Reinstatement of item-specific contextual details during retrieval supports recombination-related false memories.

Flexible retrieval mechanisms that allow us to infer relationships across events may also lead to memory errors or distortion when details of one event are misattributed to the related event. Here, we tested how making successful inferences alters representation of overlapping events, leading to false memories. Participants encoded overlapping associations ('AB' and 'BC'), each of which was superimposed on different indoor and outdoor scenes that were pre-exposed prior to associative learning. Participants were subsequently tested on both the directly learned pairs ('AB' and 'BC') and inferred relationships across pairs ('AC'). We predicted that when people make a correct inference, features associated with overlapping events may become integrated in memory. To test this hypothesis, participants completed a final detailed retrieval test, in which they had to recall the scene associated with initially learned 'AB' pairs (or 'BC' pairs). We found that the outcome of inference decisions impacted the degree to which neural patterns elicited during detailed 'AB' retrieval reflected reinstatement of the scene associated with the overlapping 'BC' event. After successful inference, neural patterns in the anterior hippocampus, posterior medial prefrontal cortex, and our content-reinstatement region (left inferior temporal gyrus) were more similar to the overlapping, yet incorrect 'BC' context relative to after unsuccessful inference. Further, greater hippocampal activity during inference was associated with greater reinstatement of the incorrect, overlapping context in our content-reinstatement region, which in turn tracked contextual misattributions during detailed retrieval. These results suggest recombining memories during successful inference can lead to misattribution of contextual details across related events, resulting in false memories.

Constructive episodic simulation, flexible recombination, and memory errors.

According to Mahr & Csibra (M&C), the view that the constructive nature of episodic memory is related to its role in simulating future events has difficulty explaining why memory is often accurate. We hold this view, but disagree with their conclusion. Here we consider ideas and evidence regarding flexible recombination processes in episodic retrieval that accommodate both accuracy and distortion.

False memories, false preferences: Flexible retrieval mechanisms supporting successful inference bias novel decisions.

Prior research suggests that episodic memory can guide value-based decisions when single episodes are encoded in relation to the specific reward-context in which they were experienced. The current experiments examine the role that a flexible recombination-related retrieval mechanism that allows one to link together distinct events plays in the misattribution of specific reward-contexts across distinct episodes. To determine whether the same recombination-related retrieval mechanism supports both successful inference and transfer of reward-context across episodes, we developed a modified version of an associative inference paradigm in which participants encoded overlapping associations (AB, BC) that could later be linked to support inferential retrieval (AC), where one element ("A") was tied to reward. Our key experimental manipulation concerned whether value memory (Experiments 1 and 2) or decision bias tests (Experiment 3) were probed before or after the associative inference test, thereby allowing us to assess whether false value transfer and decision bias scores increased after as compared to before successful versus unsuccessful inference. Results revealed that participants more frequently misattributed the specific reward-context ("A") to unrewarded items ("C;" Experiments 1 and 2) and showed higher decision bias scores when asked to choose between two previously unrewarded items ("C;" Experiment 3) for successful compared with unsuccessful inference, but only when the value memory and decision bias tests were given after the associative inference test. These results suggest that a recombination-related retrieval mechanism that supports successful inference also contributes to the misattribution of reward-context in memory and further biases participants' novel value-based decisions. (PsycINFO Database Record

Flexible retrieval mechanisms supporting successful inference produce false memories in younger but not older adults.

Episodic memory involves flexible retrieval processes that allow a person to link elements of distinct episodes in order to make novel inferences across events. In younger adults, we recently found that the same retrieval-related recombination mechanism that supports successful associative inference produces source misattributions as a consequence of erroneous binding of contextual elements from distinct episodes. In the current experiment, we found that older adults, in contrast to younger adults, did not show an increase in source misattributions following successful associative inference. We observed this pattern both when (a) younger and older adults were tested under identical experimental conditions and (b) younger and older adults were matched on associative inference accuracy and overall source memory errors. We suggest that the differing patterns of results are a consequence of age-related deficits in associative binding during successful inferential retrieval. (PsycINFO Database Record

Are eyewitness accounts biased? Evaluating false memories for crimes involving in-group or out-group conflict.

