Neuroimaging studies of semantic memory: inferring "how" from "where".

For nearly two decades, functional neuroimaging studies have attempted to shed light on questions about the representation, organization, and retrieval of semantic knowledge. This review examines some of the major findings in this area. For example, functional neuroimaging studies have examined the extent to which there is a unitary semantic system or a series of multiple semantic subsystems organized by input modality, knowledge attribute, and/or taxonomic category. Additionally, functional neuroimaging studies have investigated the contributions of frontal cortex to semantic retrieval and selection. Collectively, these studies demonstrate that functional neuroimaging can offer more than neuroanatomical localization information; in addition, these studies offer new insights into longstanding questions about semantic memory.