Neural Representation of Motion and Cognition Verbs.

Abstract:
Evidence from neuroimaging studies and brain-damaged patients has yielded competing claims regarding the neural representation of verb meanings. Hypotheses have linked lexical access to perceptual processes inherent in a word's referent: A verb's physical or observable action properties may require recruitment of motor-kinesthetic or visual-perceptual areas, respectively. Verb stimuli have been limited to imageable action words. This study used fMRI to compare cerebral activity during semantic processing of motion and cognition verbs (e.g., climb and assure), using concrete and abstract nouns or pseudowords as a baseline. Ten young subjects judged visually presented words for pleasantness. Stimuli were presented every four seconds, in 40 second word-category blocks, for a total of six blocks per category. We observed bilateral posterior activation involving left BA 39 and right BA 18 during verb judgments compared to noun judgments. Separate contrasts of motion verbs and cognition verbs, using pseudowords as baseline for each, revealed visual cortex activation (BA 17 and 18) in both conditions, left BA 39 and right BA 22 for motion verbs, and bilateral medial frontal (BA 10) and ventral temporal (BA 37) activation for cognition verbs. These results suggest that action verbs are not tied to motor-kinesthetic representations in frontal cortex. Previous studies (e.g., verb generation procedures) may reflect non-semantic processes such as noun-to-verb conversion.