Neuromagnetic evidence for early semantic access in word recognition

Magnetic brain responses recorded in the human magnetoencephalogram (MEG) d istinguished between words with different semantics but carefully matched f or frequency and length. Multiple recordings from a single subject showed t hat 100 ms following stimulus onset, significantly stronger neuromagnetic r esponses were elicited by words with strong multimodal semantic association s than by other word material. At this early processing step, there was a h ighly significant correlation (0.80) between the magnitude of brain respons es to individual words recorded over parieto-occipital areas and their sema ntic association strengths, Subsequent to this early difference related to word meaning, additional differences in MEG responses emerged for words fro m different grammatical categories. Together, these results suggest that wo rd meaning can be reflected by early neuromagnetic brain responses and befo re the grammatical information about the word is encoded.