Visual agnosia contrasted with visual-verbal disconnection

Larrabee, Glenn J.; Levin, Harvey S.; Huff, F. Jacob; Kay, Marilyn; Guinto, Faustino C.

doi:10.1016/0028-3932(85)90039-9

Cited by 62 publications

(10 citation statements)

References 18 publications

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“…One possible contribution to this difference is that the definition of visual similarity may be more stringent for objects than for words. However, with presumab1,y the same criteria for visual similarity, some other visual agnosics make a high proportion of visual errors in naming objects (e.g., 46% for FZ; Levine, 1978; also see Larrabee, Levin, Huff, Kay, & Guinto, 1985). Thus, the rarity of visual errors by optic aphasics cannot be completely explained by a criterion difference.…”

Section: Dyslexiamentioning

confidence: 97%

“…Turning to gesturing tasks, in fact adequate gesturing to misnamed objects has been demonstrated in only three cases (Gil et al, 1985;Lhermitte & Beauvois, 1973; Riddoch & Humphreys, 1 9 8 7 t i n two others (Coslett & Saffran, 1989;Larrabee et al, 1985) gestures incorrectly corresponded to the named object, and in an additional two cases (Assal & Regli, 1980;PeAa-Casanova & RoigRovira, 1985), gesturing and naming visual stimuli were equally impaired. To explain relatively preserved gesturing, Riddoch and Hurnphreys (1987) point out that gesturing is often judged less stringently than naming, and typically requires less precise semantics.…”

Section: Individual Casesmentioning

confidence: 99%

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Perseverative and Semantic Influences on Visual Object Naming Errors in Optic Aphasia: A Connectionist Account

Plaut

Shallice²

1993

Journal of Cognitive Neuroscience

145

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Although perseveration-the inappropriate repetition of previous responses-is quite common among patients with neurological damage, relatively few detailed computational accounts of its various forms have been put forth. A particularly well-documented variety involves the pattern of errors made by "optic aphasic" patients, who have a selective deficit in naming visually presented objects. Based on our previous work in modeling impaired reading via meaning in deep dyslexia, we develop a connectionist simulation of visual object naming. The major extension in the present work is the incorporation of short-term correlational weights that bias the network towards reproducing patterns of activity that have occurred on recently preceding trials. Under damage, the network replicates the complex semantic and perseverative effects found in the optic aphasic error pattern. Further analysis reveals that the perseverative effects are strongest when the lesions are near or within semantics, and are relatively mild when the preceding object evokes no response. Like optic aphasics, the network produces predominantly semantic rather than visual errors because, in contrast to reading, there is some structure in the mapping from visual to semantic representations for objects. Viewed together with the dyslexia simulations, the replication of complex empirical phenomena concerning impaired visual comprehension based on a small set of general connectionist principles strongly suggests that these principles provide important insights into the nature of semantic processing of visual information and its breakdown following brain damage.

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Section: Dyslexiamentioning

confidence: 97%

Section: Individual Casesmentioning

confidence: 99%

Perseverative and Semantic Influences on Visual Object Naming Errors in Optic Aphasia: A Connectionist Account

Plaut

Shallice²

1993

Journal of Cognitive Neuroscience

145

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“…A review of patients classified as either associative agnosic or optic aphasic (Iorio et al, 1992) revealed that those with posterior unilateral left-hemisphere lesions exhibited symptoms associated with optic aphasia, whereas patients with bilateral lesions typically exhibited associated agnosia. The few cases of associative agnosia that have been reported following unilateral lefthemisphere lesions (e.g., Benke, 1988;De Renzi et al, 1987;Ferro & Santos, 1984;Larrabee, Levin, Huff, Kay, & Guinto, 1985;McCarthy & Warrington, 1986) resolved into optic aphasia after about a month (see Endo et al, 1996). Schnider et al (1994) argued that optic aphasia can also be distinguished from associative agnosia by the presence of damage to the splenium of the corpus collosum, although splenial damage is absent in some optic aphasic patients (e.g., Teixeira Ferreira et al, 1997) and present in some associative agnosic patients (see De Renzi & Saetti, 1997).…”

