Stimulus repetition and hemodynamic response refractoriness in event‐related fMRI

Abstract

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. Hum. Brain Mapping 20:1-12, 2003.

Language-Related Activations in the Left Prefrontal Regions Are Differentially Modulated by Age, Proficiency, and Task Demands

“…Schlaggar et al (2002) reported age-related activation differences independent of language tasks, which may reflect general cognitive factors. Indeed, previous neuroimaging studies have reported a repetition priming effect in which the repeated presentation of visual objects resulted in an activation decrease in broad regions, including the frontal and occipital cortices (Schacter and Buckner, 1998;Van Turennout et al, 2000;Dehaene et al, 2001;Soon et al, 2003). Because the order of tasks was counterbalanced across subjects in the present study, the repetition or familiarization effects on activation, if any, cannot explain the results of JP-JM (Fig.…”

The engagement of mid‐ventrolateral prefrontal cortex and posterior brain regions in intentional cognitive activity

“…These findings could be explained by stimulus repetition effects. Such effects have been observed in the PPA [Epstein et al, 1999Menon et al, 2000] and the FFA [Eger et al, 2004;Ishai et al, 2004;Soon et al, 2003;Vuilleumier et al, 2003], although the opposite finding has also been observed [Henson, 2003]. Interestingly, these repetition effects were specific to scenes in the PPA, but were not specific to faces in the FFA.…”

Nonlinearities in rapid event-related fMRI explained by stimulus scaling

“…A large number of prior studies have documented failures of temporal superposition in fMRI data (Boynton et al, 1996;Dale and Buckner, 1997;Robson et al, 1998;Vazquez and Noll, 1998;Glover, 1999;Ances et al, 2000b;Huettel and McCarthy, 2000;Liu and Gao, 2000;Birn et al, 2001;Huettel and McCarthy, 2001;Miller et al, 2001;Boynton and Finney, 2003;Soon et al, 2003;Huettel et al, 2004a,b;Soltysik et al, 2004;Gu et al, 2005;Murray et al, 2006). Other studies have found additional nonlinearities in fMRI; for example, when neural activity increases by a certain percentage, fMRI response fails to increase by the same percentage (e.g., Logothetis et al, 2001;Devor et al, 2003;Jones et al, 2004;Sheth et al, 2004;Hewson-Stoate et al, 2005;Wan et al, 2006).…”

“…If superposition holds, then subtracting the response to an individual event from the response to a sequence of two events should yield a response that is identical in shape to the individual response. In actual fMRI data the subtracted response is smaller, often as little as 60-70% of the individual response (Dale and Buckner, 1997;Glover, 1999; McCarthy, 2000, 2001;Boynton and Finney, 2003;Soon et al, 2003;Huettel et al, 2004a;Murray et al, 2006). Similar nonlinearities in response occur in sequences of blocks of events (Boynton et al, 1996;Robson et al, 1998;Vazquez and Noll, 1998;Glover, 1999;Ances et al, 2000b;Liu and Gao, 2000;Birn et al, 2001;Miller et al, 2001;Huettel et al, 2004b;Soltysik et al, 2004;Gu et al, 2005).…”