Authors:

Orfanidou, E., DAVIS, M.H., & MARSLEN-WILSON, W.D.

Reference:

Year of publication:

2004

CBU number:

5783

Abstract:

Regions of the superior temporal lobe surrounding auditory cortex play an important role in early, acoustic stages of spoken language comprehension (Davis & Johnsrude, 2003). However, the neural basis of spoken word recognition remains unclear with some researchers (Hickok & Poeppel, 2000) proposing a posterior, inferior temporal system and others (Scott & Johnsrude, 2003) emphasising anterior temporal regions. This study used repetition priming of words and pseudowords in fMRI to investigate these issues.13 participants were scanned (3T-Bruker system) while performing a delayed repetition auditory lexical decision task. To avoid interference from scanner noise, we used a rapid, sparse-imaging design (TR=2.5sec, TA=1.1.sec), presenting stimuli in the silent period between scans (SOA=2.5sec). Participants heard 120 words and 120 pseudowords, each presented twice, separated by ~12 intervening items with filler items added to disguise repetition. The stimuli were recorded by either a male or female speaker, with 50% of repetitions in a different voice.Behavioural results showed greater priming for words than pseudowords, irrespective of voice changes (cf. Luce, 1998). The fMRI data revealed reduced activation for second presentations (priming) in left posterior inferior temporal regions and in bilateral frontal regions (inferior frontal gyrus, anterior cingulate), though this was more pronounced in the left hemisphere. Again, no voice effect was observed. Words produced an elevated response compared to pseudowords in several regions including, supramarginal gyrus, anterior middle-temporal gyrus and left fusiform, suggesting that multiple temporal lobe regions contribute to word recognition. However, there was no interaction between this lexicality effect and priming.