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1.
Neuropsychologia ; 161: 108017, 2021 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-34487736

RESUMO

Object and scene recognition both require mapping of incoming sensory information to existing conceptual knowledge about the world. A notable finding in brain-damaged patients is that they may show differentially impaired performance for specific categories, such as for "living exemplars". While numerous patients with category-specific impairments have been reported, the explanations for these deficits remain controversial. In the current study, we investigate the ability of a brain injured patient with a well-established category-specific impairment of semantic memory to perform two categorization experiments: 'natural' vs. 'manmade' scenes (experiment 1) and objects (experiment 2). Our findings show that the pattern of categorical impairment does not respect the natural versus manmade distinction. This suggests that the impairments may be better explained by differences in visual features, rather than by category membership. Using Deep Convolutional Neural Networks (DCNNs) as 'artificial animal models' we further explored this idea. Results indicated that DCNNs with 'lesions' in higher order layers showed similar response patterns, with decreased relative performance for manmade scenes (experiment 1) and natural objects (experiment 2), even though they have no semantic category knowledge, apart from a mapping between pictures and labels. Collectively, these results suggest that the direction of category-effects to a large extent depends, at least in MS' case, on the degree of perceptual differentiation called for, and not semantic knowledge.


Assuntos
Agnosia , Lesões Encefálicas , Animais , Encéfalo , Humanos , Conhecimento , Reconhecimento Visual de Modelos , Semântica
2.
Neurol India ; 69(4): 931-936, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34507415

RESUMO

Background: Reflected image processing is a unique brain function and its abnormalities result in problems of localizing, recognizing the images, and utilizing this information in everyday life. Objectives: The aim of this study was to characterize clinical and neuropsychological profiles and to identify the probable neural substrate for this phenomenon in major cognitive disorder. Materials and Methods: We conducted a prospective study from February 2015 to May 2017 in patients with Major Cognitive Disorder (MCD, DSM-5 criteria). All patients were tested for problems in reflected image processing using the detailed protocol after ethical approval of the institute and consent. They also underwent a detailed neuropsychological evaluation, biochemical tests and neuroimaging (structural, diffusion, and resting-state functional MRI) as per established protocol. Results: Of the 18 patients, 11 had mirror agnosia (MA), 5 had mirror image agnosia (MIA) and 2 had both. MRI of MA patients showed parietal atrophy and whereas diffuse pattern of atrophy was seen with MIA. In the MA group, the left superior longitudinal fasciculus showed significantly greater fractional anisotropy and the left angular gyrus showed increased functional connectivity with left anterior cingulate, left dorsolateral prefrontal and bilateral posterior cingulate regions. Conclusion: Mirror image processing defects were not related to the type of MCD, severity or pattern of neuropsychological dysfunction. There are structural and functional alterations in localized regions as well as both hemispheres. Therefore, it is more likely to be a network disorder, irrespective of the MCD type or severity.


Assuntos
Agnosia , Substância Branca , Agnosia/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética , Testes Neuropsicológicos , Estudos Prospectivos
3.
Curr Neurol Neurosci Rep ; 21(10): 54, 2021 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-34586544

RESUMO

PURPOSE OF REVIEW: Historical and contemporary treatments of visual agnosia and neglect regard these disorders as largely unrelated. It is thought that damage to different neural processes leads directly to one or the other condition, yet apperceptive variants of agnosia and object-centered variants of neglect share remarkably similar deficits in the quality of conscious experience. Here we argue for a closer association between "apperceptive" variants of visual agnosia and "object-centered" variants of visual neglect. We introduce a theoretical framework for understanding these conditions based on "scale attention", which refers to selecting boundary and surface information at different levels of the structural hierarchy in the visual array. RECENT FINDINGS: We review work on visual agnosia, the cortical structures and cortico-cortical pathways that underlie visual perception, visuospatial neglect and object-centered neglect, and attention to scale. We highlight direct and indirect pathways involved in these disorders and in attention to scale. The direct pathway involves the posterior vertical segments of the superior longitudinal fasciculus that are positioned to link the established dorsal and ventral attentional centers in the parietal cortex with structures in the inferior occipitotemporal cortex associated with visual apperceptive agnosia. The connections in the right hemisphere appear to be more important for visual conscious experience, whereas those in the left hemisphere appear to be more strongly associated with the planning and execution of visually guided grasps directed at multi-part objects such as tools. In the latter case, semantic and functional information must drive the selection of the appropriate hand posture and grasp points on the object. This view is supported by studies of grasping in patients with agnosia and in patients with neglect that show that the selection of grasp points when picking up a tool involves both scale attention and semantic contributions from inferotemporal cortex. The indirect pathways, which include the inferior fronto-occipital and horizontal components of the superior longitudinal fasciculi, involve the frontal lobe, working memory and the "multiple demands" network, which can shape the content of visual awareness through the maintenance of goal- and task-based abstractions and their influence on scale attention. Recent studies of human cortico-cortical pathways necessitate revisions to long-standing theoretical views on visual perception, visually guided action and their integrations. We highlight findings from a broad sample of seemingly disparate areas of research to support the proposal that attention to scale is necessary for typical conscious visual experience and for goal-directed actions that depend on functional and semantic information. Furthermore, we suggest that vertical pathways between the parietal and occipitotemporal cortex, along with indirect pathways that involve the premotor and prefrontal cortex, facilitate the operations of scale attention.


