MAPPING DRUG-INDUCED CHANGES IN CEREBRAL R(2)ASTERISK BY MULTIPLE GRADIENT RECALLED ECHO FUNCTIONAL MRI

A Multiple Gradient Recalled Echo MRI sequence was used to map spatial and temporal changes in the rate of MR signal decay (R(2)()) in resp onse to L-3,4-dihydroxyphenylalanine (levodopa) in the striatal dopami nergic system of a rhesus monkey unilaterally lesioned with 4-phenyl-1 ,2,3,6-tetrahydropyridine hydrochloride (MPTP). R(2)() decreased sign ificantly in the right (dopamine depleted) putamen and caudate followi ng levodopa. More focal areas of smaller R(2)() decline were also obs erved in these structures in the left hemisphere. The observed spatial and temporal patterns of R(2)() change support the view that the met hod is monitoring changes in neural activity.