State-Dependent Memory

Rats taught to run a maze under the influence of a depressant drug will often forget the route through the maze if tested later without the drug. Given the drug again, they retrieve their memory and run the maze successfully. This is called state-dependent memory (or state-dependent learning). The assumption made by researchers is that the animal's state of mind affects the encoding of the memory. When the same conditions are reinstated, it helps memory retrieval.

How can state-dependent learning be demonstrated in rats? What form of drug-induced state-dependent forgetting is known to occur in humans?

Alcohol-related state-dependent memory is known to occur with humans. Heavy drinkers may forget what they did while drunk, only to remember again the next time they drink. This phenomenon has been documented under experimental conditions using word lists.

Here is a less formal example:

While we were studying memory, I remembered a situation in which my friend and I were at a Rush concert at the Omni in Atlanta. We were talking about a particular song that the band was playing. After the show, the next week, I asked the same fellow if he remembered what he said about the song during the concert. He said that he didn't because he was pretty drunk that evening. I gave him specifics about what he said but he still didn't remember.

Later, after a couple pitchers, he asked me if he had told me about that same song. I told him he had and asked him the same questions again. This time he remembered that, during the concert, he told me the order of songs to expect. I guess he "stored" this information in some place in his head while drunk and couldn't retrieve it until slightly intoxicated again. [Author's files]

Alcohol-related effects on memory are well established. Does the same sort of state-dependent forgetting occur with caffeine? Many students drink coffee, tea, or soft drinks with caffeine to stay awake while they study. (A counselor at Florida State said that Diet Coke was the most common addiction on campus.) If caffeine caused state-dependent learning, students should do poorly on a test unless they took caffeine again before the test. But does caffeine work this way? Apparently not!

Does state-dependent forgetting occur with caffeine?

Blount and Cox (1982) tested 80 college students at the University of Minnesota in Morris, looking for evidence of state-dependent learning effects due to caffeine. Subjects who consumed caffeinated drinks during the learning phase were compared with subjects who did not. Half of each group was given caffeinated drinks before the memory test. There was no effect due to the caffeine. The researchers concluded, "Caffeine's effects on memory are different from the effects of depressants."


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Copyright © 2007 Russ Dewey