Hurtig R R, Hichwa R D, O'Leary D S, Boles Ponto L L, Narayana S, Watkins G L, Andreasen N C
Department of Speech Pathology and Audiology, University of Iowa, Iowa City.
J Cereb Blood Flow Metab. 1994 May;14(3):423-30. doi: 10.1038/jcbfm.1994.53.
The multiple injection [15O]water method offers unique opportunities for studying cognitive processing by the human brain. The influence of the duration and temporal placement of an activation task, in relation to the arrival of the radiotracer in the brain, is a fundamental methodologic question for cognitive activation studies. A quantitative positron emission tomography (PET) study of five normal volunteers was performed in which the stimulation consisted of a visual activation task (alternating checkerboard pattern) superimposed on an auditory baseline task (syllable monitoring). Ten injection conditions, with varying duration and timing of the visual activation, were used. Regional CBF (rCBF) in visual cortex was measured quantitatively using the autoradiographic method. A 20-s stimulation, centered on the bolus arrival in the brain, produced significant changes in rCBF. Because varying the duration and timing of the activation task technically violates the temporal homogeneity assumption of the autoradiographic model, a mathematical simulation was formulated to evaluate the potential influence of these variations. Results of the simulation are consistent with the PET data and suggest that activation can be limited to a narrow temporal window centered on the radiotracer uptake. The ability to observe significant changes in rCBF with short stimulation intervals is of particular interest in the use of [15O]water PET for studies of cognitive processes with a short time course.
多次注射[15O]水法为研究人类大脑的认知加工提供了独特的机会。激活任务的持续时间和时间安排相对于放射性示踪剂到达大脑的影响，是认知激活研究的一个基本方法学问题。对五名正常志愿者进行了一项定量正电子发射断层扫描（PET）研究，其中刺激包括叠加在听觉基线任务（音节监测）上的视觉激活任务（交替棋盘图案）。使用了十种注射条件，视觉激活的持续时间和时间各不相同。使用放射自显影法对视觉皮层的局部脑血流量（rCBF）进行了定量测量。以团注到达大脑为中心的20秒刺激使rCBF产生了显著变化。由于改变激活任务的持续时间和时间在技术上违反了放射自显影模型的时间同质性假设，因此制定了一个数学模拟来评估这些变化的潜在影响。模拟结果与PET数据一致，并表明激活可以局限于以放射性示踪剂摄取为中心的狭窄时间窗口内。在使用[15O]水PET研究短时间进程的认知过程时，能够在短刺激间隔下观察到rCBF的显著变化特别令人感兴趣。
