Dichotic listening performance, language impairment, and lesion location in aphasic listeners

This investigation sought to identify relations between dichotic listening performance and both specific language functions and CT scan evidence of lesion location in order to determine whether the nature of these relations would support either "dominance effect" or "lesion effect" interpretations of the dichotic scores. Twenty-five aphasic patients completed our digit dichotic listening test, the Boston Diagnostic Aphasia Examination (BDAE), an experimental sentence comprehension test, and a digit immediate memory span test. Right ear scores (and the ear advantage) accurately reflected the integrity of the central auditory structures for all but one of the patients, and thus were interpreted as "lesion effects." These same right ear scores also were related more strongly to performance on phrase repetition subtests of the BDAE and to scores obtained on our sentence comprehension test than to the other language measures analyzed. These relations were maintained even when general measures of auditory comprehension and immediate memory were held constant through the use of partial correlations. Both "dominance" and "lesion" effect interpretations were discussed, but the "lesion effect" interpretation more adequately characterized the data. That is, the integrity of the posterior, superior temporal area seemed to be essential for perception of right ear stimuli on the digit dichotic test and for accurate performance on specific language tests.