Person:

Bedny, Marina

Many empiricist theories hold that concepts are composed of sensory–motor primitives. For example, the meaning of the word “run” is in part a visual image of running. If action concepts are partly visual, then the concepts of congenitally blind individuals should be altered in that they lack these visual features. We compared semantic judgments and neural activity during action verb comprehension in congenitally blind and sighted individuals. Participants made similarity judgments about pairs of nouns and verbs that varied in the visual motion they conveyed. Blind adults showed the same pattern of similarity judgments as sighted adults. We identified the left middle temporal gyrus (lMTG) brain region that putatively stores visual–motion features relevant to action verbs. The functional profile and location of this region was identical in sighted and congenitally blind individuals. Furthermore, the lMTG was more active for all verbs than nouns, irrespective of visual–motion features. We conclude that the lMTG contains abstract representations of verb meanings rather than visual–motion images. Our data suggest that conceptual brain regions are not altered by the sensory modality of learning.

Several regions of the posterior-lateral-temporal cortex (PLTC) are reliably recruited when participants read or listen to action verbs, relative to other word and nonword types. This PLTC activation is generally interpreted as reflecting the retrieval of visual-motion features of actions. This interpretation supports the broader theory, that concepts are comprised of sensory–motor features. We investigated an alternative interpretation of the same activations: PLTC activity for action verbs reflects the retrieval of modality-independent representations of event concepts, or the grammatical types associated with them, i.e., verbs. During a functional magnetic resonance imaging scan, participants made semantic-relatedness judgments on word pairs varying in amount of visual-motion information. Replicating previous results, several PLTC regions showed higher responses to words that describe actions versus objects. However, we found that these PLTC regions did not overlap with visual-motion regions. Moreover, their response was higher for verbs than nouns, regardless of visual-motion features. For example, the response of the PLTC is equally high to action verbs (e.g., to run) and mental verbs (e.g., to think), and equally low to animal nouns (e.g., the cat) and inanimate natural kind nouns (e.g., the rock). Thus, PLTC activity for action verbs might reflect the retrieval of event concepts, or the grammatical information associated with verbs. We conclude that concepts are abstracted away from sensory–motor experience and organized according to conceptual properties.