title: The effects of visual object priming on brain activation before and after recognition.
abstract: BACKGROUND
  Recognizing an object is improved by recent experience with that object even if one cannot recall seeing the object. This perceptual facilitation as a result of previous experience is called priming. In neuroimaging studies, priming is often associated with a decrease in activation in brain regions involved in object recognition. It is thought that this occurs because priming causes a sharpening of object representations which leads to more efficient processing and, consequently, a reduction in neural activity. Recent evidence has suggested, however, that the apparent effect of priming on brain activation may vary as a function of whether the neural activity is measured before or after recognition has taken place.
  
  
  RESULTS
  Using a gradual 'unmasking' technique, we presented primed and non-primed objects to subjects, and measured activation time courses using high-field functional magnetic resonance imaging (fMRI). As the objects were slowly revealed, but before recognition had occurred, activation increased from baseline level to a peak that corresponded in time to the subjects' behavioural recognition responses. The activation peak for primed objects occurred sooner than the peak for non-primed objects, and subjects responded sooner when presented with a primed object than with a non-primed object. During this pre-recognition phase, primed objects produced more activation than non-primed objects. After recognition, activation declined rapidly for both primed and non-primed objects, but now activation was lower for the primed objects.
  
  
  CONCLUSIONS
  Priming did not produce a general decrease in activation in the brain regions involved in object recognition but, instead, produced a shift in the time of peak activation that corresponded to the shift in time seen in the subjects' behavioural recognition performance.
authors.affiliation: Department of Psychology, The University of Western Ontario, London, Ontario, N6A 5C2, Canada. twjames@julian.uwo.ca
authors.forename: T W
authors.initials: TW
authors.lastname: James
authors.forename: G K
authors.initials: GK
authors.lastname: Humphrey
authors.forename: J S
authors.initials: JS
authors.lastname: Gati
authors.forename: R S
authors.initials: RS
authors.lastname: Menon
authors.forename: M A
authors.initials: MA
authors.lastname: Goodale
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D014796:Visual Perception