Neural correlates underlying true and false associative memories

Despite the fact that associative memory studies produce a large number of false memories, neuroimaging analyses utilizing this paradigm typically focus only on neural activity mediating successful retrieval. The current study sought to expand on this prior research by examining the neural basis of both true and false associative memories. Though associative false memories are substantially different than those found in semantic or perceptual false memory paradigms, results suggest that associative false memories are mediated by similar neural mechanisms. Specifically, we found increased frontal activity that likely represents enhanced monitoring and evaluation compared to that needed for true memories and correct rejections. Results also indicated that true, and not false associative memories, are mediated by neural activity in the MTL, specifically the hippocampus. Finally, while activity in early visual cortex distinguished true from false memories, a lack of neural differences between hits and correct rejections failed to support previous findings suggesting that activity in early visual cortex represents sensory reactivation of encoding-related processing.     

Mood-congruent true and false memory: Effects of depression

The Deese/Roediger-McDermott paradigm was used to investigate the effect of depression on true and false recognition. In this experiment true and false recognition was examined across positive, neutral, negative, and depression-relevant lists for individuals with and without a diagnosis of major depressive disorder. Results showed that participants with major depressive disorder falsely recognised significantly more depression-relevant words than non-depressed controls. These findings also parallel recent research using recall instead of recognition and show that there are clear mood congruence effects for depression on false memory performance.     

Mood-congruent true and false memory: effects of depression

The Deese/Roediger-McDermott paradigm was used to investigate the effect of depression on true and false recognition. In this experiment true and false recognition was examined across positive, neutral, negative, and depression-relevant lists for individuals with and without a diagnosis of major depressive disorder. Results showed that participants with major depressive disorder falsely recognised significantly more depression-relevant words than non-depressed controls. These findings also parallel recent research using recall instead of recognition and show that there are clear mood congruence effects for depression on false memory performance.     

Effects of exact and category repetition in true and false recognition memory

Two experiments used the distinction between remembering and knowing to investigate the effects of exact and category repetition in recognition memory. In Experiment 1, exact repetition enhanced remember responses but had no reliable effect on know responses. In Experiment 2, category repetition enhanced correct know responses but had no effect on correct remember responses. Category repetition also increased false positive remember and know responses. It is argued that exact repetition influences the recollection component of recognition memory via the creation of multiple episodic traces, each of which is potentially capable of supporting a remember response, whereas category repetition influences the familiarity component of recognition memory by enhancing the fluency with which test items are processed.     

The development of automatic and controlled inhibitory retrieval processes in true and false recall

In three experiments, we investigated the role of automatic and controlled inhibitory retrieval processes in true and false memory development in children and adults. Experiment 1 incorporated a directed forgetting task to examine controlled retrieval inhibition. Experiments 2 and 3 used a part-set cue and retrieval practice task to examine automatic retrieval inhibition. In the first experiment, the forget cue had no effect on false recall for adults but reduced false recall for children. In Experiments 2 and 3, both tasks caused retrieval impairments for true and false recall, and this occurred for all age groups. Implicit inhibition, which occurs outside of our conscious control, appears early in childhood. However, because young children do not process false memories as automatically as adults, explicit inhibition can reduce false memory output.     

Children's false memory and true disclosure in the face of repeated questions

The current study was designed to investigate children's memory and suggestibility for events differing in valence (positive or negative) and veracity (true or false). A total of 82 3- and 5-year-olds were asked repeated questions about true and false events, either in a grouped order (i.e., all questions about a certain event asked consecutively) or in a nongrouped order (i.e., questions about a certain event were interspersed with questions about other events). Interviewer gender was also varied. Individual differences, including attachment style, inhibition, and behavioral adjustment, were examined as potential predictors of memory and suggestibility. Results revealed significant age, valence, and veracity effects on children's memory reports. Path analysis demonstrated that individual differences in behavioral problems and inhibitory ability predicted children's provision of inaccurate information. Implications for psychological theory and legal application are discussed.     

