Experimental manipulations of the phenomenology of memory

Real-world implications of aphantasia: episodic recall of eyewitnesses with aphantasia is less complete but no less accurate than typical imagers

Individuals with aphantasia report an inability to voluntarily visually image and reduced episodic memory, yet episodic accounts provided by witnesses and victims are fundamental for criminal justice. Using the mock-witness paradigm, we investigated eyewitness memory of individuals with aphantasia versus typical imagers. Participants viewed a mock crime and 48 hours later were interviewed about the event, randomly allocated to one of three conditions. Two interview conditions included techniques designed to support episodic retrieval mode, namely (i) Mental Reinstatement of Context (MRC) and (ii) Sketch Reinstatement of Context (Sketch-RC). A third Control condition did not include retrieval support. Aphantasic mock-eyewitnesses recalled 30% less correct information and accounts were less complete, but they made no more errors and were as accurate as typical imagers. Interaction effects revealed reduced correct recall and less complete accounts for aphantasic participants in MRC interviews versus Sketch-RC and Control. Aphantaisic participants in the Control outperformed those in both the Sketch-RC and MRC, although Sketch-RC improved completeness by 15% versus MRC. Our pattern of results indicates reduced mental imagery ability might be compensated for by alternative self-initiated cognitive strategies. Findings offer novel insights into episodic recall performance in information gathering interviews when ability to voluntarily visualize is impoverished.

The ability to recall scenes is a stable individual difference: Evidence from autobiographical remembering

Four behavioral studies (ns ~ 200 to 400) extended neural studies of ventral stream damage and fMRI activation and behavioral studies of scene recall conducted on individual memories to individual differences in normal populations. Ratings of scene and contents were made on one set of autobiographical memories. Ratings of reliving, vividness, belief, emotional intensity, and temporal specificity were made on different memories. Thus, correlations between these ratings were due to variability in the participants, not the events remembered. Scene correlated more highly than contents with reliving, vividness, belief, and emotional intensity but not temporal specificity. Scene correlated more highly than other visual imagery tests with reliving, vividness, and belief. Scene correlated with individual differences tests of episodic memories and future events more highly than it did with tests of semantic memory and spatial navigation abilities. Moreover, scene had high test-retest correlations measured at periods of up to one month. The ability to recall scenes is a stable disposition, with both convergent and divergent validity, which predicts basic qualities of autobiographical memories. A Scene Recall Imagery Test is introduced.

Memory and mental time travel in humans and social robots

From neuroscience, brain imaging and the psychology of memory, we are beginning to assemble an integrated theory of the brain subsystems and pathways that allow the compression, storage and reconstruction of memories for past events and their use in contextualizing the present and reasoning about the future-mental time travel (MTT). Using computational models, embedded in humanoid robots, we are seeking to test the sufficiency of this theoretical account and to evaluate the usefulness of brain-inspired memory systems for social robots. In this contribution, we describe the use of machine learning techniques-Gaussian process latent variable models-to build a multimodal memory system for the iCub humanoid robot and summarize results of the deployment of this system for human-robot interaction. We also outline the further steps required to create a more complete robotic implementation of human-like autobiographical memory and MTT. We propose that generative memory models, such as those that form the core of our robot memory system, can provide a solution to the symbol grounding problem in embodied artificial intelligence. This article is part of the theme issue 'From social brains to social robots: applying neurocognitive insights to human-robot interaction'.

Observer memories may not be for everyone

Six studies explored the preponderance of people who experience third-person perspective observer memories during autobiographical memory retrieval. The concept of first-person field versus observer memories has been extensively used in the areas of cognitive, social, and clinical psychology. An implicit assumption is the idea that most people use both of these perspectives. What varies are the circumstances that bias people to use one perspective over another for a given autobiographical memory. We challenge that assumption across six studies by showing that, while there are some people who report to regularly have observer memories, there are also those that report to rarely or never have them. These reports were found to be related to levels of reported dissociative experiences. We discuss how this difference in the experience of observer memories may also reflect other innate characteristics, and may correspond to predispositions for various pathologies, including depression, social phobia, and post-traumatic stress disorder.

