Exploring the roles of the executive and short-term feature-binding functions in retrieval of retrograde autobiographical memories in severe traumatic brain injury

Cognitive vulnerabilities and depressed mood in acquired brain injury

ABSTRACTAcquired Brain Injury (ABI), an important cause of long-term disability, is associated with increased rates of depression in addition to common cognitive and physical consequences. Past research has linked post-ABI depression to injury severity (e.g., extent of physical or cognitive impairment) and premorbid mood problems. In the general (non-ABI) population, depression is associated with cognitive vulnerabilities that have informed the development of psychological interventions. In this observational study in a heterogeneous sample of individuals with chronic stage ABI, we examine two cognitive vulnerabilities - dysfunctional attitudes (DAs) and autobiographical memory specificity - and explore whether these are linked to depression symptoms and ongoing cognitive difficulties as in the general population. Compared to control participants, individuals with an ABI demonstrated increased endorsement of DAs and reduced specificity of autobiographical memory recall. Within the ABI group, cognitive vulnerability-depression symptom correlations were detected for an explicit measure of DAs, but not for a more implicit DA measure or for autobiographical memory specificity. While individual differences in injury severity and other factors likely obscured subtle relationships between mood and cognitive vulnerabilities, evidence of these vulnerabilities may be relevant to changes in identity and psychological interventions that target low mood in ABI.

Effects of saccadic eye movements on episodic & semantic memory fluency in older and younger participants

Research has demonstrated that performing a sequence of saccadic horizontal eye movements prior to retrieval facilitates performance on tests of episodic memory. This has been observed in both laboratory tasks of retention and autobiographical memory. To date, the work has centred on performance in younger individuals. This paper extends previous investigations by examining the effects of saccadic eye movements in older persons. Autobiographical episodic and semantic memory fluency was assessed in younger (age range 18-35, mean = 22.50), and older (age range 55-87, mean = 70.35) participants following saccadic (vs. fixation control) manipulations. The main effects of eye movements and age were found for episodic autobiographical memory (greater fluency after eye movements and in younger participants). Semantic autobiographical memory showed a main effect of age (greater fluency in younger participants), whereas general semantic memory showed no effect of age or eye movement. These findings indicate that saccadic horizontal eye movements can enhance episodic personal memory in older individuals. This has implications as a technique to improve autobiographical recollection in the elderly and as an adjunct in reminiscence therapy.

Self-defining memories after severe traumatic brain injury: A preliminary study

Autobiographical memory plays a major role in the (re)construction of sense of identity, a recurrent issue after a traumatic brain injury (TBI). Although the recall of specific autobiographical events is frequently impaired in patients with TBI, little is known about how these changes affect their sense of self and identity. Thus, we examined self-defining memories (SDMs), that is, the most significant personal memories supporting one's sense of identity, in 16 patients with severe TBI and in matched controls. To this end, participants recalled three SDMs and rated their emotions in response to memory retrieval. In addition, characteristics of SDMs such as specificity, meaning-making, self-connections that reflect identity stability or identity change, content (theme, presence of tension, and redemption sequences) were analysed by independent raters. The main results showed that patients' SDMs were less specific and contained fewer redemption sequences than did those of controls but did not significantly differ in thematic content, presence of tension, meaning-making, self-connections that reflect identity stability or identity change and affective responses to memory retrieval. Furthermore, among the patients' memories that refer to the TBI-related event itself, only one contained an explicit meaning. Despite the lack of specificity in memories, patients with severe TBI were able to extract meaning from personal memories although they could struggle with integrating the TBI-related event into their sense of identity. These characteristics of SDMs may contribute to disturbances in sense of self and continuity in patients with severe TBI, as well as difficulties in personal or social adjustment. These results also open up relevant prospects for psychological interventions in identity-related issues in patients with TBI.

Retrograde Autobiographical Memory From PTA Emergence to Six-Month Follow-Up in Moderate to Severe Traumatic Brain Injury

OBJECTIVE

The overwhelming focus of research on memory following traumatic brain injury (TBI) has been on anterograde amnesia, and very little attention has been paid to retrograde amnesia. There is evidence to suggest that retrograde autobiographical memory deficits exist after severe TBI, although there have been no prospective studies of autobiographical memory in a representative sample of moderate to severe cases recruited from hospital admissions.

