An fMRI study of semantic priming: modulation of brain activity by varying semantic distances.
OBJECTIVE
Our purpose was to study the effect of semantic priming at varying semantic distances on brain activation during a lexical decision experiment, using functional magnetic resonance imaging (fMRI).


BACKGROUND
Neuroimaging studies have demonstrated decreased brain activation for primed versus unprimed stimuli in language areas due to semantic priming, suggesting facilitated semantic retrieval. However, the effect of varying semantic distances on brain activation has not been studied. Therefore we examined direct and indirect priming effects on cerebral activation to provide information regarding spread of activation in the semantic network.


METHODS
Participants were presented with closely, distantly, and unrelated word pairs during fMRI, and asked to make a lexical decision on the second word.


RESULTS
Behavioral measurements demonstrated significant priming effects for all semantic distances. Imaging results showed modulation of brain activation due to different semantic relationships in the left inferior frontal gyrus, bilateral middle frontal gyrus and anterior temporal lobe, and consisted of decreased magnitude of activation when primed stimuli were processed compared with unprimed stimuli, with the greatest effect observed for closely related words.


CONCLUSIONS
This study demonstrates graduated effects of semantic priming on fMRI in semantic but not attentional brain regions, contributing to explain how semantic knowledge is organized and retrieved. These findings support the network model for organization of the semantic lexicon.
Tivarus
Madalina E
ME
Biophysics Program and Department of Neurology, the Ohio State University, Columbus, OH 43210, USA.
Ibinson
James W
JW
Hillier
Ashleigh
A
Schmalbrock
Petra
P
Beversdorf
David Q
DQ
D000328:Adult; D000704:Analysis of Variance; D001245:Association Learning / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D003344:Cortical Synchronization; D003463:Cues; D003657:Decision Making / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011930:Reaction Time / Q000502:physiology; D012660:Semantics; D014706:Verbal Learning / Q000502:physiology*