Longitudinal Associations among Posttraumatic Stress Disorder Symptoms, Traumatic Brain Injury, and Neurocognitive Functioning in Army Soldiers Deployed to the Iraq War

OBJECTIVES

Military deployment is associated with increased risk of adverse emotional and cognitive outcomes. Longitudinal associations involving posttraumatic stress disorder (PTSD), relatively mild traumatic brain injury (TBI), and neurocognitive compromise are poorly understood, especially with regard to long-term outcomes, and rigorous research is necessary to better understand the corresponding relationships. The objective of this study was to examine short-term and long-term (>5 years) longitudinal associations among PTSD, neurocognitive performance, and TBI following military deployment.

METHODS

In this prospective study, N=315 U.S. Army soldiers were assessed at military installations before (2003-2005) and after (2004-2006) an index deployment to the Iraq War, and again an average of 7.6 years later (2010-2014) as a nationally dispersed cohort of active duty soldiers, reservists, and veterans. Thus, the study design allowed for two measurement intervals over which to examine changes. All assessments included the PTSD Checklist, civilian version, and individually-administered performance-based neurocognitive tests. TBI history was derived from clinical interview.

RESULTS

Autoregressive analyses indicated that visual reproduction scores were inversely related to subsequent PTSD symptom severity at subsequent assessments. Conversely, increases in PTSD symptom severity over each measurement interval were associated with poorer verbal and/or visual recall at the end of each interval, and less efficient reaction time at post-deployment. TBI, primarily mild in this sample, was associated with adverse PTSD symptom outcomes at both post-deployment and long-term follow-up.

CONCLUSIONS

These results suggest longitudinal relationships among PTSD symptoms, TBI, and neurocognitive decrements may contribute to sustained emotional and neurocognitive symptoms over time. (JINS, 2018, 24, 311-323).

Shifting visual perspective during memory retrieval reduces the accuracy of subsequent memories

Memories for events can be retrieved from visual perspectives that were never experienced, reflecting the dynamic and reconstructive nature of memories. Characteristics of memories can be altered when shifting from an own eyes perspective, the way most events are initially experienced, to an observer perspective, in which one sees oneself in the memory. Moreover, recent evidence has linked these retrieval-related effects of visual perspective to subsequent changes in memories. Here we examine how shifting visual perspective influences the accuracy of subsequent memories for complex events encoded in the lab. Participants performed a series of mini-events that were experienced from their own eyes, and were later asked to retrieve memories for these events while maintaining the own eyes perspective or shifting to an alternative observer perspective. We then examined how shifting perspective during retrieval modified memories by influencing the accuracy of recall on a final memory test. Across two experiments, we found that shifting visual perspective reduced the accuracy of subsequent memories and that reductions in vividness when shifting visual perspective during retrieval predicted these changes in the accuracy of memories. Our findings suggest that shifting from an own eyes to an observer perspective influences the accuracy of long-term memories.

A Basic-Systems Approach to Autobiographical Memory

Memory for complex everyday events involving vision, hearing, smell, emotion, narrative, and language cannot be understood without considering the properties of the separate systems that process and store each of these forms of information. Using this premise as a starting point, my colleagues and I found that visual memory plays a central role in autobiographical memory: The strength of recollection of an event is predicted best by the vividness of its visual imagery, and a loss of visual memory causes a general amnesia. Examination of autobiographical memories in individuals with posttraumatic stress disorder (PTSD) suggests that the lack of coherence often noted in memories of traumatic events is not due to a lack of coherence either of the memory itself or of the narrative that integrates the memory into the life story. Rather, making the traumatic memory central to the life story correlates positively with increased PTSD symptoms. The basic-systems approach has yielded insights into autobiographical memory's phenomenology, neuropsychology, clinical disorders, and neural basis.

