SEMANTIC REPETITION PRIMING FOR VERBAL AND PICTORIAL KNOWLEDGE - A FUNCTIONAL MRI STUDY OF LEFT INFERIOR PREFRONTAL CORTEX

Functional neuroimaging studies of single-word processing have demonst rated decreased activation in left inferior prefrontal cortex (LIPC) d uring repeated semantic processing relative to initial semantic proces sing. This item-specific memory effect occurs under implicit test inst ructions and represents a word-to-word semantic repetition priming. Th e present study examined the stimulus generality of LIPC function by m easuring prefrontal cortical activation during repeated relative to in itial semantic processing of words (word-to-word semantic repetition p riming) and of pictures (picture-to-picture semantic repetition primin g). For both words and pictures, LIPC activation decreased with repeti tion, suggesting that this area subserves semantic analysis of stimuli regardless of perceptual form. Decreased activation was greater in ex tent for words than for pictures. The LIPC area may act as a semantic executive system that mediates on-line retrieval of long-term conceptu al knowledge necessary for guiding task performance.