Cases reported "Agnosia"

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21/117. Neuropsychological testing following head injuries: prosopagnosia without visual field defect.

    Assessment of residual cerebral dysfunction in the post-traumatic patient poses considerable problems particularly when the neurological examination yields minimal or equivocal findings. The clinical picture is frequently complicated by emotional disturbance not easily differentiated from "post-traumatic neurosis." This report describes such a patient whose disorder was elicidated by neuropsychological testing. Numerous studies have established the validity of neuropsychological tests particularly when they are interpreted by psychologists specifically trained in their use. These procedures are also useful in differentiating patients with neurologic complaints of a nonorganic etiology from patients with similar complaints secondary to confirmed brain lesions. Although the findings reported here pertain to a patient exhibiting a rare neurologic consequence of closed head injury, the methods employed are applicable to subtle behavioral manifestations of diverse etiologies. Neurophyshological findings in a patient unable to recognize faces of familiar persons (prosopagnosia) disclosed a severe impairment of visual perception despite intact visual acuity and fields. The prosopagnosia was also associated with a pervasive memory deficit without dementia. Our results challenge current concepts of prosopagnosia and support the need for neuropsychological evaluation of post-traumatic patients.
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ranking = 1
keywords = perception
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22/117. A longitudinal study of category-specific agnosia.

    We report a 12-year longitudinal case study on a 60-year-old male patient (DW) with category-specific agnosia. The extent to which DW's impairment has changed over time was evaluated using identical tests at time 1 (1988) and time 2 (2000). In particular, we assessed his ability to identify pictures and real objects, to draw from memory, and to access stored semantic information about living and non-living things. The principal findings were: (i). DW was significantly better at identifying real objects in comparison with line drawings. (ii). DW presented with a category-specific impairment for living things that remained consistent over the 12-year period. (iii). He significantly improved in his ability to identify real non-living objects over the 12-year period but real living objects remained at floor. (iv). His ability to access stored visual knowledge declined over time. On the basis of these data, we suggest that visual perception is required to maintain intact visual memories over a period of time. We also suggest that integrative visual agnosia co-occurs with a category-specific impairment for living things because the recognition of these items requires more global processing than for non-living things. In addition, we suggest that degradation to stored visual knowledge can cause category-specific naming impairments for living compared with non-living things because naming living things requires access to more detailed visual knowledge.
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ranking = 1
keywords = perception
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23/117. Implicit face perception in a patient with visual agnosia? Evidence from behavioural and eye-tracking analyses.

    This paper investigates face perception in a visual agnosic and prosopagnosic patient (SB). Despite very extensive lesions of visual areas, SB remains capable of some visual processing [brain 125 (2002) 58]. However, in everyday situations SB does not exhibit signs of specific face recognition. To investigate how SB may process faces, we tested two hypotheses. According to the 'spared module hypothesis,' SBs abilities come from spared modules of implicit face processing. According to the 'general strategy hypothesis,' SB may have developed some deliberate compensatory strategies. A two-session experimental design was constructed. In both sessions, face and non-face pictures were shown to participants. In Session 1 (implicit condition), participants had to decide whether each picture was a vegetable. In Session 2 (explicit condition), participants had to decide whether each picture was a face. Verbal reports showed that SB was not aware of faces in Session 1. However, behavioural results showed that (1). SB could process faces; (2). even when SB was not aware of faces, he processed them differently than non-faces; (3). when knowing the presence of faces, he did not process faces better. In addition, eye-tracking data suggested that SB did not change the nature of his processing from Sessions 1 to 2. pupil diameters showed that fixated facial features were processed similarly as in control participants. Together, these results are not compatible with a general compensatory strategy hypothesis and suggest sparing of an implicit face processing module in SB.
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ranking = 5
keywords = perception
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24/117. Pure agnosia for mirror stimuli after right inferior parietal lesion.

    This study reports the experimental investigation of G.R., a patient suffering from a highly specific disorder in discriminating mirror stimuli following a right temporoparietal cerebrovascular accident. G.R. showed intact perceptual, attentional, mnestic, linguistic and executive abilities. Object recognition was accurate even under unusual viewing conditions. He was highly accurate in defining the canonical orientation of common objects and in discriminating misoriented objects among identical distracters. However, he was severely impaired in tasks requiring mirror-stimulus discrimination, a deficit that persisted even when the object's coordinates were systematically misaligned with respect to his body. The disorder was also dependent upon the frame of reference (allocentric versus egocentric) activated on the basis of task demands. These results demonstrate the existence of a highly specific disorder in discriminating mirror stimuli defined in object-based coordinates, suggesting a failure in processing the directionality of an object's intrinsic x-axis.
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ranking = 1.2957216882323
keywords = discrimination
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25/117. Auditory agnosia in children after herpes encephalitis.