Assuntos
Agnosia , Transtornos da Percepção , Humanos , Vias Visuais , Percepção Visual
4.
Conscious Cogn ; 94: 103180, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34392025

RESUMO

Since the description of anosognosia for hemiplegia by Babinski (who also stressed the links between anosognosia and right hemisphere damage) both motivational and cognitive mechanisms have been advanced to explain this awareness disorder. In this review I will discuss first the neurophysiological mechanisms that can impede the discovery of the motor deficits contralateral to the brain lesion and then suggest that some instances of anosognosia for left-sided hemiplegia may also be due to motivational mechanisms of denial. Among the cognitive mechanisms, sensory feedback and intentional feed-forward disorders can lead to a poor awareness of the motor defects, whereas denial mechanisms could result from an interaction between the right hemisphere dominance for emotions and the anxiety raised by the catastrophic consequences of the brain damage. In particular, a maladaptive reaction to the personal implications of the brain lesion could be revealed by the presence of an implicit acknowledgement of the motor defect.


Assuntos
Agnosia , Hemiplegia , Conscientização , Emoções , Humanos , Motivação
5.
Cortex ; 143: 281, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34376282
6.
J Alzheimers Dis ; 83(1): 111-126, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34250942

RESUMO

BACKGROUND: Anosognosia, or unawareness of memory deficits, is a common manifestation of Alzheimer's disease (AD), but greatly variable in subjective cognitive decline (SCD) and amnestic mild cognitive impairment (aMCI) subjects. Self-referential network (SRN) is responsible for self-referential processing and considered to be related to AD progression. OBJECTIVE: Our aim is to explore connectivity changes of SRN and its interaction with memory-related network and primary sensorimotor network (SMN) in the AD spectrum. METHODS: About 444 Alzheimer's Disease Neuroimaging Initiative subjects (86 cognitively normal [CN]; 156 SCD; 146 aMCI; 56 AD) were enrolled in our study. The independent component analysis (ICA) method was used to extract the SRN, SMN, and memory-related network from all subjects. The alteration of functional connectivity (FC) within SRN and its connectivity with memory-related network/SMN were compared among four groups and further correlation analysis between altered FC and memory awareness index as well as episodic memory score were performed. RESULTS: Compared with CN group, individuals with SCD exhibited hyperconnectivity within SRN, while aMCI and AD patients showed hypoconnectivity. Furthermore, aMCI patients and AD patients both showed the interruption of the FC between the SRN and memory-related network compared to CN group. Pearson correlation analysis showed that disruptive FC within SRN and its interaction with memory-related network were related to memory awareness index and episodic memory scores. CONCLUSION: In conclusion, impaired memory awareness and episodic memory in the AD spectrum are correlated to the disconnection within SRN and its interaction with memory-related network.


