subjects encode and retrieve new information under drugs such as alcohol or valium. This may reflect separate and partially independent effects of the same drug on: (1) the acquisition or retrieval of conceptually driven traces; and (2) the neural systems involved in consolidation. Drugs may interfere with the acquisition and retrieval of conceptually driven memories and enhance other memory systems that are more difficult to study in humans.
Enhanced remembering of predrug experiences may reflect drug-induced stimulation of reward-driven consolidation processes. Even in humans, the neural substrates of recently formed representations remain labile shortly after encoding. Drugs with a high liability for abuse have reinforcing and rewarding effects that may enhance trace consolidation. This particular action of drugs could stimulate research on memory systems more relevant to drug-seeking behavior than research on conceptually driven memory systems. Individuals who are particularly susceptible to rewarding effects of drugs and to the retrograde facilitation effect may be at risk for alcohol or drug abuse.
In a purely speculative vein, we suggest that the retrograde facilitation effect may reflect a precognitive system that enabled primitive organisms to identify significant features of their environment. Through phylogenetic development, with growth and elaboration of the cerebral cortex in humans, conceptual encoding systems evolved to permit rapid, flexible, arid structured analysis of experience. Discrete representations could occur almost simultaneously with the event. These more recent, conceptual systems reduced dependence on responsively driven consolidation processes. However, the fact that certain drugs facilitate memory indicates that these primitive systems continue to function and affect cognition. It is a challenge to think about strategies to examine experimentally this component of human memory that has hitherto eluded our scrutiny but not our behavior.
We thank Ralph U. Esposito, Shahin Hashtroudi, Mortimer Mishkin, and Barbara Schwarz for their critiques, advice, and discussions surrounding earlier versions of this manuscript.
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