METHODS

The purpose of the present study was to report changes in autobiographical memory performance among a group of patients soon after emergence from posttraumatic amnesia (PTA) and at the 6-month follow-up compared with a healthy control (HC) group. The authors also examined associations with anterograde memory function and community integration to assist in understanding the functional impact of autobiographical memory deficits and potential underlying mechanisms. The Autobiographical Memory Interview and the Rey Auditory Verbal Learning Test were used as measures of retrograde and anterograde memory, respectively, and the Community Integration Questionnaire was used as a measure of functional outcome in the TBI group.

RESULTS

The results demonstrated that both personal semantic and episodic autobiographical memory scores were impaired following emergence from PTA and at the 6-month follow-up. Only subtle differences emerged in change over time in different injury severity groups. Recent retrograde memory function was associated with anterograde memory performance, which supports some degree of overlap in underlying mechanisms.

CONCLUSIONS

The findings suggest that autobiographical memory deficits are prevalent following moderate to severe TBI and warrant consideration in rehabilitation.

Retrograde Personal Semantic Memory During Post-Traumatic Amnesia and Following Emergence

OBJECTIVES

Anecdotal reports suggest that following traumatic brain injury (TBI) retrograde memories are initially impaired and recover in order of remoteness. However, there has been limited empirical research investigating whether a negative gradient in retrograde amnesia-relative preservation of remote over recent memory-exists during post-traumatic amnesia (PTA) compared with the acute phase post-emergence. This study used a repeated-measures design to examine the pattern of personal semantic (PS) memory performance during PTA and within two weeks of emergence to improve understanding of the nature of the memory deficit during PTA and its relationship with recovery.

METHODS

Twenty patients with moderate-severe TBI and 20 healthy controls (HCs) were administered the Personal Semantic Schedule of the Autobiographical Memory Interview. The TBI group was assessed once during PTA and post-emergence. Analysis of variance was used to compare the gradient across lifetime periods during PTA relative to post-emergence, and between groups.

RESULTS

PS memory was significantly lower during PTA than post-emergence from PTA, with no relative preservation of remote memories. The TBI group was still impaired relative to HCs following emergence from PTA. Lower overall PS memory scores during PTA were associated with increased days to emerge from PTA post-interview.

CONCLUSIONS

These results suggest a global impairment in PS memory across lifetime periods particularly during PTA, but still present within 2 weeks of emergence from PTA. PS memory performance may be sensitive to the diffuse nature of TBI and may, therefore, function as a clinically valuable indicator of the likely time to emerge from PTA. (JINS, 2018, 24, 1064-1072).

Neuropsychology of traumatic brain injury: An expert overview

Traumatic brain injury (TBI) is a serious healthcare problem, and this report is a selective review of recent findings on the epidemiology, pathophysiology and neuropsychological impairments following TBI. Patients who survive moderate-to-severe TBI frequently suffer from a wide range of cognitive deficits and behavioral changes due to diffuse axonal injury. These deficits include slowed information-processing and impaired long-term memory, attention, working memory, executive function, social cognition and self-awareness. Mental fatigue is frequently also associated and can exacerbate the consequences of neuropsychological deficits. Personality and behavioral changes can include combinations of impulsivity and apathy. Even mild TBI raises specific problems: while most patients recover within a few weeks or months, a minority of patients may suffer from long-lasting symptoms (post-concussion syndrome). The pathophysiology of such persistent problems remains a subject of debate, but seems to be due to both injury-related and non-injury-related factors.