Assuntos
Agnosia , Doença de Alzheimer/psicologia , Conscientização , Disfunção Cognitiva/psicologia , Transtornos da Memória/fisiopatologia , Rede Nervosa/fisiopatologia , Idoso , Amnésia/psicologia , Encéfalo/fisiopatologia , Feminino , Humanos , Masculino , Memória Episódica
7.
Artigo em Inglês | MEDLINE | ID: mdl-34299988

RESUMO

More research is needed to better understand the impact of occupational therapy (OT) in stroke patients and syndromes of unilateral neglect (UN) and anosognosia. A prospective, observational, longitudinal design was conducted on a sample of 27 OT patients. The objectives were to examine: (1) the presence of UN and anosognosia; (2) the functional outcomes; and (3) the association of UN at baseline with functional status at discharge from OT. The outcomes were Barthel (functional independence) and the Rivermead Mobility Index (RMI). The baseline proportion of participants with UN was 33% according to the Star Cancellation Test (STC), and 48.1% according to the Catherine Bergego Scale (CBS) therapist-version. There was a significant difference between the therapist and participant-rated CBS scores (p = 0.004). Functional independence improved significantly between the initial and final assessments (p < 0.001); the effect size (r) was large (r = 0.61). There was a significant improvement in RMI scores (p < 0.001), which was large in size (r = 0.59). Both the STC and CBS-therapist scores were significantly correlated with the Barthel (p < 0.001, p = 0.005, respectively) and with the RMI (p = 0.004, p = 0.028, respectively). The participants substantially enhanced their functional status skills. UN and anosognosia were common problems, and neglect was associated with worse OT program outcomes.


Assuntos
Agnosia , Terapia Ocupacional , Transtornos da Percepção , Reabilitação do Acidente Vascular Cerebral , Acidente Vascular Cerebral , Atividades Cotidianas , Humanos , Testes Neuropsicológicos , Transtornos da Percepção/epidemiologia , Transtornos da Percepção/etiologia , Estudos Prospectivos
8.
Arq Neuropsiquiatr ; 79(4): 334-342, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-34133514

RESUMO

BACKGROUND: Anosognosia, i.e. lack of awareness of one's own symptoms, is a very common finding in patients with dementia and is related to neuropsychiatric symptoms and worse prognosis. Although dementia with Lewy bodies (DLB) is the second most common form of degenerative dementia, literature on anosognosia in this disease is scarce. OBJECTIVES: This paper aimed to review the current evidence on anosognosia in patients with DLB, including its prevalence in comparison with other neurological conditions, its severity and anatomical correlations. METHODS: Database searches were performed in PubMed, Web of Knowledge and PsycINFO for articles assessing anosognosia in DLB. A total of 243 studies were retrieved, but only six were included in the review. RESULTS: Potential risk of selection, comparison or outcome biases were detected in relation to all the studies selected. Most of the studies used self-report memory questionnaires to assess cognitive complaints and compared their results to scores from informant-based instruments or to participants' cognitive performance in neuropsychological tasks. Subjects with DLB had worse awareness regarding memory than healthy older controls, but the results concerning differences in anosognosia between DLB and Alzheimer's disease (AD) patients were inconsistent across studies. Presence of AD pathology and neuroimaging biomarkers appeared to increase the prevalence of anosognosia in individuals with DLB. CONCLUSION: Anosognosia is a common manifestation of DLB, but it is not clear how its prevalence and severity compare with AD. Co-existence of AD pathology seems to play a role in memory deficit awareness in DLB.


Assuntos
Agnosia , Doença de Alzheimer , Doença por Corpos de Lewy , Biomarcadores , Humanos , Neuroimagem , Testes Neuropsicológicos
9.
Am J Phys Med Rehabil ; 100(11): e172-e174, 2021 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-34001836

RESUMO

ABSTRACT: Acquired focal visuoperceptual deficits are rarely reported, and rehabilitation strategies are not well established. This is a report on visuoperceptual deficit after traumatic brain injury that initially went unnoticed. Missing visual agnosia is not unusual especially when perceptual deficits present with visual field defects, impaired insight, and inattention. This case is made more interesting because of the rarity of visual agnosia with predominant ventral pathway involvement, affecting object and face recognition. This report provides a brief discussion on visual agnosia spectrum deficits and rehabilitation measures.


