Remote Memory Loss Research Articles

Chronic exposure of alcohol triggers microglia-mediated synaptic elimination inducing cognitive impairment

Background and aimsLong-term alcohol intake leads to cognitive impairment and dementia. The impairment of the cerebral cortex and limbic structures in alcoholics is associated with the loss of synapses instead of neurons. Synapse loss is considered to be an early and key feature of many neurodegenerative diseases, in which microglia-mediated synapse elimination is vital. However, the underlying mechanisms of synapse loss and cognitive impairment caused by long-term alcohol intake are still largely unknown. MethodsWe investigated the relationship of synapse impairment, the microglial innate immune receptor—TREM2, and microglia-mediated synaptic elimination in long-term alcohol exposure. ResultsWe found that long-term alcohol exposure increased expression of TREM2, decreased expression of synaptic proteins and glutamate receptor subunits, reduced dendrite spine density, and impaired long-term potentiation (LTP) in the hippocampus. Minocycline reduced the amount of the postsynaptic marker PSD95 in microglia, attenuated dendrite spine density loss, and slow down the forgetting process of already-formed memory. Furthermore, we found that TREM2 participated in microglia-mediated synapse elimination in chronic alcohol exposure in vivo. Significantly fewer PSD95 were detectable in microglial phagolysosomes in TREM2 knockdown mice. Besides, TREM2 gene silencing ameliorated synapse loss, LTP impairment, and forgetting of remote memories. ConclusionsOur data suggests that TREM2 is associated with synaptic plasticity impairment and memory deficits, indicating microglia-mediated synaptic pruning might be the underlying mechanism involved in synapse loss and memory impairment induced by long-term alcohol intake. These findings provide new evidence for the receptor's participation in neurodegeneration diseases.

Personal semantic and episodic autobiographical memories in Korsakoff syndrome: A comparison of interview methods

ABSTRACTObjective: The temporal gradient in patients with Korsakoff’s syndrome has been of particular interest in the literature, as many studies have found evidence for a steep temporal gradient, but others have observed more uniform remote memory impairment across all past time periods. Inconsistencies might be the result of the nature of remote memory impairment under study (i.e., nonpersonal or autobiographical memory) and of methodological differences in the examination of remote memory loss. The aim of this study was to examine whether differences between autobiographical memory interview (AMI) and autobiographical interview (AI) procedures influence the presence of a temporal gradient in semantic and episodic autobiographical memory in Korsakoff patients. Method: The procedure used in the present study combined the AMI and AI into one study session. We compared the performance of 20 patients with Korsakoff’s syndrome and 27 healthy controls. First, participants were asked to recall knowledge from different life periods. Second, participants were asked to recall memories from five life periods. Thirdly, participants were asked to rate their subjective experience of each event recalled on a 5-point scale. Finally, we analyzed the findings in terms of all the memories recalled versus the first memory from each life-period only. Results: Both the AMI and the AI showed a temporally graded retrograde amnesia in the Korsakoff patients for personal semantic and episodic autobiographical memories. The pattern of amnesia in Korsakoff patients was not affected by examining only one event per life-period. Subjective ratings of recalled memories were largely comparable between the groups. Conclusions: The findings were generally consistent across the AMI and AI. Varying the number of events did not affect the pattern of the gradient. Hence, the temporal gradient in Korsakoff patients is not an artefact of either the AMI or the AI method.

015 Remote memory deficits in transient epileptic amnesia

AimsTransient epileptic amnesia (TEA) is a recently recognised form of temporal lobe epilepsy in which sufferers often complain of irretrievable loss of remote memories. We aimed to answer the following...

Remote memory deficits in transient epileptic amnesia

Transient epileptic amnesia is a form of temporal lobe epilepsy in which sufferers often complain of irretrievable loss of remote memories. We used a broad range of memory tests to clarify the extent and nature of the remote memory deficits in patients with transient epileptic amnesia. Performance on standard tests of anterograde memory was normal. In contrast, there was a severe impairment of memory for autobiographical events extending across the entire lifespan, providing evidence for the occurrence of 'focal retrograde amnesia' in transient epileptic amnesia. There was a milder impairment of personal semantic memory, most pronounced for midlife years. There were limited deficits of public semantic memory for recent decades. These results may reflect subtle structural pathology in the medial temporal lobes or the effects of the propagation of epileptiform activity through the network of brain regions responsible for long-term memory, or a combination of these two mechanisms.

