ACTIVATION OF REGIONAL CEREBRAL BLOOD-FLOW BY A MEMORIZATION TASK IN EARLY PARKINSONS-DISEASE PATIENTS AND NORMAL SUBJECTS

Task-induced changes in regional cerebral blood flow (rCBF) during mem ory activation were compared in 18 right-handed patients with early Pa rkinson's disease (PD) and 20 normal volunteers using the same activat ion paradigm. We used single-photon emission computed tomography and X e-133 in 21 regions of interest during rest, passive listening of a wo rd list, and memorization of another word list, which was followed by a free recall test immediately after completion of the rCBF measuremen t. The average performance on free recall was not significantly lower in PD patients than in controls. In normal subjects, five left-sided r egions (anterior middle frontal, posterior inferior frontal, superior middle temporal, thalamic, and lenticular) showed a significant increa se in memorizing compared to passive listening. This pattern of activa tion suggests the existence of a verbal rehearsal strategy during the memorization task in normals. In PD patients, increases in these regio ns did not reach significance, whereas significant activations were no ted in superior prefrontal regions. Such alterations in the pattern of activation in PD patients, despite a memory performance similar to th at of controls are viewed as a consequence of an early dysfunction of the articulatory loop system and of compensatory mechanisms in other p arts of the frontal lobe emerging in the early stages of the disease.