Section: Optic Aphasia As Mild Visual Associative Agnosiamentioning

confidence: 99%

Graded modality-specific specialisation in semantics: A computational account of optic aphasia

Plaut¹

2002

Cognitive Neuropsychology

202

200

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A long-standing debate regarding the representation of semantic knowledge is whether such knowledge is represented in a single, amodal system or whether it is organised into multiple subsystems based on modality of input or type of information. The current paper presents a distributed connectionist model of semantics that constitutes a middle ground between these unitary-versus multiple-semantics accounts. In the model, semantic representations develop under the pressure of learning to mediate between multiple input and output modalities in performing various tasks. The system has a topographic bias on learning that favours short connections, leading to a graded degree of modality-specific functional specialisation within semantics. The model is applied to the specific empirical phenomena of optic aphasia-a neuropsychological disorder in which patients exhibit a selective deficit in naming visually presented objects that is not attributable to more generalised impairments in object recognition (visual agnosia) or naming (anomia). As a result of the topographic bias in the model, as well as the relative degrees of systematicity among tasks, damage to connections from vision to regions of semantics near phonology impairs visual object naming far more than visual gesturing or tactile naming, as observed in optic aphasia. Moreover, as in optic aphasia, the system is better at generating the name of an action associated with an object than at generating the name of the object itself, because action naming receives interactive support from the activation of action representations. The ability of the model to account for the pattern of performance observed in optic aphasia across the full range of severity of impairment provides support for the claim that semantic representations exhibit graded functional specialisation rather than being entirely amodal or modality-specific.

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“…For example, they can classify objects as animate or inanimate, or classify faces as famous or unknown, but cannot do the same with the printed names of these objects or people. This condition arises in a number of forms of acquired dyslexia including pure alexia (Chialant & Caramazza, 1998;Larrabee, Levin, Huff, Kay, & Guinto, 1985; for a review of this form of acquired dyslexia, see Coltheart, 1999) and "word-meaning blindness" (Lambon Ralph, Ellis, & Sage, 1998;Lambon Ralph, Sage, & Ellis, 1996). The existence of this condition strongly suggests that the cognitive system that we use to go from seen objects or faces to semantics is not identical to the system we use to go from printed words to semantics.…”

Section: Comprehension Of Visual Stimulimentioning

confidence: 99%

Are There Lexicons?

Coltheart

2004

The Quarterly Journal of Experimental Psychology Section A

105

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Many models of the processing of printed or spoken words or objects or faces propose that systems of local representations of the forms of such stimuli--lexicons--exist. This is denied by partisans of the distributed-representation connectionist approach to cognitive modelling. An experimental paradigm of key theoretical importance here is lexical decision and its analogue in the domain of objects, object decision. How does each theoretical camp account for our ability to perform these two tasks? The localists say that the tasks are done by matching or failing to match a stimulus to a local representation in a lexicon. Advocates of distributed representations often do not seek to explain these two tasks; however, when they do, they propose that patterns of activation evoked in a semantic system can be used to discriminate between words and nonwords, or between real objects and false objects. Therefore the distributed-representation account of lexical and object decision tasks predicts that performance on these tasks can never be normal in patients with an impaired semantic system, nor in patients who cannot access semantics normally from the stimulus domain being tested. However, numerous such patients have been reported in the literature, indicating that semantic access is not needed for normal performance on these tasks. Such results support the localist form of modelling rather than the distributed-representation approach.

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Visual agnosia contrasted with visual-verbal disconnection

Cited by 62 publications

References 18 publications

Perseverative and Semantic Influences on Visual Object Naming Errors in Optic Aphasia: A Connectionist Account

Perseverative and Semantic Influences on Visual Object Naming Errors in Optic Aphasia: A Connectionist Account

Graded modality-specific specialisation in semantics: A computational account of optic aphasia

Are There Lexicons?

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