Transient epileptic amnesia: regional brain atrophy and its relationship to memory deficits

Transient epileptic amnesia (TEA) is a recently recognised form of epilepsy of which the principle manifestation is recurrent, transient episodes of isolated memory loss. In addition to the amnesic episodes, many patients describe significant interictal memory difficulties. Performance on standard neuropsychological tests is often normal. However, two unusual forms of memory deficit have recently been demonstrated in TEA: (i) accelerated long-term forgetting (ALF): the excessively rapid loss of newly acquired memories over a period of days or weeks and (ii) remote autobiographical memory loss: a loss of memories for salient, personally experienced events of the past few decades. The neuroanatomical bases of TEA and its associated memory deficits are unknown. In this study, we first assessed the relationship between subjective and objective memory performance in 41 patients with TEA. We then analysed MRI data from these patients and 20 matched healthy controls, using manual volumetry and voxel-based morphometry (VBM) to correlate regional brain volumes with clinical and neuropsychological data. Subjective memory estimates were unrelated to performance on standard neuropsychological tests but were partially predicted by mood, ALF and remote autobiographical memory. Manual volumetry identified subtle hippocampal volume loss in the patient group. Both manual volumetry and VBM revealed correlations between medial temporal lobe atrophy and standard anterograde memory scores, but no relation between atrophy and ALF or remote autobiographical memory. These results add weight to the hypothesis that TEA is a syndrome of mesial temporal lobe epilepsy. Furthermore, they suggest that although standard anterograde memory test performance is related to the degree of mesial temporal lobe damage, this is not true for ALF and autobiographical amnesia. It is possible that these unusual memory deficits have a more diffuse physiological basis rather than being a consequence of discrete structural damage.

Retrograde amnesia in patients with rupture and surgical repair of anterior communicating artery aneurysms.

The retrograde amnesia of patients with memory loss related to rupture and surgical repair of anterior communicating artery (ACoA) aneurysms is compared with the retrograde amnesia of temporal amnesic patients and nonamnesic control participants. Two tests which focus on popular culture but which differ according to extent of news exposure and the cognitive processes necessary for task performance were used to measure retrograde memory. ACoA patients demonstrated more significant retrograde memory problems than did nonamnesic controls; however, the severity and pattern of their memory loss was less severe than that seen in association with temporal amnesia. Different factors influenced the remote memory loss of respective groups: ACoA patients' problems were related to impaired lexical retrieval whereas temporal amnesic patients had problems secondary to both retrieval and storage deficits.

Unexpected amnesia: are there lessons to be learned from cases of amnesia following unilateral temporal lobe surgery?

Cases of amnesia following unilateral temporal lobe surgery are rare, but they may provide important insights into human brain functioning. Such cases are reconsidered here in the light of recent developments in clinical and cognitive neuroscience. Descriptions of preoperative seizure activity in these cases indicate the potentially valuable role of ictal semiology in localizing the source of epileptiform discharges. Cases of amnesia after unilateral temporal lobectomy illustrate the complexity of intra- and inter-hemispheric propagation of epileptiform discharges and highlight possible neurophysiological mechanisms underlying false localization of abnormal EEG activity. This review points to the value of preoperative neuropsychological assessment in providing information on the likely primary locus of pathology and in predicting outcome after surgery. The analysis of cases upholds the benefits of the Wada procedure, but it highlights the variability in Wada test procedures and the fact that Wada test scores themselves may be open to varying interpretation. These cases of postoperative amnesia are further considered in the context of the cognitive neuroscience of human memory and, in particular, mechanisms underlying the human amnesic syndrome. They confirm the critical role of bilateral medial temporal lobe structures in anterograde memory, but they also highlight the complexity in teasing apart neural mechanisms underlying remote memory loss.

Profound Retrograde Amnesia Following Mild Head Injury: Organic or Functional?

