The purpose of this study was to examine the characteristics of prosody of utterance of ambiguous sentences in patients with neurogenic communication disorders. Ambiguous words or sentences on which prosody may have an impact were used to investigate ...
The purpose of this study was to examine the characteristics of prosody of utterance of ambiguous sentences in patients with neurogenic communication disorders. Ambiguous words or sentences on which prosody may have an impact were used to investigate this matter. The characteristics of tone duration, pitch and intensity were analyzed to examine the characteristics of prosody in patients with lesions in the left or right hemisphere. It is hoped that the results will provide us with a better understanding of the characteristics of prosody in patients with neurogenic communication disorders and eventually, will allow us to develop better treatment strategies.
There were two major objectives in this study; 1) to differentiate the characteristics of prosody between patients with neurogenic communication disorders due to lesions in the left and the right hemisphere and 2) to identify the characteristics of prosody in patients with neurogenic communication disorders based on the characteristics of tone duration, pitch and intensity. The key questions were;
1. Are there any differences in the prosody of utterance of lexically ambiguous sentences between study groups?
2. Are there any differences in the prosody of utterance of ambiguous sentencesin different scopes of negative words between study groups?
3. Are there any differences in the prosody in structurally ambiguous sentences between study groups?
Three groups including patients with lesions in the left hemisphere, patients with lesions in the right hemisphere and people with no brain lesions were selected to compare the ability to interpret the ambiguous sentences. The first two groups of sample populations were those patients diagnosed with cerebrovascular accident (CVA) and had no significant articulation problem or psychological problems. The Korean-Western Aphasic Battery test (K-WAB) was carried out on 52 patients with a stroke at 4 different hospitals in Daegu, Korea. The whole process was evaluated by two researchers and based on the evaluation, 8 patients with lesions in the left hemisphere, 8 patients with lesions in the right hemisphere were chosen. Also, 8 people with no brain lesions were selected for the control group.
Three types of ambiguous sentences with homograph or homonym, ambiguous sentences in different scopes of negative words, and structurally ambiguous sentences were prepared for reading tests. In some tests, participants read the sentences while having conversations with examiners. Only the participants read the sentences in the rest.
Reading tests were conducted three times in each patient and the third test was recorded. A Praat 4.3.14 (Boersma & Weenink, 2005) was used to record and analyze the tests. The sampling rate was set up as 22,050 Hz and a microphone with a fundamental frequency of 20-20,000 Hz (Philips SBC HG 100) was used in the recording. The distance between the microphone and mouth was 10-15 cm.
When choosing spectrogram sections, both acoustic and auditory perception factors were taken into account. The recorded data were checked for five times and each section was selected. The duration of syllables and F0(fundamental frequency) were measured for the analysis of lexically ambiguous sentences. For the analysis of prosody of utterance of ambiguous sentences in different scopes of negative words, the F0, duration, and tone of the word before the verb, the verb, and the negative word affecting the verb were compared.
Among the collected data, 25% was randomly selected and acoustically analyzed to evaluate reliability in inter- and intra-examiners, using Chronbach's Alpha method. The inter-examiners reliability was measured as 0.9959, 0.9929, and 0.9934 for F0, duration, and tone based on acoustic factors, respectively. The intra-examiner reliability was 0.829.
This study was conducted from December 1, 2007 to May 10, 2008 and each individual was tested for two or three times. The whole process was recorded using a Praat 4.3.14 and also video recorded using Sony video camera DCR-SR200. For statistical analyses, the one-way, two-way Anova and multiple comparative analyses were carried out using SPSS10.0 for Windows. Scheff？ method was used for verification.
The results of this study are as follows;
1. There were significant differences between groups in the duration of vowel depending on short and long of homograph. There were significant differences depending on meaning and interaction between meaning and groups in the duration of vowel. There were significant differences in the duration and rate of duration of syllables depending on short and long of homograph. The only significant difference in verification was the one between patients with lesions in the left hemisphere and other groups. Therefore the duration of vowel depending on long and short of homograph were related to the changes of meanings and the differences between groups. Each group responded differently to ambiguous sentences resolved with contexts but not to the changes of meanings.
There was a difference in the pitch of ambiguous words between groups, however, the difference according to the changes of meanings was insignificant. Verification results showed that patients with lesions in the right hemisphere were found to be differentiable but the distribution of tone was similar.
2. Under the influence of negative words, significant differences between groups were observed in the duration syllables of the final syllable of pre-phrasing and final syllable of the verbs when reading negative sentences. The only significant difference in verification was the one between patients with lesions in the left hemisphere and other groups. Also, significant differences between groups were observed in the pitch ratio of the final syllable of the verbs and negative words. Verification results showed that there was a significant difference between patients with lesions on the right hemisphere and people with no brain lesions.
3. There was a slight difference between groups in the duration and pitch in broad range of pre- and post- section syllables and narrow range of section syllables of structurally ambiguous sentences. Verification results showed that there was a significant difference between patients with lesions on the left hemisphere and other groups in the duration and significant difference between lesion groups and normals in pitch change. However, no differences were identified in the event of changes of meanings.
The conclusions of this study are as follows;
1. The length of vowel in homograph in Korean was different depending on the meaning and the duration of vowel was the longest in patients with lesions in the left hemisphere. There was showed that they had problem of timing of prosody. On the other hand, there found that patients with lesions in the right hemisphere had deficiency of changeability in pitch.
2. When resolving the ambiguity of negative sentences, the duration of the final syllable in verbs influenced on resolving of ambiguity. There was found that patients with lesion in the left had the deficiency with timing of prosody. On the other hand, There was showed that patients with lesion in the right of hemisphere had narrow dynamic range in pitch.
3. Inpre- and post- section syllables of structurally ambiguous sentences, the duration were the longest in patients with lesion in the left hemisphere and there showed that they had a little competence in timing of prosody. On the other hand, there was showed that all the patients in lesion groups had narrow dynamic range in pitch . Further research is required to understand the broad range of pre- and post- prosodic boundaries and the narrow range of prosodic boundaries.
Among various acoustic parameters, this study focused on the duration and pitch which are closely related to suprasegmental characteristics of prosody. More acoustic parameters should be taken into account in future studies. The results of this study will provide us with a better understanding as to the characteristics of prosody in patients with neurogenic communication disorders. When dealing with patients with communication disorders, linguistic prosody should be considered. Based on the results of this study, treatment programs for these patients can be developed.
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