Abstract: Encoding and retrieval are two important phases of memory. Encoding produces memory engraved and re-trieval reactivates previously encoded information. The approach to the relationship between encoding and re-trieval is meaningful for the better understanding of the nature of memory. As for explicit memory, the relation of encoding and retrieval has been investigated by many researchers who have found out that the performance of a secondary task during encoding reduced the later memory performance, but the division of the attention in the same way during retrieval had virtually no effect on memory performance, which indicated an asymmetry be-tween encoding and retrieval processes. With respect to implicit memory, an asymmetry was also found in one of our previous studies (Meng & Guo, 2006), but the asymmetry is somewhat different from that in explicit mem-ory, that is, the performance of a concurrent task during encoding had no effect on later task performance, but interference during retrieval disrupted priming, and reduced task performance. In order to clarify the issues we conducted an ERP experiment.
The experiment was conducted with 16 undergraduate students as subjects and Chinese characters as stim-uli. The experiment adopted a study-to-test paradigm, in which participants performed a “shallow” (color) study task or a “deep” (pleasant) study task, followed by either a lexical decision (implicit) test (section 1) or a recog-nition (explicit) test (section 2). In interference task participants were asked to account the total number of “+” in a regulated orientation which appeared with a word, and was performed concurrently with either the encoding or the retrieval phase of the memory task for encoding interference condition or retrieval interference condition.
The results showed that: (1) the effects of interference to encoding in implicit memory test were different from that to retrieval. Interference during encoding had virtually no effect on N400 or P600 old/new ERP components, but interference during retrieval significantly reduced N400 old/new and P600 old/new components, which ab-olished behavior priming. (2) The effects of interference to encoding on ERP components in explicit memory test were different from that to retrieval. Interference during encoding had significant influence on later P600 old/new effect, but interference during retrieval did not produce such effect.
The results confirmed the finding of Meng & Guo (2006), that is, interference during encoding had effect on explicit memory, but left implicit memory intact. Interference during retrieval affected implicit memory, but had little effect on explicit memory. So the relationship between encoding and retrieval was different between implicit and explicit memory, thus providing further evidence on the dissociation between implicit and explicit memory.

Key words: implicit memory, explicit memory, encoding, retrieval, asymmetry, ERP old/new effect