Visual imagery in autobiographical memory: The role of repeated retrieval in shifting perspective

Recent memories are generally recalled from a first-person perspective whereas older memories are often recalled from a third-person perspective. We investigated how repeated retrieval affects the availability of visual information, and whether it could explain the observed shift in perspective with time. In Experiment 1, participants performed mini-events and nominated memories of recent autobiographical events in response to cue words. Next, they described their memory for each event and rated its phenomenological characteristics. Over the following three weeks, they repeatedly retrieved half of the mini-event and cue-word memories. No instructions were given about how to retrieve the memories. In Experiment 2, participants were asked to adopt either a first- or third-person perspective during retrieval. One month later, participants retrieved all of the memories and again provided phenomenology ratings. When first-person visual details from the event were repeatedly retrieved, this information was retained better and the shift in perspective was slowed.

Negative autobiographical memories in social anxiety disorder: A comparison with panic disorder and healthy controls

BACKGROUND AND OBJECTIVES

Empirical interest in mental imagery in social anxiety disorder (SAD) has grown over the past years but still little is known about the specificity to SAD. The present study therefore examines negative autobiographical memories in participants with social anxiety disorder (SAD), compared to patients with panic disorder (PD), and healthy controls (HCs).

METHODS

A total of 107 participants retrieved four memories cued by verbal phrases associated with either social anxiety (SA) or panic anxiety (PA), with two memories for each cue category.

RESULTS

PA-cued memories were experienced with stronger imagery and as more traumatic. They were also rated as more central to identity than SA-cued memories, but not among participants with SAD, who perceived SA-cued memories as equally central to their identity. When between-group effects were detected, participants with anxiety disorders differed from HCs, but not from each other.

LIMITATIONS

Central limitations include reliance on self-report measures, comorbidity in the anxiety disorder groups, and lack of a neutrally cued memory comparison.

CONCLUSIONS

The findings align with models of SAD suggesting that past negative social events play a central role in this disorder. Future research is suggested to further explore the function of negative memories, not only in SAD, but also in other anxiety disorders.

Setting the Records Straight: Impossible Memories and the Persistence of Their Phenomenological Qualities

This article offers a new perspective on the study of “recollections” that feel like memories despite the fact that people come to believe they are based on events that could not possibly have happened. Indeed this feeling of remembering can persist long after people change their beliefs. This new perspective emerges from the integration of the work of memory scientists with that of literary writers and historians. Shedding light on assumptions about the strength of these persistence effects, the perspective serves as an effective heuristic for guiding the study of precipitating factors that may lead people to question their recollections in the first place. This integrative perspective also invites a broader consideration of the circumstances giving rise to changes in beliefs as well as resistance to such changes. In the process, this new perspective extends and sharpens theoretical discussions about memory reconstruction processes, highlighting the role of scene making and social interactions.

The Basic-Systems Model of Episodic Memory

Behavior, neuropsychology, and neuroimaging suggest that episodic memories are constructed from interactions among the following basic systems: vision, audition, olfaction, other senses, spatial imagery, language, emotion, narrative, motor output, explicit memory, and search and retrieval. Each system has its own well-documented functions, neural substrates, processes, structures, and kinds of schemata. However, the systems have not been considered as interacting components of episodic memory, as is proposed here. Autobiographical memory and oral traditions are used to demonstrate the usefulness of the basic-systems model in accounting for existing data and predicting novel findings, and to argue that the model, or one similar to it, is the only way to understand episodic memory for complex stimuli routinely encountered outside the laboratory.

