Autobiographical memory, autonoetic consciousness, and identity in Asperger syndrome

Previous results from research on individuals with Asperger syndrome (AS) suggest a diminished ability for recalling episodic autobiographical memory (AM). The primary aim of this study was to explore autobiographical memory in individuals with Asperger syndrome and specifically to investigate whether memories in those with AS are characterized by fewer episodic ‘remembered’ events (due to a deficit in autonoetic consciousness). A further aim was to examine whether such changes in AM might also be related to changes in identity, due to the close relationship between memory and the self and to the established differences in self-referential processes in AS. Eleven adults with AS and fifteen matched comparison participants were asked to recall autobiographical memories from three lifetime periods and for each memory to give either a remember response (autonoetic consciousness) or a know response (noetic consciousness). The pattern of results shows that AS participants recalled fewer memories and that these memories were more often rated as known, compared to the comparison group. AS participants also showed differences in reported identity, generating fewer social identity statements and more abstract, trait-linked identities. The data support the view that differences in both memory and reported personal identities in AS are characterized by a lack of specificity.     

The effect of impaired verbal memory retrieval on autobiographical memory across different life periods in schizophrenia

ObjectivesAutobiographical memory (AM) involves recollection of personal events and facts about one's life. Αim of the present study was to investigate AM in schizophrenia patients, and, in particular, patients' ability to recall autobiographical memories after controlling for verbal memory and verbal fluency deficits.MethodParticipants included 40 schizophrenia patients (23 male) and 40 healthy controls (23 male), matched for age, gender, educational level, and premorbid intellectual functioning. Participants' verbal memory (list learning and story recall) and verbal fluency were assessed. AM was evaluated by the Questionnaire of Autobiographical Memory, consisting of the Personal Semantic Memory scale and the Autobiographical Incidents scale. Furthermore, personal incidents' specificity was examined.ResultsSchizophrenia patients showed deficits in verbal memory and verbal fluency, as well as in both semantic and episodic AM compared with healthy controls. Deficits were shown in episodic and semantic memories of events and facts dating to three different life periods (childhood, early adulthood and recent life). Regarding specificity of recalled events, patients reported fewer specific autobiographical incidents than controls. After controlling AM deficits for patients' verbal memory and verbal fluency impairment, it was shown that schizophrenia patients recalled fewer memories of autobiographical incidents dating only to recent life, compared with healthy controls.ConclusionsSchizophrenia patients showed impaired AM after controlling for verbal memory and verbal fluency impairment only in regard with personal episodic memories from recent life. Current findings raise the important issue of cognitive remediation therapy in schizophrenia.     

Overgeneral autobiographical memory in Parkinson's disease

Autobiographical memory (AM) concerns the ability to remember past events from one's own life and consists of autobiographical knowledge (personal facts) and autobiographical incidents (personal events). The novelty of this research was to assess both personal factual and personal event AM in Parkinson's disease (PD) for specified lifetime periods. An autobiographical fluency task was used in which participants were asked to recall personal events and personal facts from five separate lifetime periods. Previous findings as well the brain regions affected in PD lead to the hypothesis that Parkinson's patients would recall less autobiographical memories especially for the most recent lifetime periods. Sixteen non-demented and non-depressed Parkinson's patients and sixteen age-education-matched controls participated. The results showed a temporal gradient for the recall of personal events in Parkinson's patients as they recalled fewer events for recent time periods. The PD group also had more difficulties in recalling autobiographical events rather than an autobiographical knowledge. The difficulty in recalling autobiographical events was characterized by overgenerality, with PD patients failing to generate specific episodic memories.     

Impairment of episodic and semantic autobiographical memory in patients with mild cognitive impairment and early Alzheimer's disease

Autobiographical memory includes the retrieval of personal semantic data and the remembrance of incident or episodic memories. In retrograde amnesias, it has been observed that recall of autobiographical memories of recent events is poorer than recall of remote memories. Alzheimer's disease (AD) may also be associated with a temporal gradient (TG) in memory decline, though studies have yielded inconsistent results on this point. They have also yielded inconsistent results on whether AD might differentially affect semantic and episodic remembrance. Here, we compared autobiographical memory of childhood, early adulthood, and recent life among healthy control (HC) subjects, patients with early AD, and patients with amnesic mild cognitive impairment (aMCI). Both the aMCI and AD patients exhibited declines in recall of autobiographical incidents and semantic information. In AD patients, both components of autobiographical memory had a clear TG, with better preservation of memories of childhood than those of early adulthood and recent life. The TG of autobiographical memory decline in AD patients is more compatible with the Cortical Reallocation Theory than with the Multiple Trace Theory of memory consolidation. In contrast to AD patients, aMCI patients exhibited impaired recall of personal facts and autobiographical incidents relating only to recent life. The significant decline in autobiographical memory for recent life that occurred in aMCI patients suggests that deterioration of consolidation of personal facts and events begins with commencement of functional impairment in the hippocampus.     