Assuntos
Agnosia/reabilitação , Lesão Encefálica Crônica/reabilitação , Reabilitação Neurológica , Percepção Visual , Adolescente , Agnosia/etiologia , Lesão Encefálica Crônica/complicações , Feminino , Humanos , Ilustração Médica , Testes Neuropsicológicos
10.
Neuropsychology ; 35(6): 668, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33983762

RESUMO

Reports an error in "Anosognosia for prospective and retrospective memory deficits: Assessment and theoretical considerations" by Silvia Chapman, Nicoletta Beschin, Stephanie Cosentino, Mitchell S. V. Elkind, Sergio Della Sala and Gianna Cocchini (Neuropsychology, 2019[Oct], Vol 33[7], 1020-1031). In the article (http://dx.doi.org/10.1037/neu0000568), the racial and ethnic description of the participants was missing. The following text has been added to the first paragraph under the "Participants" heading in the "Method" section: "The racial and ethnic distribution of the participants was 76.5% (n = 39) White, 13.7% (n = 7) Black, 5.9% (n = 3) Hispanic, and 3.9% (n = 2) Asian." The online version of this article has been corrected. (The following abstract of the original article appeared in record 2019-33671-001.) Objective: Patients who suffer from memory loss after an Acquired Brain Injury (ABI) may also suffer from anosognosia, or unawareness of their memory loss. How we define and measure anosognosia can have critical implications for its study and clinical assessment. Commonly used measures often lack standardization and reliability checks for responses. Moreover, these methods rely heavily on cognitive abilities (e.g., language abilities) that are often affected after brain injury. The aim of this study is to elucidate how to best conceptualize and detect anosognosia for memory loss by introducing a new method of assessment, the Visual-Analogue Test for Anosognosia for memory impairment (VATAmem). Method: A total of 51 patients (M = 61 years, M = 13 years of education) with memory difficulties after ABI were recruited from outpatient clinics. A total of 73 informants were also recruited (M = 51 years old, M = 13 years of education). Both patients and informants evaluated the severity of patients' everyday memory mistakes on the VATAmem, for prospective and retrospective memory deficits by using visual analogue scales, vignettes, and check questions to ensure reliability. Results and Conclusion: A total of 30% of the patients were deemed unaware of their memory deficits. Patients were less aware of their prospective (29%) than their retrospective memory difficulties (18%). The new method of assessment provided by the VATAmem reduced possible false positives and enhanced reliability. We conclude that careful consideration of methodology is a key step to interpreting anosognosia findings within a theoretical framework. (PsycInfo Database Record (c) 2021 APA, all rights reserved).


Assuntos
Agnosia , Agnosia/diagnóstico , Agnosia/etiologia , Humanos , Transtornos da Memória/diagnóstico , Transtornos da Memória/etiologia , Pessoa de Meia-Idade , Testes Neuropsicológicos , Estudos Prospectivos , Reprodutibilidade dos Testes , Estudos Retrospectivos
13.
J Alzheimers Dis ; 82(2): 493-502, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34057092

RESUMO

BACKGROUND: D. Frank Benson and colleagues first described the clinical and neuropathological features of posterior cortical atrophy (PCA) from patients in the UCLA Neurobehavior Program. OBJECTIVE: We reviewed the Program's subsequent clinical experience with PCA, and its potential for clarifying this relatively rare syndrome in comparison to the accumulated literature on PCA. METHODS: Using the original criteria derived from this clinic, 65 patients with neuroimaging-supported PCA were diagnosed between 1995 and 2020. RESULTS: On presentation, most had visual localization complaints and related visuospatial symptoms, but nearly half had memory complaints followed by symptoms of depression. Neurobehavioral testing showed predominant difficulty with visuospatial constructions, Gerstmann's syndrome, and Balint's syndrome, but also impaired memory and naming. On retrospective application of the current Consensus Criteria for PCA, 59 (91%) met PCA criteria with a modification allowing for "significantly greater visuospatial over memory and naming deficits." There were 37 deaths (56.9%) with the median overall survival of 10.3 years (95% CI: 9.6-13.6 years), consistent with a slow neurodegenerative disorder in most patients. CONCLUSION: Together, these findings recommend modifying the PCA criteria for "relatively spared" memory, language, and behavior to include secondary memory and naming difficulty and depression, with increased emphasis on the presence of Gerstmann's and Balint's syndromes.


