Review articleVisual agnosia☆
Section snippets
The “father” of agnosia: Lissauer
Lissauer was the first scientist to provide a detailed account of a patient with visual agnosia [1]. He presented his clinical observations at a meeting of neurologists in 1888 in the context of a theoretic framework. He suggested that, from early stages of visual processing, the processing of color, form, and motion might be affected separately as a result of brain damage (as indeed subsequent work has proved; see later discussion of “Deficits in peripheral visual processing”). At the level of
Color and motion perception
Distinct areas of the brain are specific for the processing of color, form, and motion, as indicated by independent neurologic deficits. Achromatopsia refers to the syndrome in which a patient loses the ability to see colors after cortical damage. The loss may be partial or complete and it may or may not be accompanied by other visual defects. Typically, the patient reports seeing the world in black and white and shades of gray [2] but has no difficulty in the recognition of objects (provided
Summary
As was originally proposed by Lissauer, visual recognition may break down either at an apperceptive or at an associative level. At an apperceptive level, finer grain distinctions may be made; the authors distinguished here between disorders of shape recognition and perceptual integration. It is not the case, however, that all patients with visual recognition deficits have impaired perception: poor recognition and naming may also result from damage to stored perceptual knowledge (eg, structural
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2021, NeuropsychologiaCitation Excerpt :Such ambiguity illustrates the problems of the quasi-dichotomous classification of visual agnosias, which dates back to Lissauer's (1890) distinction between impairments affecting the early perceptual processing on the one hand, and the activation of related memory representations on the other. Given the finding that many variants of visual agnosias tend to affect both of these stages to a varying extent, the now preferred concept is that of an apperceptive-associative continuum of visual disorders (Riddoch and Humphreys, 2003), or an agnosia spectrum (Behrman and Nishimura, 2010). Such a notion also appears more adequate given the diagnostic challenges raised by the apperceptive-associative distinction in the clinical practice (Grüsser and Landis, 1991).
Object recognition and visual object agnosia
2021, Handbook of Clinical NeurologyCitation Excerpt :Answer: suitcase.) It is commonly accepted that visual agnosia can be fractionated into subtypes (Riddoch and Humphreys, 2003; Farah, 2004; Behrmann and Nishimura, 2010), and these will be described in detail later. It is less clear how distinct the subtypes are.
Disorders of Higher Cortical Visual Function
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2014, Encyclopedia of the Neurological SciencesAccent processing in dementia
2012, NeuropsychologiaCitation Excerpt :As an aspect of human meta-linguistic communication, accent processing is likely to bear some similarities to the processing of voice identity (Berman, Mandelkern, Phan, & Zaidel, 2003; Clarke & Garrett, 2004; Clopper & Pisoni, 2004b; Remez, Fellowes, & Rubin, 1997): like voice processing (Belin, Fecteau, & Bedard, 2004; Ellis, Jones, & Mosdell, 1997), the processing of accents is likely to be a computationally demanding, multi-component neural operation recruiting brain mechanisms separable from those encoding the verbal content of speech. In cognitive neuropsychological terms, a word or phoneme spoken in an unfamiliar (foreign or regional) accent has been viewed as an extreme form of native inter-speaker variation (Best, McRoberts, & Goodell, 2001; Clarke & Garrett, 2004; Evans & Iverson, 2004; Floccia et al., 2006; Nathan, Wells, & Donlan, 1998; Schmale & Seidl, 2009) and could be regarded as a ‘non-canonical view’ of that auditory object; a priori, processing non-native accents may engage auditory apperceptive mechanisms analogous to the visual apperceptive mechanisms that process unusual views of visual objects (Goll, Crutch, & Warren, 2010b; Riddoch & Humphreys, 2003; Warrington & James, 1988). The processing of accents therefore generally entails two broadly complementary tasks: processing of the accent as an informative vocal signal in its own right (Adank, Noordzij, & Hagoort, 2012; Berman et al., 2003; Clopper & Pisoni, 2004a,b; Scharinger, Monaham, & Idsardi, 2011; Van Bezooijen & Gooskens, 1999), and processing the effects of the accent on the prototypical speech signal (Adank, Evans, Stuart-Smith, and Scott, 2009; Best et al., 2001; Clarke & Garrett, 2004; Evans & Iverson, 2004; Floccia et al., 2006; Floccia, Butler, Goslin, & Ellis, 2009).
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This work was supported by grants from the MRC, Welcome Foundation, and the Stroke Association.