Biomedical subjects

Carter Wendelken

Publications and source records attributed to Carter Wendelken.

6 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↗

PubMed2006

Neurocognitive development of the ability to manipulate information in working memory.

The ability to manipulate information in working memory is a key factor in cognitive development. Here, we used event-related functional MRI to test the hypothesis that developmental improvements in manipulation, relative to pure maintenance, are associated with increased recruitment of dorsolateral (DL) prefrontal cortex (PFC) and superior parietal cortex. Three age groups (8-12 years old, 13-17 years old, and 18-25 years old) performed an object-working memory task with separate maintenance and manipulation conditions. We found that 8- to 12-year-olds did not perform the task as well as adolescents or adults, particularly on trials requiring manipulation in addition to maintenance. In this study, no age differences were observed in the activation profile of ventrolateral PFC, a region associated with online maintenance. In contrast, unlike the older participants, 8- to 12-year-olds failed to recruit right DL PFC and bilateral superior parietal cortex during the delay period for manipulation relative to maintenance. This group difference was observed specifically during the delay period, while participants reordered items in working memory, and could not be accounted for by group differences in performance. Across participants, activation levels in right DL PFC and superior parietal cortex, but not ventrolateral PFC, were positively correlated with performance on manipulation trials. These results indicate that increased recruitment of right DL PFC and bilateral parietal cortex during adolescence is associated with improvements in the ability to work with object representations.

Adolescent↗

PubMed2005

Attachment-style differences in the ability to suppress negative thoughts: exploring the neural correlates.

Beginning in infancy, people can be characterized in terms of two dimensions of attachment insecurity: attachment anxiety (i.e., fear of rejection and abandonment) and attachment avoidance (distancing oneself from close others, shunning dependency; Bowlby, J., 1969/1982. Attachment and loss: Vol. 1. Attachment, 2nd ed., Basic Books, New York). The capacity for emotion regulation varies with attachment style, such that attachment-anxious individuals become highly emotional when threatened with social rejection or relationship loss, whereas avoidant individuals tend to distance themselves or disengage from emotional situations. In the present study, 20 women participated in an fMRI experiment in which they thought about--and were asked to stop thinking about--various relationship scenarios. When they thought about negative ones (conflict, breakup, death of partner), their level of attachment anxiety was positively correlated with activation in emotion-related areas of the brain (e.g., the anterior temporal pole, implicated in sadness) and inversely correlated with activation in a region associated with emotion regulation (orbitofrontal cortex). This suggests that anxious people react more strongly than non-anxious people to thoughts of loss while under-recruiting brain regions normally used to down-regulate negative emotions. Participants high on avoidance failed to show as much deactivation as less avoidant participants in two brain regions (subcallosal cingulate cortex; lateral prefrontal cortex). This suggests that the avoidant peoples' suppression was less complete or less efficient, in line with results from previous behavioral experiments. These are among the first findings to identify some of the neural processes underlying adult attachment orientations and emotion regulation.

Adult↗

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↗

PubMed2004

Analogical reasoning and prefrontal cortex: evidence for separable retrieval and integration mechanisms.

The present study examined the contributions of prefrontal cortex (PFC) subregions to two component processes underlying verbal analogical reasoning: semantic retrieval and integration. Event-related functional magnetic resonance imaging data were acquired while subjects performed propositional analogy and semantic decision tasks. On each trial, subjects viewed a pair of words (pair 1), followed by an instructional cue and a second word pair (pair 2). On analogy trials, subjects evaluated whether pair 2 was semantically analogous to pair 1. On semantic trials, subjects indicated whether the pair 2 words were semantically related to each other. Thus, analogy--but not semantic--trials required integration across multiple retrieved relations. To identify regions involved in semantic retrieval, we manipulated the associative strength of pair 1 words in both tasks. Anterior left inferior PFC (aLIPC) was modulated by associative strength, consistent with a role in controlled semantic retrieval. Left frontopolar cortex was insensitive to associative strength, but was more sensitive to integration demands than was aLIPC, consistent with a role in integrating the products of semantic retrieval to evaluate whether distinct representations are analogous. Right dorsolateral PFC exhibited a profile consistent with a role in response selection rather than retrieval or integration. These findings indicate that verbal analogical reasoning depends on multiple, PFC-mediated computations.

Adult↗