THC disrupts the encoding of perceptual details while sparing item-context bindings.
Manoj Doss1, Jessica Weafer1, David Gallo1, Harriet de Wit1; 1University of Chicago
Although it is known that the main psychoactive constituent of marijuana, Δ9-tetrahydrocannabinol (THC), impairs memory encoding, it is unclear which sub-processes are specifically affected. This is important, as marijuana is increasingly being prescribed for posttraumatic stress disorder (PTSD), which consists of existing memory impairments such as weak item-context bindings and decreased memory specificity. In a double-blind, placebo-controlled, within-subjects design, we tested the effects of 15 mg of THC on a task developed in our lab that produces a memory illusion via item-context bindings (Doss et al., in review). Healthy participants studied objects overlaid onto scenes while under the influence of THC or placebo. Forty-eight hours later, memory for the objects was tested by presenting participants with the exact same object pictures (targets), similar versions (similar lures), or completely new object exemplars. Context reinstatement was manipulated for targets and similar lures by presenting objects on their original scene or switching it to one of the other familiar scenes. We replicated our previous findings that context reinstatement increases false alarm rates for similar lures, representing a context-based memory illusion. Furthermore, THC reduced memory accuracy, but critically, THC did not interact with the context-based memory illusion, consistent with the idea that this illusion is driven by conceptual associations that are robust to drug effects. Therefore, in spite of decreasing perceptual specificity in memory, THC did not magnify the distorting effects of intact item-context bindings, suggesting that THC may not necessarily exasperate the overgeneralities in memory observed in disorders like PTSD.
Topic Area: LONG-TERM MEMORY: Episodic