title: Stimulus repetition and hemodynamic response refractoriness in event-related fMRI.
abstract: We investigated the extent of hemodynamic recovery following the paired presentation of either identical or different faces at two different inter-stimulus intervals (ISI). Signal recovery was consistently better at an ISI of 6 sec compared to 3 sec. Significantly less signal recovery was associated with identical faces compared to different faces in bilateral mid-fusiform and right prefrontal regions but not in the calcarine and posterior fusiform regions. Repetition suppression effects contributed significantly to incomplete signal recovery in a region-specific manner. Simulations using empirically derived data suggest that experiments with shorter ISI (average 4.5-6.0 sec) are as sensitive as experiments with intermediate ISI (average 9 sec) in detecting response differences if experimental duration is equivalent. However, designs using intermediate ISI may be more appropriate if the expected difference in responses is small and if the number of suitable stimuli is limited.
authors.affiliation: Cognitive Neuroscience Laboratory, Singapore General Hospital, Singapore.
authors.forename: Chun-Siong
authors.initials: CS
authors.lastname: Soon
authors.forename: Vinod
authors.initials: V
authors.lastname: Venkatraman
authors.forename: Michael W L
authors.initials: MW
authors.lastname: Chee
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D003198:Computer Simulation; D005145:Face; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D010775:Photic Stimulation; D017397:Prefrontal Cortex / Q000502:physiology; D013997:Time Factors; D014796:Visual Perception