Kristin K Wenger | PubMed Health

PubMed2006

A core system for the implementation of task sets.

When performing tasks, humans are thought to adopt task sets that configure moment-to-moment data processing. Recently developed mixed blocked/event-related designs allow task set-related signals to be extracted in fMRI experiments, including activity related to cues that signal the beginning of a task block, "set-maintenance" activity sustained for the duration of a task block, and event-related signals for different trial types. Data were conjointly analyzed from mixed design experiments using ten different tasks and 183 subjects. Dorsal anterior cingulate cortex/medial superior frontal cortex (dACC/msFC) and bilateral anterior insula/frontal operculum (aI/fO) showed reliable start-cue and sustained activations across all or nearly all tasks. These regions also carried the most reliable error-related signals in a subset of tasks, suggesting that the regions form a "core" task-set system. Prefrontal regions commonly related to task control carried task-set signals in a smaller subset of tasks and lacked convergence across signal types.

Adolescent↗

PubMed2004

Comparison of sustained and transient activity in children and adults using a mixed blocked/event-related fMRI design.

The ability to make direct comparisons between adult and child neuroimaging data is important to the study of the neural basis of cognitive development. Recent fMRI studies in adults have used mixed blocked/event-related designs to extract activity consistent with separable sustained, task-related processes and transient, trial-related processes. Because brain regions with different time courses of activity may have different roles in cognitive processing, the ability to distinguish between sustained and transient signals would contribute to understanding the functional roles of regions involved in cognitive processing. The developmental profile of such activity would give insight into how cognitive processing develops over time. The purpose of this study was to assess the utility of the mixed design to detect and dissociate sustained and transient activity in children, and to determine if the time courses or magnitudes of the extracted signals differ from those extracted from adults. An fMRI experiment was performed on 10 adults and 10 children (ages 7-8) using counterphase flickering checkerboard stimuli that produced sustained, transient, and a combination of sustained and transient responses in visual cortex. Analyses were performed using the general linear model (GLM) assuming a shape for sustained effects, but not for transient effects. In visual cortex, neither transient nor sustained effects showed significant between-group differences. For both groups, flickering checkerboard stimuli produced robust responses in visual cortex contralateral but not ipsilateral to the stimulus. Results extend the feasibility of direct statistical comparison of adults and children; mixed designs provide a means to examine neural activity in both adults and children related to sustained, task-level processes, likely related to task-level control.

Adult↗