Abstract
The term priming typically denotes a behavioral change (usually an improvement) in the speed or ability to identify a stimulus following a prior exposure to the same, or a related, stimulus. Experience-based facilitation of object recognition is also achieved through context-specific expectations about which objects are likely to appear together in a specific scene. Seeing a computer mouse, for instance, can facilitate subsequent recognition of contextually related objects such as a keyboard and a monitor. The benefit of prior experience during object recognition is typically associated with a physiological response reduction in occipito-temporal cortex. Moreover, the specific regions that exhibit response reductions in priming tasks can vary according to the nature of the relation between the target objects and the preceding prime objects. Using event-related fMRI, we sought to elaborate the cortical network involved in experience-based facilitation of object recognition; specifically, by examining the different foci of response reductions for targets preceded by primes that were either the same object or were contextually related (but perceptually different). Priming in both cases was reflected by improvements in RTs and a reduced fMRI signal relative to that for novel objects. Context-related facilitation was uniquely associated with response reduction in bilateral parahippocampal cortex (PHC). Perceptual-related facilitation was uniquely associated with reductions in bilateral mid-fusiform gyrus and occipito-temporal sulcus, reflecting item specific effects. Response reductions were observed for both types of primes in left anterior fusiform gyrus and inferior frontal and lateral occipital cortices. Finding contextually mediated response reductions in object processing regions suggests that contextual facilitation of object recognition is mediated by the sensitization of the representations of contextually related objects in the occipito-temporal cortex.
Supported by R01NS44319, R01NS050615, James S. McDonnell Foundation #21002039, and MIND Institute.