图形项目记忆与位置来源提取的ERP研究

采用事件相关电位（ERP）方法研究大学生图形项目记忆与位置来源提取新/旧效应的时、空分布特征。学习屏幕左侧（或右侧）呈现的图形后在屏幕中央呈现某一测验项目（已学图形或新图形），对受试者进行两类测验：其一是判断该项目是否已学过；其二是将从某侧学过的测验项目判断为目标，而将其它测验项目判断为非目标的来源测验（排除任务）。实验结果表明：图形位置来源提取比项目再认新/旧效应的头皮分布更广，持续时程更长；与前人相同实验范式的研究结果相比，本研究位置来源提取效应的头皮分布范围较广；非目标-旧图形与目标图形新/旧效应的头皮激活程度不同。上述结果说明：图形位置来源提取比项目再认激活的大脑区域更多，这与双重加工模型的观点一致；实验范式和来源知觉的特性共同调节来源记忆新/旧效应的时、空分布特征；意识水平对来源信息提取的新/旧效应存在一定的影响

An Event-Related Potentials Study of Item Memory and Location Source Retrieval of Line Drawing

Background Item memory and source memory are two important aspects of episodic memory. Recent studies about the behavioral characteristics and neural basis of item memory and source memory indicate that they are two different psychological processions. Two models have been proposed to describe the relation between these two kinds of memories: single-process model and dual-process model. Each model is supported by substantial evidence. Up to now, three kinds of paradigms have been formed to discriminate the relation between item memory and source memory:sequential task, three-button task and exclusion task. Reviews of these paradigms indicate that the results based on sequential task and three-button task are consistent whereas the results with exclusion task are not. Based on many event-related potential (ERP) studies, Cycowicz, et al. (2003) argued that the inconsistent results of exclusion task were due to the sensory-specific of source but not the test paradigm. To validate the results by Cycowicz, et al. and to extend previous study on item memory and source memory, the present ERP study was conducted to investigate the temporal and spatial distributions of the old/new effects for item recognition and location source retrieval on line drawing. Method Sixteen healthy undergraduates participated in this study. The stimuli were 400 drawings which were divided into 8 blocks. In each block, 30 drawings were presented either on left or on right screen during study phase, and then two tests were performed with 20 other drawings added. The first task was to decide whether each drawing presented at the central of the screen was learned or not, and the second task was to judge drawings learned from one location (left or right) as targets and other drawings as non-targets (called non-target-old or non-target-new) (exclusion task). Each drawing was displayed 500ms with the ISI of 1300ms and 1800ms during study phase and test phase respectively. EEG was recorded continuously using an Electro-cap with 62 locations (extended 10-20 system placements). Results The results were analyzed using a three-way repeated-measures ANOVA for three windows: 200~600ms, 600~1000ms,1000~1400ms. The three factors were memory judgment, left-right electrode sites and anterior-posterior sites. The ANOVA results indicated that the temporal distribution of the old/new effect for location source retrieval was longer than that of the old/new effect for item memory.Moreover, the spatial distribution of the former effect was wider than that of the latter. In other words, the old/new effect during 1000~1400ms for location source retrieval was not significant in item memory. The spatial and temporal distributive characteristics of the old/new effect for source memory were different from those of the previous studies. In addition, the old/new effects for target and non-target-old drawings were different. Conclusions First, location source retrieval is more difficult than item memory for drawing, which supports dual-process model. Second, Experimental paradigm and source characteristics regulate the spatial and temporal distributions of source retrieval effect together. Third, the level of consciousness during retrieval is also an important factor affecting source retrieval.