Talks and Conference Presentations
Organization for Human Brain Mapping
9th Annual Meeting
June 19-22, 2003
New York, New York
Executive processes of rule and response selection: Evidence from event-related fMRI
Scott A. Huettel1,2, Judyta Misiurek3
We used a novel rule learning task to dissociate rule selection and response selection components of executive processing using fMRI at 4.0T. Subjects learned rules separating target stimuli from non-target stimuli, flexibly changed the learned rules based upon new information, and responded to infrequent probe stimuli that tested knowledge about the current rule. By temporally separating rule learning from response selection, we were able to identify brain systems associated with each component of the task. Response selection, in the absence of rule selection, evoked activity in anterior insular cortex and in the caudate nucleus. In contrast, rule changes evoked activity in dorsolateral prefrontal cortex, parietal cortex, and the caudate. We coded each stimulus according to the amount of information it provided, and found that highly informative stimuli evoked more activity in the caudate, dorsolateral prefrontal cortex, and orbitofrontal cortex. We conclude that rule selection, even in the absence of overt behavioral responses, evokes activity in brain regions associated with executive processing.
Domain Specificity and Domain Switching in a Sequential Judgment Task
Gregory McCarthy1-3,5,7, Brian T. Miller6, Allen Song1,2, Peter B. Mack1, Scott A. Huettel1,3-5
We investigated brain regions that become active when subjects make match/mismatch judgments on stimuli that change domain randomly on a trial-by-trial basis. Subjects made same-different judgments on pairs of words or pairs of faces that were matched for judgment difficulty. We were particularly interested in whether specific brain regions would be engaged by a domain switch per se, regardless of the nature of the switch. Functional images were acquired on a 4 Tesla GE NVi scanner using an inverse-spiral pulse sequence. As expected from prior studies, the fusiform gyrus demonstrated strong domain specificity in that word judgments strongly activated the left fusiform gyrus and face judgments strongly activated the right fusiform gyrus. Domain specificity was also clearly evident in prefrontal cortex, where activity evoked by word and face judgments were similarly lateralized to the left and right inferior frontal gyrus. Domain switches strongly activated the intraparietal sulcus bilaterally, while additional regions in prefrontal cortex were strongly activated by all decisions, regardless of domain or judgment sequence.