    Four pediatric patients whose bilateral auditory cortices were damaged by herpes encephalitis at an early age were studied. Their brain CT and MRI scans demonstrated common bilateral lesions of the auditory cortices. Their auditory perception was investigated by means of behavioral and objective hearing tests and auditory perception tests. All four patients showed mild or moderate hearing loss in the behavioral hearing test and normal auditory brainstem responses but did not manifest total deafness. Moreover, perception tests involving speech, environmental sounds and music demonstrated that most auditory perception ability had been lost in all patients. On reaching school age, the patients were enrolled in schools for the deaf or special schools for handicapped children.
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ranking = 4.0269732878044
keywords = perception, speech
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26/117. Visual agnosia in a child with non-lesional occipito-temporal CSWS.

    In this paper we describe a case of severe visual agnosia in a child with an electrophysiological pattern of continuous spike-wave discharges in slow sleep (CSWS) in the occipito-temporal regions. The neuropsychological spectrum related to this phenomenon is discussed. Published paediatric reports associate visual agnosia (i.e. an inability to recognize objects without impairment of visual acuity) mainly with symptomatic occipito-temporal aetiology (e.g. cortical dysplasia, vascular insults) and other neurological symptoms (e.g. autism). We describe a detailed 2 year electrophysiological and neuropsychological follow-up of an 8-year-old boy with sporadic seizures, occipito-temporal CSWS and visual agnosia. The growth and neurological development of the child had been considered as normal, neurological examination did not reveal any focal signs, visual acuity was intact and MRI was normal. First EEG and six consecutive 24 h video EEG recordings during the follow-up of 22 months showed continuous spike-and-wave activity covering over 85% of the non-REM sleep. According to structured neuropsychological tests (Wechsler intelligence Scale for Children--Third Edition, A Developmental Neuropsychological Assessment (NEPSY), Test of Visual-Perceptual Skills, Corsi block, Hooper Visual Organization Test) the boy had normal verbal intelligence but major deficits in visual perception, especially in object recognition, impaired shape discrimination and detection, and poor copying skills. attention and executive functions were intact. There were no difficulties in short- or long-term memory. Verbal cues and naming the objects improved visual memory. Tracing the objects with a finger or by moving the head improved object recognition. Currently the boy attends a special school with a rehabilitation plan including neuropsychological and occupational therapies. This case adds a new facet to the spectrum of neuropsychological deficits in children with CSWS. sleep EEG should be included in the etiological studies of children with specific neuropsychological problems and detailed neuropsychological assessment is needed for diagnostic and rehabilitation purposes.
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ranking = 2.2957216882323
keywords = discrimination, perception
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27/117. Visual agnosia.

    As was originally proposed by Lissauer, visual recognition may break down either at an apperceptive or at an associative level. At an apperceptive level, finer grain distinctions may be made; the authors distinguished here between disorders of shape recognition and perceptual integration. It is not the case, however, that all patients with visual recognition deficits have impaired perception: poor recognition and naming may also result from damage to stored perceptual knowledge (e.g., structural descriptions), from problems in accessing semantic knowledge, from perceptual knowledge, or from impairments to semantic knowledge itself. These represent different types of associative deficit. In some cases, mild damage to stored perceptual knowledge also generates problems that are more severe on naming than on recognition and more severe for some categories of objects than others.
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ranking = 1
keywords = perception
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28/117. Hearing of a presence.

    Here we describe a patient with epilepsy (secondary to left parieto-temporal brain damage) suffering from the paroxysmal unilateral experience of hearing a person in her near extrapersonal space. The paroxysmal auditory experience was associated with a deficit in spatial auditory perception and other paroxysmal disorders of somatognosia. Based on these findings, it is suggested that the paroxysmal hearing of a person nearby corresponds to an auditory disorder of somatognosia.
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ranking = 1
keywords = perception
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29/117. Formant interaction as a cue to vowel perception: a case report.

    Accumulating evidence indicates that cerebral processing of consonants and vowels is separable. It has been shown that disordered temporal acuity leads to disturbed consonant perception in cases with pure word deafness. In contrast, there has been no clear explanation of how vowel perception is impaired. We examined a patient with auditory agnosia, who showed a differential ability to identify the five Japanese vowels after bilateral cerebral lesions. He correctly identified the vowel [a] in more than 70% of auditory presentations, whereas he identified [i] in only about 30% of presentations. The difference between the first and second formant frequencies "F2-F1" and an artificially defined value "F1-(F2-F1)" for each vowel correlated significantly with the percentage of correct identifications. These findings support the hypothesis that vowel perception is based on formant interactions.
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ranking = 7
keywords = perception
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30/117. Dissociation between mental imagery and object recognition in a brain-damaged patient.

    Visual imagery is the creation of mental representations that share many features with veridical visual percepts. Studies of normal and brain-damaged people reinforce the view that visual imagery and visual perception are mediated by a common neural substrate and activate the same representations. Thus, brain-damaged patients with intact vision who have an impairment in perception should have impaired visual imagery. Here we present evidence to the contrary from a patient with severely impaired object recognition (visual object agnosia) but with normal mental imagery. He draws objects in considerable detail from memory and uses information derived from mental images in a variety of tasks. In contrast, he cannot identify visually presented objects, even those he has drawn himself. He has normal visual acuity and intact perception of equally complex material in other domains. We conclude that rich internal representations can be activated to support visual imagery even when they cannot support visually mediated perception of objects.
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ranking = 4
keywords = perception
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