"Identify-to-reject": a specific strategy to avoid false memories in the DRM paradigm

Transcranial direct current stimulation over the left posterior temporal lobe modulates semantic control: Evidence from episodic memory distortions

Evidence accumulates to show that semantic cognition requires, in addition to semantic representations, control processes that regulate the accessibility and use of semantic knowledge in a task- and time-appropriate fashion. Semantic control has been recently proposed to rely on a distributed network that includes the posterior temporal cortex. Along these lines, recent meta-analyses of neuroimaging data and studies with patients suffering from semantic aphasia have suggested that the left posterior middle temporal gyrus (pMTG) is critically involved whenever situational context must constrain semantic retrieval. In the present experiment, we used transcranial direct current stimulation over the left posterior temporal lobe in an attempt to interfere with semantic control while participants performed a DRM task, a procedure for inducing conceptually-based false recognition that is contingent on both activation and control processes. Paralleling findings with patients suffering from brain damage restricted to the temporoparietal cortex, anodal stimulation (relative to sham stimulation) resulted in increased false recognition but intact true recognition. These findings fit well with the idea that the left pMTG is a key component of a semantic control network, the alteration of which results in memory performance that is affected by the intrusion of contextually-inappropriate semantic information.

Feelings of Contrast at Test Reduce False Memory in the Deese/Roediger-McDermott Paradigm

False memories in the Deese/Roediger-McDermott (DRM) paradigm are explained in terms of the interplay between error-inflating and error-editing (e.g., monitoring) mechanisms. In this study, we focused on disqualifying monitoring, a decision process that helps to reject false memories through the recollection of collateral information (i.e., recall-to-reject strategies). Participants engage in recall-to-reject strategies using one or two metacognitive processes: (1) applying the logic of mutual exclusivity or (2) experiencing feelings of contrast between studied items and unstudied lures. We aimed to provide, for the first time in the DRM literature, evidence favorable to the existence of a recall-to-reject strategy based on the experience of feelings of contrast. One hundred and forty participants studied six-word DRM lists (e.g., spy, hell, fist, fight, abduction, mortal), simultaneously associated with three critical lures (e.g., WAR, BAD, FEAR). Lists differed in their ease to identify their critical lures (extremely low-BAS lists vs. high-BAS lists). At recognition test, participants saw either one or the three critical lures of the lists. Participants in the three-critical-lure condition were expected to increase their monitoring, as they would experience stronger feelings of contrast than the participants in the one-critical-lure condition. Results supported our hypothesis, showing lower false recognition in the three-critical-lure condition than in the one-critical-lure condition. Critically, in the three-critical-lure condition, participants reduced even more false memory when they could also resort to another monitoring strategy (i.e., identify-to-reject). These findings suggest that, in the DRM context, disqualifying monitoring could be guided by experiencing feelings of contrast between different types of words.

Manipulations of List Type in the DRM Paradigm: A Review of How Structural and Conceptual Similarity Affect False Memory

The use of list-learning paradigms to explore false memory has revealed several critical findings about the contributions of similarity and relatedness in memory phenomena more broadly. Characterizing the nature of "similarity and relatedness" can inform researchers about factors contributing to memory distortions and about the underlying associative and semantic networks that support veridical memory. Similarity can be defined in terms of semantic properties (e.g., shared conceptual and taxonomic features), lexical/associative properties (e.g., shared connections in associative networks), or structural properties (e.g., shared orthographic or phonological features). By manipulating the type of list and its relationship to a non-studied critical item, we review the effects of these types of similarity on veridical and false memory. All forms of similarity reviewed here result in reliable error rates and the effects on veridical memory are variable. The results across a variety of paradigms and tests provide partial support for a number of theoretical explanations of false memory phenomena, but none of the theories readily account for all results.

Closing the door to false memory: the effects of levels-of-processing and stimulus type on the rejection of perceptually vs. semantically dissimilar distractors

False recognition memory for nonstudied items that share features with targets can be reduced by retrieval monitoring mechanisms. The recall-to-reject process, for example, involves the recollection of information about studied items that disqualifies inconsistent test probes. Monitoring for specific features during retrieval may be enhanced by an encoding orientation that is recapitulated during retrieval. In two experiments, we used concrete words or door scenes as materials and manipulated the level of processing at study and the type of distractors presented at test. We showed that for the verbal material, semantic level of processing at study results in an effective rejection of semantically inconsistent distractors. However, for the pictorial material, the perceptual level of processing leads to an effective rejection of perceptually inconsistent distractors. For targets, the effect of levels of processing was observed for words but not for pictures. The results suggest that retrieval monitoring mechanisms depend on interactions between encoding orientation, study materials, and differentiating features of distractors.

