M., Folstein, S., & McHugh, P. (1975). Mini-Mental State Examination. Lutz, FL: Psychological Assessment Resources (PAR), Inc.
Hartelius, L., and Lillvik, M. (2003). Lip and tongue function differently affected in individuals with Multiple Sclerosis. Folia Phoniatrica et Logopaedia,
55, 1-9.
Hartelius, L., Runamaker, B., Anderson, O., & Nord, L. (2000). Temporal speech characteristics of individuals with Multiple Sclerosis and ataxic
dysarthria: ‘scanning speech’ revisited. Folia Phoniatrica et Logopaedia, 52(2), 228-238.
Hartelius, L., Nord, L., & Buder, E. (1995). Acoustic analysis of dysarthria associated with Multiple Sclerosis. Clinical Linguistics & Phonetics, 9(2),
95-120.
Hartelius, L., Svensson, P, & Bubach, A. (1993). Clinical assessment of dysarthria: Performance on a dysarthria test by normal adult subjects, and by
individuals with Parkinson’s disease or with Multiple Sclerosis. Scandinavian Journal of Log. Phonetics, 18, 131-141.
Hedlung, & Vieweg (Adapted from…) (1979). The Hamilton rating scale for depression (HAM-D), Journal of Operational Psychiatry, 10(2),149-165.
Triangle Park, NC: GlaxoWellcome Inc. (1997).
Kent, R., Kent, J., Rosenbek, J., Voperian, H., and Weismer, G. (1997). A speaking task analysis of the dysarthria in cerebellar disease. Folia
Phoniatrica et Logopaedia, 49, 63-82
K. Konstantopoulos, Xifara, K., Vikelis, M., & Mitsikostas, D. (2004). Phonatory instability in Multiple Sclerosis. [Proposal].
Kurtzke, J. (1983). Expanded disability status scale (EDSS). Neurology, 33(11), 1444-1452.
Murdoch, B., Chenery, H., Stokes, P., & Hardcastle, W. (1991). Respiratory kinematics is speakers with cerebellar disease. Journal of Speech and
Hearing Research, 34, 768-780.