| The aphasia literature supports a dissociation between automatic and controlled processing of lexical-semantic information in Wernicke's aphasia, with the evidence originating primarily from studies contrasting off-line conscious or controlled processing with on-line automatic processing. These findings suggest difficulty for individuals with Wernicke's aphasia in consciously operating on semantic information, but preserved automatic access. The first part of this present study involved a further look at controlled processing using an on-line task, a variation of the Stroop test, to investigate whether the underlying mechanism of inhibition is faulty at the controlled processing level.;The second part of the study involved re-examination of automatic processing, given recent findings (Prather et al., 1997) of an abnormal priming pattern associated with Wernicke's aphasia, suggesting an impaired inhibitory mechanism in the automatic processing realm. The Prather et al. List Priming Paradigm (LPP) was administered to a larger subject pool to further examine lexical activation and deactivation in Wernicke's aphasia. The participants for both tasks were six adults with Wernicke's aphasia and twelve age- and education-matched normal controls.;Analysis of the Stroop reaction time and error percentage data confirmed an impairment of inhibition in Wernicke's aphasia. In addition, correlational analyses revealed that the magnitude of Stroop interference was significantly positively correlated with the clinical-behavioral symptom of severity of auditory comprehension deficits, as measured by the Token Test.;The LPP reaction time findings indicated that, although the average response times of the participants with Wernicke's aphasia were significantly longer than those of the normal controls, the two groups demonstrated a similar priming pattern. Both lexical activation and deactivation appeared preserved in Wernicke's aphasia. Furthermore, correlational analyses revealed no significant positive correlation between impaired Stroop inhibition and LPP priming, suggesting that performance on these two measures reflects different underlying processes.;In summary, neither slowed activation nor prolonged activation is the basis for the disproportionate impairment of auditory comprehension in Wernicke's aphasia. However, when controlled processing is demanded, the individual with Wernicke's aphasia cannot effectively ignore the automatically evoked, distracting stimulus, contributing to a reduction in attention allocation and in the resulting effectiveness of auditory processing. |
