Duka T, Weissenborn R, Dienes Z
Laboratory of Experimental Psychology, University of Sussex, Falmer, Brighton, UK.
Psychopharmacology (Berl). 2001 Jan;153(3):295-306. doi: 10.1007/s002130000564.
Explicit memory (EM) is the memory for events which occurs with full awareness of where and how the recalled events took place, whereas implicit memory (IM) is the memory which is unfolded without any awareness of these events and usually becomes apparent when performance is facilitated by its presence. These two types of memory can be understood as different systems. Findings attempting to differentiate between the two systems in normal subjects have been controversial, with some researchers arguing that there is a single memory system and only the match in processes used during learning and later at retrieval can be important.
The present study compared the effects of alcohol (0.8 g/kg) or placebo administered prior to encoding and/or retrieval on measures of explicit and implicit memory in terms of recollective experience and familiarity.
At encoding subjects studied a list of 80 words presented in pairs. At retrieval, participants first carried out an implicit stem completion task, followed by an explicitly cued recall task (stem completion) which measured IM and EM respectively. After stem completion participants were required to indicate whether the items from the studied list were consciously recollected ("remember" response) or was known for a fact that were presented in the studied list ("know" response). In the IM task completed items from the studied list but not recognised by the subjects as such indicated memory without awareness. Studied items were of high and low associations. Forty-eight participants were tested in one of four drug conditions: alcohol-alcohol, placebo-placebo, placebo-alcohol, alcohol-placebo.
In the implicit stem completion task, alcohol did not affect overall correct completion rates. However, participants who received alcohol prior to encoding reported lower awareness of correctly completed study items. In the cued recall task, alcohol also did not affect overall performance. However, participants in the same drug-state conditions (SS) reported greater recollection than familiarity with study material, whereas participants who encoded and retrieved material in different drug-state conditions (DS) reported recollection and familiarity to the same extent. In addition, DS participants showed more familiarity with study material compared to SS participants. Direct comparisons between IM and EM tasks demonstrated that alcohol at retrieval decreased the cued recall of items from high associations compared to placebo, but did not have any effect on implicit stem completion.
In summary, these results demonstrate a dissociation of alcohol effects on measures of EM and IM. Alcohol administered prior to encoding reduced awareness of implicitly retrieved material, but did not impair IM per se, confirming previous findings with alcohol. In addition, the data provided new evidence for state-dependent retrieval effects on EM but not IM. It was also shown that for explicitly retrieved items, recollective experience benefits from same drug state, whereas familiarity benefits from different drug state between encoding and retrieval.
外显记忆（EM）是对在充分意识到回忆事件发生的地点和方式的情况下所发生事件的记忆，而内隐记忆（IM）是在没有对这些事件的任何意识的情况下展开的记忆，并且通常在其存在促进表现时变得明显。这两种类型的记忆可以被理解为不同的系统。试图在正常受试者中区分这两个系统的研究结果一直存在争议，一些研究人员认为存在单一的记忆系统，并且只有学习期间和随后检索时所使用过程的匹配才可能是重要的。
本研究比较了在编码和/或检索之前给予酒精（0.8克/千克）或安慰剂对基于回忆体验和熟悉度的外显和内隐记忆测量的影响。
在编码时，受试者学习80个成对呈现的单词列表。在检索时，参与者首先进行一项内隐词干补全任务，然后进行一项明确提示的回忆任务（词干补全），分别测量内隐记忆和外显记忆。在词干补全之后，参与者被要求指出来自学习列表的项目是有意识地回忆起来的（“记得”反应）还是事实上知道在学习列表中呈现过（“知道”反应）。在内隐记忆任务中，来自学习列表但未被受试者识别的完成项目表明是无意识的记忆。学习项目具有高关联性和低关联性。48名参与者在四种药物条件之一中接受测试：酒精-酒精、安慰剂-安慰剂、安慰剂-酒精、酒精-安慰剂。
在内隐词干补全任务中，酒精不影响总体正确完成率。然而，在编码前接受酒精的参与者报告对正确完成的学习项目的意识较低。在提示回忆任务中，酒精也不影响总体表现。然而，处于相同药物状态条件（SS）的参与者报告对学习材料的回忆多于熟悉度，而在不同药物状态条件（DS）下编码和检索材料的参与者报告回忆和熟悉度程度相同。此外，与SS参与者相比，DS参与者对学习材料表现出更多的熟悉度。内隐记忆和外显记忆任务之间的直接比较表明，与安慰剂相比，检索时的酒精降低了高关联性项目的提示回忆，但对内隐词干补全没有任何影响。
总之，这些结果表明酒精对外显记忆和内隐记忆测量的影响存在分离。编码前给予酒精降低了对内隐检索材料的意识，但本身并未损害内隐记忆，这证实了先前关于酒精的研究结果。此外，数据为状态依赖性检索对外显记忆而非内隐记忆的影响提供了新证据。还表明，对于明确检索的项目，回忆体验受益于相同的药物状态，而熟悉度受益于编码和检索之间的不同药物状态。
