Visuospatial word search task only effective at disrupting declarative memory when prediction error is present during retrieval.

Prediction error is recognized as a necessary boundary condition for memory reactivation and reconsolidation. Furthermore, behavioral manipulations (e.g., visuospatial interference tasks, like Tetris) have been shown to be effective at disrupting reactivated memory. In the present study, participants created a memory with positive valence by viewing an uplifting video of a young boy who built an arcade out of cardboard boxes. Two weeks later, memory for the video was reactivated with a prediction error (i.e., new information was added) or without a prediction error (i.e., no new information was added). Following memory reactivation, participants completed a novel visuospatial interference task (i.e., a complex word search) or a control task (i.e., sitting quietly). One week following reactivation, participants completed two memory tests (i.e., free recall and recognition). Results showed that the visuospatial interference task was effective in reducing free recall, but only in the group that received a prediction error during retrieval. No other significant differences were observed, including on the recognition test. These results expand the literature on reconsolidation by showing that destabilization of memory with a positive emotional valence requires a prediction error and that a novel visuospatial interference task (i.e., complex word search) is an effective behavioral manipulation for decreasing free recall.

Reconsolidation of appetitive odor discrimination requires protein synthesis only when reactivation includes prediction error.

Reconsolidation theory has supported the notion that active memory is vulnerable to the effects of an amnesic agent. An extension of reconsolidation theory posits that active memory, while necessary for creating vulnerability in memory, is not sufficient. Prediction error (i.e., when expectation is inconsistent with reality) may be a key factor in the destabilization of memory. The present study examined the role of prediction error in appetitive memory reconsolidation. Rats learned to dig in cups of scented sand to retrieve buried sweet cereal rewards. Forty-eight hours following acquisition, a single reactivation trial was given during which a prediction error or no prediction error was included. The prediction error consisted of a single extinction trial, while the no prediction error condition consisted of an additional reinforced trial. Cycloheximide (CHX; 1 mg/kg) or vehicle (VEH: distilled water; 1 mg/kg) was administered intraperitoneally immediately following reactivation. One week following reactivation, rats received 2 nonreinforced test trials. Results showed longer latencies to dig for rats that received CHX following a prediction error (CHX/PE) compared to rats that received VEH (VEH/PE) or did not receive a prediction error (CHX/NoPE or VEH/NoPE). These results add to a growing literature demonstrating that protein synthesis is necessary in appetitive memory reconsolidation only when reactivation includes a prediction error. (PsycINFO Database Record

Extinction of appetitive learning is disrupted by cycloheximide and propranolol in the sand maze in rats.

The present study investigated whether memory for extinction in an appetitive task (the sand maze) could be attenuated by administration of cycloheximide (protein synthesis inhibitor) or propranolol (ß-adrenergic receptor antagonist). Ninety-day-old male Long-Evans rats were trained to retrieve a sweet cereal reinforcer from an open container in the sand maze. One day following this non-spatial training, rats received three extinction trials in which they were placed in the maze with the reinforcer present, but unattainable. Thirty minutes prior to the first extinction trial, rats received an intraperitoneal injection of cycloheximide (1mg/kg), propranolol (25mg/kg), or vehicle (1mg/kg distilled water). Twenty-four hours later, rats were tested in the sand maze with the reinforcer again available. Results from the test trial showed that both cycloheximide and propranolol groups found the reinforcer more quickly than controls. Two weeks later, rats were trained on a spatial version of the sand maze in which they had to search for a buried reinforcer using extramaze cues. Cycloheximide and propranolol groups learned this task significantly faster than the control group, demonstrating the long-lasting effect of cycloheximide and propranolol on the blocking of memory for extinction.

Cycloheximide produces amnesia for extinction and reconsolidation in an appetitive odor discrimination task in rats.

A considerable literature has shown deficits in memory resulting from the administration of protein synthesis inhibitors; however, most of the past literature in this field has focused on acquisition of new memory using aversively-motivated tasks. The effect of protein synthesis inhibition on appetitive learning and memory as well as extinction is less clear. The present study employed an appetitive odor discrimination paradigm to examine the effects of acute cycloheximide administration (1mg/kg) on reconsolidation and extinction. Male, Long-Evans adult rats were trained to discriminate between two odors (i.e., cocoa and cinnamon) and then received extinction trials following an intraperitoneal injection of cycloheximide or vehicle. Twenty-four hours later, rats were tested via one non-reinforced test trial. Results showed amnesia for extinction as well as original training (i.e., correct odor choice) in cycloheximide-injected rats in this appetitive task, while vehicle-injected controls showed good memory for extinction. These data add to a growing literature showing the importance of protein synthesis inhibition for extinction and reconsolidation in appetitive learning and memory.