The Experts below are selected from a list of 120 Experts worldwide ranked by ideXlab platform
Martha J. Farah - One of the best experts on this subject based on the ideXlab platform.
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chapter 21 visual Agnosia
Handbook of Clinical Neurology, 2008Co-Authors: Orrin Devinsky, Martha J. Farah, William B BarrAbstract:Publisher Summary This chapter provides an overview of the clinical types of visual Agnosia and related syndromes, the anatomic systems underlying normal and abnormal visual processing, and information regarding clinical assessment of these conditions. Visual Agnosia is divided into two types: apperceptive Agnosia and Associative Agnosia. Apperceptive Agnosia is a disorder of complex visual perceptual processing. Individuals with this condition are not blind since they can describe their visual experience, yet they do not have sufficient higher-level visual perception to accurately recognize objects. An individual with visual Associative Agnosia experiences a normal percept stripped of its meaning. The problem is in the process of associating a perception with more general knowledge-based representations. The most common cause of Associative visual Agnosia is bilateral infarction of the posterior cerebral arteries. Bilateral lesions involving the inferior temporo-occipital junction and subjacent white matter are the most common anatomic lesions associated with this Associative visual Agnosia. A patient with visual Agnosia will have normal or near-normal visual capacity. More detailed tests of visual and perceptual processing are often needed to make distinctions among the various types of visual Agnosia. A battery of tests of higher-order visual perceptual processing (Visual Object and Space Perception Battery—VOSP) are developed. This test is useful for demonstrating deficits in object and space perception. A similar test, focusing on object recognition (Birmingham Object Recognition Battery—BORB), is also available.
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Associative visual Agnosia and alexia without prosopAgnosia
Contraception, 1994Co-Authors: T E Feinberg, R J Schindler, P C Kwan, Esmeralda De Ochoa, Martha J. FarahAbstract:Disagreement over the neuroanatomical substrate of Associative visual Agnosia encompasses such basic issues as: (1) the necessity for bilateral lesions; (2) the intrahemispheric locus of damage; and (3) the roles of disconnection versus cortical damage. We examined three patients whose Associative visual Agnosia encompassed objects and printed words but spared faces. CAT scans revealed unilateral dominant occipitotemporal strokes. CAT scans of four previously reported cases with this same profile of Associative Agnosia were obtained. Dominant parahippocampal, fusiform and lingual gyri were the most extensively damaged cortical regions surveyed and were involved in all cases. Of white matter tracts surveyed, only temporal white matter including inferior longitudinal fasciculus was severely and universally involved. Splenium of the corpus callosum was frequently but not always involved. We conclude there is a form of Associative visual Agnosia with Agnosia for objects and printed words but sparing face recognition which has a characteristic unilateral neuropathology. Damage or disconnection of dominant parahippocampal, fusiform and lingual gyri is the necessary and sufficient lesion.
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cognitive neuropsychology patterns of co occurrence among the Associative Agnosias implications for visual object representation
Cognitive Neuropsychology, 1991Co-Authors: Martha J. FarahAbstract:Abstract The patterns of co-occurrence among Associative Agnosia for faces, words and other objects are analysed and found to be consistent with the existence of two, rather than three, underlying visual recognition capacities. Different degrees and combinations of damage to these two capacities can account for the five different combinations of word, face, and object Agnosia that are found, as well as for the apparent absence of two particular combinations. A tentative interpretation of the two inferred visual recognition capacities is offered, in terms of the idea of structural representations.
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Patterns of co-occurrence among the Associative Agnosias: implications for visual object representation
Cognitive Neuropsychology, 1991Co-Authors: Martha J. FarahAbstract:Abstract The patterns of co-occurrence among Associative Agnosia for faces, words and other objects are analysed and found to be consistent with the existence of two, rather than three, underlying visual recognition capacities. Different degrees and combinations of damage to these two capacities can account for the five different combinations of word, face, and object Agnosia that are found, as well as for the apparent absence of two particular combinations. A tentative interpretation of the two inferred visual recognition capacities is offered, in terms of the idea of structural representations.