Emotional content enhances true but not false memory for categorized stimuli

Past research has shown that emotion enhances true memory, but that emotion can either increase or decrease false memory. Two theoretical possibilities—the distinctiveness of emotional stimuli and the conceptual relatedness of emotional content—have been implicated as being responsible for influencing both true and false memory for emotional content. In the present study, we sought to identify the mechanisms that underlie these mixed findings by equating the thematic relatedness of the study materials across each type of valence used (negative, positive, or neutral). In three experiments, categorically bound stimuli (e.g., funeral, pets, and office items) were used for this purpose. When the encoding task required the processing of thematic relatedness, a significant true-memory enhancement for emotional content emerged in recognition memory, but no emotional boost to false memory (Exp. 1). This pattern persisted for true memory with a longer retention interval between study and test (24 h), and false recognition was reduced for emotional items (Exp. 2). Finally, better recognition memory for emotional items once again emerged when the encoding task (arousal ratings) required the processing of the emotional aspect of the study items, with no emotional boost to false recognition (Exp. 3). Together, these findings suggest that when emotional and neutral stimuli are equivalently high in thematic relatedness, emotion continues to improve true memory, but it does not override other types of grouping to increase false memory.     

The true and the false

A dispositional property is a tendency, or potency, to manifest some characteristic behaviour in some appropriate context. The mainstream view in the twentieth century was that such properties are to be explained in terms of more fundamental non-dispositional properties, together with the laws of nature. In the last few decades, however, a rival view has become popular, according to which some properties are essentially dispositional in nature, and the laws of nature are to be explained in terms of these fundamental dispositions. The supposed ability of fundamental dispositions to ground natural laws is one of the most attractive features of the dispositional essentialist position. In this paper, however, I cast doubt on the ability of dispositional essences to ground the laws of nature. In particular I argue that the dispositional essentialist position is not able to coherently respond—sympathetically or otherwise—to Cartwright's challenge that there are no true general laws of nature.     

Threat-related processing supports prospective memory retrieval for people with obsessive tendencies

Obsessive-compulsive disorder can result in a variety of deficits to cognitive performance, including negative consequences for attention and memory performance. The question addressed in the current study concerned whether this disorder influenced performance in an event-based prospective memory task. The results from a subclinical population indicated that, relative to non-anxious controls and mildly depressed controls, people with obsessive-compulsive tendencies (washing compulsions) incur decrements in remembering to respond to cues related to a neutral intention (respond to animals). This deficit was ameliorated by giving the subclinical group an intention about a threat-related category (respond to bodily fluids) and cueing them with concepts that they had previously rated as particularly disturbing to them. Thus, their normal attentional bias for extended processing of threat-related information overcame their natural deficit in event-based prospective memory.     

Neural correlates of autobiographical memory retrieval in children and adults

Autobiographical memory (AM) is a critically important form of memory for life events that undergoes substantial developmental changes from childhood to adulthood. Relatively little is known regarding the functional neural correlates of AM retrieval in children as assessed with fMRI, and how they may differ from adults. We investigated this question with 14 children ages 8–11 years and 14 adults ages 19–30 years, contrasting AM retrieval with semantic memory (SM) retrieval. During scanning, participants were cued by verbal prompts to retrieve previously selected recent AMs or to verify semantic properties of words. As predicted, both groups showed AM retrieval-related increased activation in regions implicated in prior studies, including bilateral hippocampus, and prefrontal, posterior cingulate, and parietal cortices. Adults showed greater activation in the hippocampal/parahippocampal region as well as prefrontal and parietal cortex, relative to children; age-related differences were most prominent in the first 8?sec versus the second 8?sec of AM retrieval and when AM retrieval was contrasted with semantic retrieval. This study is the first to characterise similarities and differences during AM retrieval in children and adults using fMRI.     

Non-ruminative processing reduces overgeneral autobiographical memory retrieval in students

It has been suggested that overgeneral memory (OGM) represents a vulnerability marker for depression [Williams, J. M. G., Barnhofer, T., Crane, C., Hermans, D., Raes, F., Watkins, E., et al. (2007). Autobiographical memory specificity and emotional disorder. Psychological Bulletin, 133, 122-148]. One important underlying mechanism involved is rumination [e.g., Watkins, E., & Teasdale, J. D. (2001). Rumination and overgeneral memory in depression: Effects of self-focus and analytic thinking. Journal of Abnormal Psychology, 110, 353-357; Watkins, E., & Teasdale, J. D. (2004). Adaptive and maladaptive self-focus in depression. Journal of Affective Disorders, 82, 1-8]. It is as yet unclear to what extent the relationship between rumination and OGM also applies to nonclinical groups. The present study investigated this relationship in a nonclinical student sample, using an innovative sentence completion procedure to assess OGM. As hypothesized, the experimental induction of a concrete, process-focused (or non-ruminative) thinking style (n=102) led to less OGMs as compared to the experimental induction of an abstract, evaluative (or ruminative) thinking style (n=93). The present results add to the accumulating body of evidence that abstract, evaluative (or ruminative) thinking is a crucial underlying process of OGM, and expand prior literature by extending this idea to nonclinical individuals and by using a new procedure to assess OGM.     

