DIFFERENTIAL PATTERNS OF LANGUAGE AND MOTOR REORGANIZATION FOLLOWING EARLY LEFT-HEMISPHERE LESION - A PET STUDY

Objective: There is extensive evidence for postlesional plasticity in the language and motor domains. We examined possible domain-specific d ifferences in reorganizational patterns, hypothesizing that interhemis pheric reorganization would be predominantly homotopic for language, b ut predominantly nonhomotopic for motor control. Design: Using oxygen 15-water positron emission tomography, regional cerebral blood flow wa s studied during rest, listening to sentences, repetition of sentences , and finger tapping of the right hand, Task-specific primary, seconda ry, and tertiary regions of interest were defined according to the deg ree of regional involvement in language/motor functions as documented in previous studies. Regional activations were compared within and acr oss functional domains. Patients: Nine patients (aged 4-20 years) with unilateral left hemisphere lesion involving both the primary motor an d perisylvian language cortices were studied. Two samples of healthy a dults were included for additional comparisons. Main Outcome Measure: Hemispheric asymmetry of blood Row changes within regions of interest. Results: As predicted, rightward asymmetry of activations in primary and secondary regions was stronger for language than for movement, but the expected inverse difference for tertiary regions (greater rightwa rd asymmetry of motor activations) was not found. Within-domain compar isons showed that for listening to sentences, rightward asymmetry was strongest in primary and weakest in tertiary regions, whereas the inve rse differences were found for movement. Conclusion: The findings sugg est a greater potential for homotopic interhemispheric reorganization in the language than in the motor domain. Interhemispheric motor reorg anization was generally limited.