William B Barr - One of the best experts on this subject based on the ideXlab platform.
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chapter 21 visual Agnosia
Handbook of Clinical Neurology, 2008Co-Authors: Orrin Devinsky, Martha J. Farah, William B BarrAbstract:Publisher Summary This chapter provides an overview of the clinical types of visual Agnosia and related syndromes, the anatomic systems underlying normal and abnormal visual processing, and information regarding clinical assessment of these conditions. Visual Agnosia is divided into two types: apperceptive Agnosia and Associative Agnosia. Apperceptive Agnosia is a disorder of complex visual perceptual processing. Individuals with this condition are not blind since they can describe their visual experience, yet they do not have sufficient higher-level visual perception to accurately recognize objects. An individual with visual Associative Agnosia experiences a normal percept stripped of its meaning. The problem is in the process of associating a perception with more general knowledge-based representations. The most common cause of Associative visual Agnosia is bilateral infarction of the posterior cerebral arteries. Bilateral lesions involving the inferior temporo-occipital junction and subjacent white matter are the most common anatomic lesions associated with this Associative visual Agnosia. A patient with visual Agnosia will have normal or near-normal visual capacity. More detailed tests of visual and perceptual processing are often needed to make distinctions among the various types of visual Agnosia. A battery of tests of higher-order visual perceptual processing (Visual Object and Space Perception Battery—VOSP) are developed. This test is useful for demonstrating deficits in object and space perception. A similar test, focusing on object recognition (Birmingham Object Recognition Battery—BORB), is also available.
M Poncet - One of the best experts on this subject based on the ideXlab platform.
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optic aphasia with pure alexia a mild form of visual Associative Agnosia a case study
Cortex, 1998Co-Authors: V Chanoine, Teixeira C Ferreira, Jeanfrancois Demonet, J L Nespoulous, M PoncetAbstract:Abstract A single-case study is reported of a naming disorder selective to the visual modality. The patient showed intact access to structural knowledge of objects and letters, but impaired access to complete semantic knowledge of objects and alphabetical knowledge of letters from visual input. The impairment was most striking when the patient had to discriminate between semantically similar objects or within a given symbolic repertoire, i.e. letters. The co-occurrence of a partial deficit of visual recognition for objects and for letters indicated features of optic aphasia and pure alesia. This symmetric performance between object and letter processing may also constitute a mild form of visual Associative Agnosia.
Dario Grossi - One of the best experts on this subject based on the ideXlab platform.
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visual Associative Agnosia and optic aphasia a single case study and a review of the syndromes
Cortex, 1992Co-Authors: Lucio Iorio, Angelamaria Falanga, Nina A Fragassi, Dario GrossiAbstract:Abstract The case is presented of a patient who showed visual naming disturbances caused by a left occipital infarction. His performance on tests of visual naming, of recognition not requiring a verbal response, and of verbal-visual matching demonstrated a wide range of qualitatively different errors, including complete inability to recognize the object, access to partial semantic knowledge, and mere name finding difficulty. On the basis of the present case and of a review of the recent literature, the clinical distinction between visual Associative Agnosia and optic aphasia and the relation of these disorders with the anatomical site of lesion are discussed.
Teixeira C Ferreira - One of the best experts on this subject based on the ideXlab platform.
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optic aphasia with pure alexia a mild form of visual Associative Agnosia a case study
Cortex, 1998Co-Authors: V Chanoine, Teixeira C Ferreira, Jeanfrancois Demonet, J L Nespoulous, M PoncetAbstract:Abstract A single-case study is reported of a naming disorder selective to the visual modality. The patient showed intact access to structural knowledge of objects and letters, but impaired access to complete semantic knowledge of objects and alphabetical knowledge of letters from visual input. The impairment was most striking when the patient had to discriminate between semantically similar objects or within a given symbolic repertoire, i.e. letters. The co-occurrence of a partial deficit of visual recognition for objects and for letters indicated features of optic aphasia and pure alesia. This symmetric performance between object and letter processing may also constitute a mild form of visual Associative Agnosia.