Event memory: A theory of memory for laboratory, autobiographical, and fictional events

An event memory is a mental construction of a scene recalled as a single occurrence. It therefore requires the hippocampus and ventral visual stream needed for all scene construction. The construction need not come with a sense of reliving or be made by a participant in the event, and it can be a summary of occurrences from more than one encoding. The mental construction, or physical rendering, of any scene must be done from a specific location and time; this introduces a "self" located in space and time, which is a necessary, but need not be a sufficient, condition for a sense of reliving. We base our theory on scene construction rather than reliving because this allows the integration of many literatures and because there is more accumulated knowledge about scene construction's phenomenology, behavior, and neural basis. Event memory differs from episodic memory in that it does not conflate the independent dimensions of whether or not a memory is relived, is about the self, is recalled voluntarily, or is based on a single encoding with whether it is recalled as a single occurrence of a scene. Thus, we argue that event memory provides a clearer contrast to semantic memory, which also can be about the self, be recalled voluntarily, and be from a unique encoding; allows for a more comprehensive dimensional account of the structure of explicit memory; and better accounts for laboratory and real-world behavioral and neural results, including those from neuropsychology and neuroimaging, than does episodic memory.

Development and psychometric properties of a new measure for memory phenomenology: The Autobiographical Memory Characteristics Questionnaire

The purpose of this study is to develop a valid and reliable measure for the phenomenology of autobiographical memories. The psychometric properties of the Autobiographical Memory Characteristics Questionnaire (AMCQ) were tested in three studies: the factor structure of the AMCQ was examined for childhood memories in Study 1 (N = 305); for autobiographical memories related to romantic relationships in Study 2 (N = 197); and for self-defining memories in Study 3 (N = 262). The explanatory factor analyses performed for each memory type demonstrated the consistency of the AMCQ factor structure across all memory types; while a confirmatory factor analysis on the data garnered from all three studies supported the constructs for the autobiographical memory characteristics defined by the researchers. The AMCQ consists of 63 items and 14 factors, and the internal consistency values of all 14 scales were ranged between .66 and .97. The relationships between the AMCQ scales related to gender and individual emotions, as well as the intercorrelations among the scales, were consistent with both theoretical expectations and previous findings. The results of all the three studies indicated that this new instrument is a reliable and robust measure for memory phenomenology.

Imagination perspective affects ratings of the likelihood of occurrence of autobiographical memories

Two experiments tested and confirmed the hypothesis that when the phenomenological characteristics of imagined events are more similar to those of related autobiographical memories, the imagined event is more likely to be considered to have occurred. At Time 1 and 2-weeks later, individuals rated the likelihood of occurrence for 20 life events. In Experiment 1, 1-week after Time 1, individuals imagined 3 childhood events from a first-person or third-person perspective. There was a no-imagination control. An increase in likelihood ratings from Time 1 to Time 2 resulted when imagination was from the third-person but not first-person perspective. In Experiment 2, childhood and recent events were imagined from a third- or first-person perspective. A significant interaction resulted. For childhood events, likelihood change scores were greater for third-person than first-person perspective; for recent adult events, likelihood change scores were greater for first-person than third-person perspective, although this latter trend was not significant.

Dysphoric students show higher use of the observer perspective in their retrieval of positive versus negative autobiographical memories

Autobiographical memories are retrieved as images from either a field perspective or an observer perspective. The observer perspective is thought to dull emotion. Positive affect is blunted in depressed mood. Consequently, are positive events recalled from an observer perspective in depressed mood? We investigated the relationship between memory vantage perspective and depressive symptoms in a student sample. Participants completed the Autobiographical Memory Test (AMT; Williams & Broadbent, 1986) and assessed the perspective accompanying each memory. The Beck Depression Inventory-II (BDI-II; Beck, Steer, & Brown, 1996) and the Responses to Positive Affect questionnaire (RPA; Feldman, Joormann, & Johnson, 2008) were administered. The results showed a small positive association between depressive symptoms and the use of an observer perspective for positive autobiographical memories, but not for negative memories. Furthermore, comparing a subgroup with clinically significant symptom levels (dysphoric students) with non-dysphoric individuals revealed that dysphoric students used an observer perspective more for positive memories compared with negative memories. This was not the case for non-dysphoric students. The observer perspective in dysphorics was associated with a dampening cognitive style in response to positive experiences.

