The relationship between fMRI adaptation and repetition priming of visually presented objects

Abstract

The neural correlates of fMRI adaptation and repetition priming provide useful insight as to how visual information is perceived and stored in the brain. Yet, although both phenomena are typically associated with reduced activation in visually responsive brain regions, it is presently unknown whether they rely on common or dissociable neural mechanisms. In an event-related fMRI experiment, we manipulated fMRI adaptation and repetition priming orthogonally. Subjects made comparative size judgments for pairs of visual stimuli that depicted either the same or different objects; some of the pairs presented during scanning had been shown previously and others were new. This design allowed us to examine whether object-selective regions in occipital and temporal cortex were sensitive to adaptation, priming, or both. Critically, it also allowed us to test whether any region showing sensitivity to both manipulations displayed interactive or additive effects. Only a partial overlap was found between areas that were sensitive to fMRI adaptation and those sensitive to repetition priming. Moreover, in most of the object-selective regions that showed both effects, the reduced activation associated with the two phenomena were additive rather than interactive. Together, these findings suggest that fMRI adaptation and repetition priming can be dissociated from one another in terms of their neural mechanisms.

Footnotes

 This work was supported by grants from the Canadian Institutes for Health Research (CIHR) to SK and MAG and a grant from the Natural Sciences and Engineering Research Council of Canada to SK.