Episodic autobiographical memory(AM) allows one, through the recollection of sensory-perceptual details, thoughts and feelings, to become aware of an event as belonging to one's own past as well as being able to p...Episodic autobiographical memory(AM) allows one, through the recollection of sensory-perceptual details, thoughts and feelings, to become aware of an event as belonging to one's own past as well as being able to project into one's future. Because AM provides a sense of self-continuity, contributes to the integrity of the self, and helps predicting future experiences, any deficit of AM may have debilitating consequences for everyday life functioning. Understanding AM failure and the underlying neural mechanisms has the potential to shed light on brain reorganization mechanisms and engagement of compensatory processes. Functional magnetic resonance imaging(fMRI) provides the most promising imaging method to tackle these issues. We reviewed evidence from the few studies that used fMRI to investigate the functionality of the residual tissue, the neural reorganization and compensatory mechanisms in patients with neurological conditions due to impaired medial temporal lobe. Overall, these studies highlight the importance of the left hippocampus, which when atrophied and not functional leads to AM deficits but its residual functionality may support relatively normal AM recollection. When damaged hippocampal tissue is not functional, other brain regions(e.g., the medial prefrontal cortex) may be involved to compensate impairment, but they appear generally ineffective to support detailed episodic recollection.展开更多
The medial temporal lobe (MTL) has been assigned a central role in human episodic memory and learning. Evidence for this comes from PET and fMRI studies as well as lesion studies. This study aimed at comparing the eff...The medial temporal lobe (MTL) has been assigned a central role in human episodic memory and learning. Evidence for this comes from PET and fMRI studies as well as lesion studies. This study aimed at comparing the effect of atrophy at repeated trials of a supraspan test of memory. Included in the study were patients with Alzheimer’s Disease, Mild Cognitive Impairment, and Subjective Memory Disorders as well as Controls (n = 116). The supraspan test used was the Rey Auditory Verbal Learning test (RAVLT). Comparisons between extreme groups with high (Stanine 6 - 9) and low (Stanine 1 - 4) intracranial proportions (IP) of MTL were made at the five trials of RAVLT. There was a significantly higher rate of learning among subjects with high MTL IP compared to those with low MTL IP in both hemispheres. There was no difference in the rate of list learning performance due to education or age and interestingly: the list learning rates among subjects with high/low Lateral Temporal Lobe IPs were almost similar. The hemispheric differences regarding learning rate were small and insignificant. Results are discussed in terms of hippocampal involvement in associative processes necessary in supraspan list learning.展开更多
This case study addresses episodic memory impairment or focal retrograde amnesia related to limbic encephalitis. The patient in question was a right-handed man in his 60s who developed focal retrograde amnesia due to ...This case study addresses episodic memory impairment or focal retrograde amnesia related to limbic encephalitis. The patient in question was a right-handed man in his 60s who developed focal retrograde amnesia due to limbic encephalitis. An abnormal MRI signal was observed in the right medial temporal lobe. Immediately after the encephalitis onset, mental symptoms—including impaired consciousness, disorientation, hallucinations, and delusions—appeared;however, his condition improved with medical treatment. After transfer to a convalescent and rehabilitation hospital, various neuropsychological tests were conducted but no apparent functional decline was observed in intellectual function, attention, memorization, or retention. However, the patient exhibited impairments related to autobiographical memory and memory of events 4?-?5 years before the onset of limbic encephalitis. Based on these observations, the patient was considered to exhibit focal retrograde amnesia due to limbic encephalitis. Despite exhibiting retrograde amnesia, he had no difficulty in his daily life in the ward. Moreover, after discharge from hospital, smooth work reinstatement was possible. This case demonstrates that, even after exhibiting retrograde amnesia, if its duration is relatively short and physical function and other higher-order brain functions are sustained, social rehabilitation—including work reinstatement—is feasible.展开更多
文摘Episodic autobiographical memory(AM) allows one, through the recollection of sensory-perceptual details, thoughts and feelings, to become aware of an event as belonging to one's own past as well as being able to project into one's future. Because AM provides a sense of self-continuity, contributes to the integrity of the self, and helps predicting future experiences, any deficit of AM may have debilitating consequences for everyday life functioning. Understanding AM failure and the underlying neural mechanisms has the potential to shed light on brain reorganization mechanisms and engagement of compensatory processes. Functional magnetic resonance imaging(fMRI) provides the most promising imaging method to tackle these issues. We reviewed evidence from the few studies that used fMRI to investigate the functionality of the residual tissue, the neural reorganization and compensatory mechanisms in patients with neurological conditions due to impaired medial temporal lobe. Overall, these studies highlight the importance of the left hippocampus, which when atrophied and not functional leads to AM deficits but its residual functionality may support relatively normal AM recollection. When damaged hippocampal tissue is not functional, other brain regions(e.g., the medial prefrontal cortex) may be involved to compensate impairment, but they appear generally ineffective to support detailed episodic recollection.
文摘The medial temporal lobe (MTL) has been assigned a central role in human episodic memory and learning. Evidence for this comes from PET and fMRI studies as well as lesion studies. This study aimed at comparing the effect of atrophy at repeated trials of a supraspan test of memory. Included in the study were patients with Alzheimer’s Disease, Mild Cognitive Impairment, and Subjective Memory Disorders as well as Controls (n = 116). The supraspan test used was the Rey Auditory Verbal Learning test (RAVLT). Comparisons between extreme groups with high (Stanine 6 - 9) and low (Stanine 1 - 4) intracranial proportions (IP) of MTL were made at the five trials of RAVLT. There was a significantly higher rate of learning among subjects with high MTL IP compared to those with low MTL IP in both hemispheres. There was no difference in the rate of list learning performance due to education or age and interestingly: the list learning rates among subjects with high/low Lateral Temporal Lobe IPs were almost similar. The hemispheric differences regarding learning rate were small and insignificant. Results are discussed in terms of hippocampal involvement in associative processes necessary in supraspan list learning.
文摘This case study addresses episodic memory impairment or focal retrograde amnesia related to limbic encephalitis. The patient in question was a right-handed man in his 60s who developed focal retrograde amnesia due to limbic encephalitis. An abnormal MRI signal was observed in the right medial temporal lobe. Immediately after the encephalitis onset, mental symptoms—including impaired consciousness, disorientation, hallucinations, and delusions—appeared;however, his condition improved with medical treatment. After transfer to a convalescent and rehabilitation hospital, various neuropsychological tests were conducted but no apparent functional decline was observed in intellectual function, attention, memorization, or retention. However, the patient exhibited impairments related to autobiographical memory and memory of events 4?-?5 years before the onset of limbic encephalitis. Based on these observations, the patient was considered to exhibit focal retrograde amnesia due to limbic encephalitis. Despite exhibiting retrograde amnesia, he had no difficulty in his daily life in the ward. Moreover, after discharge from hospital, smooth work reinstatement was possible. This case demonstrates that, even after exhibiting retrograde amnesia, if its duration is relatively short and physical function and other higher-order brain functions are sustained, social rehabilitation—including work reinstatement—is feasible.