This paper describes a 56 year old female patient (JJ) who suffered a minor head injury at work and presented with profound retrograde amnesia for both public events and autobiographical material spanning her entire life. In addition, she complained of word-finding difficulties and anterograde memory impairment and neuropsychological assessment found evidence of mild executive dysfunction. Neurological investigations (CT and EEG) were essentially normal although changes indicative of small vessel disease were noted on MRI brain scan. Various forms and aetiologies of remote memory loss were considered including, simulated, psychogenic and organic amnesia, but differential diagnosis proved difficult. It is proposed that criteria used in clinical practice to differentiate functional and organic complaints are limited and this may be because (1) both factors can be involved in the aetiology of amnesia, and (2) a similar underlying brain mechanism, such as a retrieval deficit could underlie many instances of organic and psychogenic amnesia. Future research, complemented by functional brain imaging, is needed to explore the nature of retrieval deficits.

IMPAIRED KNOWLEDGE OF FAMOUS PEOPLE AND EVENTS WITH INTACT AUTOBIOGRAPHICAL MEMORY IN A CASE OF PROGRESSIVE RIGHT TEMPORAL LOBE DEGENERATION: IMPLICATIONS FOR THE ORGANISATION OF REMOTE MEMORY

VH, a 71-year-old woman with a progressive deterioration of the right temporal lobe, was shown to be gravely impaired on tests of publicly acquired semantic information, including both visual and verbal knowledge of famous people and events. In contrast, autobiographical knowledge of personally relevant people and personal event memory appeared to be completely normal. Interestingly, some information was elicited regarding public events that impinged upon the patient's own life. This represents the first quantitative study of remote memory in a patient with right temporal lobe degeneration, and a pattern of remote memory loss that has not been previously reported. We argue that VH's preserved autobiographical memory performance does not imply the presence of specialised subsystems dedicated to autobiographical versus nonautobiographical material. Instead, we propose a “supporting activation” account of retrieval from remote memory. Autobiographical memory consists of distributed representations involving multiple types of information. During a retrieval attempt, supporting activation from intact regions may assist VH's retrieval of autobiographically relevant material from her damaged right temporal lobe.

Minding Your “ps and qs” When Using Forced-Choice Recognition Tests

Denney (1996), and Frederick, Carter, and Powel (1995) described a forced-choice recognition test (FCRT) to evaluate suspicious complaints of remote memory loss. Although the two-alternative forced-choice trials in symptom validity testing have equal prior probabilities of correct answers (p) and incorrect answers (q), ps and qs might vary from 0.5 on individual trials of FCRTs. FCRTs nonetheless remain conservative procedures for evaluating suspicious memory loss, as long as the overall p approximates 0.5. In computer simulations, distributions in which p q 0.5 resulted in more conservative decision making than distributions in which p = q = 0.5. The authors demonstrate the ease in constructing FCRTs with overall p = 0.5 and discuss the proper application of FCRT findings in a clinical evaluation.

Severe remote memory loss with minimal anterograde amnesia: a clinical note

Severe remote memory loss with minimal anterograde amnesia: a clinical note

Symptom validity testing of remote memory in a criminal forensic setting

Symptom Validity Testing (SVT) has been used effectively with sensory perception and short-term memory. The procedure was recently adapted to assess remote memory for specific events. Memory for remote events is particularly important to the criminal justice system, and courts are beginning to draw on neuropsychology to assist in the assessment of claimed remote memory loss. This report discusses the importance of this objective technique to neuropsychologists involved with criminal courts and presents its use in three cases from the criminal forensic arena. Normative results for the three case study tests are presented and suggest the procedure is a robust version of SVT. Implications of these results are discussed.

Symptom validity testing of remote memory in a criminal forensic setting

Symptom Validity Testing (SVT) has been used effectively with sensory perception and short-term memory. The procedure was recently adapted to assess remote memory for specific events. Memory for remote events is particularly important to the criminal justice system, and courts are beginning to draw on neuropsychology to assist in the assessment of claimed remote memory loss. This report discusses the importance of this objective technique to neuropsychologists involved with criminal courts and presents its use in three cases from the criminal forensic arena. Normative results for the three case study tests are presented and suggest the procedure is a robust version of SVT. Implications of these results are discussed.

Anterograde and retrograde amnesia following bitemporal infarction.

A patient suffered very severe anterograde and retrograde amnesia following infarction of both medial temporal lobes (hippocampus and adjacent cortex) and the left inferior temporo-occipital area. The temporal stem and the amygdala were intact; these structures do not appear to be critical for new learning in humans. Extension of the left-sided infarct into the inferior temporo-occipital lobe, an area critically involved in visual processing, appears to be responsible for our patient's loss of remote memories.

