Abstract WMP26: Acute Left Superior Temporal Damage Results In Phonological Errors In Word Comprehension

Abstract

Right hemisphere deactivation by right carotid injection of sodium amytal (Wada testing) in chronic epilepsy results in few phonological errors in word comprehension. Based on this finding, recent models of language processing indicate that speech sound and spoken word processing is bilateral, so that unilateral stroke should not affect distinguishing phonologically similar words (e.g. boat/note) for word comprehension. We tested the alternative hypothesis that acute left hemisphere stroke in superior temporal gyrus (STG) results in phonological errors in a word-picture verification task, which would support the proposal that the right hemisphere does not support speech sound processing and word comprehension before recovery through reorganization of structure/function relationships. Methods: A series of 218 participants were tested with a word-picture verification test with targets and phonologically similar words and had brain MRI within 4 days of stroke onset. We evaluated associations between any damage to left STG and phonological errors using chi square, and the correlation between degree of damage to STG and number of errors using Spearman Rho. Results: We found a very strong association between infarct in left STG and the production of phonological errors in word comprehension (chi squared= 31.2; p <0.00001). Furthermore, the number of phonological errors was strongly correlated with the degree of infarct in left STG (rho=0.49; p<0.00001). Results indicate that left STG, when acutely damaged, often results in phonological errors in word comprehension. These results indicate that the paucity of such errors in comprehension in studies of chronic left hemisphere stroke or Wada testing is a result of reorganization following chronic left temporal dysfunction. Patients with acute left STG stroke should be tested with sensitive tests for word comprehension deficits, including phonologically similar words, before giving verbal direction on exam or obtaining informed consent for procedures.