Neural Correlates Of Retrieval Of Cross-Domain Inter-Item Associative Memory

Binding is an important cognitive process. During the encoding phase of episodic memory, we should integrate all kinds of perceived features of the objects into an untized presentation, only so can we retrieve the information in need correctly and resovle the problems effectively. There are many research fields on binding process, including source memory, context memory, and associative memory etc.. Dual process theory posits that, compared to item memory, more context details need to be retrieved in these kinds of memory, i.e. more recollective process. According to source monitoring framework, these kinds of memory need more executive process. With the use of cognitive neuroscience research techniques in memory, it was proved that multiple brain systems, especially prefrontal cortex and medial temporal lobes, contribute to retrieval of episodic memory. However, so far, there are different opinions about their roles in memory.Using event-related potentials, with face-word materials, we explored the neural correlates of retrieval of cross-domain inter-item associative memory. It was supposed that there were two different processes in disengaging the associative information:ecphorc process and executive process. The present research included four studies, which used classical associative recognition paradigm and cued recognition paradigm. In the first study, we explored the time course of these two processes. In the second and third studies, we manipulated encoding repetition pattern and confidence to dissociate them empirically. In the fourth study, with cued recognition task, we further dissociated the ERPs old/new effects indexed these two processes. The main results were as follows:1. The retrieval of cross-domain inter-item associative memory included item retrieval and relational retrieval. The correct response for relation retrieval was smaller than that of item retrieval, and the reaction time was longer than that of item retrieval.2. There were significant differences between massed repetition and spaced repetition on associative memory peformance. The accuracy of spaced repetition was higher than massed repetition, and the reaction time was less than that of massed repetition.3. Using classical associative recognition paradigm, it was found that the ERPs old/new effect emerged at about200-300ms after stimulus. As the time went on, at about700ms, the scalp distribution of old/new changed qualitily. On general, before700ms, the early old/new effect emerged at the more posterior brain cortex, whereas, after700ms, the late old/new effect was maximal over prefrontal cortex.4. Manipulating encoding repetition pattern, it was found that during about350-700ms after stimulus, the amplitude of ERPs of space repetition was more positive than that of massed repetition at fronto-central and central areas for "same" condition. Manipulating confidence, it was found that from about350ms after stimulus, at prefrontal areas, the amplitude of ERPs of low confidence was more positive than that of high confidence, and the same pattern also appeared from about250ms, at frontal and fronto-central cortex.5. Using cued recognition paradigm, it were found that during the face item recognition phase,400～600ms after stimulus, the ERPs old/new effect of face emerged at posterior cortex, and during800～1300ms, at prefrontal cortex, the amplitude of ERPs of old face was higher than that of new face; at posterior cortex, there was reversed old/new effect. During the associative recognition phase,300-450ms after the verb was presented, both same/new effect and rearranged/new effect distributed at posterior cortex; during300～450ms and450～700ms, same/rearranged effect emerged at the frontal-central-parietal-occipital cortex.Based the above results, it was suggested that there were two distinct processes:ecphorc process and executive process in the retrieval of cross-domain inter-item associative memory. Early posterior ERPs old/new effect indexed the ecphorc process, and late prefrontal ERPs old/new effect indexed executive process. At the early phase of retrievel, ecphorc process dominated, while at the same time, there might be retrieval attempt process and monitoring process in prefrontal cortex. At the late phase of retrieval, evaluating the products of retrieval became the core cognitive process. It was inferred that during the retrieval of episodic memory, people should firstly recover the memory, and then evaluate the retrieved information before making a decision. These conclusions enriched the researches on brain mechanism in episodic memory and provided supports for the two-component framework. At the same time, this research promoted our understanding of retrieval processes and provided the basis for us to explain human learning and memory.