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  • 1
    Online Resource
    Online Resource
    Neural Substrates of Visuospatial Processing in Distinct Reference Frames: Evidence from Unilateral Spatial Neglect
    MIT Press ; 2009
    In:  Journal of Cognitive Neuroscience Vol. 21, No. 11 ( 2009-11-01), p. 2073-2084
    Details
    In: Journal of Cognitive Neuroscience, MIT Press, Vol. 21, No. 11 ( 2009-11-01), p. 2073-2084
    Abstract: There is evidence for different levels of visuospatial processing with their own frames of reference: viewer-centered, stimulus-centered, and object-centered. The neural locus of these levels can be explored by examining lesion location in subjects with unilateral spatial neglect (USN) manifest in these reference frames. Most studies regarding the neural locus of USN have treated it as a homogenous syndrome, resulting in conflicting results. In order to further explore the neural locus of visuospatial processes differentiated by frame of reference, we presented a battery of tests to 171 subjects within 48 hr after right supratentorial ischemic stroke before possible structural and/or functional reorganization. The battery included MR perfusion weighted imaging (which shows hypoperfused regions that may be dysfunctional), diffusion weighted imaging (which reveals areas of infarct or dense ischemia shortly after stroke onset), and tests designed to disambiguate between various types of neglect. Results were consistent with a dorsal/ventral stream distinction in egocentric/allocentric processing. We provide evidence that portions of the dorsal stream of visual processing, including the right supramarginal gyrus, are involved in spatial encoding in egocentric coordinates, whereas parts of the ventral stream (including the posterior inferior temporal gyrus) are involved in allocentric encoding.
    Type of Medium: Online Resource
    ISSN: 0898-929X , 1530-8898
    URL: Article
    DOI: 10.1162/jocn.2008.21160
    Language: English
    Publisher: MIT Press
    Publication Date: 2009
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  • 2
    Online Resource
    Online Resource
    Representation of Grammatical Categories of Words in the Brain
    MIT Press ; 1995
    In:  Journal of Cognitive Neuroscience Vol. 7, No. 3 ( 1995-07-01), p. 396-407
    Details
    In: Journal of Cognitive Neuroscience, MIT Press, Vol. 7, No. 3 ( 1995-07-01), p. 396-407
    Abstract: We report the performance of a patient who, as a consequence of left frontal and temporoparietal strokes, makes far more errors on nouns than on verbs in spoken output tasks, but makes far more errors on verbs than on nouns in written input tasks. This double dissociation within a single patient with respect to grammatical category provides evidence for the hypothesis that phonological and orthographic representations of nouns and verbs are processed by independent neural mechanisms. Furthermore, the opposite dissociation in the verbal output modality, an advantage for nouns over verbs in spoken tasks, by a different patient using the same stimuli has also been reported (Caramazza & Hillis, 1991). This double dissociation across patients on the same task indicates that results cannot be ascribed to "greater difficulty" with one type of stimulus, and provides further evidence for the view that grammatical category information is an important organizational principle of lexical knowledge in the brain.
    Type of Medium: Online Resource
    ISSN: 0898-929X , 1530-8898
    URL: Article
    DOI: 10.1162/jocn.1995.7.3.396
    Language: English
    Publisher: MIT Press
    Publication Date: 1995
    SSG: 5,2
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  • 3
    Online Resource
    Online Resource
    Cognitive Rehabilitation Interventions for Neglect and Related Disorders: Moving from Bench to Bedside in Stroke Patients
    MIT Press ; 2006
    In:  Journal of Cognitive Neuroscience Vol. 18, No. 7 ( 2006-07-01), p. 1223-1236
    Details
    In: Journal of Cognitive Neuroscience, MIT Press, Vol. 18, No. 7 ( 2006-07-01), p. 1223-1236
    Abstract: The spatial neglect syndrome, defined by asymmetric attention and action not attributed to primary motor or sensory dysfunction and accompanied by functional disability, is a major cause of post-stroke morbidity. In this review, we consider the challenges and obstacles facing scientific researches wishing to evaluate the mechanisms and effectiveness of rehabilitation interventions. Spatial neglect is a heterogeneous disorder, for which consensus research definitions are not currently available, and it is unclear which of the deficits associated with the syndrome causes subsequent disability. We review current opinion about methods of assessment, suggest a rational approach to selecting therapies which requires further study, and make systems-level and theoretical recommendations for building theory. We lastly review some creative questions for consideration in future research.
