Cases reported "Memory Disorders"

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1/9. Fractionation of visual memory: evidence from a case with multiple neurodevelopmental impairments.

    It is known that the adult visual memory system is fractionable into functionally independent cognitive subsystems, selectively susceptible to brain damage. However, it is unclear whether these cognitive subsystems can fractionate developmentally. The present study describes an investigation of visual memory of a patient (PE) with multiple developmental disorders. PE was congenitally deaf, had Gilles de la tourette syndrome and autism, with non-verbal ability in the normal range. The patient presented with a recognition memory impairment for unknown human faces. This contrasted with his superior recognition memory for unknown buildings, landscapes and outdoor scenes. PE's memory impairment for faces could not be explained by a general deficit in face processing. Interestingly, PE also showed a recognition memory impairment for animals. These findings indicate that different domains of the visual memory system can be fractionated developmentally. In particular, it demonstrates that topographical memory can develop independently from other aspects of visual memory.
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2/9. Impaired declarative memory for emotional material following bilateral amygdala damage in humans.

    Everyday experience suggests that highly emotional events are often the most memorable, an observation supported by psychological and pharmacological studies in humans. Although studies in animals have shown that nondeclarative emotional memory (behaviors associated with emotional situations) may be impaired by lesions of the amygdala, little is known about the neural underpinnings of emotional memory in humans, especially in regard to declarative memory (memory for facts that can be assessed verbally). We investigated the declarative memory of two rare patients with selective bilateral amygdala damage. Both subjects showed impairments in long-term declarative memory for emotionally arousing material. The data support the hypothesis that the human amygdala normally enhances acquisition of declarative knowledge regarding emotionally arousing stimuli.
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3/9. Impaired allocentric spatial memory underlying topographical disorientation.

    The cognitive processes supporting spatial navigation are considered in the context of a patient (CF) with possible very early Alzheimer's disease who presents with topographical disorientation. Her verbal memory and her recognition memory for unknown buildings, landmarks and outdoor scenes was intact, although she showed an impairment in face processing. By contrast, her navigational ability, quantitatively assessed within a small virtual reality (VR) town, was significantly impaired. Interestingly, she showed a selective impairment in a VR object-location memory test whenever her viewpoint was shifted between presentation and test, but not when tested from the same viewpoint. We suggest that a specific impairment in locating objects relative to the environment rather than relative to the perceived viewpoint (i.e. allocentric rather than egocentric spatial memory) underlies her topographical disorientation. We discuss the likely neural bases of this deficit in the light of related studies in humans and animals, focusing on the hippocampus and related areas. The specificity of our test indicates a new way of assessing topographical disorientation, with possible application to the assessment of progressive dementias such as Alzheimer's disease.
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4/9. Assessment of desmopressin-enhanced cognitive function in a neurosurgical patient.

    The vasopressin analog desmopressin (DDAVP) is known to enhance memory in animals and man but its precise mechanism of action is uncertain. We report the case of a patient who experienced chronic memory dysfunction with impaired job performance following transsphenoidal resection of a pituitary adenoma. A prospective double-blind, placebo-controlled trial of the effects of DDAVP was performed. memory storage and recall improved with DDAVP treatment and declined within 1 week after drug withdrawal both by subjective and objective criteria. The Buschke Selective Reminding Test was clearly the most responsive out of a battery of standard memory testing paradigms employed to track the presence or absence of DDAVP treatment.
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5/9. Loss of memory for people following temporal lobe damage.

    A 40-yr-old woman, K.S., is reported, who shows a severe loss of memory for people following a history of epilepsy and right anterior temporal lobectomy. Despite this memory problem, K.S. is not clinically amnesic, has a memory Quotient of 122 on the Wechsler memory Scale in line with her IQ of 119, and performs well on conventional tests of recognition and recall. She does not have a generalized semantic memory deficit for living things, but her deficit extends beyond people to include famous animals, buildings and product names. Autobiographical memory is good, except where memory for people is concerned. The nature of the memory store that is impaired in K.S. is discussed, as are the implications of her case for theories of the organization of long-term memory.
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6/9. anomia for animals in a child.

    The occurrence of anomia which particularly affected the category of animals is described in a 12-year-old boy. This difficulty cannot be accounted for by frequency or familiarity and is unaffected by whether the stimulus is a line drawing, photograph or model. The deficit does not represent development lag, as normal children of the same naming age differ qualitatively. The results, which include a one year follow-up, are discussed in relation to unitary versus multiple semantic systems. The disorder includes a disturbance of memory arising during the developmental period. It is suggested that items which are involved in daily actions can be more easily remembered than those which are identified by sensory features alone, and that the preserved learning of motor skills in acquired amnesia may be of relevance.
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7/9. Two visual systems in mental imagery: dissociation of "what" and "where" in imagery disorders due to bilateral posterior cerebral lesions.

    We studied two patients with impaired visual perception and imagery caused by bilateral posterior cerebral lesions. The first had prosopagnosia and achromatopsia, and the imagery disorder involved the description of objects from memory, especially faces and animals, and colors of objects. The second had visual disorientation; the imagery problem involved the description of spatial relations from memory. Impairments of visual imagery, like disorders of visual perception, can be dissociated. Object and color imagery may be dissociated from imagery for spatial relations. A given imagery deficit tends to be associated with the corresponding type of perceptual deficit.
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8/9. Loss of topographic memory with learning deficits.

    A case is reported in which a patient with a vascular accident involving the posterior portion of the minor hemisphere presented a topographic memory loss and also deficits in his ability to learn certain types of new material. The study of this case has led us to re-examine spatial functioning in light of both human and animal research. Based on clinical and experimental evidence we have proposed that a unitary interpretation can account for the various spatial deficits associated with posterior righ hemisphere lesions. We have also suggested that the establishment of a spatial map for orientation probably depends not only on posterior right hemisphere structures but also may require the participation of structures which are more specifically concerned with learning and memory, such as the hippocampus or at least the connections between the hippocampus and these structures.
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9/9. Partial recovery from visual object agnosia: a 10 year follow-up study.

    We describe a young woman, J.R., who sustained a very severe head injury in 1981 at the age of 17 years. She was assessed in 1982 and found to have visual agnosia. Since then J.R. has been assessed on several occasions over a period of ten years. Her agnosia for real objects has resolved and she has improved on the identification of other classes of stimuli. However, she still has some problems with the identification of line drawings, photographs and model animals. Her drawing from memory remains particularly poor and she has difficulty with visual imagery. We consider her residual deficits in the light of Farah's (1990) theoretical framework; this proposes that associative agnosia could be due to a disconnection syndrome, a loss of stored visual representations or to the loss of knowledge of how to perceive objects. J.R.'s residual impairments appear to be mainly due to a loss of access to visual representations in the absence of visual input.
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