The production of false recognition and the associated state of consciousness following encoding in a naturalistic context in aging

Using virtual reality, we implemented a naturalistic variant of the DRM paradigm in young and older adults to evaluate false recall and false recognition. We distinguished false recognition related to the highest semantic association (the critical lures), semantic similarity (i.e. items that belong to the same semantic category), and perceptual similarity (i.e. items that are similar, but not identical in terms of shape or color). The data revealed that younger adults recalled and recognized more correct elements than older adults did while the older adults intruded more critical items than younger adults. Both age groups produced false recognition related to the critical items, followed by perceptually and then semantically related items. False recognitions were highly recollective as they were mainly associated with a sense of remembering, even more so in older adults than in young adults. The decline of executive functions and working memory predicted age-related increases in false memories.

Memory illusions and category malleability: False recognition for goal-derived reorganizations of common categories

Four studies explore semantic memory intrusions for goal-derived subcategories (e.g., "sports good for backache") embedded in taxonomic categories (e.g., "sports"). Study 1 presented hybrid lists (composed of typical items from both representations: taxonomic categories and subcategories) together with names of subcategories, names of taxonomic categories, or with no names. Subcategory names produced levels of false recognitions for critical lures from subcategories comparable with critical lures from taxonomic categories. Study 2 presented lists of exemplars either from taxonomic categories or subcategories (between participants). Lists of subcategories paired with their names produced higher levels of false recognition for subcategories lures compared with taxonomic lures. Study 3 replicated this result and showed that even though distinctiveness of taxonomic lures in a subcategory context (i.e., subcategory list with a subcategory name) may facilitate rejection of these lures, subcategory lures were still more falsely recognized than were taxonomic lures when retrieval monitoring was hindered through speeded recognition. Study 4 replicated the results with lists in which production frequency was better controlled and with a larger sample allowing for increased power of the test. Although confirming the critical role of preexistent categorical structures in the generation of false memories, results show that false memories for goal-derived subcategories can occur with the same frequency as false memories stemming from better established taxonomic categories. Such results broaden the scope of occurrence of false memories to goal-derived semantic organizations, which are often closer to categorizations used in real-world environments.

Explaining the persistence of false memories: a proposal based on associative activation and thematic extraction

This study aimed to analyse the effect of retention intervals on associative and thematic false memories. Two experiments, using two types of critical items that were either associatively or thematically related to studied material, were conducted. In both experiments, one group of participants performed a recognition test immediately after the presentation of lists, and another group performed the task one week later. In Experiment 1, the recognition test consisted of pairs of items with four response alternatives (both items had been presented, only the left item had been presented, only the right item had been presented or none of the items had been presented). Critical items were also manipulated so that they were either presented in or absent from the list. In Experiment 2, a standard recognition test that differed in the mode of presentation was used: self-paced or speeded response. Both experiments showed that associative critical items were more recognised than thematic critical items in the immediate condition. However, whereas associative critical items decayed after a one-week delay, thematic critical items were similarly recognised at both retention intervals. The findings of the present study suggest that each type of process - associative and thematic - behave differently over time.

Normative study of theme identifiability: Instructions with and without explanation of the false memory effect

False-memory illusions have been widely studied using the Deese/Roediger-McDermott paradigm (DRM). In this paradigm, words semantically related to a single nonpresented critical word are studied. In a later memory test, critical words are often falsely recalled and recognized. The present normative study was conducted to measure the theme identifiability of 60 associative word lists in Spanish that include six words (e.g., stove, coat, blanket, scarf, chill, and bonnet) that are simultaneously associated with three critical words (e.g., HEAT, COLD, and WINTER; Beato & Díez, Psicothema, 26, 457-463, 2011). Different levels of backward associative strength were used in the construction of the DRM lists. In addition, we used two types of instructions to obtain theme identifiability. In the without-explanation condition, traditional instructions were used, requesting participants to write the theme list. In the with-explanation condition, the false-memory effect and how the lists were built were explained, and an example of a DRM list and critical words was shown. Participants then had to discover the critical words. The results showed that all lists produced theme identifiability. Moreover, some lists had a higher theme identifiability rate (e.g., 61 % for the critical words LOVE, BOYFRIEND, COUPLE) than others (e.g., 24 % for CITY, PLACE, VILLAGE). After comparing the theme identifiabilities in the different conditions, the results indicated higher theme identifiability when the false-memory effect was explained than without such an explanation. Overall, these new normative data provide a useful tool for those experiments that, for example, aim to analyze the wide differences observed in false memory with DRM lists and the role of theme identifiability.