Patterns of autobiographical memory loss in dementia

BACKGROUND: Several studies have found impaired recall of remote autobiographical memories relative to recent memories in semantic dementia (SD), a pattern opposite to that in Alzheimer's disease (AD). OBJECTIVE: To document dissociation of memory for autobiographical incidents and personal semantic information in individuals with AD, frontotemporal dementia (FTD), and SD. METHODS: The authors administered the Autobiographical Memory Interview to eight individuals with AD, 11 with FTD, eight with SD, and eight normal controls . Autobiographical incidents and personal semantic memory was assessed from three time periods: childhood, early adulthood, and recent life. RESULTS: Individuals with SD recalled more details of autobiographical incidents from the most recent 5 years than from childhood and early adulthood (childhood vs recent life: t(7) = -3.59, p = 0.009; early adulthood vs recent life: t(7) = -4.33, p = 0.003). No difference was found between childhood and early adulthood (t(7) = 1.11, p = 0.305). Recall of personal semantic information was related to the age of the memory with less remembered from earlier time periods (childhood vs recent life: t(7) = -6.52, p < 0.001; childhood vs early adulthood: t(7) = -2.61, p = 0.035; early adulthood vs recent life: t(7) = -9.15, p < 0.001). CONCLUSIONS: SD is a compelling model in which to study the anatomy of episodic memory.     

Autobiographical memory in semantic dementia: implication for theories of limbic-neocortical interaction in remote memory

We examined autobiographical memory performance in two patients with semantic dementia using a novel measure, the Autobiographical Interview [Levine, Svoboda, Hay, Winocur, & Moscovitch (2002). Aging and autobiographical memory: Dissociating episodic from semantic retrieval. Psychology and Aging, 17, 677-689], that is capable of dissociating episodic and personal semantic recall under varying levels of retrieval support. Earlier reports indicated that patients with semantic dementia demonstrate autobiographical episodic memory loss following a "reverse gradient" by which recent memories are preserved relative to remote memories. We found limited evidence for this pattern at conditions of low retrieval support. When structured probing was provided, patients' autobiographical memory performance was similar to that of controls. Retesting of one patient after 1 year indicated that retrieval support was insufficient to bolster performance following progressive prefrontal volume loss, as documented with quantified structural neuroimaging. These findings are discussed in relation to theories of limbic-neocortical interaction in autobiographical memory.     

Episodic, but not semantic, autobiographical memory is reduced in amnestic mild cognitive impairment

Amnestic mild cognitive impairment (aMCI) is characterized by decline in anterograde memory as measured by the ability to learn and remember new information. We investigated whether retrograde memory for autobiographical information was affected by aMCI. Eighteen control (age 66-84 years) and 17 aMCI (age 66-84 years) participants described a personal event from each of the five periods across the lifespan. These events were transcribed and scored according to procedures that separate episodic (specific happenings) from semantic (general knowledge) elements of autobiographical memory. Although both groups generated protocols of similar length, the composition of autobiographical recall differentiated the groups. The aMCI group protocols were characterized by reduced episodic and increased semantic information relative to the control group. Both groups showed a similar pattern of recall across time periods, with no evidence that the aMCI group had more difficulty recalling recent, rather than remote, life events. These results indicate that episodic and semantic autobiographical memories are differentially affected by the early brain changes associated with aMCI. Reduced autobiographical episodic memories in aMCI may be the result of medial temporal lobe dysfunction, consistent with multiple trace theory, or alternatively, could be related to dysfunction of a wider related network of neocortical structures. In contrast, the preservation of autobiographical semantic memories in aMCI suggests neural systems, such as lateral temporal cortex, that support these memories, may remain relatively intact.     

