title: Short- and long-term changes in anterior cingulate activation during resolution of task-set competition.
abstract: Alternating between task sets involves detection that the current task set is unfavorable, initiation of a change in set, and application of the new task set while fine-tuning to optimally adjust to the demands of the environment. Functional magnetic resonance imaging (fMRI) studies of cognitive flexibility consistently report activation of the anterior cingulate cortex and/or adjacent pre-supplementary motor regions (ACC/pre-SMA, medial Brodmann's areas 24/32/6), suggesting that these cortical regions are involved in switching task set. In the current study, our objective was to probe whether ACC/pre-SMA activation would decrease for a number of trials following a switch in task set, implying longer-term involvement in fine-tuning adjustments. By measuring activation when switching between word reading and color naming in response to Stroop stimuli, ACC/pre-SMA activation was observed when actively countering the influence of the irrelevant task set, and this activation decreased as a function of the number of trials since a task switch. Basal ganglia and thalamic regions also displayed a decreased response over successive trials after task switches. These findings suggest that the ACC/pre-SMA are not only involved in generating a new course of action, but are also involved (along with subcortical regions) in fine-tuning operations that resolve competition between task sets over subsequent repetitions of the same task.
authors.affiliation: Department of Research, Riverview Hospital, Coquitlam, Canada. toddswoodward@gmail.com
authors.forename: Todd S
authors.initials: TS
authors.lastname: Woodward
authors.forename: Christian C
authors.initials: CC
authors.lastname: Ruff
authors.forename: Elton T C
authors.initials: ET
authors.lastname: Ngan
mesh_terms: D000328:Adult; D001479:Basal Ganglia / Q000502:physiology; D003118:Color Perception / Q000502:physiology; D003627:Data Interpretation, Statistical; D005260:Female; D006179:Gyrus Cinguli / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D011932:Reading