Senior house officer training. Improved training may have more to do with money than with new shifts.
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Humans↗
Biomedical subjects
N Kapur
Publications and source records attributed to N Kapur.
Very long-term amnesia in association with temporal lobe epilepsy: evidence for multiple-stage consolidation processes.
The temporal fractionation of long-term retention remains a relatively uncharted area in human memory research, and in particular there is little in the way of neuropsychological data that address this issue. We describe a patient with temporal lobe epilepsy who complained of amnesia for important events that had occurred in the previous 3-24 months, but who reported that her short-term and medium-term memory were normal. She displayed normal performance on traditional tests of short-term and long-term retention, performing at a very similar level to that of age- and sex-matched healthy control subjects on immediate and half-hour delayed recall measures. Forty days later, however, she showed a dense amnesia for recall of such information, whereas control subjects could readily recall much of the original stimuli. She also showed evidence of memory loss for news events that had occurred over the previous few years. MRI scanning and EEG brain mapping indicated left temporal lobe pathology, with a possible epileptogenic focus in the left anterior hippocampus. These data provide empirical evidence for the existence of a distinct very long-term consolidation process in human episodic memory and point to its neural correlates in the temporal lobe. Transfer of information into a permanent long-term memory store may entail multiple-stage consolidation processes rather than a single-stage, unitary consolidation process.
Amnesia↗
A study of recovery of memory function in a case of witnessed functional retrograde amnesia.
We describe a case of transient functional retrograde amnesia that had features of a fugue state, and that was accompanied by loss of personal identity and significant autobiographical amnesia. Uniquely, we were able to gather information from witnesses who observed the episode from its onset, and we were also able to monitor the acute stages of recovery of memory function over the subsequent four-week period. The profile of memory loss was characterised by impaired performance on both autobiographical and public events memory tasks, in the context of normal anterograde memory test scores. Shrinkage of retrograde amnesia took place over a four-week period, with autobiographical and public events components of retrograde memory recovering at the same rate. We discuss the possible role of unconscious processes underlying the episode, as compared to conscious simulation. We argue that most cases of functional retrograde amnesia may represent a combination of conscious simulation and unconscious processes.
Journal Article↗
Long-term perceptual priming in transient global amnesia.
This paper addresses the question as to whether long-term perceptual priming can occur during transient global amnesia. A patient who displayed the classical features of transient global amnesia was assessed during the episode and again 7 days later. During the episode, she was administered a task that required the perceptual identification of fragmented pictures over a number of learning trials. Seven days later, after recovery from the episode, she was required to identify the same fragmented pictures together with a new set of pictures that she had never seen before. She was significantly better at identifying the old pictures than the new pictures, in spite of having amnesia for the period of the attack. Matched control subjects who had never seen either set of pictures before, were also tested and performed at a similar level on the old and the new pictures. Our findings extend the clinical domain of implicit memory phenomena and parallel similar observations in chronic amnesia (Cave & Squire, 1992). We provide the first demonstration of a residual capacity for long-term perceptual priming during an acute episode of apparent total loss of memory.
Amnesia↗
Neural activation during covert processing of positive emotional facial expressions.
Lesion studies indicate distinct neural systems for recognition of facial identity and emotion. Split-brain experiments also suggest that emotional evaluation of a stimulus can occur without conscious identification. The present study tested a hypothesis of a differential neural response, independent of explicit conscious mediation, to emotional compared to nonemotional faces. The experimental paradigm involved holding in mind an image of a face across a 45-s delay while regional cerebral blood flow was measured using positron emission tomography. Prior to the delay, a single face was presented with an explicit instruction to match it to one of two faces, photographed at different angles from the target face, presented at the end of the delay. Repeated blood flow measures were obtained while subjects held happy or neutral faces in mind or during a neutral control fixation condition without initial face presentation. The representation of emotional faces over a delay period, compared to either the nonemotional or the fixation condition, was associated with significant activation in the left ventral prefrontal cortex, the left anterior cingulate cortex, and the right fusiform gyrus. The findings support our hypothesis of a differential neural response to facial emotion, independent of conscious mediation, in regions implicated in the processing of faces and of emotions.
Adult↗
Anterograde but not retrograde memory loss following combined mammillary body and medial thalamic lesions.
We report the first human case of combined mammillary body and medial thalamic lesions due to focal pathology. A patient presented with a multi-lobular lesion that affected the mammillary bodies, the medial thalamus and the brain stem. On neuropsychological testing, he showed significant anterograde memory impairment, with marked impairment on delayed story recall, but normal or only mildly impaired performance on retrograde memory tasks. Our findings corroborate the results of recent non-human lesion studies and indicate that some of the well-established features of the amnesic syndrome, such as severe retrograde amnesia, may not be due to primary diencephalic pathology. Significant retrograde amnesia may result from cortical pathology or from an interaction between cortical and subcortical pathology.
Adult↗
The 'petites Madeleines' phenomenon in two amnesic patients. Sudden recovery of forgotten memories.
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Adult↗
Paradoxical functional facilitation in brain-behaviour research. A critical review.
