Anterior aphasia as a natural category of acquired cognitive-communicative impairment : implications for cognitive neurolinguistic theory, experimental methods, and clinical practice
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Anterior aphasia, the set of cognitive-communicative deficits associated with a left anterior cerebrovascular accident (CVA), is characterized by omission of closed-class words, deletion of syntactic morphemes, and simplified syntax. Although this has been the traditional characterization of anterior aphasia, there is no standard set of unique criteria for diagnosis or patient classification. Patients with anterior aphasia display a great degree of heterogeneity in cognitive-communicative performance. This finding has led some researchers to conclude that single-subject case studies are more effective and valid than traditional sampling and quasi-experimental designs. Despite the performance heterogeneity and imprecision of diagnostic criteria, other researchers claim that a left anterior CVA can be associated with an underlying natural category of impairment. This study investigated the hypothesis that anterior aphasia from a left anterior CVA is a valid, natural category of impairment that is separate from neurologically normal processing. This study accounted for grammatical deficits, frontal lobe cognitive deficits, and use of pragmatically acceptable compensatory strategies in language output. Twelve patients with left anterior CVA were evaluated for single-word naming and sentence formulation abilities in pictorial and nonpictorial structured and unstructured measures. Performance was compared to that of a group of 57 neurologically normal speakers on the same measures. Analysis of performance consisted of qualitative and quantitative analysis procedures within and between the two subject groups. Results indicated that a left anterior CVA can be associated with a complex natural category of acquired cognitive-communicative impairment called anterior aphasia. This natural category is separate from normal cognitive-communicative processing. However, patients have a wide range of severity of impairment, a tendency toward lower raw scores on formal cognitive-communicative tests, a tendency toward higher use of compensatory strategies, and at least as much natural within-group variability as in neurologically normal subjects. Results of this study also revealed some qualitative processing and compensatory similarities between the groups, significant group differences on almost all variables, and low discriminability between the groups. Results provided support for a quasiexperimental method framework, use of a neurologically normal control group, use of nonparametric statistical tests, and a multimethod orientation to data collection and analysis.