A new empirical angle on the variability debate: quantitative neurosyntactic analyses of a large data set from Broca's aphasia.
Behavioral variation in Broca's aphasia has been characterized as boundless, calling into question the validity of the syndrome-based schema and related diagnostic methods of acquired language disorders. More generally, this putative variability has cast serious doubts on the feasibility of localizing linguistic operations in cortex. We present a new approach to the quantitative analysis of deficient linguistic performance, and apply it to a large data set, constructed from the published literature: Comprehension data of 69 carefully selected Broca's aphasic patients, tested on nearly 6000 stimulus sentences, were partitioned in different ways, and subjected to a series of analyses. While a certain amount of variability is indeed evident in the data, our quantitative analyses reveal a highly robust selective impairment pattern for the group: the patients' ability to analyze syntactic movement is severely compromised, in line with the Trace-Deletion Hypothesis. Further analyses suggest that patients' performance on no-movement sentence types exhibits less variation than on sentences that contain movement. We discuss the clinical and theoretical implications of our results.
Drai
Dan
D
Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel.
Grodzinsky
Yosef
Y
D001039:Aphasia, Broca / Q000175:diagnosis* / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology*; D016001:Confidence Intervals; D036262:Empirical Research; D006801:Humans; D007806:Language Disorders / Q000175:diagnosis; D008037:Linguistics / Q000379:methods*; D008954:Models, Biological; D012720:Severity of Illness Index