Differential patterns of language and motor reorganization following early left hemisphere lesion: a PET study

There is extensive evidence for post-lesional plasticity in the language and motor domains. We examined possible domain-specific differences in reorganizational patterns, hypothesizing that interhemispheric reorganization would be predominantly homotopic for language, but predominantly nonhomotopic for motor control.

Using oxygen 15-water positron emission tomography, regional cerebral blood flow was studied during rest, listening to sentences, repetition of sentences, and finger tapping of the right hand. Task-specific primary, secondary, and tertiary regions of interest were defined according to the degree of regional involvement in language/motor functions as documented in previous studies. Regional activations were compared within and across functional domains.

Nine patients (aged 4-20 years) with unilateral left hemisphere lesion involving both the primary motor and perisylvian language cortices were studied. Two samples of healthy adults were included for additional comparisons.

Hemispheric asymmetry of blood flow changes within regions of interest.

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 rightward asymmetry of motor activations) was not found. Within-domain comparisons showed that for listening to sentences, rightward asymmetry was strongest in primary and weakest in tertiary regions, whereas the inverse differences were found for movement.

The findings suggest a greater potential for homotopic interhemispheric reorganization in the language than in the motor domain. Interhemispheric motor reorganization was generally limited.