Long-term memory following transient global amnesia: an investigation of episodic and semantic memory

BACKGROUND: Several studies noted persistence of memory impairment following an episode of transient global amnesia (TGA) with standard tests. AIM: To specify long-term memory impairments in a group of patients selected with stringent criteria. METHODS: Both retrograde and anterograde memory were investigated in 32 patients 13-67 months after a TGA episode with original tasks encompassing retrograde semantic memory (academic, public and personal knowledge), retrograde episodic memory (autobiographical events) and anterograde episodic memory. RESULTS: Patients had preserved academic and public knowledge. Pathological scores were obtained in personal verbal fluency for the two most recent periods, and patients produced less autobiographical events than controls. However, when they were provided time to detail, memories were as episodic as in controls regardless of their remoteness. Anterograde episodic tasks revealed a mild but significant impairment of the capacity of re-living the condition of encoding, i.e. the moment at which words were presented. CONCLUSIONS: Patients who have suffered from an episode of TGA manifest deficits of memory focused on the retrieval of both recent semantic information and episodic memories and especially the capacity of re-living. These deficits may not result from a deterioration of memory per se but rather from difficulties in accessing memories.     

Autobiographical significance in past and future public semantic memory: A case-study

Refined investigation of infrequent dissociations within remote memory, such as preservation of autobiographical episodic memory and selective impairment of public semantic memory could provide some insight on the interactions of long-term memory systems and their underlying brain correlates. Combining clinical neuropsychological and neuroimaging methods in the present study, we examined a patient surgically treated for temporal lobe epilepsy showing this rare pattern of dissociation. Specifically, we investigated along the two temporal directions, past and future, his autobiographical episodic memory, semantic memory for public events and famous people and their interaction through the concept of autobiographical significance (AS). The results showed impaired ability not only to recall past but also to imagine future public events in a context of preserved past and future personal episodic memory. Remarkably, impersonal future thinking was impaired regardless of AS, while the autobiographical-significant public past knowledge relied exclusively on the patient's spared autobiographical episodic memory. These results were corroborated by neuroimaging data showing the absence of brain activation for public knowledge devoid of personal significance and activation of the autobiographical memory cerebral network for personally significant public knowledge. Our findings suggest that AS did not ‘restore’ the code to access public semantic memory, but bypassed it by using personal memory sources successful only for past public recollections. Therefore, remembering impersonal and imagining public events seems to require the contribution of public semantic knowledge per se. The patient's cognitive profile suggested a reorganization of memory systems.     

Neural correlates of autobiographical memory in amnestic Mild Cognitive Impairment

Episodic memory dysfunction, commonly assessed with word list recall, is the main characteristic of amnestic Mild Cognitive Impairment (aMCI). While brain pathology underlying this kind of memory impairment is well established in aMCI, little is known about the effect of neurodegeneration on autobiographical memory. The present study investigated neuronal correlates of autobiographical memory in aMCI patients (n=12) and healthy elderly controls (n=13) using functional magnetic resonance imaging (fMRI). Additionally, voxel-based morphometry (VBM) was employed to reveal brain pathology in aMCI patients. Neuropsychological assessment showed significant impairment in episodic memory tasks (immediate and delayed word list recall) in aMCI patients. Moreover, VBM revealed significantly reduced gray matter concentration, which was most pronounced in the temporal lobes of aMCI patients. Despite episodic memory impairment and atrophy in areas that are associated with encoding and recall of episodic memories, aMCI patients showed no alterations in brain activation associated with autobiographical memory retrieval. These findings could suggest that autobiographical memory is subserved by a different neuronal network than episodic memory and that the two memory systems are differently affected by aMCI.     

Alteration of autobiographical memory in amnestic mild cognitive impairment

The concept of amnestic mild cognitive impairment (aMCI) concerns a population of older individuals at high risk of developing probable Alzheimer's disease. Although anterograde memory deficits have been largely documented in patients with aMCI, little is known about the integrity of their autobiographical memory (AuM). This study aimed at evaluating AuM in aMCI individuals and at investigating whether their ability to retrieve AuMs varied as a function of whether the tests used required recognition or effortful retrieval processes. Fourteen aMCI patients and 14 matched controls underwent a standard neuropsychological evaluation and an extensive autobiographical assessment. AuM was explored using verbal material, the Autobiographical Memory Interview, and a visual task of personal photographs. Together, these tests tapped the semantic and episodic components of AuM and different cognitive processes involved in retrieval (recall and recognition). Results indicate that AuM is altered in aMCI patients. This impairment affects both episodic and semantic components of AuM, and is characterized by a general difficulty in recollecting personal episodes covering the entire lifespan, along with a loss of recognition of recently experienced episodes. Furthermore, recollection of personal episodes was correlated with scores on tests requiring retrieval abilities, while recognition of familiar photographs was correlated with scores on tests assessing encoding/storage of new information. Results suggest that the AuM deficit in aMCI patients may result from the combination of two mechanisms, an anterograde memory impairment impeding the storage of newly experienced events, and a global alteration of recollection affecting the recall of AuM covering all periods of life. Alteration of these processes may possibly be related to the progression and distribution of the neuropathological lesions in medial temporal and frontal lobe structures found in Alzheimer's disease.     

