1. Positron emission tomography (PET) studies were performed in six normal right-handed male volunteers (age 30 +/- 3) to investigate the relationship between cerebral activation as measured by relative regional cerebral blood flow (rCBF) and force peak exerted during right index finger flexion. The purpose was to determine in which central motor structures activity is directly correlated with force for repeatedly executed movements. 2. Twelve PET rCBF measurements were performed in each volunteer with the use of H2(15)O as a perfusion tracer. Volunteers pressed a Morse-key repetitively with their right index finger for 2 min while lying in a supine position in the PET camera. The device was fitted with strain gauges to measure the force peaks exerted upon it. Scans were collected twice each at five different levels of exerted force peak and in a resting state. Individual and group results were co-registered with anatomic magnetic resonance images (MRI). 3. Group analysis revealed four major regions with a high correlation between rCBF and different degrees of repetitively exerted force peaks. One was located in the arm area of the left lateral surface [primary somatosensory and motor cortex (SI, MI)]. The second area was situated on the left mesial surface of the brain, posterior to the anterior commissure (AC) and encompassing the first gyrus dorsal to the cingulate sulcus. This area is thought to be homologous to the posterior part of the supplementary motor area (SMA) in the monkey. The third area was the dorsal bank of the posterior cingulate sulcus. The fourth area showing a significant correlation between rCBF and force peaks was in the cerebellar vermis. 4. Individual PET data were co-registered with each individual's MRI in order to identify precisely the locations of structures demonstrating a positive correlation between rCBF and force peak. Activated areas on the mesial surface consisted of the same two distinct regions seen in the group data. In three subjects the focus on the lateral surface of the cortex appeared to extend into the caudal premotor area; in two it extended into the rostral part of the superior parietal area. In no subject did blood flow in the anterior cingulate areas and anterior SMA show a correlation with the force exerted. Cerebellar correlations were present in the vermis in all subjects.(ABSTRACT TRUNCATED AT 400 WORDS)

Summary: Local cerebral hemodynamics and oxygen metabolism were measured by positron emission tomog raphy (PET) with the oxygen-15 C50) steady-state method in baboons, immediately before (TO), 1 (Tl), and 3-4 (T2) h after permanent middle cerebral artery occlu sion (MCAO). At Tl, there was a marked fall in both cerebral blood flow (CBF) and the CBF/cerebral blood volume (CBV) ratio in the occluded territory; these changes were sustained at T2, indicating stable reduction in cerebral perfusion pressure and lack of spontaneous reperfusion within this time range. Compared with pre occlusion conditions, the oxygen extraction fraction (OEF) in the occluded territory was elevated at both Tl and T2, indicative of a persistent oligemia/ischemia for up to 3 h after MCAO. At T2, however, this OEF increase had lessened, concomitantly with a decline in cerebral metabolic rate of oxygen (CMR02). This impairment of Positron emission tomography (PET) studies in humans have provided a unique insight into the metabolic and hemodynamic events which charac terize the evolution of acutely ischemic tissue, es pecially in relation to its function and viability (Baron et aI., 1981(Baron et aI., , 1983 Lenzi et aI., 1982; Wise et aI., 1983;Powers and Raichle, 1985; Hakim et aI.,

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