Eyewitness testimony has been shown to be unreliable and susceptible to false memories. Whether eyewitness memory errors are influenced by the victim's group membership (relative to both the eyewitness and perpetrator) is underexplored. The current study used complementary behavioral and neuroimaging approaches to test the hypothesis that intragroup conflict heightens participants' susceptibility to subsequent false memories. Healthy young adults witnessed and later answered questions about events in which the perpetrator and victim were either 1) identified as in-group members relative to each other and the eyewitness, 2) out-group members relative to the eyewitness, but not each other, or 3) out-group members relative to each other (Experiments 1a and 1b). When perpetrators and victims were in-group members (intragroup conflict), participants showed heightened false memory rates. Moreover, false memories increased upon crime realization. Neuroimaging data analysis revealed that salient (as compared to ambiguous) intragroup conflict elicited heightened activation in neural regions associated with resolving cognitive conflict (anterior cingulate cortex; ACC). Increased functional connectivity between the ACC and dorsomedial prefrontal cortex was associated with subsequent false memories (Experiment 2). Results suggest that the social salience of the intragroup conflict may have been associated with participants' increased susceptibility to false memories.

Remembering and imagining alternative versions of the personal past.

Although autobiographical memory and episodic simulations recruit similar core brain regions, episodic simulations engage additional neural recruitment in the frontoparietal control network due to greater demands on constructive processes. However, previous functional neuroimaging studies showing differences in remembering and episodic simulation have focused on veridical retrieval of past experiences, and thus have not fully considered how retrieving the past in different ways from how it was originally experienced may also place similar demands on constructive processes. Here we examined how alternative versions of the past are constructed when adopting different egocentric perspectives during autobiographical memory retrieval compared to simulating hypothetical events from the personal past that could have occurred, or episodic counterfactual thinking. Participants were asked to generate titles for specific autobiographical memories from the last five years, and then, during functional magnetic resonance (fMRI) scanning, were asked to repeatedly retrieve autobiographical memories or imagine counterfactual events cued by the titles. We used an fMRI adaptation paradigm in order to isolate neural regions that were sensitive to adopting alternative egocentric perspectives and counterfactual simulations of the personal past. The fMRI results revealed that voxels within left posterior inferior parietal and ventrolateral frontal cortices were sensitive to novel visual perspectives and counterfactual simulations. Our findings suggest that the neural regions supporting remembering become more similar to those underlying episodic simulation when we adopt alternative egocentric perspectives of the veridical past.

Flexible retrieval: When true inferences produce false memories.

Episodic memory involves flexible retrieval processes that allow us to link together distinct episodes, make novel inferences across overlapping events, and recombine elements of past experiences when imagining future events. However, the same flexible retrieval and recombination processes that underpin these adaptive functions may also leave memory prone to error or distortion, such as source misattributions in which details of one event are mistakenly attributed to another related event. To determine whether the same recombination-related retrieval mechanism supports both successful inference and source memory errors, we developed a modified version of an associative inference paradigm in which participants encoded everyday scenes comprised of people, objects, and other contextual details. These scenes contained overlapping elements (AB, BC) that could later be linked to support novel inferential retrieval regarding elements that had not appeared together previously (AC). Our critical experimental manipulation concerned whether contextual details were probed before or after the associative inference test, thereby allowing us to assess whether (a) false memories increased for successful versus unsuccessful inferences, and (b) any such effects were specific to after compared with before participants received the inference test. In each of 4 experiments that used variants of this paradigm, participants were more susceptible to false memories for contextual details after successful than unsuccessful inferential retrieval, but only when contextual details were probed after the associative inference test. These results suggest that the retrieval-mediated recombination mechanism that underlies associative inference also contributes to source misattributions that result from combining elements of distinct episodes. (PsycINFO Database Record