Autobiographical memory and structural brain changes in chronic phase TBI

Traumatic brain injury (TBI) is associated with a range of neuropsychological deficits, including attention, memory, and executive functioning attributable to diffuse axonal injury (DAI) with accompanying focal frontal and temporal damage. Although the memory deficit of TBI has been well characterized with laboratory tests, comparatively little research has examined retrograde autobiographical memory (AM) at the chronic phase of TBI, with no prior studies of unselected patients drawn directly from hospital admissions for trauma. Moreover, little is known about the effects of TBI on canonical episodic and non-episodic (e.g., semantic) AM processes. In the present study, we assessed the effects of chronic-phase TBI on AM in patients with focal and DAI spanning the range of TBI severity. Patients and socioeconomic- and age-matched controls were administered the Autobiographical Interview (AI) (Levine, Svoboda, Hay, Winocur, & Moscovitch, 2002) a widely used method for dissociating episodic and semantic elements of AM, along with tests of neuropsychological and functional outcome. Measures of episodic and non-episodic AM were compared with regional brain volumes derived from high-resolution structural magnetic resonance imaging (MRI). Severe TBI (but not mild or moderate TBI) was associated with reduced recall of episodic autobiographical details and increased recall of non-episodic details relative to healthy comparison participants. There were no significant associations between AM performance and neuropsychological or functional outcome measures. Within the full TBI sample, autobiographical episodic memory was associated with reduced volume distributed across temporal, parietal, and prefrontal regions considered to be part of the brain's AM network. These results suggest that TBI-related distributed volume loss affects episodic autobiographical recollection.

Cognitive Decline and Reorganization of Functional Connectivity in Healthy Aging: The Pivotal Role of the Salience Network in the Prediction of Age and Cognitive Performances

Normal aging is related to a decline in specific cognitive processes, in particular in executive functions and memory. In recent years a growing number of studies have focused on changes in brain functional connectivity related to cognitive aging. A common finding is the decreased connectivity within multiple resting state networks, including the default mode network (DMN) and the salience network. In this study, we measured resting state activity using fMRI and explored whether cognitive decline is related to altered functional connectivity. To this end we used a machine learning approach to classify young and old participants from functional connectivity data. The originality of the approach consists in the prediction of the performance and age of the subjects based on functional connectivity by using a machine learning approach. Our findings showed that the connectivity profile between specific networks predicts both the age of the subjects and their cognitive abilities. In particular, we report that the connectivity profiles between the salience and visual networks, and the salience and the anterior part of the DMN, were the features that best predicted the age. Moreover, independently of the age of the subject, connectivity between the salience network and various specific networks (i.e., visual, frontal) predicted episodic memory skills either based on a standard assessment or on an autobiographical memory task, and short-term memory binding. Finally, the connectivity between the salience and the frontal networks predicted inhibition and updating performance, but this link was no longer significant after removing the effect of age. Our findings confirm the crucial role of episodic memory and executive functions in cognitive aging and suggest a pivotal role of the salience network in neural reorganization in aging.

The role of working memory and verbal fluency in autobiographical memory in early Alzheimer's disease and matched controls

Retrieval of autobiographical memories (AMs) is important for "sense of self". Previous research and theoretical accounts suggest that working memory (WM) and semantic and phonemic fluency abilities facilitate the hierarchical search for, and reliving of past, personal events in the mind's eye. However, there remains a lack of consensus as to the nature of the relationships between these cognitive functions and the truly episodic aspects of AM. The present study therefore aimed to explore the associations between these variables in a sample with a wide range of cognitive abilities. The study incorporated a between-groups component, and a correlational component with multiple regression. Participants with Alzheimer's disease (n=10) and matched healthy controls (n=10) were assessed on measures of semantic and episodic AM search and retrieval, auditory and spatial WM, and semantic and phonemic fluency. The AD group produced less episodic AM content compared to controls. Semantic fluency predicted episodic AM retrieval independent of age effects but there were no significant relationships between measures of phonemic fluency, WM and episodic AM. The results suggest that the ability to maintain hierarchical search of the semantic knowledge-base is important for truly episodic reliving, and interventions for people with AM impairment might therefore benefit from incorporating structured, individualised external memory-aids to facilitate AM search and retrieval.

Autobiographical Periods: A Review and Central Components of a Theory

Autobiographical periods refer to subjectively defined life periods with perceived beginnings and endings, including information about the people, places, activities, and objects associated with the period. Autobiographical periods are serial, parallel, and hierarchical and are associated with specific and categoric memories. Individuals construct autobiographical periods for the future and have knowledge of periods in other people's lives. The review shows that (a) autobiographical periods may facilitate the recall of specific memories; (b) specific memories from the beginning and end of autobiographical periods are more often recalled compared with specific memories from other time points; (c) autobiographical periods are used to place specific memories in time; (d) autobiographical periods play an important role in the construction of life stories; and (e) autobiographical periods are related to personality traits and well-being. The central components of a theory of autobiographical periods are outlined. Thinking of life as extended time periods is suggested to be the central process through which autobiographical periods are constructed. Sociocultural processes, experience, and goals are assumed to inform life period thinking, and thus the construction of autobiographical periods.