Watching my mind unfold versus yours: an fMRI study using a novel camera technology to examine neural differences in self-projection of self versus other perspectives

Self-projection, the capacity to re-experience the personal past and to mentally infer another person's perspective, has been linked to medial prefrontal cortex (mPFC). In particular, ventral mPFC is associated with inferences about one's own self, whereas dorsal mPFC is associated with inferences about another individual. In the present fMRI study, we examined self-projection using a novel camera technology, which employs a sensor and timer to automatically take hundreds of photographs when worn, in order to create dynamic visuospatial cues taken from a first-person perspective. This allowed us to ask participants to self-project into the personal past or into the life of another person. We predicted that self-projection to the personal past would elicit greater activity in ventral mPFC, whereas self-projection of another perspective would rely on dorsal mPFC. There were three main findings supporting this prediction. First, we found that self-projection to the personal past recruited greater ventral mPFC, whereas observing another person's perspective recruited dorsal mPFC. Second, activity in ventral versus dorsal mPFC was sensitive to parametric modulation on each trial by the ability to relive the personal past or to understand another's perspective, respectively. Third, task-related functional connectivity analysis revealed that ventral mPFC contributed to the medial temporal lobe network linked to memory processes, whereas dorsal mPFC contributed to the fronto-parietal network linked to controlled processes. In sum, these results suggest that ventral-dorsal subregions of the anterior midline are functionally dissociable and may differentially contribute to self-projection of self versus other.

The influence of pre-deployment neurocognitive functioning on post-deployment PTSD symptom outcomes among Iraq-deployed Army soldiers

This study evaluated associations between pre-deployment neurocognitive performance and post-deployment posttraumatic stress disorder (PTSD) symptoms in a sample of deployed active duty Army soldiers. As part of a larger longitudinal study, each participant completed baseline measures of memory, executive attention, and response inhibition, and baseline and post-deployment self-report measures of PTSD symptom severity. Data were subjected to multiple regression analyses that examined associations between baseline neurocognitive performances and longitudinal PTSD symptom outcome. Results revealed that pre-trauma immediate recall of visual information was associated with post-deployment PTSD symptom severity, even after controlling for pre-deployment PTSD symptom levels, combat intensity, age, gender, and test-retest interval. There was also an interaction between pre-deployment PTSD symptom severity and pre-deployment immediate visual recall and verbal learning, indicating that neurocognitive performances were more strongly (and negatively) associated with residualized post-deployment PTSD symptoms at higher levels of pre-deployment PTSD symptoms. These findings highlight the potential role of pre-trauma neurocognitive functioning in moderating the effects of trauma exposure on PTSD symptoms

A memory-based model of posttraumatic stress disorder: evaluating basic assumptions underlying the PTSD diagnosis

In the mnemonic model of posttraumatic stress disorder (PTSD), the current memory of a negative event, not the event itself, determines symptoms. The model is an alternative to the current event-based etiology of PTSD represented in the Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; American Psychiatric Association, 2000). The model accounts for important and reliable findings that are often inconsistent with the current diagnostic view and that have been neglected by theoretical accounts of the disorder, including the following observations. The diagnosis needs objective information about the trauma and peritraumatic emotions but uses retrospective memory reports that can have substantial biases. Negative events and emotions that do not satisfy the current diagnostic criteria for a trauma can be followed by symptoms that would otherwise qualify for PTSD. Predisposing factors that affect the current memory have large effects on symptoms. The inability-to-recall-an-important-aspect-of-the-trauma symptom does not correlate with other symptoms. Loss or enhancement of the trauma memory affects PTSD symptoms in predictable ways. Special mechanisms that apply only to traumatic memories are not needed, increasing parsimony and the knowledge that can be applied to understanding PTSD.

