Concepts are considered to be the building blocks of human higher-order cognition. Yet theories differ according to how these semantic representations are instantiated within the brain. The amodal characteristics of word meaning imply that this knowledge is stored independent of perceptual experiences. However, mounting evidence suggests that concepts depend upon cortical regions typically ascribed to sensory input. This embodiment of semantic representations through perceptual mechanisms can crucially explain the relationship between the meaning conveyed by words and experience with the associated objects. Across two experiments, this research used functional MRI to examine the role of sensory and prefrontal brain regions while participants verified semantic properties (e.g., sounds loud?; lays eggs?) of word items. The results show that perceptual properties activate the predicted cortical regions associated with vision, audition, taste and smell, and touch. Increased response times for these perceptual decisions were not associated with increased activity in the identified sensory areas but were associated with increased activity in prefrontal brain regions. In contrast, more abstract semantic decisions led to increased activity in the prefrontal cortex but no such increases were seen for the more difficult decisions. These findings indicate that multiple and widely distributed brain regions used to encode perceptual experiences also support semantic knowledge of those sensory experiences. The prefrontal cortex may represent abstract knowledge and control retrieval with increasing semantic demands for decisions further removed from perceptual experiences
