Kuo Trudy Y, Van Petten Cyma
Department of Psychology, University of Arizona, Tucson, AZ 85721, USA.
Neuropsychologia. 2008;46(8):2243-57. doi: 10.1016/j.neuropsychologia.2008.02.018. Epub 2008 Feb 26.
It is well established that source memory retrieval--remembering relationships between a core item and some additional attribute of an event--engages prefrontal cortex (PFC) more than simple item memory. In event-related potentials (ERPs), this is manifest in a late-onset difference over PFC between studied items which mandate retrieval of a second attribute, and unstudied items which can be immediately rejected. Although some sorts of attribute conjunctions are easier to remember than others, the role of source retrieval difficulty on prefrontal activity has received little attention. We examined memory for conjunctions of object shape and color when color was an integral part of the depicted object, and when monochrome objects were surrounded by colored frames. Source accuracy was reliably worse when shape and color were spatially separated, but prefrontal activity did not vary across the object-color and frame-color conditions. The insensitivity of prefrontal ERPs to this perceptual manipulation of difficulty stands in contrast to their sensitivity to encoding task: deliberate voluntary effort to integrate objects and colors during encoding reduced prefrontal activity during retrieval, but perceptual organization of stimuli did not. The amplitudes of ERPs over parietal cortex were larger for frame-color than object-color stimuli during both study and test phases of the memory task. Individual variability in parietal ERPs was strongly correlated with memory accuracy, which we suggest reflects a contribution of visual working memory to long-term memory. We discuss multiple bottlenecks for source memory performance.
众所周知，来源记忆检索——记住核心项目与事件的某些附加属性之间的关系——比简单的项目记忆更能激活前额叶皮层（PFC）。在事件相关电位（ERP）中，这表现为在PFC上，需要检索第二个属性的已研究项目与可以立即排除的未研究项目之间存在晚期差异。虽然某些类型的属性联结比其他类型更容易记忆，但来源检索难度对前额叶活动的作用却很少受到关注。我们研究了在颜色是所描绘物体的一个组成部分时，以及单色物体被彩色边框包围时，对物体形状和颜色联结的记忆。当形状和颜色在空间上分离时，来源准确性确实更差，但前额叶活动在物体颜色和边框颜色条件下并没有变化。前额叶ERP对这种难度的感知操作不敏感，这与它们对编码任务的敏感性形成对比：在编码过程中刻意自愿地努力整合物体和颜色会降低检索过程中的前额叶活动，但刺激的感知组织则不会。在记忆任务的学习和测试阶段，顶叶皮层上ERP的振幅对于边框颜色刺激比物体颜色刺激更大。顶叶ERP的个体差异与记忆准确性密切相关，我们认为这反映了视觉工作记忆对长期记忆的贡献。我们讨论了来源记忆表现的多个瓶颈。