Patterns of autobiographical memory loss in medial-temporal lobe amnesic patients

The issue of whether the hippocampus and related structures in the medial-temporal lobe (MTL) play a temporary or permanent role in autobiographical episodic memory remains unresolved. One long-standing belief is that autobiographical memory (AM), like semantic memory, is initially dependent on the MTL but ultimately can be retained and recovered independently of it. However, evidence that hippocampal amnesia results in severe loss of episodic memory for a lifetime of personally experienced events suggests otherwise. To test the opposing views, we conducted detailed investigations of autobiographical episodic memory in people with amnesia resulting from MTL lesions of varying extent. By combining precise quantification of MTL and neocortical volumes with sensitive measures of recollection of one's personal past, we show that the severity of episodic, but not semantic, AM loss is best accounted for by the degree of hippocampal damage and less likely related to additional neocortical compromise.     

Autobiographical memory in semantic dementia: A longitudinal fMRI study

Whilst patients with semantic dementia (SD) are known to suffer from semantic memory and language impairments, there is less agreement about whether memory for personal everyday experiences, autobiographical memory, is compromised. In healthy individuals, functional MRI (fMRI) has helped to delineate a consistent and distributed brain network associated with autobiographical recollection. Here we examined how the progression of SD affected the brain's autobiographical memory network over time. We did this by testing autobiographical memory recall in a SD patient, AM, with fMRI on three occasions, each one year apart, during the course of his disease. At the outset, his autobiographical memory was intact. This was followed by a gradual loss in recollective quality that collapsed only late in the course of the disease. There was no evidence of a temporal gradient. Initially, AM's recollection was supported by the classic autobiographical memory network, including atrophied tissue in hippocampus and temporal neocortex. This was subsequently augmented by up-regulation of other parts of the memory system, namely ventromedial and ventrolateral prefrontal cortex, right lateral temporal cortex, and precuneus. A final step-change in the areas engaged and the quality of recollection then preceded the collapse of autobiographical memory. Our findings inform theoretical debates about the role of the hippocampus and neocortical areas in supporting remote autobiographical memories. Furthermore, our results suggest it may be possible to define specific stages in SD-related memory decline, and that fMRI could complement MRI and neuropsychological measures in providing more precise prognostic and rehabilitative information for clinicians and carers.     

Episodic autobiographical memory in amnestic mild cognitive impairment: What are the neural correlates?

Autobiographical memory in amnestic Mild Cognitive Impairment (aMCI) is characterized by impaired retrieval of episodic memories, but relatively preserved personal semantic knowledge. This study aimed to identify (via FDG‐PET) the neural substrates of impaired episodic specificity of autobiographical memories in 35 aMCI patients compared with 24 healthy elderly controls. Significant correlations between regional cerebral activity and the proportion of episodic details in autobiographical memories from two life periods were found in specific regions of an autobiographical brain network. In aMCI patients, more than in controls, specifically episodic memories from early adulthood were associated with metabolic activity in the cuneus and in parietal regions. We hypothesized that variable retrieval of episodic autobiographical memories in our aMCI patients would be related to their variable capacity to reactivate specific sensory‐perceptual and contextual details of early adulthood events linked to reduced (occipito‐parietal) visual imagery and less efficient (parietal) attentional processes. For recent memories (last year), a correlation emerged between the proportion of episodic details and activity in lateral temporal regions and the temporo‐parietal junction. Accordingly, variable episodic memory for recent events may be related to the efficiency of controlled search through general events likely to provide cues for the retrieval of episodic details and to the ability to establish a self perspective favouring recollection. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc.     

I cannot remember,but I know my past events: remembering and knowing in a patient with amnesic syndrome

Case Y.K. has severe anterograde amnesia and a selective loss of specific personal episodes in his remote memories (Hirano & Noguchi, 1998). In this paper, we attempted to analyze remembering (R) and knowing (K) responses, that is, the relationship between autobiographical remembering and remembering accompanied by subjective experience. Although the rate of R responses was significantly higher than that of K responses in control subjects, Y.K.'s R responses were rare in all subtypes of remote memories. Based on these results, we conclude that Y.K.'s memories on autobiographical incident task were not based on episodic memory but rather on semantic memory. Thus, the autobiographical incidents he could recall were not episodic memory, and his semantic memory made him recall information as fact rather than episode.     