    Type of Medium: Online Resource
    ISSN: 0898-929X , 1530-8898
    URL: Article
    DOI: 10.1162/jocn.2006.18.7.1223
    Language: English
    Publisher: MIT Press
    Publication Date: 2006
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  • 4
    Online Resource
    Online Resource
    Corticocerebellar White Matter Integrity Is Related to Naming Outcome in Post-Stroke Aphasia
    MIT Press ; 2023
    In:  Neurobiology of Language Vol. 4, No. 3 ( 2023-07-20), p. 404-419
    Details
    In: Neurobiology of Language, MIT Press, Vol. 4, No. 3 ( 2023-07-20), p. 404-419
    Abstract: Studies have shown that the integrity of white matter tracts connecting different regions in the left cerebral hemisphere is important for aphasia recovery after stroke. However, the impact of the underlying structural connection between the cortex and the cerebellum in post-stroke aphasia is poorly understood. We studied the microstructural integrity of the cerebellum and the corticocerebellar connections and their role in picture naming. Fifty-six patients with left cerebral infarcts (sparing the cerebellum) underwent diffusion tensor imaging (DTI) and Boston Naming Test. We compared the fractional anisotropy (FA) and mean diffusivity (MD) values of the right and the left cerebellum (lobular gray and white matter structures) and cerebellocortical connections. Recursive feature elimination and Spearman correlation analyses were performed to evaluate the relationship between naming performance and the corticocerebellar connections. We found that the right, relative to left, cerebellar structures and their connections with the left cerebrum showed lower FA and higher MD values, both reflecting lower microstructural integrity. This trend was not observed in the healthy controls. Higher MD values of the right major cerebellar outflow tract were associated with poorer picture naming performance. Our study provides the first DTI data demonstrating the critical importance of ascending and descending corticocerebellar connections for naming outcomes after stroke.
    Type of Medium: Online Resource
    ISSN: 2641-4368
    URL: Article
    DOI: 10.1162/nol_a_00107
    Language: English
    Publisher: MIT Press
    Publication Date: 2023
    detail.hit.zdb_id: 3011523-1
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  • 5
    Online Resource
    Online Resource
    Neural Correlates of Modality-specific Spatial Extinction
    MIT Press ; 2006
    In:  Journal of Cognitive Neuroscience Vol. 18, No. 11 ( 2006-11-01), p. 1889-1898
    Details
    In: Journal of Cognitive Neuroscience, MIT Press, Vol. 18, No. 11 ( 2006-11-01), p. 1889-1898
    Abstract: Sites of lesions responsible for visual, tactile, and/or motor extinction have not been clearly identified. We sought to determine the frequency of extinction in various modalities immediately after acute ischemic stroke, the rate of co-occurrence of extinction across modalities, and areas of infarct and/or hypoperfusion associated with each modality of extinction. A total of 148 patients with right supratentorial stroke were studied. In Study 1, 88 patients without hemiplegia, hemianesthesia, or visual field cuts were tested within 24 hours of onset for visual, tactile, and motor extinction, and underwent magnetic resonance diffusion and perfusion imaging. Associations between modality of extinction and areas of neural dysfunction (hypoperfusion/infarct) were identified. Of the 88 patients, 19 had only tactile extinction, 8 had only visual extinction, 12 had only motor extinction, 14 had extinction in two or more modalities, and 35 had no extinction. Tactile extinction was associated with neural dysfunction in the inferior parietal lobule; visual extinction was associated with dysfunction in the visual association cortex; and motor extinction was associated with neural dysfunction in the superior temporal gyrus. In Study 2, data from 60 patients who were excluded from Study 1 because of motor deficits were analyzed in the same way to determine whether frontal lesions contributed to visual or tactile extinction. Results again demonstrated that tactile extinction is associated with inferior parietal dysfunction, and visual extinction is associated with dysfunction of the visual association cortex. Potential accounts of the results, based on the “hemisphere rivalry” model of extinction and the limited attentional capacity model, are considered.
    Type of Medium: Online Resource
    ISSN: 0898-929X , 1530-8898
    URL: Article
    DOI: 10.1162/jocn.2006.18.11.1889
    Language: English
    Publisher: MIT Press
    Publication Date: 2006
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  • 6
    Online Resource
    Online Resource
    Modality-Specific Deterioration in Naming Verbs in Nonfluent Primary Progressive Aphasia
    MIT Press ; 2002
    In:  Journal of Cognitive Neuroscience Vol. 14, No. 7 ( 2002-10-01), p. 1099-1108
    Details
    In: Journal of Cognitive Neuroscience, MIT Press, Vol. 14, No. 7 ( 2002-10-01), p. 1099-1108
    Abstract: A longitudinal study of oral and written naming and comprehension of nouns and verbs in an individual (M. M. L.) with nonfluent primary progressive aphasia (PPA) is reported. M. M. L. showed progressive deterioration of oral naming of verbs well before deterioration of written naming of verbs and before deterioration of oral or written naming of nouns. Her comprehension of both nouns and verbs remained intact, at least relative to oral naming of verbs. Her performance is compared to that of two other individuals with nonfluent PPA, who were tested at two time points. These patients showed similar patterns with respect to grammatical word class (verbs more impaired than nouns) and modality (spoken production more impaired than written production), but somewhat different courses of deterioration. The modality-specific nature of the observed verb production deficits rules out a semantic locus for the grammatical class effects. The results provide a new source of evidence for the hypothesis that there are distinct neural mechanisms for accessing lexical representations of nouns and verbs in language production.