Information processing and reasoning with premises that are empirically false: Interference,working memory,and processing speed

In this study, we looked at the contributions of individual differences in susceptibility to interference and working memory to logical reasoning with premises that were empirically false (i.e., not necessarily true). A total of 97 university students were given a sentence completion task for which a subset of stimuli was designed to generate inappropriate semantic activation that interfered with the correct response, a measure of working memory capacity, and a series of logical reasoning tasks with premises that were not always true. The results indicate that susceptibility to interference, as measured by the error rate on the relevant subset of the sentence completion task, and working memory independently account for variation in reasoning performance. The participants who made more errors in the relevant portion of the sentence completion task also showed more empirical intrusions in the deductive reasoning task, even when the effects of working memory were partialed out. Working memory capacity was more clearly related to processes involved in generating uncertainty responses to inferences for which there was no certain conclusion. A comparison of the results of this study with studies of children's reasoning suggests that adults are capable of more selective executive processes than are children. An analysis of latency measures on the sentence completion task indicated that high working memory participants who made no errors on the sentence completion task used a strategy that involved slower processing speed, as compared with participants with similar levels of working memory who did make errors. In contrast, low working memory participants who made no errors on the sentence completion task had relatively shorter reaction times than did comparable participants who did make errors.     

Not strange but not true: self-reported interest in a topic increases false memory

People are more likely to recall both true and false information that is consistent with their pre-existing stereotypes, schemata and desires. In addition, experts in a particular field are more likely to experience false memory in relation to their area of expertise. Here, we investigate whether level of interest, as distinct from level of knowledge, and in the absence of self-professed expertise, is associated with increased false memory. 489 participants were asked to rank 7 topics from most to least interesting. They were then asked if they remembered the events described in four news items related to the topic they selected as the most interesting and four items related to the topic selected as least interesting. In each case, three of the events depicted had really happened and one was fictional. A high level of interest in a topic increased true memories for the topic and doubled the frequency of false memories, even after controlling for level of knowledge. We interpret the results in the context of the source-monitoring framework and suggest that false memories arise as a result of interference from existing information stored in domain-related schemata.     

Neural networks supporting autobiographical memory retrieval in posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) affects the functional recruitment and connectivity between neural regions during autobiographical memory (AM) retrieval that overlap with default and control networks. Whether such univariate changes relate to potential differences in the contributions of the large-scale neural networks supporting cognition in PTSD is unknown. In the present functional MRI study, we employed independent-component analysis to examine the influence of the engagement of neural networks during the recall of personal memories in a PTSD group (15 participants) as compared to non-trauma-exposed healthy controls (14 participants). We found that the PTSD group recruited similar neural networks when compared to the controls during AM recall, including default-network subsystems and control networks, but group differences emerged in the spatial and temporal characteristics of these networks. First, we found spatial differences in the contributions of the anterior and posterior midline across the networks, and of the amygdala in particular, for the medial temporal subsystem of the default network. Second, we found temporal differences within the medial prefrontal subsystem of the default network, with less temporal coupling of this network during AM retrieval in PTSD relative to controls. These findings suggest that the spatial and temporal characteristics of the default and control networks potentially differ in a PTSD group versus healthy controls and contribute to altered recall of personal memory.     

Emotional true and false memories in children with callous-unemotional traits

Several studies have found that children with callous-unemotional (CU) traits have a deficit in processing emotionally negative material. The present study examined whether this deficit also affects emotional memory. Twenty-two children with low CU traits and 24 children with high CU traits between 8 and 12 years of age were selected from a community sample and presented with neutral and negative emotional words, using the Deese–Roediger–McDermott paradigm. On true recall, there was no difference between the groups. Both groups had higher true recall rates for the neutral word lists than for the negative lists. However, on false recall, although there were no group differences for neutral word lists, the high CU group recalled significantly fewer critical lures on the negative word lists than the low CU group. Furthermore, the high CU group had significantly less false recall on the negative word lists compared to the neutral word lists, while the low CU group showed no difference in false recall between the word lists. These results indicate that children with high CU traits have no deficiencies in true memory performance, yet are less susceptible to developing false memories concerning emotionally negative material.     

