Associative Visual Agnosia Research Articles

Neuroanatomic correlates of visual agnosia in Alzheimer's disease: a clinicopathologic study.

To examine the neuroanatomic correlates of visual agnosia in AD. The authors performed an anterograde clinicopathologic study of 23 patients with clinically and neuropathologically confirmed AD in a 305-bed acute care geriatric hospital and a 165-bed acute care psychiatric hospital. The presence of apperceptive visual agnosia was assessed using the Ghent's overlapping figure test and the Gottschaldt's hidden figure test. Associative visual agnosia was examined using the conceptual items of the Columbia Mental Maturity Test. Correlations between neurofibrillary tangle (NFT) and senile plaque (SP) densities and visual agnosia were studied using forward stepwise logistic regression. A statistically significant relation was found between NFT densities in Brodmann's areas 18, 19, and 37, and associative visual agnosia, whereas NFT densities in the areas studied did not correlate with the presence of apperceptive visual agnosia. Senile plaque counts did not correlate with any of the neuropsychological parameters. These results support the existence of a dichotomy between associative and apperceptive agnosia, and show that only the former is related to the damage of secondary and high-order visual association areas in AD. In addition, the results suggest that SP densities do not represent a valuable pathologic correlate of visual agnosia in this disorder.

Optic Aphasia with Pure Alexia: A Mild Form of Visual Associative Agnosia? A Case Study

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.

Visual associative agnosia and optic aphasia. A single case study and a review of the syndromes

Visual associative agnosia and optic aphasia. A single case study and a review of the syndromes

The Right Hemisphere and Optic Aphasia/Optic Apraxia

Abstract We describe a patient with inordinate impairment in oral picture naming (as opposed to oral naming to definitions and viewed gestures). His naming errors were primarily semantically related or perseverative responses. He also had greater difficulty gesturing in response to viewed pictures than gesturing to verbal commands, and produced many semantic and perseverative gesture errors. He performed relatively well in some visual tasks (e.g. matching, object decision, and drawing), but was impaired on others (e.g. copying pictures). He had intact abilities for basic semantic processing of pictures (category sorting, cross-modal matching), but he demonstrated impairment in picture comprehension tasks requiring more detailed semantic information (matching associated pictures). We propose that this patient's impairment may be classified as optic aphasia and optic apraxia, and not visual associative agnosia in which we expect greater recognition Impairment. Current cognitive models that attempt to explai...

Consciousness of perception after brain damage.

Disturbances of visual perception after brain damage provide clues to understanding consciousness and the brain. In this article we review six visual disorders in which perception and consciousness are dissociated as a result of brain damage: blindsight, implicit shape perception in apperceptive visual agnosia, covert recognition of faces in prosopagnosia, unconscious perception in neglect and extinction, implicit reading in pure alexia, and implicit object recognition in associative visual agnosia. We consider these six disorders from the standpoint of three main schools of thought concerning consciousness and the brain, namely a localized system for consciousness, consciousness as a state of integration, and consciousness as a property of graded representation. The findings suggest that these syndromes do not share a single mechanism and that it is conceivable that more than one explanation will be necessary both within and across syndromes. We conclude on the basis of the current evidence that it is unlikely that any single brain system is necessary for conscious awareness of perception that does not play a role in perception as well.

The right hemisphere and optic aphasia/optic apraxia

We describe a patient with inordinate impairment in oral picture naming (as opposed to oral naming to definitions and viewed gestures). His naming errors were primarily semantically related or perseverative responses. He also had greater difficulty gesturing in response to viewed pictures than gesturing to verbal commands, and produced many semantic and perseverative gesture errors. He performed relatively well in some visual tasks (e.g. matching, object decision, and drawing), but was impaired on others (e.g. copying pictures). He had intact abilities for basic semantic processing of pictures (category sorting, cross-modal matching), but he demonstrated impairment in picture comprehension tasks requiring more detailed semantic information (matching associated pictures). We propose that this patient's impairment may be classified as optic aphasia and optic apraxia, and not visual associative agnosia in which we expect greater recognition Impairment. Current cognitive models that attempt to explain optic aphasia would have difficulty accounting entirely for this patient's impairments. We suggest that the information gained from right hemisphere visual processing is unable fully to activate and specify phonological and gestural output representations in the left hemisphere, either directly or by way of right hemisphere semantic processing.