Age-related changes in the functional network underlying specific and general autobiographical memory retrieval: a pivotal role for the anterior cingulate cortex

Age-related changes in autobiographical memory (AM) recall are characterized by a decline in episodic details, while semantic aspects are spared. This deleterious effect is supposed to be mediated by an inefficient recruitment of executive processes during AM retrieval. To date, contrasting evidence has been reported on the neural underpinning of this decline, and none of the previous studies has directly compared the episodic and semantic aspects of AM in elderly. We asked 20 young and 17 older participants to recall specific and general autobiographical events (i.e., episodic and semantic AM) elicited by personalized cues while recording their brain activity by means of fMRI. At the behavioral level, we confirmed that the richness of episodic AM retrieval is specifically impoverished in aging and that this decline is related to the reduction of executive functions. At the neural level, in both age groups, we showed the recruitment of a large network during episodic AM retrieval encompassing prefrontal, cortical midline and posterior regions, and medial temporal structures, including the hippocampus. This network was very similar, but less extended, during semantic AM retrieval. Nevertheless, a greater activity was evidenced in the dorsal anterior cingulate cortex (dACC) during episodic, compared to semantic AM retrieval in young participants, and a reversed pattern in the elderly. Moreover, activity in dACC during episodic AM retrieval was correlated with inhibition and richness of memories in both groups. Our findings shed light on the direct link between episodic AM retrieval, executive control, and their decline in aging, proposing a possible neuronal signature. They also suggest that increased activity in dACC during semantic AM retrieval in the elderly could be seen as a compensatory mechanism underpinning successful AM performance observed in aging. These results are discussed in the framework of recently proposed models of neural reorganization in aging.

Effects of saccadic bilateral eye movements on episodic and semantic autobiographical memory fluency

Performing a sequence of fast saccadic horizontal eye movements has been shown to facilitate performance on a range of cognitive tasks, including the retrieval of episodic memories. One explanation for these effects is based on the hypothesis that saccadic eye movements increase hemispheric interaction, and that such interactions are important for particular types of memory. The aim of the current research was to assess the effect of horizontal saccadic eye movements on the retrieval of both episodic autobiographical memory (event/incident based memory) and semantic autobiographical memory (fact based memory) over recent and more distant time periods. It was found that saccadic eye movements facilitated the retrieval of episodic autobiographical memories (over all time periods) but not semantic autobiographical memories. In addition, eye movements did not enhance the retrieval of non-autobiographical semantic memory. This finding illustrates a dissociation between the episodic and semantic characteristics of personal memory and is considered within the context of hemispheric contributions to episodic memory performance.

Don't be Too Strict with Yourself! Rigid Negative Self-Representation in Healthy Subjects Mimics the Neurocognitive Profile of Depression for Autobiographical Memory

Autobiographical memory (AM) comprises representation of both specific (episodic) and generic (semantic) personal information. Depression is characterized by a shift from episodic to semantic AM retrieval. According to theoretical models, this process ("overgeneralization"), would be linked to reduced executive resources. Moreover, "overgeneral" memories, accompanied by a negativity bias in depression, lead to a pervasive negative self-representation. As executive functions and AM specificity are also closely intricate among "non-clinical" populations, "overgeneral" memories could result in depressive emotional responses. Consequently, our hypothesis was that the neurocognitive profile of healthy subjects showing a rigid negative self-image would mimic that of patients. Executive functions and self-image were measured and brain activity was recorded, by means of fMRI, during episodic AMs retrieval in young healthy subjects. The results show an inverse correlation, that is, a more rigid and negative self-image produces lower performances in both executive and specific memories. Moreover, higher negative self-image is associated with decreased activity in the left ventro-lateral prefrontal and in the anterior cingulate cortex, repeatedly shown to exhibit altered functioning in depression. Activity in these regions, on the contrary, positively correlates with executive and memory performances, in line with their role in executive functions and AM retrieval. These findings suggest that rigid negative self-image could represent a marker or a vulnerability trait of depression by being linked to reduced executive function efficiency and episodic AM decline. These results are encouraging for psychotherapeutic approaches aimed at cognitive flexibility in depression and other psychiatric disorders.