Nouns with a high degree of semantic specificity (e.g., ‘robin’) can be assumed to be more closelyrelated to sensory information as opposed to more non-specific nouns belonging to the same lexicalsemantic hierarchy (e.g., ‘animal’) (Rosch, 1978). As the majority of concrete nouns denote thingsthat can be experienced visually, activation of visual information might be necessary for concrete noun processing, in which case damage to visual (occipital) cortex might selectively affect morespecific nouns. Supporting this idea, nouns (e.g., ’table’) and verbs (e.g., ’kick’) have been found toactivate brain regions involved in experiencing their referred objects and actions (Pulvermüller & Fadiga 2010).

Individuals with lesions in visual brain areas have previously been shown to have difficulties accessing words related to the visual modality (Manning 2000; Gainotti 2004). In these studies, the focus has been on comparing different modes of presentation (e.g., visual/tactile/verbal). However, it could further be hypothesised that when visual areas are damaged, the degree of visual semantic content would also affect performance.

The present study investigated hierarchical lexical semantic structure in free oral descriptions of concrete word meanings produced by a subject (ZZ) diagnosed with anomic aphasia due to left occipital lesions. The focus of the analysis was production of a) nouns at different levels of semanticspecificity (e.g. ‘robin’–‘bird’–‘animal’) and b) words describing sensory or motor experiences (e.g. ‘blue’, ‘soft’, ‘fly’).

Results showed that in contrast to healthy and aphasic controls, who produced words at all levels of specificity and mainly vision-related sensory information, ZZ produced almost exclusively nouns at the most non-specific levels and words associated with sound and movement, suggesting that his anomia is sensory-specific and dependent on the modality of the semantic content of words.

References

Crutch, S.J. & Warrington, E.K. (2008). Contrasting patterns of comprehension for superordinate, basic level, and subordinate names in semantic dementia and aphasic stroke patients. Cognitive Neuropsychology 25(4), 582-600.

Gainotti, G. (2004). A metanalysis of impaired and spared naming for different categories of knowledge in patients with a visuo-verbal disconnection. Neuropsychologia 42, 299-319.

Manning, L. (2000). Loss of visual imagery and defective recognition of parts of wholes in optic aphasia.NeuroCase 6 (2), 111-128.

Rosch, E. (1978). Principles of categorization. In: Rosch, Eleanor and Barbara B. Lloyd, eds., Cognition and Categorization. Hillsdale, NJ: Lawrence Erlbaum, pp. 27-48.

Pulvermüller, F. & Fadiga, L. (2010). Active perception: sensorimotor circuits as a cortical basis for language. Nature Reviews Neuroscience 11, 351-360.