Seeing double: levels of processing can cause false memory.

Ordinarily, deeper levels of processing in a study session increase the accuracy of later remembering. We modified the standard levels-of-processing procedure by presenting items either once or twice in the study phase, each item being the subject of a semantic, phonemic, or graphemic question. At test, the subjects judged the frequency with which each word had occurred in the study phase. Deeper processing during encoding increased accuracy in judging twice-presented items. However, it also caused an illusion of repetition for items presented only once. The result underlines the importance of thinking of remembering as a process of evaluation and inference, rather than simple retrieval.     

Emotional content of true and false memories

Many people believe that emotional memories (including those that arise in therapy) are particularly likely to represent true events because of their emotional content. But is emotional content a reliable indicator of memory accuracy? The current research assessed the emotional content of participants' pre-existing (true) and manipulated (false) memories for childhood events. False memories for one of three emotional childhood events were planted using a suggestive manipulation and then compared, along several subjective dimensions, with other participants' true memories. On most emotional dimensions (e.g., how emotional was this event for you?), true and false memories were indistinguishable. On a few measures (e.g., intensity of feelings at the time of the event), true memories were more emotional than false memories in the aggregate, yet true and false memories were equally likely to be rated as uniformly emotional. These results suggest that even substantial emotional content may not reliably indicate memory accuracy.     

Emotional content of true and false memories

Many people believe that emotional memories (including those that arise in therapy) are particularly likely to represent true events because of their emotional content. But is emotional content a reliable indicator of memory accuracy? The current research assessed the emotional content of participants’ pre-existing (true) and manipulated (false) memories for childhood events. False memories for one of three emotional childhood events were planted using a suggestive manipulation and then compared, along several subjective dimensions, with other participants’ true memories. On most emotional dimensions (e.g., how emotional was this event for you?), true and false memories were indistinguishable. On a few measures (e.g., intensity of feelings at the time of the event), true memories were more emotional than false memories in the aggregate, yet true and false memories were equally likely to be rated as uniformly emotional. These results suggest that even substantial emotional content may not reliably indicate memory accuracy.     

Modulation of retrieval processing reflects accuracy of emotional source memory

There is considerable evidence that encoding and consolidation of memory are modulated by emotion, but the retrieval of emotional memories is not well characterized. Here we manipulated the emotional context with which affectively neutral stimuli were associated during encoding, allowing us to examine neural activity associated with retrieval of emotional memories without confounding the emotional attributes of cue items and the retrieved context. Using a source memory procedure we were also able to compare how retrieval processing was modulated when the emotional encoding context was recollected or not. An interaction between emotional encoding context and accuracy of source memory revealed that successful retrieval of emotional context was associated with activity in left amygdala, and a left frontotemporal network including anterior insula, prefrontal cortex and cingulate. In contrast, when contextual retrieval was unsuccessful, items encoded in emotional contexts elicited enhanced activity in right amygdala and a right-lateralized network that included extrastriate visual areas. These findings indicate distinct effects of emotion on successful and unsuccessful retrieval of source information, including lateralization of amygdala responses.     

An activation-based model of sentence processing as skilled memory retrieval

We present a detailed process theory of the moment-by-moment working-memory retrievals and associated control structure that subserve sentence comprehension. The theory is derived from the application of independently motivated principles of memory and cognitive skill to the specialized task of sentence parsing. The resulting theory construes sentence processing as a series of skilled associative memory retrievals modulated by similarity-based interference and fluctuating activation. The cognitive principles are formalized in computational form in the Adaptive Control of Thought–Rational (ACT–R) architecture, and our process model is realized in ACT–R. We present the results of 6 sets of simulations: 5 simulation sets provide quantitative accounts of the effects of length and structural interference on both unambiguous and garden-path structures. A final simulation set provides a graded taxonomy of double center embeddings ranging from relatively easy to extremely difficult. The explanation of center-embedding difficulty is a novel one that derives from the model' complete reliance on discriminating retrieval cues in the absence of an explicit representation of serial order information. All fits were obtained with only 1 free scaling parameter fixed across the simulations; all other parameters were ACT–R defaults. The modeling results support the hypothesis that fluctuating activation and similarity-based interference are the key factors shaping working memory in sentence processing. We contrast the theory and empirical predictions with several related accounts of sentence-processing complexity.