The aim in this review article is to document research findings that have shown paradoxical effects of nervous system changes, whereby direct or indirect neural damage may result in facilitation of behavioural functions. Such findings have often been ignored or undervalued in the brain-behaviour research literature. A further aim is to consider possible mechanisms and theoretical insights related to this facilitation. Analyses of relevant studies show that two major types of paradoxical functional facilitation (PFF) effects may be distinguished. (i) Situations where damage to intact brain tissue brings to normal or near normal a previously subnormal or abnormal level of functioning. I refer to improved levels of functioning in such contexts as restorative PFF effects. One of the best documented examples of such PFF effects is the 'Sprague effect', whereby collicular lesions may bring about an improvement in visual functioning following an initial occipital lesion. (ii) Situations where a subject with nervous system pathology or sensory loss performs better than normal control subjects on a particular task. I refer to improved levels of performance in these contexts as enhancing PFF effects. Restorative and enhancing PFF effects have been found in a range of domains, including memory, sensory and perceptual functions, and language functioning. A potential contribution of PFF effects is that they highlight two important neural mechanisms, i.e. inhibition and compensatory plasticity. Two broad classes of theoretical insights related to PFF effects are therefore discussed: (i) inhibitory mechanisms, which form part of an interactive view of brain function where competitive opponent-processing is a significant feature; (ii) 'compensatory augmentation', which occurs as a specific manifestation of CNS plasticity. Both of these mechanisms are considered in relation to paradoxical increases in CBF and anatomical annexation effects that are seen in neurological patients and in subjects with sensory loss. Paradoxical functional facilitation paradigms represent a powerful methodological tool for confirming or refuting hypotheses in brain-behaviour research. The counter-intuitive nature of PFF findings provides a particularly persuasive set of evidence in support of neural, conceptual or computational models of brain function that specifically predict paradoxical facilitation of cognitive functioning.
Behavior↗
Activation of human hippocampal formation during memory for faces: a PET study.
Using positron emission tomography, we examined cerebral blood flow changes in human subjects whilst engaged in the visual processing of face stimuli. A task requiring anterograde memory of faces was compared with a control task involving simple gender classification--considered an automatic process that did not require any significant memory component. A second task requiring recognition of famous politicians' faces, and therefore involving long-term "semantic" memory, was also contrasted with the control task. To identify brain regions associated with primary visual processing of the face we compared all tasks against a control population scanned with eyes closed. Our results indicate--(1) The involvement of bilateral lingual/fusiform gyri and the right parahippocampal gyrus in addition to striate cortex in primary visual processing of the face; (2) the involvement of the left hippocampal gyrus in both types of memory; (3) a relative decrease in local cerebral blood flow in the inferior parietal lobules in long-term "semantic" memory. In addition, both memory tasks resulted in a suppression of cerebral blood flow in the left superior temporal cortex. We conclude that right hippocampal regions are involved in a largely automatic, primary processing of faces, while left hippocampal regions are additionally involved when explicit memory for faces is required.
Adult↗
Dense amnesia in a professional musician following herpes simplex virus encephalitis.
We describe the memory functioning of C, a professional musician who became amnesic following herpes simplex encephalitis in 1985. Although transient amnesia in a professional musician has previously been described, this is the first reported case of chronic amnesia in a highly talented professional musician. C is unusual in three respects. First, his amnesia is particularly severe. Second, his amnesia includes semantic as well as episodic memory deficits. Third, he believes he has just woken up and his preoccupation with this state of 'just wakening' has persisted for over 9 years. This appears to be the result of a delusion rather than the consequence of his amnesia.
Amnesia↗
Bilateral temporal lobe pathology with sparing of medial temporal lobe structures: lesion profile and pattern of memory disorder.
The lesion sustained by the amnesic patient H.M. consisted of bilateral ablation of medial temporal lobe structures with relative sparing of more lateral white matter and neocortical structures. We present the first detailed report of a case where the reverse pattern of lesions predominated, namely bilateral pathology of white matter and neocortical temporal lobe structures, with spared medial temporal lobe structures. This damage, which was particularly severe in anterior loci in the temporal lobes, was sustained as a result of radionecrosis. High-resolution magnetic resonance imaging was carried out to document the distinctive anatomical profile of our patient, and this profile was compared to that reported for the patient H.M. At the anatomical level, there was an almost "mirror image" profile, with contrasting involvement of lateral and medial temporal lobe structures. At the neuropsychological level, our patient was not amnesic but showed patchy impairment on traditional tests of anterograde memory functioning, in the context of notable "semantic" memory loss for knowledge acquired before and after the onset of his illness. Our findings demonstrate that bilateral temporal lobe pathology by itself does not lead to a classical amnesic syndrome, but may result in a significant but more subtle "semantic" memory loss. Our data highlight the distinctive and dissociable contribution of lateral and medial temporal lobe structures to human memory processing, and suggest a major role for anterior-inferior neocortical temporal lobe mechanisms in aspects of knowledge acquisition, storage and retrieval.
Amnesia↗
Herpes simplex encephalitis: long term magnetic resonance imaging and neuropsychological profile.