Childhood Visual Agnosia: A Seven-Year Follow-up

Abstract We describe the case of a child who developed an associative visual agnosia and document her neuropsychological and neuroimaging progression over the past 7 years. AR contracted a viral encephalitis at age 9 that destroyed the right temporal lobe and a portion of the left inferotemporal region. A triad of symptoms was observed: associative visual agnosia, prosopagnosia and color agnosia. With time, AR has shown limited behavioral improvement. Neuroimaging showed that, apart from the initial ‘normal’ findings, the neuroanatomical correlates remained stable over time. Strikingly, a clear dissociation between object and spatial representations is present in this patient, which is the basis for her apparent recovery of function. Indeed, she uses spatial as well as local cues to compensate for her recognition deficits. AR's inability to recognize objects is interpreted as a deficit in the inferior temporal ventral pathway specialized for object perception, whereas the posterior parietal dorsal pathway specialized for spatial localization remains functional. The contribution of the residual contralateral temporal lobe seems to account for her use of discrete details in visual recognition. Finally, the limited recovery displayed by AR indicates limits in cerebral plasticity for visual processes mediated by the right temporal lobe.

Childhood visual agnosia: A seven-year follow-up

We describe the case of a child who developed an associative visual agnosia and document her neuropsychological and neuroimaging progression over the past 7 years. AR contracted a viral encephalitis at age 9 that destroyed the right temporal lobe and a portion of the left inferotemporal region. A triad of symptoms was observed: associative visual agnosia, prosopagnosia and color agnosia. With time, AR has shown limited behavioral improvement. Neuroimaging showed that, apart from the initial ‘normal’ findings, the neuroanatomical correlates remained stable over time. Strikingly, a clear dissociation between object and spatial representations is present in this patient, which is the basis for her apparent recovery of function. Indeed, she uses spatial as well as local cues to compensate for her recognition deficits. AR's inability to recognize objects is interpreted as a deficit in the inferior temporal ventral pathway specialized for object perception, whereas the posterior parietal dorsal pathway specialized for spatial localization remains functional. The contribution of the residual contralateral temporal lobe seems to account for her use of discrete details in visual recognition. Finally, the limited recovery displayed by AR indicates limits in cerebral plasticity for visual processes mediated by the right temporal lobe.

Multiple meaning systems in the brain: A case for visual semantics

In this study we report our investigations of a category specific visual associative agnosia. The patient D.R.S.'s spoken language skills were excellent. Although he could name objects from their description, he was unable to name them by sight nor was he able to mime their use. On visual-visual matching tasks his performance was impaired and affected by semantic proximity. In two tasks his knowledge of visual objects was demonstrated to be significantly more impaired than his knowledge of visual living things. It is argued that these findings support a multiple knowledge base hypothesis.

Associative Visual Agnosia and Alexia Without Prosopagnosia

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.

Reply

Around 25% of patients with visual hallucinations secondary to eye disease report hallucinations of text. The hallucinated text conveys little if any meaning, typically consisting of individual letters, words, or nonsense letter strings (orthographic hallucinations). A patient is described with textual visual hallucinations of a very different linguistic content following bilateral occipito-temporal infarcts. The hallucinations consisted of grammatically correct, meaningful written sentences or phrases, often in the second person and with a threatening and command-like nature (syntacto-semantic visual hallucinations). A detailed phenomenological interview and visual psychophysical testing were undertaken. The patient showed a classical ventral occipito-temporal syndrome with achromatopsia, prosopagnosia, and associative visual agnosia. Of particular significance was the presence of pure alexia. Illusions of colour induced by monochromatic gratings and a novel motion–direction illusion were also observed, both consistent with the residual capacities of the patient’s spared visual cortex. The content of orthographic visual hallucinations matches the known specialisations of an area in the left posterior fusiform gyrus—the visual word form area (VWFA)—suggesting the two are related. The VWFA is unlikely to be responsible for the syntacto-semantic hallucinations described here as the patient had a pure alexic syndrome, a known consequence of VWFA lesions. Syntacto-semantic visual hallucinations may represent a separate category of textual hallucinations related to the cortical network implicated in the auditory hallucinations of schizophrenia.

A Spurious Category-Specific Visual Agnosia for Living Things in Normal Human and Nonhuman Primates

Abstract Patients with visual associative agnosia have a particular difficulty in identifying visually presented living things (plants and animals) as opposed to nonliving things. It has been claimed that this effect cannot be explained by differences in the inherent visual discriminability of living and nonliving things. To test this claim further, we performed two experiments with normal subjects. In Experiment 1 normal human observers were asked to identify objects in tachistoscopically presented line drawings. They made more errors with living things than with nonliving things. In Experiment 2 normal monkeys learned to discriminate among the same line drawings for food reward. They made many more errors in discriminating among living things than nonliving things. Agnosic patients' responses to the same line drawings were made available to us for correlative analysis with the subjects' responses to these drawings in Experiments 1 and 2. We conclude that a category-specific visual agnosia for living things can arise as a consequence of a modality-specific but not category-specific impairment in visual representation, since living things are more similar to each other visually than nonliving things are.

