Cases reported "Amnesia"

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1/14. Recovery from anterograde and retrograde amnesia after percutaneous drainage of a cystic craniopharyngioma.

    A case is reported of a cystic craniopharyngioma involving the floor and walls of the third ventricle. Pronounced anterograde and retrograde amnesia were documented preoperatively by formal testing. Rapid improvement in both new learning capacity and remote memory occurred after percutaneous twist drill drainage of the cystic portion of the tumour. The relevance of these observations to the amnesic syndrome and its neuropathological basis is discussed.
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2/14. Medial temporal lobe amnesia: Gradual acquisition of factual information by nondeclarative memory.

    Most amnesic patients with damage to the medial temporal lobe retain some capacity to learn new information about facts and events. In many cases, the learning appears to depend on a residual ability to acquire conscious (declarative) knowledge. We have studied the capacity for semantic (fact) learning in the profoundly amnesic patient E.P., who has extensive damage limited primarily to the medial temporal lobe. E.P. was presented with factual information (novel three-word sentences) during 24 study sessions across 12 weeks. E.P. performed much more poorly than controls but demonstrated unmistakable improvement across the sessions, achieving after 12 weeks a score of 18.8% correct on a cued-recall test and 64.6% correct on a two-alternative, forced-choice test. Unlike controls, E.P.'s learning was not accompanied by conscious knowledge about which answers were correct. He assigned the same confidence ratings to his correct answers as his incorrect answers. Moreover, on the forced-choice test his response times were identical for correct and incorrect responses. Furthermore, unlike controls, he could not respond correctly when the second word in each sentence was replaced by a synonym. Thus, what E.P. learned was rigidly organized, unavailable as conscious knowledge, and in all respects exhibited the characteristics of nondeclarative memory. Thus, factual information, which is ordinarily learned as declarative (conscious) knowledge and with the participation of the medial temporal lobe, can be acquired as nondeclarative memory, albeit very gradually and in a form that is outside of awareness and that is not represented as factual knowledge. We suggest that E.P.'s learning depended on a process akin to perceptual learning and occurred directly within neocortex.
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3/14. Developmental amnesia: a new pattern of dissociation with intact episodic memory.

    A case of developmental amnesia is reported for a child, CL, of normal intelligence, who has intact episodic memory but impaired semantic memory for both semantic knowledge of facts and semantic knowledge of words, including general world knowledge, knowledge of word meanings and superordinate knowledge of words. In contrast to the deficits in semantic memory, there are no impairments in episodic memory for verbal or visual material, assessed by recall or recognition. Lexical decision was also intact, indicating impairment in semantic knowledge of vocabulary rather than absence of lexical representations. The case forms a double dissociation to the cases of Vargha-Khadem et al. [science 277 (1997) 376; Episodic memory: new directions in research (2002) 153]; Gadian et al. [brain 123 (2000) 499] for whom semantic memory was intact but episodic memory was impaired. This double dissociation suggests that semantic memory and episodic memory have the capacity to develop separately and supports models of modularity within memory development and a functional architecture for the developmental disorders within which there is residual normality rather than pervasive abnormality. knowledge of arithmetical facts is also spared for CL, consistent with adult studies arguing for numeracy knowledge distinct from other semantics. reading was characterised by difficulty with irregular words and homophones but intact reading of nonwords. CL has surface dyslexia with poor lexico-semantic reading skills but good phonological reading skills. The case was identified following screening from a population of normal schoolchildren suggesting that developmental amnesias may be more pervasive than has been recognised previously.
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4/14. Permanent global amnesia: case report.

    PURPOSE: To present a case of permanent global amnesia related to hippocampal damage. Permanent global amnesia is a very rare condition of unknown etiology; lesions restricted to the hippocampus are uncommon, which hinders investigations of this pattern of memory loss. This case is unusually well documented, as the patient underwent extensive neuropsychological evaluations. CLINICAL FEATURES: A cheerful right-handed, 83-year-old retired electrician was first evaluated in 1990 for progressive difficulty in learning new information and in recalling events over the preceding 3-4 years. Tests over the next 5 years showed that the impairment was confined to episodic declarative memory. New verbal information could be stored only in episodic memory in a restricted manner, limited by short-term memory capacity. A relatively mild retrograde amnesia was detected. Semantic and implicit memory was spared, as were other functions evaluated. The patient's language and executive function were strikingly efficient. magnetic resonance imaging of the brain showed bilateral atrophy of the hippocampi and amygdalae, ruling out conditions such as tumour growth. A diagnosis of permanent global amnesia was made. In the ensuing years, the retrograde amnesia worsened, but no new deficits were identified. CONCLUSION: This case, the first with a detailed cognitive examination, is evidence of a relatively pure hippocampal pattern for memory loss in permanent global amnesia.
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5/14. Evidence for semantic learning in profound amnesia: an investigation with patient H.M.

