WAIS performance IQ in aphasia as a function of auditory comprehension and constructional apraxia

This study investigated differences in nonverbal intelligence between diagnostic subgroups of aphasics using the Performance Tests of the Wechsler Adult Intelligence Scale (WAIS). Subjects were 98 right-handed hospitalized males with unilateral left-hemisphere damage who had unambiguous clinical diagnoses of Broca's, Anomic, Conduction, Mixed Non-Fluent, Wernicke's, or Global aphasia. Group differences were examined using the WAIS Performance IQ (PIQ), and subscores for spatial organization (Block Design and Object Assembly) and for verbalizability (Picture Completion and Picture Arrangement). There were significant group differences for each WAIS score, determined by the impaired performance of the Global aphasics. With covariance correction for level of auditory comprehension, group differences were eliminated on the verbalizable subtests, but not on the spatial organization subtests. Covarying for level of constructional apraxia (assessed with drawings, sticks, and blocks), however, eliminated group differences for both subscores. Using demographic, neurological, and linguistic variables, multiple regression analyses confirmed the covariate analysis findings; constructional apraxia was the most predictive variable for both spatial and verbalizability subscores, while auditory comprehension and education level predicted performance on the verbalizable subtests.