Functional reorganization of spatial transformations after a parietal lesion.

Background: Mental spatial transformations are ubiquitous and necessary for everyday spatial cognition, such as packing luggage into a car or repairing a broken vase. The posterior parietal cortex is known to be involved in performing such transformations.

Objective: To measure reorganization after lesioning of posterior parietal cortex areas subserving spatial transformation.

Method: Brain activity in a patient who underwent a resection of right parietal cortex to manage intractable epilepsy was measured using fMRI while he performed a set of spatial transformation tasks. These data were compared with data from a group of healthy control subjects.

Results: During spatial transformations, activity in the regions overlapping the resection was reduced in the patient compared with control subjects, but activity in the contralateral cortex was greater than that of control subjects.

Conclusions: After a lesion the left hemisphere can adopt components of spatial reasoning normally subserved by the right hemisphere. This converges with evidence that components of language processing normally subserved by the left hemisphere can be taken over by the right hemisphere, suggesting that plasticity of function in the adult human cortex is a general characteristic.