Assuntos
Agnosia , Doença de Alzheimer/diagnóstico , Síndrome de Gerstmann/diagnóstico , Lobo Occipital , Lobo Parietal , Agnosia/diagnóstico , Agnosia/metabolismo , Agnosia/psicologia , Atrofia , Biomarcadores/líquido cefalorraquidiano , Diagnóstico Diferencial , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neuroimagem/métodos , Testes Neuropsicológicos , Lobo Occipital/diagnóstico por imagem , Lobo Occipital/patologia , Lobo Parietal/diagnóstico por imagem , Lobo Parietal/patologia
15.
Nutrients ; 13(4)2021 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-33919840

RESUMO

The novel severe acute respiratory syndrome coronavirus (COVID-19) has hit older adults harder due to a combination of age-related immunological and metabolic alterations. The aim of this review was to analyze the COVID-19 literature with respect to nutritional status and nutrition management in older adults. No studies only on people aged 65+ years were found, and documentation on those 80+ was rare. Age was found to be strongly associated with worse outcomes, and with poor nutritional status. Prevalence of malnutrition was high among severely and critically ill patients. The studies found a need for nutrition screening and management, and for nutrition support as part of follow-up after a hospital stay. Most tested screening tools showed high sensitivity in identifying nutritional risk, but none were recognized as best for screening older adults with COVID-19. For diagnosing malnutrition, the Global Leadership Initiative on Malnutrition (GLIM) criteria are recommended but were not used in the studies found. Documentation of olfactory and gustatory dysfunction in relation to nutritional status is missing in older adults. Other COVID-19-associated factors with a possible impact on nutritional status are poor appetite and gastrointestinal symptoms. Vitamin D is the nutrient that has attracted the most interest. However, evidence for supplementation of COVID-19 patients is still limited and inconclusive.


Assuntos
Envelhecimento , COVID-19/epidemiologia , Avaliação Nutricional , Terapia Nutricional/métodos , Estado Nutricional , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Agnosia/epidemiologia , COVID-19/terapia , Síndrome da Liberação de Citocina/epidemiologia , Feminino , Gastroenteropatias/epidemiologia , Hospitalização , Humanos , Masculino , Desnutrição/epidemiologia , Pessoa de Meia-Idade , Transtornos do Olfato/epidemiologia , Prevalência , Fatores de Risco , SARS-CoV-2 , Sarcopenia/epidemiologia , Vitamina D/uso terapêutico
16.
Int J Mol Sci ; 22(8)2021 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-33924222

RESUMO

Deficits in olfaction and taste are among the most frequent non-motor manifestations in Parkinson's disease (PD) that start very early and frequently precede the PD motor symptoms. The limited data available suggest that the basis of the olfactory and gustatory dysfunction related to PD are likely multifactorial and may include the same determinants responsible for other non-motor symptoms of PD. This review describes the most relevant molecular and genetic factors involved in the PD-related smell and taste impairments, and their associations with the microbiota, which also may represent risk factors associated with the disease.


Assuntos
Agnosia/etiologia , Suscetibilidade a Doenças , Microbiota , Percepção Olfatória , Doença de Parkinson/complicações , Percepção Gustatória , Agnosia/diagnóstico , Biomarcadores , Predisposição Genética para Doença , Variação Genética , Humanos , Modelos Biológicos
17.
Handb Clin Neurol ; 178: 155-173, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33832675

RESUMO

The term visual agnosia is used to refer to recognition disorders that are confined to the visual modality, that are not due to an impairment in sensory functions, and that cannot be explained by other cognitive deficits or by general reduction in intellectual ability. Here, we describe the different types of visual agnosia that have been reported (form agnosia, integrative agnosia, associative agnosia, transformational and orientation agnosia as well as category-specific impairments such as pure alexia and prosopagnosia) and how they relate to the current understanding of visual object recognition. Together with related disorders such as simultanagnosia, texture agnosia, aphantasia, and optic aphasia, these visual perceptual impairments can have severe consequences for those affected. We suggest how in-depth assessment can be carried out to determine the type and the extent of these impairments. In the context of clinical assessment, a step-by-step approach reflecting a posterior to anterior gradient in visual object recognition, from more perceptual to more memory-related processes, is suggested. Individually tailored interventions targeting the identified impairments can be initiated based on the results of the assessment.


