Automatic priming of semantically related words reduces activity in the fusiform gyrus

We used rapid, event-related fMRI to identify the neural systems underlying object semantics. During scanning, subjects silently read rapidly presented word pairs (150 msec, SOA = 250 msec) that were either unrelated in meaning (ankle-carrot), semantically related (fork-cup), or identical (crow-crow). Activity in the left posterior region of the fusiform gyrus and left inferior frontal cortex was modulated by word-pair relationship. Semantically related pairs yielded less activity than unrelated pairs, but greater activity than identical pairs, mirroring the pattern of behavioral facilitation as measured by word reading times. These findings provide strong support for the involvement of these areas in the automatic processing of object meaning. In addition, words referring to animate objects produced greater activity in the lateral region of the fusiform gyri, right superior temporal sulcus, and medial region of the occipital lobe relative to manmade, manipulable objects, whereas words referring to manmade, manipulable objects produced greater activity in the left ventral premotor, left anterior cingulate, and bilateral parietal cortices relative to animate objects. These findings are consistent with the dissociation between these areas based on sensory- and motor-related object properties, providing further evidence that conceptual object knowledge is housed, in part, in the same neural systems that subserve perception and action.