Thèse--Universit́e de Paris. / "Bibliographie": p. [65]-66.

Thèse--Universit́e de Paris. / "Index bibliographique": p. [41]-42.

Thesis (Ph. D. 1957)--Dept. of Speech, University of Utah. / Bibliography: ℓ.[72]-76.

Using medically diagnosed aphasics, this study attempted to develop a classification system, based on statistical or, more precisely, variance criteria. Aphasia is a language disorder resulting from insult to the brain. Besides having direct ramifications on aphasia theory and research strategies, the techniques used here may be applicable to other atypical populations. Specifically, the outlined multivariate procedures can provide insight into intra-population distributions. The resulting distribution can then be used as a basis for factorial designs in future research. The sample consisted of seventy-two medically diagnosed aphasics who had received speech therapy for varying time periods. Prior to and at the termination of treatment, subjects were assessed on a well-standardized and reliable aphasia battery, the Porch Index of Communication Ability. This instrument consists of eighteen subtests and purports to measure three dimensions of communication ability: one verbal, one gestural, and one graphic. Post-treatment subtest scores were factor analyzed to determine the factor structure of the P.I.C.A. and this structure was compared with Porch's formulations. Two subtests were deleted from this analysis due to ceiling effects. Using the factor score coefficients from this analysis, factor scores for the pre-treatment subtests were generated. These factor scores were submitted to a hierarchical cluster analysis in order to determine the optimal number of groups within this sample. A series of step-wise, discriminant analyses, using the factor scores as predictors, confirmed that a six-group solution was best. Group distributions were then examined with respect to current models of aphasia. The findings support Porch's formulations with respect to the underlying demensions of the P.I.C.A. However, the results suggested that 1) two subtests were too easy for all subjects and therefore should be discarded, and 2) two other subtests may not, in fact, reflect symbolic language function. In addition, evidence of a general language factor was also found. These findings were also compared to a factor analysis on Porch's standardization sample. The five derived dimensions of communication ability were : 1) verbal fluency, 2) writing (agraphia), 3) gestural demonstration with, varying input modalities, 4) pantomime, and 5) copying. These dimensions were discussed within the context of previous aphasia research. The grouping analysis indicated that the groups were distributed on a severity continuum not a salient features model of aphasia. Only one of the six groups was suggestive of differential impairment with respect to communication modalities, but this group was small (n = 4) and therefore must be considered judiciously, In addition, the applicability of these procedures was discussed within the context of multivariate research. The power of multivariate designs rests on minimizing the number of groups and dependent variables and maximizing the number of subjects, and the present procedures should aid in meeting these criteria. Specifically, factor analysis reduces the number of dependent variables and yet allows for a representative sample of dependent variables. Cluster analysis groups Individuals Based on the similarities of their performance and thus relatively homogenous groups are formed. The distribution of these groups can form the basis for subsequent factorial designs. / Education, Faculty of / Graduate

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The Reitan-Indiana Aphasia Screening Test was examined using a latent structure analysis which involved the assumptions that a latent variable X (brain function), could explain the relationships among the manifest variables A, B, C, D (categories of responses to the Aphasia Test). It was further assumed that within the latent variable a four-class model would be the preferred model. And, it was assumed that persons clinically assigned to the latent classes would be similarly assigned by their test responses. The model was represented by mathematical equations which express the probability of a given response pattern in a contingency table in terms of the joint probabilities of each latent class and the response pattern. Chi-square values were obtained for the model of independence, for the four-class model, for the three-class model and for two two-class models. Hierarchical subtractions were made which resulted in a preferred model, leaving a Chi-square value to be referred to the Chi-square distribution to determine whether or not the latent class model offered an improvement of fit to the data. Twelve comparisons were made using different item combinations. All 12 showed the four-class model offered a significant improvement over the model of independence and either of two two-class models tested. Eleven of the twelve comparisons showed that a four-class model provided an adequate fit to the data. In seven of those instances the four-class model was accepted as the preferred model. In the remaining four instances the heirarchical subtractions showed that a four-class model did not offer significant improvement over the three-class model, so the three-class model was accepted as the preferred model due to the criterion of parsimony. The study showed that there are four categories of brain function which can be identified by means of a behavioral test. It also gave the exact coefficient of agreement between assignment of individuals into those categories by clinical and test classification. It was concluded that latent structure analysis is an effective technique to describe brain-behavior relationships. It was further suggested that consideration be given to the use of latent trait statistics to continue to refine the Aphasia Test without compromising the extensive results already achieved.

A growing body of literature has documented attention impairments in individuals with aphasia. This study extended that literature by examining the effects of lesion location (anterior versus posterior left hemisphere lesion) and nature of distractor task (nonverbal versus verbal) on aphasic individuals' performances of a variety of listening and speaking tasks under isolation, focused and divided attention conditions. Across tasks, conditions, and experiments, both anterior and posterior groups of aphasic individuals demonstrated greater disruption of language skills than a group of healthy individuals. Although it was initially hypothesized that the anterior group would display greater attention impairments than the posterior group, few differences were found; generally, the two aphasic groups performed similarly, both quantitatively and qualitatively. Independent of group, all individuals showed greater disruption of listening and speaking skills when the distractor task was verbal rather than nonverbal in nature. Performance decrements on most tasks were poorly predicted by severity of language impairment, time post-onset and other demographic characteristics of the aphasic individuals. Within a capacity framework of attention, the results of this study suggest that the attention impairments of aphasic individuals may reflect one or a combination of the following: decreased attentional capacity, inefficient attention allocation, or poor task-demand evaluation.

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