Recovery of Neglect After Right Hemispheric Damage

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Abstract
Background: The neural correlates of recovery of uni- lateral neglect (ULN), as well as of other consequences of focal brain damage, are largely unknown. Functional neuroimaging methods (in particular, positron emis- sion tomography (PET)) can be applied to the in vivo study of recovery mechanisms in neurologic patients. Objective: To evaluate the functional cerebral corre- lates of recovery from ULN in patients with right-sided lesions, with the use of a PET activation paradigm. Methods: Study of 3 patients with cerebrovascular le- sions that involved corticosubcortical (patient 1) or sub- cortical (patients 2 and 3) areas of the right hemisphere. Unilateral neglect was tested twice, before and after completion of a 2-month rehabilitation program, after which all 3 patients showed considerable improvement. Similarly, 2 PET examinations were performed, before and after recovery, during the performance of a visuos- patial task requiring the patients to detect and respond to visual targets moving on a computer screen from the right to the left visual hemifield (experimental condi- tion). The cerebral activation was compared with a base- line task in which subjects responded to a black dot flash- ing in a fixed position of the right hemifield. Results: The brain areas activated by the performance of the visuospatial task before and after recovery were compared. In all 3 patients, the regions notably more active after recovery were almost exclusively found in right-sided cortical areas and largely overlapped with those observed in a group of 4 normal subjects per- forming the same task. Other areas, which have been shown to be involved in attentional and oculomotor tasks in other PET studies, were also activated in patients with ULN. Conclusions: The behavioral recovery of ULN in these patients with predominantly subcortical lesions is mainly associated with cerebral activations in cortical regions similar to those observed in normal subjects. There is some evidence of functional reorganization in individual sub- jects, which involves other areas related to space repre- sentation and exploration. Arch Neurol. 1998;55:561-568

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