It has long been a matter of debate whether recovery from aphasia after left perisylvian lesions is mediated by the preserved left hemispheric language zones or by the homologous right hemisphere regions. Using PET, we investigated the short-term changes in the cortical network involved in language comprehension during recovery from aphasia. In 12 consecutive measurements of regional cerebral blood flow (rCBF), four patients with Wernicke's aphasia, caused by a posterior left middle cerebral artery infarction, were tested with a language comprehension task. Comprehension was estimated directly after each scan with a modified version of the Token Test. In the interval between the scans, the patients participated in brief, intense language comprehension training. A significant improvement in performance was observed in all patients. We correlated changes in blood flow measured during the language comprehension task with the scores achieved in the Token Test. The regions which best correlated with the training-induced improvement in verbal comprehension were the posterior part of the right superior temporal gyrus and the left precuneus. This study supports the role of the right hemisphere in recovery from aphasia and demonstrates that the improvement in auditory comprehension induced by specific training is associated with functional brain reorganization.

A total of 181 human immunodeficiency virus (HIV)-seropositive hemophiliacs and 28 hemophilic controls were evaluated by psychometric tests and by electroencephalogram (EEG). Patients were classified from stages 1-6 according to the immunological criteria of the Walter Reed staging system. Statistical analysis of psychometric data showed an effect of the stage of the disease on test performances, indicating a decline in attention, accumulation of perceptual interferences, decline in visuoperceptual speed and visuomotor response speed and reduced verbal memory performance, especially in stage 6 patients. Comparison of performance levels with normative test data already revealed cognitive deficits in about 20-30% of the patients in stages 2-5. As regards verbal memory, especially learning and recognition of new verbal information were impaired. In contrast, there was no significant deficit for nonverbal memory processing. Compared with the controls, patients exhibited an increasing number of abnormal EEG findings in stages 2-6. As a conclusion, in the stages before acquired immunodeficiency syndrome (AIDS) develops, EEG findings as well as psychometric findings indicate central nervous system involvement of AIDS in about 20-30% of cases, whereas in full-blown AIDS there is a marked increase to 80%. Besides a more general deficit of attention and psychomotor speed as is seen in subcortical dementia, there is evidence for a particular verbal learning disorder, suggesting additional selective impairment of the brain.

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