The short and long of it: neural correlates of temporal-order memory for autobiographical events

Previous functional neuroimaging studies of temporal-order memory have investigated memory for laboratory stimuli that are causally unrelated and poor in sensory detail. In contrast, the present functional magnetic resonance imaging (fMRI) study investigated temporal-order memory for autobiographical events that were causally interconnected and rich in sensory detail. Participants took photographs at many campus locations over a period of several hours, and the following day they were scanned while making temporal-order judgments to pairs of photographs from different locations. By manipulating the temporal lag between the two locations in each trial, we compared the neural correlates associated with reconstruction processes, which we hypothesized depended on recollection and contribute mainly to short lags, and distance processes, which we hypothesized to depend on familiarity and contribute mainly to longer lags. Consistent with our hypotheses, parametric fMRI analyses linked shorter lags to activations in regions previously associated with recollection (left prefrontal, parahippocampal, precuneus, and visual cortices), and longer lags with regions previously associated with familiarity (right prefrontal cortex). The hemispheric asymmetry in prefrontal cortex activity fits very well with evidence and theories regarding the contributions of the left versus right prefrontal cortex to memory (recollection vs. familiarity processes) and cognition (systematic vs. heuristic processes). In sum, using a novel photo-paradigm, this study provided the first evidence regarding the neural correlates of temporal-order for autobiographical events.

Memories of early childhood: Qualities of the experience of recollection

Memories judged to be recollections were contrasted with memories known to be based on second-hand sources in order to investigate the phenomenological qualities that underlie the experience of recollection. Adults rated the qualities of their recollections of an early childhood experience. Their ratings were compared with ratings of the qualities of memories of a similar autobiographical experience where the information was known to derive from other sources. Reported recollections were rated higher than memories based on other sources for many qualities, including sensory and spatial detail, location, thoughts, feelings, completeness, event detail, and pictorial representation. Comparison of the ratings of memories dating from different ages suggests that a memory may be judged to be recollected even if only a subset of the qualities characterizing recollections are present. This provides partial support for and clarification of Rubin's multiple-systems model of autobiographical memory.

Stability in autobiographical memories

A total of 30 undergraduates recalled the same 20 autobiographical memories at two sessions separated by 2 weeks. At each session they dated their memories and rated them on 18 properties commonly studied in autobiographical memory experiments. Individuals showed moderate stability in their ratings on the 18 scales (r approximately .5), with consistency of dating being much higher (r = .96). There was more stability in the individuals' average rating on each scale (r approximately .8), even when the averages were calculated on different memories in the different sessions. The results are consistent with a constructive view of autobiographical memory, in which stable individual differences in cognitive style are important.

Emotional intensity predicts autobiographical memory experience

College students generated autobiographical memories from distinct emotional categories that varied in valence (positive vs. negative) and intensity (high vs. low). They then rated various perceptual, cognitive, and emotional properties for each memory. The distribution of these emotional memories favored a vector model over a circumplex model. For memories of all specific emotions, intensity accounted for significantly more variance in autobiographical memory characteristics than did valence or age of the memory. In two additional experiments, we examined multiple memories of emotions of high intensity and positive or negative valence and of positive valence and high or low intensity. Intensity was a more consistent predictor of autobiographical memory properties than was valence or the age of the memory in these experiments as well. The general effects of emotion on autobiographical memory properties are due primarily to intensity differences in emotional experience, not to benefits or detriments associated with a specific valence.

The episodic nature of involuntary autobiographical memories

Involuntary autobiographical memories are conscious and unintended recollections of personal experiences. In Study 1, involuntary memories were compared with voluntary word-cued memories, both retrieved in naturalistic settings via a self-paced procedure. The involuntary memories more frequently referred to specific episodes, came with more physical reaction, had more impact on mood, and dealt with more unusual and less positive events. Study 2 demonstrated that these differences were not due to differences between verbal and nonverbal cues, by using Francis Galton's "memory walk" as a nonverbal method to cue voluntary memories. In both studies, systematic differences were found between specific and nonspecific memories. The findings show that the way autobiographical memories are sampled greatly affects the findings and that involuntary retrieval more often provides access to memories of specific episodes and associated emotional states.