Autobiographical memory in depression: an fMRI study

Depression is associated with three distinct alterations in memory functioning: mood-congruent recall, over-generality, and intrusive memories. These concern the autobiographical memory system, yet no previous studies have examined the neural correlates of autobiographical memory function in depression. In the present study we used functional magnetic resonance imaging (fMRI) to assess depressed and control participants during an autobiographical memory task. In their first visit to the laboratory, participants wrote a narrative account of a distressing event. Participants were scanned during the second visit while they viewed old items from their narrative and new words or phrases in a recognition memory task. Activity common to both groups during the successful identification of personal emotional memories was observed in regions previously associated with autobiographical memory retrieval. Reduced activity in the depressed group was observed in three regions of the prefrontal cortex associated with cognitive, emotional, and memory inhibition. These results are consistent with a failure by depressed individuals to inhibit task-irrelevant information during an autobiographical memory task.     

As time goes by: hippocampal connectivity changes with remoteness of autobiographical memory retrieval

The hippocampus is crucial for episodic autobiographical memory retrieval. Functional neuroimaging evidence suggests that it is similarly engaged in recent and remote retrieval when memories are matched on vividness and personal importance. Far fewer studies have investigated the nature of hippocampal-neocortical coactivation in relation to memory remoteness. The purpose of this study was to examine hippocampal activity and functional connectivity as a function of memory age. Unlike most studies of autobiographical memory, we included autobiographical memories formed in the days and weeks before scanning, in addition to truly remote memories on the order of months and years. Like previous studies, we found that the hippocampus was active bilaterally regardless of memory age, with anterior activity increasing up to 1 yr and then decreasing, and with posterior activity being less sensitive to memory age. More importantly, hippocampal functional connectivity varied with memory age. Retrieving recent memories (≤1 yr) showed a late coactivation of the hippocampus and areas of the autobiographical memory network, whereas retrieving remote memories (10 yrs) showed an early negative coactivation of the hippocampus and left inferior frontal gyrus followed by a positive coactivation with anterior cingulate. This finding may reflect that the hippocampus is more strongly integrated with the autobiographical memory network for recent than for remote memories, and that more effort is required to recover remote memories.     

Reduced levels of specific autobiographical memories in schizophrenia

Autobiographical memory is intrinsically related to the self and personal identity. This study investigated whether both personal episodic memory and semantic memory are impaired in schizophrenia, a disease characterized by an abnormal personal identity. Personal episodic memory and personal semantic memory were investigated in 24 patients with schizophrenia and 24 normal subjects using an autobiographical fluency task and an autobiographical memory inquiry. Autobiographical memory scores and the proportion of specific memories were lower in patients with schizophrenia than in normal subjects. The deficit of personal episodic and semantic memory, as assessed by the autobiographical memory inquiry and the autobiographical fluency task, respectively, was most apparent after the onset of clinical symptoms. Schizophrenia is associated with an impairment of both personal episodic and semantic memory and with a reduction of specific autobiographical memories. Those impairments are consistent with the existence of an abnormal personal identity in patients with schizophrenia.     

The perceptual richness of complex memory episodes is compromised by medial temporal lobe damage

Perceptual richness, a defining feature of episodic memory, emerges from the reliving of multimodal sensory experiences. Although the importance of the medial temporal lobe (MTL) to episodic memory retrieval is well documented, the features that determine its engagement are not well characterized. The current study assessed the relationship between MTL function and episodic memory's perceptual richness. We designed a laboratory memory task meant to capture the complexity of memory for life episodes, while manipulating memory's perceptual content. Participants encoded laboratory episodes with rich (film clips) and impoverished (written narratives) perceptual content that were matched for other characteristics such as personal significance, emotionality and story content. At retrieval, participants were probed to describe the stories' perceptual features and storyline. Participants also recalled autobiographical memories (AMs) in a comparison condition. We compared the performance of patients with unilateral medial temporal lobe epilepsy (mTLE) and healthy controls to assess how damage to the MTL affects retrieval in these conditions. We observed an overall decrease in detail count in the mTLE group, along with a disproportionate deficit in perceptual details that was most acute in the AM and the perceptually enriched film clip conditions. Our results suggest that the impaired sense of reliving the past that accompanies MTL insult is mediated by a paucity of perceptual episodic memory details. We also introduce a new protocol that successfully mimics naturalistic memories while benefiting from the experimental control provided by using laboratory stimuli. © 2014 Wiley Periodicals, Inc.