Authors:

Davis, M.H., Nugent, D., Randall, B., Tyler, L.K., & MARSLEN-WILSON, W.D.

Reference:

Year of publication:

2004

CBU number:

5781

Abstract:

Neuropsychological investigations suggest that regions of left-frontal cortex are important for processing regularly-inflected verbs (Marslen-Wilson & Tyler, 1997, Tyler et al, 2002), though specifically morphological explanations remain controversial (Bird et al, 2003). We conducted an event-related fMRI study using repetition priming to probe the neural correlates of processing operations on inflected and uninflected verbs in normal volunteers. Participants were scanned using rapid, sparse, image acquisition (TR=SOA=2.5sec, TA=1.1sec, 3T-Bruker scanner) while performing an auditory lexical decision task with delayed repetitions of critical items. Regular verb stems and past-tense forms were presented twice following ~12 intervening items. Repeated items occurred either in the same tense as before (identity priming) or as an inflectional variant ("jump" followed "jumped" or vice-versa). Matched pairs that were phonologically ("start-star") or semantically ("bump-knock") related were included to assess effects of meaning and form overlap, together with a matched set of non-words. Behavioural data collected outside the scanner showed robust priming for regular and identity conditions, though not for semantic or phonological conditions. fMRI data showed decreased activation for second presentations (identity priming) in the left inferior frontal gyrus (LIFG, pars triangularis). However, preliminary analyses showed no priming either for inflectionally related pairs, or for phonological or semantic controls. Comparisons of inflected verbs and stems showed greater activation in posterior LIFG (pars opercularis) for inflected forms, though this effect was not modulated by priming. Results will be discussed in the context of competing claims about neural systems involved in recognizing complex spoken words.