Dual processes of false recognition in kindergarten children and elementary school pupils

We investigated the contribution of monitoring processes to the emergence of false memories in children. Two age groups were compared, assuming lower monitoring ability at preschool age compared with older children. We also manipulated whether elementary school pupils responded in the memory test with or without time pressure. Furthermore, the frequency of list presentation was manipulated within participants. We found that presenting lists thrice compared with only once increased the number of false memories in kindergarten children and in elementary school pupils responding under time pressure but reduced false memories in elementary school pupils responding without time pressure. These findings indicate that kindergarten children still lack the ability to monitor the source of the activation of critical items of Deese-Roediger-McDermott lists.

List memory in young adults with language learning disability

PURPOSE

The purpose of this study was to characterize the verbal memory limitations of young adults with language learning disability (LLD).

METHOD

Sixteen young adults with LLD and 34 age- and education-matched controls with typical language participated in a Deese-Roediger-McDermott (DRM; Deese, 1959; Roediger & McDermott, 1995) list recall experiment. Participants listened to 12-item word lists that converged on a nonpresented critical item (e.g., rain) semantically (umbrella, drench, weather, hail), phonologically (train, main, ran, wren), or dually in a hybrid list (umbrella, train, drench, main) and recalled words in no particular order. Group comparisons were made on veridical recall (i.e., words that were presented) and false recall of nonpresented critical items. Recall performance was analyzed by list type and list position to examine potential differences in the quality of memorial processes.

RESULTS

The LLD group produced fewer veridical recalls than the controls. Both groups demonstrated list type and list position effects in veridical recall. False recall of the critical items was comparable in the 2 groups and varied by list type in predictable ways.

CONCLUSION

Young adults with LLD have verbal memory limitations characterized by quantitatively low levels of accurate recall. Qualitative patterns of recall are similar to those of unaffected peers. Therefore, the memory problem is characterized by limited capacity; memorial processes appear to be intact.

Repeated transcranial magnetic stimulation on dorsolateral prefrontal cortex improves performance in emotional memory retrieval as a function of level of anxiety and stimulus valence

AIMS

Anxiety behavior showed a consistent attentional bias toward negative and aversive memories, induced by a right frontal cortical superiority, based on an unbalance effect between the two hemispheres. The aim of the present study was to explore the role of the left dorsolateral prefrontal cortex (DLPFC) in the memory retrieval process of positive versus negative emotional stimulus, as a function of anxiety level.

METHODS

A repeated transcranial magnetic stimulation (rTMS) paradigm was used to induce cortical activation of the left DLPFC. Subjects (n = 27; age range, 21-36 years), who were divided into two different groups (high/low anxiety; State-Trait Anxiety Inventory), were required to perform a task consisting of two experimental phases: an encoding phase (lists composed of positive and negative emotional words); and a retrieval phase (old stimuli and new stimuli to be recognized). Moreover, new stimuli (distractors) semantically related or unrelated to the old stimuli were used to test a possible interference effect induced by the semantic association.

RESULTS

rTMS over the left DLPFC affects memory retrieval. High-anxiety subjects benefited in greater measure from frontal left stimulation with a reduced negative bias (increased accuracy and reduced response time for the positive stimuli) and a significant increased performance for the semantically related distractors (reduced interference effect).

CONCLUSION

Left DLPFC activation favors the memory retrieval of positive emotional information and might limit the unbalance effect induced by right hemispheric superiority in high levels of anxiety.

rTMS stimulation on left DLPFC increases the correct recognition of memories for emotional target and distractor words

According to a recent hypothesis, the prefrontal cortex has been proposed as the site of emotional memory integration, because it is sensitive to the recognition of emotional contents. In the present research, we explored the role of the dorsolateral prefrontal cortex (DLPFC) in memory recognition processes for positive versus negative emotional stimuli when old (target) and new (distractor, either semantically related or unrelated to the target) stimuli were presented. The role of the DLPFC was analysed using an rTMS (repeated transcranial magnetic stimulation) paradigm that induced increased cortical activation of the left DLPFC. The subjects were required to perform a task that consisted of two experimental phases (i.e., an encoding and a recognition phase) in which the targets and the distractors were presented and recognition performance was measured. rTMS stimulation was provided over the left DLPFC during the recognition phase. We found that the rTMS stimulation affected the memory recognition of positive emotional material. Moreover, related and unrelated distractors were discarded better when they were positively valenced, and a more significant effect (i.e., increased performance) was produced in response to related distractors. This result suggests that the activation of the left DLPFC favours the memory recognition of positive emotional information, and that such activation is able to induce a more appropriate selective process to distinguish target from distractor stimuli in the presence of more complex processes (related distractors). The valence model of emotional cue processing may explain this increased performance by demonstrating the distinct role of the left hemisphere in the retrieval of positive emotional information.