Neuroimaging Of Frontal Lobe Functioning During Cognitio

通过功能性神经成像来确定局部神经元活动，我们发现正常受试者在执行涉及工作记忆的任务时使用的皮质网络包括背外侧前额叶皮层、下顶叶小叶和下颞枕皮层。在其他与前额叶皮层相关的任务中，我们已经表明，在单词生成（语言流畅）任务中，语义和语音线索激活了类似的大脑区域，包括前扣带、左额叶皮层、丘脑和小脑，但它们之间存在微妙的差异，这与病变文献一致。在一项关于正常衰老中认知激活的研究中，我们发现神经生理变化是依赖于环境的。也就是说，在不同的任务中，生命周期的明显变化是不同的，这取决于特定任务中特定神经系统的作用。在年轻受试者执行任务时生理活动通常被抑制的区域，年长受试者激活的更多，而且，他们激活的越多（或未能抑制），他们在任务中的表现就越差。在其他领域，年轻人在执行任务时通常会增加生理活动，而老年人的活动较少；这些区域越不活跃，他们的表现就越差。我们还证实，系统级大脑活动的大规模变化（伴随行为的非线性变化）遵循非线性动力学理论的预测，并且我们已经定义了可区分的额叶区域（外侧前额叶皮层和前扣带皮层），它们在任务切换（分别克服先前任务需求的残留抑制和启动新任务）中为不同的认知成分提供支持。我们还表明，在个体健康受试者中激活的神经系统模式反映了他们在工作记忆任务中的表现水平和认知策略（言语与空间）。

Using functional neuroimaging to determine local neuronal activity, we have found that normal subjects performing tasks involving working memory use a cortical network including dorsolateral prefrontal cortex, inferior parietal lobule, and inferior temporo-occipital cortex. In other tasks related to prefrontal cortex, we have shown, with word generation (verbal fluency) tasks that semantic and phonologic cues activate similar brain regions including anterior cingulate, left frontal cortex, thalamus and cerebellum, but subtle differences exist between them that are consistent with the lesion literature. In a study of cognitive activation in normal aging we found that neurophysiological changes were context dependent. That is, apparent changes over the life span differed in different tasks, depending on the role of the particular neural system for the particular task. In regions where physiological activity is normally suppressed when young subjects perform the tasks older subjects activate more, and, moreover, the more they activate (or fail to suppress), the worse they perform on the tasks. In other areas, where physiological activity is normally increased in young people performing the tasks, older subjects activate less; and the less they activate these regions, the more impaired their performance. We have also confirmed that large-scale changes in brain activity at the systems level (accompanying nonlinear changes in behavior) follow predictions from nonlinear dynamical theory, and we have defined discriminable frontal lobe regions (lateral prefrontal cortex and anterior cingulate cortex) that subserve different cognitive components in switching between tasks (overcoming the residual inhibition of previous task demands and initiating a new task, respectively). We have also shown that the neural system patterns activated in individual healthy subjects reflect their levels of performance and cognitive strategies (verbal versus spatial) on a working memory task.