Note Negative priming in naming of categorically related objects: An fMRI study Greig I. de Zubicaray*, Katie L. McMahon, Mathew M. Eastburn and Alan J. Pringle Functional MRI Laboratory, Centre for Magnetic Resonance, The University of Queensland, Brisbane, QLD, Australia article info Article history: Received 20 November 2006 Reviewed 23 January 2007 Revised 13 February 2007 Accepted 27 February 2007 Action editor Carlo Umilta ´ Published online 23 December 2007 Keywords: Semantics Negative priming fMRI Object naming Categories abstract Ignoring an object slows subsequent naming responses to it, a phenomenon known as neg- ative priming (NP). A central issue in NP research concerns the level of representation at which the effect occurs. As object naming is typically considered to involve access to abstract semantic representations, Tipper 1985 proposed that the NP effect occurred at this level of processing, and other researchers supported this proposal by demonstrating a similar result with categorically related objects (e.g., Allport et al., 1985; Murray, 1995), an effect referred to as semantic NP. However, objects within categories share more phys- ical or structural features than objects from different categories. Consequently, the NP ef- fect observed with categorically related objects might occur at a structural rather than semantic level of representation. We used event related fMRI interleaving overt object naming and image acquisition to demonstrate for the first time that the semantic NP effect activates the left posterior-mid fusiform and insular–opercular cortices. Moreover, both naming latencies and left posterior-mid fusiform cortex responses were influenced by the structural similarity of prime–probe object pairings in the categorically related condi- tion, increasing with the number of shared features. None of the cerebral regions activated in a previous fMRI study of the identity NP effect (de Zubicaray et al., 2006) showed similar activation during semantic NP, including the left anterolateral temporal cortex, a region considered critical for semantic processing. The results suggest that the identity and se- mantic NP effects differ with respect to their neural mechanisms, and the label ‘‘semantic NP’’ might be a misnomer. We conclude that the effect is most likely the result of compe- tition between structurally similar category exemplars that determines the efficiency of ob- ject name retrieval. ª 2007 Elsevier Masson Srl. All rights reserved. 1. Introduction The aim of this study is to further explore whether the phe- nomenon of negative priming (NP) in object naming involves access to semantic representations. The original NP paradigm introduced by Tipper (1985) involved presenting an object as a distractor to be ignored on a prime trial, then presenting it as a target to be named on a subsequent probe trial. Prime– probe pairs that did not involve repeated or related objects served as experimental controls. Naming responses to the previously ignored objects were slowed compared to unre- lated objects. Later, the effect was referred to as identity NP, due to the repetition of objects as both distractors and targets (Fox, 1995). Analogous NP effects have since been demonstrated across a wide range of experimental tasks and stimuli (e.g., loca- tion NP; for reviews, see Fox, 1995; May et al., 1995). * Corresponding author. Centre for Magnetic Resonance, The University of Queensland, Brisbane, QLD 4072, Australia. E-mail address: greig.dezubicaray@cmr.uq.edu.au (G.I. de Zubicaray). available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/cortex 0010-9452/$ – see front matter ª 2007 Elsevier Masson Srl. All rights reserved. doi:10.1016/j.cortex.2007.02.005 cortex 44 (2008) 881–889