Conceptual processing of concrete objects in the brain

How is concrete conceptual information represented in the brain? Little is known about the neural organization for details of concrete objects when presented as words. The goal of the first two studies was to investigate this. In the third study, we examined how object concepts are automatically processed.;The first study addressed whether neuronal activation patterns elicited by concrete nouns are distinguishable by their semantic category. Participants viewed nouns representing mammals, birds, fruits, musical instruments, or hand tools during fMRI scanning. Using MVPA, we found separation of categories by animals, tools, and fruits in the left supramarginal gyrus and left temporal cortex.;The second study investigated whether the semantic organization within object categories was modulated by word frequency. Using high and low frequency animal and tool words, we found no effect of word frequency in the parietal cortex. However, temporal cortex activation patterns differentiated the words by both semantic category and word frequency.;The third study explored how much of a concept is intrinsically activated. Participants viewed black and white line drawings of objects typically associated with the colors red, green, or yellow. In the intrinsic condition, participants were asked whether the picture was an animal, plant, or man-made object; in the explicit condition, they were asked to actively think about the color of the object. We found that activation patterns in the middle occipital gyrus distinguished black and white objects by their color for both tasks. Regions identified by a color localizer task tended not to show differentiation during the implicit color task. Thus, regions involved in intrinsically processing color information overlapped more with regions that responded to explicitly thinking about color, and less with regions that explicitly responded to seeing color.;Together, these studies addressed how concrete conceptual information---category, frequency, and color---is represented in the brain. At an individual word level, there is a separation of object categories in both parietal cortex and temporal cortex. Within that temporal cortex semantic network, there is also discrimination of words by frequency. Further, intrinsic color representation involves automatic activation of cortical resources shared with color imagery.