Abstract
RationaleSeveral psychoactive drugs are known to influence episodic memory. However, these drugs’ effects on false memory, or the tendency to incorrectly remember nonstudied information, remain poorly understood.ObjectivesHere, we examined the effects of two commonly used psychoactive drugs, one with memory-enhancing properties (dextroamphetamine; AMP), and another with memory-impairing properties (Δ9-tetrahydrocannabinol; THC), on false memory using the Deese/Roediger–McDermott (DRM) illusion.MethodsTwo parallel studies were conducted in which healthy volunteers received either AMP (0, 10, and 20 mg) or THC (0, 7.5, and 15 mg) in within-subjects, randomized, double-blind designs. Participants studied DRM word lists under the influence of the drugs, and their recognition memory for the studied words was tested 2 days later, under sober conditions.ResultsAs expected, AMP increased memory of studied words relative to placebo, and THC reduced memory of studied words. Although neither drug significantly affected false memory relative to placebo, AMP increased false memory relative to THC. Across participants, both drugs’ effects on true memory were positively correlated with their effects on false memory.ConclusionsOur results indicate that AMP and THC have opposing effects on true memory, and these effects appear to correspond to similar, albeit more subtle, effects on false memory. These findings are consistent with previous research using the DRM illusion and provide further evidence that psychoactive drugs can affect the encoding processes that ultimately result in the creation of false memories.
Highlights
Memory plays a critical role in survival and must often be accurate
Our results indicate that AMP and THC have opposing effects on true memory, and these effects appear to correspond to similar, albeit more subtle, effects on false memory
Declaration on interests The authors have no conflicts of interests regarding the integrity of the reported findings. These findings are consistent with previous research using the DRM illusion and provide further evidence that psychoactive drugs can affect the encoding processes that result in the creation of false memories
Summary
Memory plays a critical role in survival and must often be accurate. Memory is sometimes inaccurate, and can be so in predictable ways. False memory processes are commonly studied using the Deese/Roediger-McDermott (DRM) illusion (Deese 1959; Roediger and McDermott 1995) This task creates a robust memory illusion, and has provided key insights into the cognitive and neural processes that regulate false memory (for a review see Gallo 2010). In the DRM task, subjects study lists of words (e.g., bed, rest, awake, tired, dream) that are semantically associated to a nonpresented word (e.g., sleep), referred to as the critical lure. These critical lures are often falsely remembered as having been presented in the study list, with false recall and false recognition rates significantly greater than baseline (unrelated lures). Unlike more traditional episodic memory tasks in which performance is highly accurate, the DRM task reliably elicits very high levels of false memories in cognitively normal participants, making it useful for testing false memory theories
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