The first comprehensive in vivo documentation of the long term profile of pathological and spared tissue is described in a group of 10 patients with a diagnosis of herpes simplex encephalitis, who were left with memory difficulties as a major residual sequel of their condition. With a dedicated MRI protocol, which included high resolution images of temporal lobe and limbic system areas, data are provided on structures that have recently gained importance as anatomical substrates for amnesia. The major features of the lesion profile were: (1) unilateral or bilateral hippocampal damage never occurred in isolation, and was often accompanied by damage to the parahippocampus, the amygdala, specific temporal lobe gyri, and the temporal poles; (2) the insula was always abnormal; (3) neocortical temporal lobe damage was usually unilateral or asymmetric. It never occurred in isolation, and was invariably associated with more medial pathological changes; (4) anterior and inferior temporal lobe gyri were damaged more often and more severely than posterior and superior temporal lobe gyri; (5) pronounced abnormality was often present in the substantia innominata (region of the basal forebrain/anterior perforated substance); (6) there was evidence of significant abnormality in the fornix; (7) there was evidence of damage to the mammillary bodies; (8) thalamic nuclei were affected in around 50% of cases, with damage usually unilateral; (9) frontal lobe damage was present in a few patients, and affected medial areas more than dorsolateral areas; (10) there was some involvement of the striatum, although this was usually unilateral and mild; (11) there was usually limited involvement of the cingulate gyrus and of the parietal and occipital lobes; (12) the cerebellum and brain stem were never damaged. Lesion covariance analysis indicated a close relation between the presence of abnormalities in temporal lobe and limbic-diencephalic regions. Unlike severe head injury, lesions in the temporal pole were not associated with the presence of lesions in the orbitofrontal cortex. Long term neuropsychological impairments were characterised by a dense amnesia in 60% of cases, and a less serve but noticeable anterograde memory impairment in the others. Naming and problem solving deficits were found in a small number of cases. Only two patients were able to return to open employment. Severity of amnesia showed a significant relation with severity of damage to medical limbic system structures such as the hippocampus, with bilateral damage being particularly important. By contrast, there was a minimal relation between memory loss and severity of damage to the thalamus, to lateral temporal lobe areas, or to the frontal lobes.
Adult↗
The coin-in-the-hand test: a new "bed-side" test for the detection of malingering in patients with suspected memory disorder.
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Adult↗
Transient memory loss for people.
A patient had transient memory loss for close family members. She could not even recognise their names as familiar. Her everyday memory was relatively preserved and she retained a clear recollection of the episode. Standard and sleep deprived EEG showed a mild abnormality of the left temporal lobe. Neuropsychological testing found evidence for a mild verbal memory impairment. The findings provide further evidence for the fractionation of transient forms of amnesia, support the dissociation of semantic/retrograde amnesia from episodic/anterograde amnesia, and offer evidence in favour of a left temporal lobe site for retrieval of past memories relating to the identification of people.
Adult↗
Focal retrograde amnesia in neurological disease: a critical review.
The condition of focal retrograde amnesia represents a new and challenging concept to our understanding of human memory disorders. Cases of both permanent and transient focal retrograde amnesia, dating from early clinical descriptions to more recent experimental reports, are critically reviewed. It is concluded that the condition of focal retrograde amnesia does represent a distinct and reliable neurological entity. Four sets of issues are discussed--methodological issues, conceptual issues, anatomical issues and therapeutic issues. Current evidence indicates an important role for temporal lobe structures in mediating focal retrograde amnesia. Both storage and retrieval deficits may contribute to the presence of focal retrograde amnesia, though available evidence points to a greater role for engram destruction/fragmentation rather than disruption of access mechanisms. In general, pharmacological and other therapies have had minimal effects in alleviating focal retrograde amnesia.
Amnesia↗
Transient epileptic amnesia--a clinical update and a reformulation.
While absence attacks and complex partial seizures have been well documented in patients with epilepsy, the delineation of pure episodes of memory loss without additional clinical manifestations remains poorly characterised. The recently described condition of transient epileptic amnesia (TEA) is critically examined, and four new cases are described, in each of which there were episodes of pure memory loss which subsequently proved to be epileptic in origin. The anatomical and pathophysiological basis of TEA is presumed to be similar to transient global amnesia (TGA), that is, it is likely to be primarily hippocampal in origin, but with more variable involvement of limbic and adjacent temporal lobe neocortical structures.
Adult↗
Focal retrograde amnesia following bilateral temporal lobe pathology. A neuropsychological and magnetic resonance study.
A patient who suffered a severe closed head injury was left with a dense retrograde amnesia for events which she had experienced prior to her injury, but she showed only mild, patchy anterograde memory impairment. Her retrograde amnesia included both public events and autobiographical material, and it extended back to her childhood. Previously learned skills such as playing a piano and driving a car were spared, even though she had no recollection at all of the original learning experience. A series of focused magnetic resonance scan images revealed major pathology in the anterior portion of both temporal lobes. No significant abnormality was found in the hippocampus, thalamus or other medial structures in the limbic-diencephalic system. Our findings indicate the independence of anterograde and retrograde memory mechanisms, and point to structures and pathways in the anterior temporal lobes as playing a critical role in memory for past events.
Adult↗