CAJ | 학술논문

本研究采用ERPs技术,探讨编码任务对来源记忆的影响及其神经机制。在学习阶段,让被试进行两种编码操作：匹配判断任务和大小判断任务;在测验阶段,让被试进行来源判断任务。行为结果发现：在编码阶段,匹配判断任务比大小判断任务需要更长的时间;在测验阶段,匹配判断任务在＂项目旧/背景旧＂和＂部分旧＂条件的正确率显著高于大小判断任务,匹配判断任务在＂项目旧/背景旧＂条件的反应时显著短于大小判断任务。测验阶段ERPs结果发现：两种编码任务的新旧效应在200～700ms均有较广泛的头皮分布,而在700～1100ms呈前额皮层最大化分布;匹配判断任务的新旧效应比大小判断任务更大,表现在600～700ms的FPz电极以及700～800ms的Pz、P4电极。由此可见,在来源记忆中,编码任务影响来源记忆,主要表现在后部顶区位置;晚期前额皮层新旧效应不受任务难度因素的影响。
본연구채용ERPs기술,탐토편마임무대래원기억적영향급기신경궤제。재학습계단,양피시진행량충편마조작：필배판단임무화대소판단임무;재측험계단,양피시진행래원판단임무。행위결과발현：재편마계단,필배판단임무비대소판단임무수요경장적시간;재측험계단,필배판단임무재＂항목구/배경구＂화＂부분구＂조건적정학솔현저고우대소판단임무,필배판단임무재＂항목구/배경구＂조건적반응시현저단우대소판단임무。측험계단ERPs결과발현：량충편마임무적신구효응재200～700ms균유교엄범적두피분포,이재700～1100ms정전액피층최대화분포;필배판단임무적신구효응비대소판단임무경대,표현재600～700ms적FPz전겁이급700～800ms적Pz、P4전겁。유차가견,재래원기억중,편마임무영향래원기억,주요표현재후부정구위치;만기전액피층신구효응불수임무난도인소적영향。
Item memory and source memory are two important aspects of episodic memory. Source memory is defined as the time, place and background information of the object that we should remember. In event-related potentials（ERPs） researches, when participants were asked to retrieve additional information about a studied stimulus in a source memory test, there are two kinds of old/new effects： early old/new effect and late old/new effect. The early old/new effect which appears across widespread regions of the scalp, but maximal at centro-parietal scalp sites is observed from around 200 to 400 ms after stimulus onset. The late old/new effect over prefrontal cortex（PFC） begins around 700 to 800 ms after stimulus onset. It is well established that source memory retrieval engages late old/new effect more than simple item memory. Some researchers think that the early old/new effect which depends on the integrity of the medial temporal lobe and diencephalon indexes successful item recognition, and the late old/new effect refl ects the executive process. Thus, this late-onset PFC old/new effect plays an important role in source retrieval. So far, it is still not clear why source retrieval places greater demands on prefrontal cortex than old/new recognition judgments. In the current experiment, using event-related potentials technique, we explored the effects of encoding task on source memory and its neural correlates. Seventeen college students（7 male, 10 females） took part in our experiment. Stimuli were 640 digitized pictures in which an object was superimposed on a background. During the study phase, subjects were received two kinds of tasks. For one kind of task, they were asked to make judgments about the congruity between items and backgrounds. For the other, they were received a size-judgment task, i.e., whether the items（object） were larger or smaller than the CRT monitor. In the subsequent test phase, there were four categories of stimuli（＂old/ old＂, ＂old/ new＂, ＂new/old＂, ＂new/ new＂）. Subjects were told to determine whether the picture was ＂completely old＂＂part old＂ or ＂completely new＂. The ERPs for ＂completely old＂ and ＂completely new＂ were averaged separately. We supposed that the early old/new effect was greater for congruity-judgment task than size-judgment task, and the prefrontal old/new effect was insensitive to encoding task and manipulation of difficulty. The behavioral results showed that, in the study phase, the reaction times of congruity-judgment task were slower than size-judgment task. In the test phase, the source accuracy of congruity-judgment task was reliably better than that of size-judgment task for the ＂completely old＂ and ＂part old＂ conditions while the reaction times of congruity-judgment task for ＂completely old＂ condition were signifi cantly faster than that of size-judgment task. The ERPs results showed that early and late old/new effect were observed under both encoding conditions. It was found that during about 600～700ms after stimulus onset, the amplitude of ERPs of congruity-judgment task was more positive than that of size-judgment task at FPz, and the same pattern also appeared from 700～800ms, at Pz and P4. Based on the above results, conclusions could be drawn that（1） early ERP old/new effect and late prefrontal ERP old/new effect may index two important processes in source memory retrieval;（2） the infl uence of encoding task on source memory was mainly manifested at the more posterior brain cortex;（3） the late prefrontal old/new effect did not co-vary with the retrieval diffi culty. This research promoted our understanding of the neural mechanism of retrieval process of episodic memory.