Preserved Visual Imagery and Categorization in a Case of Associative Visual Agnosia

A patient with associative visual agnosia secondary to a penetrating bitemporooccipital lesion remained able to draw complex objects from memory but could not subsequently recognize his sketches. His retained ability to copy and draw briefly exposed objects indicates that this is not a problem of visual perception. On tasks of categorization, mental imagery, drawing, and object decision, he demonstrates many instances of preserved visual semantic memories and imagery despite a sense of unfamiliarity with the visual stimuli. We infer a preserved ability to derive internal visual images from semantic memory. Cues may help him visualize the named object, which then serves as a model for comparison with the actual stimulus. However, his adequate visual perception and mental visual imagery, even when assisted by cues, are still insufficient to correct fully his difficulty in recognizing objects. Unique to his case is an inability to match the representation of stimulus objects with his intact internal image of the same object. Deficient lateral inhibition between neural representations of similar objects may be responsible.

Visual Associative Agnosia and Optic Aphasia. A Single Case Study and a Review of the Syndromes

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.

Visual Apperceptive Agnosia: A Clinico-Anatomical Study of Three Cases

The visuo-perceptual abilities of three cases with unilateral lesions of the right hemisphere selected on the basis of the co-occurrence of impaired performance on a test of visual object perception and normal performance on a test of shape discrimination are reported. Their performance was also impaired on other tests of visual object recognition in which the perceptual difficulty of the task was manipulated by obscuring the salient features of the representation. At the same time it was found that on a variety of other tests of visual-sensory processing their performance was entirely normal, as was their performance on tests of visual semantic knowledge, tests that were failed by a patient with a visual associative agnosia. It is argued that this syndrome has all the hallmarks of an apperceptive agnosia, a failure of perceptual categorisation in which the physical identity of the object is specified. The two discontinuities between visual-sensory processing, perceptual categorisation and visual-semantic processing are discussed in terms of a 2 categorical stage model of object recognition.

Analysis of Cognitive Functions in a Case with Associative Visual Agnosia

Analysis of Cognitive Functions in a Case with Associative Visual Agnosia

Cognitive stages in visual recognition: Visual agnosia

The clinical spectrum of visual agnosia includes a variety of cognitive deficits and the incidence and relationship of these remain problematic. The syndromes of apperceptive and associative visual agnosia overlap most often but the occasional well documented dissociation is of great interest. Experimental evidence concerning these entities is scant and at times controversial but suggests several levels of processing that may be impaired independently. In this article, I shall address myself to these syndromes and attempt to describe the cognitive stages in visual recognition with respect to their intact and defective state, so as to provide an explanation of how the visual system functions cognitively.

A Case of Visual Agnosia Showing a Disorder of Pre-Semantic Visual Classification

A case (J.R.) of associative visual agnosia (loss of meaning for visually presented objects without any serious sensory disorder) is reported. When asked to match a given name to sample the patient made both visual and semantic errors. Whereas semantic errors were reduced by priming, visual errors were intractable. It is argued that there is a disorder at the stage of pre-semantic Abstraction, similar to that postulated elsewhere for some cases of deep dyslexia, contributing to the agnosia.

Disconnexion visuo-verbale (aphasie optique) pour les objets les images, les couleurs et les visages avec alexie “abstractive”

The case is reported of a patient who, after a left occipital infarction, presented a deficit in naming visually presented objects with neither aphasia, nor perturbation in the perceptive and associative processing of visual informations. This visuo-verbal disconnection was accompanied by disturbance of the semantic function when this was explored via the visual channel. In addition the patient showed an alexia which could be described as an abstraction defect. Finally, the patient showed a deficit in naming colors and faces, without evidence for agnosia. This observation argues in favor of maintaining a distinction between visual associative agnosia and optic aphasia. It also demonstrates that the naming deficit implies a deficit in extracting semantic values from visual informations such as objects or graphic symbols.

両側‐後頭・側頭葉病変による視覚失認の１例

A patient, 54 year-old right-handed man, showed intra-cerebral hematoms in bilateral occipito-temporal areas after a fall to the ground. Besides a left upper quadrantic homonymous hemianopsia, he had associative visual agnosia, prosopagnosia, central achromatopsia, pure alexia and slight agraphia and acalculia. He matched and copied well pictures and letters which he could not recognize. After three years, object recognition and reading improved greatly, prosopagnosia and achromatopsia remained almost unchanged. He could not identify human faces, nor discriminate the kind or the individual of animals, birds, flowers and vegetables. The visual recognition process was compared between in the case of human faces, animals etc. and in that of common objects.