Discovering main concepts from core lexicon

Emily Patricia Dillow
«Narrative Discourse in Aphasia: Main Concept and Core Lexicon Analyses of the Cinderella Story»
Master's thesis. University of South Carolina - Columbia


Extracto de los apartados iniciales del capítulo 4 de la tesis en PDF. Véase la bibliografía del trabajo en el citado PDF.

«Aim 1: Investigating Core Lexicon

»MacWhinney et al. (2010) suggested core lexicon analysis during narration may provide a time-efficient and informative indication of functional communication. For example, clinicians would not need to perform lengthy transcription, but instead could generate a list of words spoken during narration for later comparison to a core lexicon.

»What is needed is a core lexicon derived from a large sample of controls, ensuring that the lexicon reflects typical discourse abilities. After analyzing transcripts of 158 adults with typical language and utilizing a more stringent criterion of 50% incidence, the resultant core lexicon reflects what is essential to successful Cinderella narration.

»This core lexicon list can be utilized by clinicians in the previously described manner as a tool for narrative discourse assessment.

»Comparison of the core lexicon production of controls and PWAs indicated markedly greater production by controls. While this result was expected, establishing this difference was a necessary initial step in core lexicon analysis. Results of the three median tests comparing core lexicon, verb, and noun productions of the four subtypes suggest that distinctions in core verb and noun production are evident between aphasia subtypes. This information may have important implications for the validity of core lexicon analysis, as it suggests that this measure may be sensitive to differences between aphasia subtypes. When specifically comparing pairs of subtypes based on entire core lexicon production, Broca’s was the only subtype that could be differentiated from others.

»This suggests that core lexicon analysis may not be sensitive enough to differences between the other subtypes.

»The same findings do not hold true when looking specifically at individual lexical class productions. While just looking at core verbs would be sufficient for differentiating Broca’s from anomic and Wernicke’s subtypes, this information would not be adequate for differentiating Broca’s from conduction. Based on findings from this study, analysis of core verb and noun productions would be necessary in order to make the distinction between Broca’s and conduction. Another interesting finding regarding core verb comparisons was that anomic and conduction subtypes were differentiated on this measure, even though this was not the case based on entire lexicon comparisons.

»Meanwhile, core noun analysis could sufficiently make distinctions between all pairs, except anomic and conduction and Broca’s and Wernicke’s subtypes. After comparing groups based on the entire core lexicon and individual classes, it is clear that the different measures result in varying degrees of discrimination between different pairs of aphasia subtypes.

»Aim 2: Investigating Main Concepts

»Standardized main concept lists for discourse tasks could allow clinicians to efficiently assess discourse skills and predict activity and participation limitations.

»The generated main concept list could potentially serve as a clinically useful checklist for narrative assessment of individuals with aphasia when the Cinderella narrative is elicited according to AphasiaBank conventions. Similarly to the procedure with core lexicon analysis, an important initial step in the exploration of main concept analysis was to ensure its ability to highlight a clear difference between discourse skill of PWAs and controls. The strong effect sizes of all tests comparing the different subtypes of aphasia to controls based on main concept scores indicate that we can be confident in this measures’ ability to detect language impairment.

»The median test comparing the four subtypes’ main concept scores suggested that the measure was also able to distinguish subtypes within subjects with aphasia. However, further median tests comparing each set of pairs indicated that anomic aphasia was the only subtype significantly different from any of the others with regard to main concept scores. Main concept scores of Broca’s, conduction, and Wernicke’s subtypes were too similar to suggest any difference between these three subtypes.

»It is interesting to note that while the median main concept score of 25 for the anomic group was significantly higher than that of the Broca’s and conduction subtypes, it was still significantly lower than the median score of 63, obtained by controls. While anomic aphasia is primarily characterized as a word-finding disorder, Andreetta, Cantagallo, and Marini (2012) suggested that narrative coherence can also be impacted in this population. Deficits in discourse skills may be so minor with this population that they are not apparent on many standardized assessment measures, but it should not be assumed that they do not exist and do not affect functional communication abilities.

»The notable gap apparent between main concept scores of controls and subjects with anomic aphasia makes main concept analysis a promising tool for detecting discourse weaknesses in anomic aphasia.

»Aim 3: Relationship Between Core Lexicon and Main Concepts

»The relationship between core lexicon production and main concept scores was investigated to determine whether the quick core lexicon analysis correlated strongly with the more thorough (but time-intensive) analysis of narrative discourse. Main concept analysis is a narrative measure which has been supported by previous studies as being a reliable and informative method of assessing adequacy of communication (Nicholas & Brookshire, 1995; Kong, 2009). Our results suggest core lexicon production is strongly related to main concept scores for all groups (controls and all subtypes of aphasia), which makes it a promising method of assessment. This finding lends support to the idea that core lexicon analysis may be a comparable and time-efficient method of characterizing discourse abilities and, potentially, charting treatment outcomes.

»Tests of whether core verbs or core nouns alone correlated with main concept scores of each group indicated that individual lexical classes due, indeed, correlate significantly with main concept productions, except in one particular case. For the Wernicke’s group, core verb productions did not correlate significantly with main concept scores. Meanwhile, the number of core nouns produced showed a stronger correlation to main concept scores than did total core lexicon production (Table 3.9).

»These results indicate a notable gap between the noun and verb usage of individual’s with Wernicke’s aphasia (e.g. “and the two girls, they go to this meeting,” contains 1 core verb “go,” but the participants fails to get credit for “stepsisters” or “ball” because of nonspecific noun usage.). This information is useful and suggests that if a clinician were to use the core verb production of a patient with Wernicke’s aphasia to estimate their likely main concept score, the clinician could be overestimating the patient’s actual abilities in the area of main concept production. In fact, core noun analysis specifically would be more appropriate than core lexicon analysis for individuals with Wernicke’s aphasia, based on results of correlational tests in this study.

»For all other groups, the best method of predicting main concept score would be core lexicon analysis, including both verbs and nouns. The only other subtype exhibiting a noticeable difference between correlations obtained with core verbs versus core nouns was the conduction group.

»Unlike the Wernicke’s group, which seemed to show a greater deficit with nouns, the conduction group seemed to show a greater deficit with verbs. However, this tendency was not strong enough to prevent the combined measurement of verb and noun production from being the stronger measurement of discourse skill, based on correlations to main concept scores. »