    Type of Medium: Online Resource
    ISSN: 0898-929X , 1530-8898
    URL: Article
    DOI: 10.1162/089892902320474544
    Language: English
    Publisher: MIT Press
    Publication Date: 2002
    SSG: 5,2
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  • 7
    Online Resource
    Online Resource
    Cognitive and Neural Mechanisms Underlying Visual and Semantic Processing: Implications from “Optic Aphasia”
    MIT Press ; 1995
    In:  Journal of Cognitive Neuroscience Vol. 7, No. 4 ( 1995-10-01), p. 457-478
    Details
    In: Journal of Cognitive Neuroscience, MIT Press, Vol. 7, No. 4 ( 1995-10-01), p. 457-478
    Abstract: We report detailed analyses of the performance of a patient, DHY, who as a consequence of strokes in the left occipital lobe and the periventricular white matter in the region of the spleniuni, showed severely impaired naming of visual stimuli despite spared recognition of visual stimuli and spared naming in other modalities. This pattern of performance—labeled “optic aphasia”—has been previously interpreted as support for the hypothesis that there are independent semantic systems, either a visual and a verbal semantic store (Beauvois, 1982; Lhermitte & Beauvois, 1973) or a right hemisphere and a left hemisphere semantic system (Coslett & Saffran, 1989, l092), which are “disconnected” in these patients. We provide evidence that DHY shows precisely the types of performance across a variety of verbal and visual tasks that have been used to support these claims of separate semantic systems: (1) good performance in naming to definition and naming objects presented for tactile exploration (which has been interpreted as evidence of spared verbal or left hemisphere semantic processing), and (2) good performance on various “semantic” tasks that do not require naming (which has been interpreted as access to spared visual or right hemisphere semantic processing). Nevertheless, when nonverbal semantic tasks were modified such that they required access to more detailed semantic information for accurate performance, DHY was Par less accurate, indicating that she did not access complete semantic information about objects in the visual modality. We argue that these data undermine the claim that cases of optic aphasia can be explained only by proposing multiple semantic systems. We propose an alternative account for this pattern of performance, within a model of visual object naming that specifies a single, modality-independent semantic system. We show that the performance of DHY and other “optic aphasic” patients can be explained by proposing a deficit in accessing a complete, modality-independent, lexical-semantic representation from an intact stored, structural description of the object. We discuss the implications of these conclusions for claims about the neuroanatomical correlates of semantic and visual object processing.
    Type of Medium: Online Resource
    ISSN: 0898-929X , 1530-8898
    URL: Article
    DOI: 10.1162/jocn.1995.7.4.457
    Language: English
    Publisher: MIT Press
    Publication Date: 1995
    SSG: 5,2
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  • 8
    Online Resource
    Online Resource
    Independent contributions of structural and functional connectivity: Evidence from a stroke model
    MIT Press ; 2021
    In:  Network Neuroscience Vol. 5, No. 4 ( 2021-11-30), p. 911-928
    Details
    In: Network Neuroscience, MIT Press, Vol. 5, No. 4 ( 2021-11-30), p. 911-928
    Abstract: Altered functional connectivity is related to severity of language impairment in poststroke aphasia. However, it is not clear whether this finding specifically reflects loss of functional coherence, or more generally, is related to decreased structural connectivity due to cortical necrosis. The aim of the current study was to investigate this issue by factoring out structural connectivity from functional connectivity measures and then relating the residual data to language performance poststroke. Ninety-seven participants with a history of stroke were assessed using language impairment measures (Auditory Verbal Comprehension and Spontaneous Speech scores from the Western Aphasia Battery–Revised) and MRI (structural, diffusion tensor imaging, and resting-state functional connectivity). We analyzed the association between functional connectivity and language and controlled for multiple potential neuroanatomical confounders, namely structural connectivity. We identified functional connections within the left hemisphere ventral stream where decreased functional connectivity, independent of structural connectivity, was associated with speech comprehension impairment. These connections exist in frontotemporal and temporoparietal regions. Our results suggest poor speech comprehension in aphasia is at least partially caused by loss of cortical synchrony in a left hemisphere ventral stream network and is not only reflective of localized necrosis or structural connectivity.
    Type of Medium: Online Resource
    ISSN: 2472-1751
    URL: Article
    DOI: 10.1162/netn_a_00207
    Language: English
    Publisher: MIT Press
    Publication Date: 2021
    detail.hit.zdb_id: 2900481-0
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