Exploring The Relationship Between Implicit And Explicit Memory By Event-related Potential (ERP) Effects Of Repeated Learning

The relationship between implicit memory and explicit memory has been heartedly argued. There are numerous influencing factors about implicit memory and explicit memory, such as, repeated learning, depth of processing, divided attention, interference, study-to-test modality changes, and age and so on. However, there is little research to explore the relationship between implicit memory and explicit memory from the aspect of repetition learning and the change of attention resource. According to some researches about repeated learning and attention resource, this dissertation put forward two hypothetical propositions: on the one hand, if ample attention resources can be gained, repeated learning can only improve the achievement of explicit memory; on the other hand, if little attention resources can be gained, the first learning can only improve the achievement of implicit memory. So, double separation phenomenon might be appeared.Numerous studies have reported distinct neural mechanisms between implicit and explicit, encoding and retrieval. Using Event-related Potentials (ERPs), the present study used a study-test paradigm to investigate the difference and similarity between repeated learning effects and old new effects during implicit and explicit memory test, in order to enclose the relationship between implicit memory and explicit memory. In the first experiment, the materials with low frequency words, in the initial encoding study phase, participants were asked to judge whether the target word was a noun or a verb. Each visual stimulus was presented either once or twice (repeated learning). One of the two words in each stimulus was a target and the other was a non-target. During the testing phase, participants performed both an explicit memory test (old/new judgment) and an indirect memory test (word/non-word judgment). ERPs were recorded during both study (encoding) and test (retrieval) phases. The results showed that (1) There were significant study type effect and repetition effect in indirect and direct test between 400 and 600ms. (2)During 400 to 600ms intervals, if there is little attention resource, first learning old/new effect only occurred over central scalp locations in indirect test. (3)Old/new effect mainly appeared over central scalp locations in indirect test. These results demonstrated that attention would effect both direct and indirect test, conscious retrieval need more attention resources during encoding. Attention and repetition learning could make conscious retrieval into automatization. These results supported multiple memory form.A further research explore the reason why target item has repeated learning effects in implicit memory test during the first study and want to confirm whether the first hypothesis proposition is right or wrong. In the second experiment, the materials with low frequency and high frequency words, in the initial encoding study phase, participants were asked to judge whether the word was a noun or a verb and there is only one word on the screen. Each visual stimulus was presented either once or twice (repeated learning). The rest is the same as the first experience. The results showed that difference from explicit memory test, during 400-570ms, there is no repeated learning effect, whether the material is high or low frequency words.The first and the second experiments have validated the two hypotheses that this dissertation put forward. These results suggest that attention resources can affect the implicit memory test, but the explicit memory test is more sensitive than implicit memory test to attention resources. Implicit memory and explicit memory are two distinct memory systems underlying different neural substrates.