膽堿是一種與記憶密切相關的物質,以往研究主要探討不同膽堿類藥物對外顯記憶的影響,內隱記憶受膽堿影響與外顯記憶是否相同仍存在爭議。實驗1采用詞匯判斷與詞匯再認任務,比較內隱記憶與外顯記憶在擬膽堿藥物尼古丁的影響下,記憶成績是否發生變化。結果表明,攝入尼古丁后,內隱與外顯記憶成績都有一定程度的下降,但內隱記憶受影響的程度更大。為進一步探討尼古丁對兩種記憶的影響,實驗2分別在編碼前與提取前攝入尼古丁,觀察其對兩種記憶不同階段的影響,并使用ERP技術觀察其中受影響的成分。結果表明,編碼前攝入尼古丁使內隱記憶與外顯記憶的概念加工都受到影響,而對知覺加工沒有影響。提取前攝入尼古丁則對兩種記憶的概念加工與知覺加工都產生影響,但是對內隱記憶的影響更大。上述結果表明,擬膽堿物質尼古丁對記憶影響的情況與實驗任務較為一致,而與記憶種類關系較小。對兩種記憶的影響不同可能主要源于兩種記憶采用不同的實驗任務導致,兩者的生理機制有一定程度的重疊。

Studies have shown that choline is a substance that is closely related to memory. Previous studies focused on the effect of cholinergic drugs on explicit memory, and those results revealed that explicit memory is sensitive to most cholinergic drugs. However, relatively few studies have discussed the effect of cholinergic drugs on implicit memory. Furthermore, whether the effect of cholinergic drugs on implicit memory is consistent with explicit memory is still uncertain. The effect of cholinergic drugs on memory was investigated by drawing a comparison between the participants with nicotine condition and those without. We used lexical decision and lexical recognition tasks to test implicit and explicit memory, respectively. In experiment 1, 30 subjects participated in two occasions, 2 days apart. They participated once in memory tasks after receiving 12 mg/ml body weight of nicotine and once after receiving 0 mg/ml placebo. Experiment 2 examined whether receiving treatment before encoding or before the retrieval phase would moderate the cholinergic effect in explicit and implicit memory. In experiment 2, 19 subjects participated in two experimental occasions, 2 days apart, as follows: after receiving 12 mg/ml body weight of nicotine before the encoding phase; after receiving nicotine before the retrieval phase. In addition, we adopted event-related potential(ERP) technology to observe the affected ERPs. Participants were instructed to response to corresponding items by pressing keyboard. The Reaction Time and Accuracy data on retrieval phase of the two memory tasks were recorded and analyzed. Implicit and explicit memory performance declined under nicotine condition in both experiments. It reflected that receiving nicotine not only impacted explicit memory but also implicit memory. Furthermore, nicotine effects are moderated by the level of processing at the encoding phase. Such impact only occurred on the deep processing level. Moreover, memory retrieval after receiving nicotine was affected. These effects were more remarkable on implicit memory retrieval than on explicit memory. The results of ERP data also showed that related ERPs of memory were affected by nicotine. In conclusion, results from the current study revealed that effects of cholinergic drugs were similar on implicit and explicit memory. The rest of the segregated results might have been due to the discrepancy of memory tasks rather than the differences in physiological mechanisms of the two memory types. Implicit memory and explicit memory might not belong to two extremely independent memory systems, because there are some covariant effects existing between them.