DESIGN OF FUNCTIONAL BRAIN MAPPING STUDIES WITH PET AND O-WATER

正电子发射断层扫描（PET）与氧-15水被广泛使用 以确定局部脑血流量（rCBF）的变化， 功能性脑映射实验，同时受试者执行特定的 神经行为任务。我们进行了模拟研究， 显示当PET扫描数据收集期间rCBF发生变化时， 测得的流量非常接近开始时的流量值， 扫描，而不是扫描期间的流量的平均值。 这对设计和解释 大脑映射研究涉及两个部分，一个学习或 实践阶段，以及回忆或执行阶段。如果这两个阶段是 在扫描过程中以交替方式执行，而无需注意 当扫描开始时，测量的rCBF将反映随机的 在两个阶段期间的rCBF曲线的组合。相反，如果 任务性能与扫描开始的时间相协调， 测量的rCBF可以反映两个阶段中的一个或另一个， 这使得人们能够确定哪些大脑区域参与了 任务组件。 这一假设正在通过视觉记忆激活任务进行测试 当受试者观看幻灯片时， 不熟悉的面孔和回忆阶段，当他们表明他们是否 以前见过他们的脸。注射时间 选择0-15水和任务的开始，使得受试者 执行这两个任务阶段中的一个或另一个， 扫描的前20秒因此，扫描应反映 编码或回忆。目前正在收集扫描数据。数据将 以确定是否检测到不同的激活区域 取决于任务的哪个阶段正在执行， 扫描的开始。结果还将与之前进行比较 实验时，使用这种激活任务，但不考虑 扫描开始的时候。

Positron emission tomography (PET) with oxygen-15 water is widely used to determine regional cerebral blood flow (rCBF) changes during functional brain mapping experiments while subjects perform specific neurobehavioral tasks. We have performed simulation studies which showed that when rCBF changes during PET scan data collection, the measured flow is very close to the flow value present at the start of the scan, rather than being an average of the flows during the scan. This has implications with regard to the design and interpretation of brain mapping studies which involve two components, a learning or practice phase, and a recall or execution phase. If the two phases are performed in an alternating fashion during the scan without attention to when the scan starts, the measured rCBF will reflect a random combination of the rCBF profiles during the two phases. Instead, if task performance is coordinated with the time the scan starts, measured rCBF may reflect one or the other of the two phases, permitting one to determine which brain regions are involved in the task components. This hypothesis is being tested with a visual memory activation task which involves an encoding phase when subjects view slides of unfamiliar faces, and a recall phase when they indicate whether they have previously seen the faces presented to them. The injection time of 0-15 water and the onset of the task are selected so that subjects are performing one or the other of these two task phases during the first 20 sec of the scan. The scans should therefore reflect either encoding or recall. Scan data are currently being collected. Data will be analyzed to determine if different areas of activation are detected depending upon which phase of the task was being performed at the start of the scan. Results will also be compared to earlier experiments when this activation task was used but without regard to when the scan began.