    Until recently, it seemed unlikely that any semantic knowledge could be acquired following extensive bilateral damage to the medial temporal lobes (MTL). Although recent studies have demonstrated some semantic learning in amnesic patients, questions remain regarding the limits of this capacity and the extent to which it relies on those patients' residual MTL function. The present study examined whether detailed, semantic memory could be acquired by a patient with no functioning hippocampus. We used cued recall and forced-choice recognition tasks to investigate whether the patient H.M. had acquired knowledge of people who became famous after the onset of his amnesia. Results revealed that, with first names provided as cues, he was able to recall the corresponding famous last name for 12 of 35 postoperatively famous personalities. This number nearly doubled when semantic cues were added, suggesting that his knowledge of the names was not limited to perceptual information, but was incorporated in a semantic network capable of supporting explicit recall. In forced-choice recognition, H.M. discriminated 87% of postmorbid famous names from foils. Critically, he was able to provide uniquely identifying semantic facts for one-third of these recognized names, describing John Glenn, for example, as "the first rocketeer" and Lee Harvey Oswald as a man who "assassinated the president." Although H.M.'s semantic learning was clearly impaired, the results provide robust, unambiguous evidence that some new semantic learning can be supported by structures beyond the hippocampus proper.
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6/14. Remembering and forgetting of semantic knowledge in amnesia: a 16-year follow-up investigation of RFR.

    We report our long-term follow-up investigations of RFR, a post-encephalitic case of very grave anterograde and retrograde amnesia. We also describe the results of quantitative neuroimaging of his brain injury that showed bilateral and severe reduction in the hippocampal formation and medial temporal structures with sparing of left lateral/posterior and right posterior temporal cortex. We established that RFR had a persistent severe anterograde and retrograde amnesia for personal and public events. His personal semantic knowledge was relatively spared for the retrograde period. There was a modest and global reduction in RFR's vocabulary for words acquired in adulthood before he became amnesic but there was no evidence of any retrograde gradient. His retrograde knowledge of people was also without any gradient. Remarkably, there had been no change in the extent of his semantic knowledge across a prolonged re-test interval indicating that the loss of semantic knowledge was stable and likely to have arisen at the time of his initial lesion. RFR also showed evidence of a limited but significant ability to acquire new word meanings and a more restricted capacity for learning about new celebrities. While he was able to demonstrate face and name familiarity for newly famous people, he was unable to provide much semantic detail. RFR's amnesia can be partially explained by contemporary theories that allow for parallel cortical and hippocampal memory systems but is difficult to reconcile in detail with any extant view.
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7/14. memory functioning following a left medial thalamic hematoma.

    A patient with a discrete, left medial thalamic hematoma developed a severe anterograde amnesia. The memory deficit was most consistent for verbal materials, but was also observed on several tests of figural memory. The patient appeared to have a normal short-term memory (STM) capacity, performed normally on a STM distractor task and was not abnormally sensitive to proactive inhibition. This case is evidence that unilateral damage to the medial thalamus alone can produce a severe memory deficit.
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8/14. Semantic, episodic, and autobiographical memory in a postmeningitic amnesic patient.

    This study is concerned with the semantic and episodic memory performance of a highly intelligent and intellectually unimpaired patient, K.J., who became amnesic following meningitis. Although densely amnesic he showed unimpaired performance on tests of vocabulary and verbal fluency, while both speed and accuracy on semantic category judgment and sentence verification tests are unimpaired. It is concluded that semantic memory performance may be intact despite dense amnesia. However, this does not necessarily imply separate semantic and episodic memory systems. K.J. showed an impaired capacity for registering new material in semantic memory, and apparently normal autobiographical memory for events occurring well before his illness. The simplest interpretation of our results would therefore appear to be in terms of the sparing of old and overlearned memories rather than the specific preservation of semantic memory.
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9/14. learning of a complex arithmetic skill in amnesia: evidence for a dissociation between compilation and production.

    Two patients with severe amnesia following rupture of anterior communicating artery aneurysms were able to learn a complex algorithm for mentally squaring two-digit numbers. Although both patients learned the algorithm at a similar rate, one patient's improvement was accounted for by savings in the steps of the algorithm. The other patient, however, showed little improvement in the steps while performance of the whole algorithm improved dramatically. Neither patient showed savings in the Hebb Digit Span procedure. The results suggested a dissociation between amnesics in their capacity to learn the constituent "productions" or steps of a skill and their capacity to organize those productions into a single coherent act.
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10/14. The implicit memory ability of a patient with amnesia due to encephalitis.

    The implicit memory ability of a patient (S.S.) with severe amnesia due to encephalitis was assessed using five independent paradigms: Perceptual priming with real words and pseudowords; Word-stem completion with and without contextual cues; Word-stem completion following presentation of high- vs. low-frequency words; Biasing of the spelling of ambiguous (homophonic) words; and Conceptual priming. On the tasks in which previously acquired knowledge could potentially be activated by a prime (e.g., perceptual priming with real words), both S.S. and the Korsakoff patients performed on a normal level. However, when new learning or new associations had to be formed prior to implicit memory testing (e.g., perceptual priming of pseudowords or contextual word-stem completion), S.S.'s implicit memory performance was superior to Korsakoff amnesics. These results suggested that new learning differentially affects the priming abilities of S.S. and alcoholic Korsakoff patients. Since S.S.'s amnesia is as severe as Korsakoff patients, it was also concluded that severity of amnesia is clearly not the sole determinant of priming capacity; etiology may be equally important.
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