Abstract
Neuropsychological and activation studies on the neural correlates of abstract and concrete words have produced contrasting results. The present study explores the anatomical substrates of abstract/concrete words in 22 brain-damaged patients with a single vascular lesion either in the right or left hemisphere. One hundred and twenty (60 concrete and 60 abstract) noun triplets were used for a semantic similarity judgment task. We found a significant interaction in word type × group since left temporal brain-damaged patients performed significantly better with concrete than abstract words. Lesion mapping of patients with predominant temporal damage showed that the left superior and middle temporal gyri and the insula were the areas of major overlapping, while the anterior portion of the left temporal lobe was generally spared. Errors on abstract words mainly concerned (although at a non-significant level) semantically associate targets, while in the case of concrete words, coordinate targets were significantly more impaired than associate ones. Our results suggest that the left superior and middle temporal gyri and the insula are crucial regions in processing abstract words. They also confirm the hypothesis of a semantic similarity vs. associative organization of concrete and abstract concepts.
Highlights
The superior cognitive processing of concrete as compared to abstract nouns has been demonstrated in a number of psycholinguistic studies, and is the rule in aphasia (e.g., [2])
The context availability theory [6], argues that the faster recognition of concrete vs. abstract nouns results from a larger contextual support of concrete words and not from a distinct non verbal system; this theory does not explicitly rule out a right hemisphere involvement, but attributes the concreteness effect purely to the access of more verbal information, which implies a predominantly left-hemisphere-based processing system. These theories assume that there is a quantitative distinction between concrete and abstract concepts, but they cannot explain the presence of brain-damaged patients with a reversal of concreteness effect, i.e., a superiority of abstract concepts with respect to concrete concepts
Patient DM [3] showed a hypoperfusion of the inferior temporal gyrus (ITG), on the left side—the mean intensity score of blood flow in the left anterior ITG was approximately 10% lower than that of the right anterior ITG, the perfusion deficit being maximal at approximately 25–30 mm from the temporal tip
Summary
The superior cognitive processing of concrete as compared to abstract nouns has been demonstrated in a number of psycholinguistic studies (for a review see [1]), and is the rule in aphasia (e.g., [2]). In a lexical decision task [17], abstract word processing was associated with selective activation of the temporal pole and amygdala on the right, and of the inferior frontal cortex bilaterally, while no brain areas were more active in response to concrete words. In a different study using offline rTMS with a synonym judgment task [24], disruption of the left or right temporal pole considerably slowed the time required to make semantic decisions, both with abstract and concrete concepts, but did not affect accuracy. In the light of the above, we aimed at examining a series of brain-damaged patients with a single vascular lesion either in the left or right hemisphere, involving the temporal or the frontal lobe to further investigate the neural correlates of abstract and concrete concepts by means of a semantic similarity judgment task, including 120 (60 abstract and 60 concrete) noun triplets, randomly intermingled. Our hypothesis was that patients with left inferior frontal or temporal posterior damage would be impaired with abstract, but not concrete words, while patients with more anterior temporal lesions would show impairment with concrete, but not abstract words
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