Biomedical subjects

Sarah E Donohue

Publications and source records attributed to Sarah E Donohue.

3 recordsLinked to original sources

PubMed2006

Brain regions mediating flexible rule use during development.

During development, children improve at retrieving and using rules to guide their behavior and at flexibly switching between these rules. In this study, we used functional magnetic resonance imaging to examine the changes in brain function associated with developmental changes in flexible rule use. Three age groups (8-12, 13-17, and 18-25 years) performed a task in which they were cued to respond to target stimuli on the basis of simple task rules. Bivalent target stimuli were associated with different responses, depending on the rule, whereas univalent target stimuli were associated with fixed responses. The comparison of bivalent and univalent trials enabled the identification of regions modulated by demands on rule representation. The comparison of rule-switch and rule-repetition trials enabled the identification of regions involved in rule switching. We have used this task previously in adults and have shown that ventrolateral prefrontal cortex (VLPFC) and the (pre)-supplementary motor area (pre-SMA/SMA) have dissociable roles in task-switching, such that VLPFC is associated most closely with rule representation, and pre-SMA/SMA is associated with suppression of the previous task set (Crone et al., 2006a). Based on behavioral data in children (Crone et al., 2004), we had predicted that regions associated with task-set suppression would show mature patterns of activation earlier in development than regions associated with rule representation. Indeed, we found an adult-like pattern of activation in pre-SMA/SMA by adolescence, whereas the pattern of VLPFC activation differed among children, adolescents, and adults. These findings suggest that two components of task-switching--rule retrieval and task-set suppression--follow distinct neurodevelopmental trajectories.

Adolescent↗

PubMed2005

Neural evidence for dissociable components of task-switching.

The ability to retrieve and flexibly switch between task rules is seen as an important component of cognitive control. It is often assumed that lateral prefrontal cortex (latPFC) is important for switching between rules. However, activation associated with rule-switching is less reliably observed in latPFC than in medial PFC (specifically, pre-supplementary motor area). In this study, we tested the hypothesis that medial PFC is important for reconfiguration of task sets, whereas latPFC is important for retrieving, maintaining and implementing relevant rules (i.e. rule representation). Twenty young adults participated in a functional magnetic resonance imaging study in which they determined the correct response to a target stimulus on the basis of an instructional cue. For bivalent targets, the appropriate response depended on the currently relevant rule. In contrast, univalent targets were always associated with the same response. Brain regions of interest were characterized according to their responsiveness to bivalent and univalent targets, on both rule-switch and rule-repetition trials. The data support the hypothesis that rule representation and task-set reconfiguration are separable cognitive processes, associated with dissociable neural activation in latPFC and medial PFC, respectively. Activation profiles of posterior parietal cortex, basal ganglia and rostrolateral PFC are also examined and discussed.

Adult↗

PubMed2005

Retrieving rules for behavior from long-term memory.

Human behavior is often dictated by rules or prescribed guides for action. Little is currently known regarding how these rules are stored in long-term memory or retrieved and implemented. Here, we examined the roles of ventrolateral prefrontal cortex (VLPFC) and posterior middle temporal gyrus (postMTG) in rule use. We tested two hypotheses: first, that knowledge about actions associated with abstract visual symbols is stored in postMTG, and second, that VLPFC is involved in the controlled retrieval of rule meanings. Subjects viewed a series of road signs during event-related fMRI data collection. Three types of signs were intermixed: highly familiar signs, novel signs whose meaning was explained to subjects prior to scanning, and novel signs whose meaning was not explained. Subjects were asked to think about the meaning of each sign as it was presented during scanning and then to give its meaning in a post-scan test. Left postMTG was more active when subjects viewed signs whose meaning they knew than signs whose meaning they did not know, consistent with a role in storing rule meanings. This region was not modulated by experience, in that it was equally engaged by newly trained and well-learned signs. In contrast, right VLPFC was more active for newly trained signs than for either well-learned or incorrect ones, consistent with a role in controlled retrieval. Left VLPFC was reliably engaged while subjects attempted to interpret the signs but did not differ according to knowledge or experience. These data implicate postMTG in rule storage and VLPFC in rule retrieval.

Adult↗