Tomasi Dardo, Ernst Thomas, Caparelli Elisabeth C, Chang Linda
Medical Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
Hum Brain Mapp. 2006 Aug;27(8):694-705. doi: 10.1002/hbm.20211.
This parametric functional magnetic resonance imaging (fMRI) study investigates the balance of negative and positive fMRI signals in the brain. A set of visual attention (VA) and working memory (WM) tasks with graded levels of difficulty was used to deactivate separate but overlapping networks that include the frontal, temporal, occipital, and limbic lobes; regions commonly associated with auditory and emotional processing. Brain activation (% signal change and volume) was larger for VA tasks than for WM tasks, but deactivation was larger for WM tasks. Load-related increases of blood oxygenation level-dependent (BOLD) responses for different levels of task difficulty cross-correlated strongly in the deactivated network during VA but less so during WM. The variability of the deactivated network across different cognitive tasks supports the hypothesis that global cerebral blood flow vary across different tasks, but not between different levels of task difficulty of the same task. The task-dependent balance of activation and deactivation might allow maximization of resources for the activated network.
这项参数化功能磁共振成像（fMRI）研究调查了大脑中负性和正性fMRI信号的平衡。使用一组具有不同难度级别的视觉注意力（VA）和工作记忆（WM）任务来使包括额叶、颞叶、枕叶和边缘叶在内的不同但重叠的网络失活；这些区域通常与听觉和情绪处理相关。VA任务的脑激活（%信号变化和体积）比WM任务更大，但WM任务的失活更大。在VA期间，不同任务难度水平下与负荷相关的血氧水平依赖（BOLD）反应增加在失活网络中强烈交叉相关，但在WM期间则较弱。失活网络在不同认知任务中的变异性支持了这样一种假设，即全脑血流量在不同任务中有所不同，但在同一任务的不同难度水平之间没有差异。激活和失活的任务依赖性平衡可能使激活网络的资源最大化。