Assuntos
Agnosia , Transtornos Cognitivos , Humanos , Testes Neuropsicológicos , Orientação , Percepção Visual
18.
Rinsho Shinkeigaku ; 61(5): 288-296, 2021 May 19.
Artigo em Japonês | MEDLINE | ID: mdl-33867413

RESUMO

A 71-year-old, right-handed woman was admitted to our hospital due to a sudden difficulty with conversation. On admission, she was alert, but had a euphoric mood, disorientation, and a disturbance of recent memory. Her speech was fluent. Her repetition and auditory word cognition were excellent, but she had a slight difficulty with naming visual objects. She frequently showed word-finding difficulty and irrelevant paraphasia during free conversation and a word fluency task. Her irrelevant paraphasia was observed more frequently when she was asked to explain her outbreak of anger at the hospital, i.e., it was situation-dependent. She also had anosognosia. MRI showed an infarct in the territory of the left tuberothalamic artery. Single-photon emission computed tomography revealed low-uptake lesions in the left thalamus and orbital frontal, medial frontal, and medial temporal lobes. The patient was diagnosed with non-aphasic misnaming. The clinical characteristics of patients with non-aphasic misnaming in the literature were reviewed. All of the patients with non-aphasic misnaming had word-finding difficulty and irrelevant paraphasia. Additionally, they had either emotional disturbance or anosognosia.


Assuntos
Transtornos da Linguagem/diagnóstico , Idoso , Agnosia/complicações , Agnosia/diagnóstico , Córtex Cerebral/diagnóstico por imagem , Infarto Cerebral/complicações , Infarto Cerebral/diagnóstico , Confusão/complicações , Confusão/diagnóstico , Feminino , Humanos , Transtornos da Linguagem/complicações , Transtornos da Linguagem/fisiopatologia , Imageamento por Ressonância Magnética , Transtornos da Memória/complicações , Transtornos da Memória/diagnóstico , Transtornos do Humor/complicações , Transtornos do Humor/diagnóstico , Tálamo/diagnóstico por imagem , Tomografia Computadorizada de Emissão de Fóton Único
19.
Neurocase ; 27(2): 190-195, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33851569

RESUMO

A 57-year-old man presented with a bilateral posterior cerebral artery attack and was visually impaired. He had a hard time identifying familiar faces and shades. He also felt that the familiar building looked different, and complained that it was not possible to tell from visual information alone whether the food was cooked or the kimono fabric was soft.We assessed the patient's visual function using real materials and material images and was diagnosed with visual texture agnosia. There are few reports of visual texture agnosia, detailed evaluation is considered important because perceiving texture is important for activities of daily living.


Assuntos
Agnosia , Infarto da Artéria Cerebral Posterior , Atividades Cotidianas , Agnosia/etiologia , Humanos , Masculino , Pessoa de Meia-Idade
20.
Neuropsychologia ; 155: 107820, 2021 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-33676958

RESUMO

Pure alexia and prosopagnosia traditionally have been seen as prime examples of dissociated, category-specific agnosias affecting reading and face recognition, respectively. More recent accounts have moved towards domain-independent explanations that postulate potential cross-links between different types of visual agnosia. According to one proposal, abnormal crowding, i.e. the impairment of recognition when features of adjacent objects are positioned too closely to each other, might provide a unified account for the perceptual deficits experienced by an agnosic patient. An alternative approach is based on the notion of complementary visual subsystems favouring the processing of abstract categories and specific exemplars, respectively. To test predictions of these two approaches with regard to pure alexia and prosopagnosia, we present previously unpublished data on digit recognition and visual crowding from two in the neuropsychological literature extensively studied patients, KD and MT (e.g., Campbell et al., 1986; Landis and Regard, 1988; Rentschler et al., 1994). Patient MT, diagnosed with pure alexia, showed pronounced abnormal foveal crowding, whereas KD, diagnosed with prosopagnosia, did not. These results form a distinct double dissociation with the performance of the two patients in other perceptual classification tasks involving Gabor micropatterns and textures, as well as Glass patterns, which revealed a significantly greater impairment in KD relative to MT. Based on an analysis of the specific task demands we argue that prosopagnosia and pure alexia may involve complementary deficits in instantiation and abstraction, respectively, during perceptual classification, beyond any category specificity. Such an explanation appears in line with previous distinctions between a predominantly left-hemispheric, abstract-category and a predominantly right-hemispheric, specific-exemplar subsystem underlying object recognition.


Assuntos
Agnosia , Alexia Pura , Prosopagnosia , Alexia Pura/diagnóstico por imagem , Humanos , Reconhecimento Visual de Modelos , Reconhecimento Psicológico , Percepção Visual
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