Anterograde and Retrograde Amnesia following Bitemporal Infarction

A patient suffered very severe anterograde and retrograde amnesia following infarction of both medial temporal lobes (hippocampus and adjacent cortex) and the left inferior temporo-occipital area. The temporal stem and the amygdala were intact; these structures do not appear to be critical for new learning in humans. Extension of the left-sided infarct into the inferior temporo-occipital lobe, an area critically involved in visual processing, appears to be responsible for our patient's loss of remote memories.

Neuropsychological and SPECT scan findings during and after transient global amnesia: evidence for the differential impairment of remote episodic memory.

A patient had neuropsychological testing during, and at two days and seven weeks after a transient global amnesia (TGA) attack. During the attack she exhibited a characteristically profound anterograde amnesia but a limited remote memory loss; the most striking impairment was a deficit in personal episodic memory revealed by her performance on the Autobiographical Memory Interview. Personal and general semantic information was less impaired although there were indications of a temporal gradient in the impairment. When tested after the attack, she demonstrated normal anterograde and retrograde memory. A SPECT scan performed during TGA showed a focal reduction in cerebral perfusion in the postero-medial temporal lobes bilaterally which had resolved after seven weeks.

Characteristics of the memory loss of a patient with Wernicke-Korsakoff's syndrome without alcoholism

The memory loss in alcoholic Wernicke-Korsakoff syndrome has been well characterized. However, it has been suggested that some of the neuropsychological defects seen in these patients are due to frontal lobe dysfunction resulting from chronic alcohol abuse. The present report details the nature and extent of the amnesia in a Wernicke-Korsakoff patient who did not have a history of alcoholism. In spite of her normal performance on measures of frontal lobe function, this patient showed many characteristics similar to those seen in alcoholic Wernicke-Korsakoff syndrome including a graded loss of remote memories and abnormal semantic information processing. Thus, the extent of the “core” features of this amnesic syndrome may be greater than was previously thought.

The neuropsychology of paramedian thalamic infarction

A longitudinal study of three patients with CT-scan documented paramedian thalamic infarctions (bilateral, primarily right, unilateral left) is reported and the neuropsychology of human paramedian thalamic infarction is reviewed. The neuropsychological deficits following these selected lesions, the nature of the clinical memory disorder, and the neuroanatomy of memory are discussed. The significance of cortical/subcortical relationship in explaining observed behavioral changes is emphasized. Brain damage with maximum involvement in the dorsomedial nuclei and mamillothalamic tracts appears to cause primarily a memory disorder and frontal-limbic behavioral changes, the severity and profile of deficits depending on lesion extent and location. Both anterograde and remote memory loss may be present. Asymmetry in memory at the level of the thalamus was observed, following the left-verbal, right-nonverbal dichotomy.

Severe remote memory loss with minimal anterograde amnesia: A clinical note

We describe a patient who presented with apparent human Klüver-Bucy syndrome. After pharmacological treatment, his problems gradually resolved, with the exception of some unconcern about this present situation, a mild naming and word list generation deficit, a severe remote memory loss and, in comparison, a minimal anterograde memory disturbance. He has been able to relearn certain details of his personal past. These relearned memories are independent of a sense of personal intimacy. The “relearned memory” was frequently associated with a memory of how and when the information had been reacquired. The results suggest that anterograde and retrograde memory functions may, in at least certain patients, be dissociable. The apparently absolute loss of personal memories indicates that either a retrieval deficit or storage depletion are plausible hypotheses of the remote memory loss in this patient.

Remote memory in a patient with circumscribed amnesia

It has been suggested that extensive and severe remote memory loss is not a component of a circumscribed amnesic syndrome but may be attributable to problem solving and retrieval deficiencies associated with the frontal lobe damage which is present in some amnesic patients. In order to assess this notion, retrograde amnesia was studied in a patient, W.H., who had no apparent cortical damage revealed by radiological examination, and who evidenced no major cognitive deficiency other than amnesia. Regardless of whether remote memory was measured by recall or recognition procedures, patient W.H. exhibited impaired memory for information from the 1960s, 1970s, and 1980s, but was unimpaired in retrieving information from the 1940s and 1950s. These results demonstrate that retrograde amnesia can occur in patients who have a circumscribed memory deficit.