Silvia A. Bunge

Rethinking Feelings: An fMRI Study of the Cognitive Regulation of Emotion

The ability to cognitively regulate emotional responses to aversive events is important for mental and physical health. Little is known, however, about neural bases of the cognitive control of emotion. The present study employed functional magnetic resonance imaging to examine the neural systems used to reappraise highly negative scenes in unemotional terms. Reappraisal of highly negative scenes reduced subjective experience of negative affect. Neural correlates of reappraisal were increased activation of the lateral and medial prefrontal regions and decreased activation of the amygdala and medial orbito-frontal cortex. These findings support the hypothesis that prefrontal cortex is involved in constructing reappraisal strategies that can modulate activity in multiple emotion-processing systems.

Immature Frontal Lobe Contributions to Cognitive Control in Children: Evidence from fMRI

Event-related fMRI was employed to characterize differences in brain activation between children ages 8-12 and adults related to two forms of cognitive control: interference suppression and response inhibition. Children were more susceptible to interference and less able to inhibit inappropriate responses than were adults. Effective interference suppression in children was associated with prefrontal activation in the opposite hemisphere relative to adults. In contrast, effective response inhibition in children was associated with activation of posterior, but not prefrontal, regions activated by adults. Children failed to activate a region in right ventrolateral prefrontal cortex that was recruited for both types of cognitive control by adults. Thus, children exhibited immature prefrontal activation that varied according to the type of cognitive control required.

Dissociable contributions of prefrontal and parietal cortices to response selection.

The ability to select between possible responses to a given situation is central to human cognition. The goal of this study was to distinguish between brain areas representing candidate responses and areas selecting between competing response alternatives. Event-related fMRI data were acquired while 10 healthy adults performed a task used to examine response competition: the Eriksen flanker task. Left parietal cortex was activated by either of two manipulations that increased the need to maintain a representation of possible responses. In contrast, lateral prefrontal and rostral anterior cingulate cortices were specifically engaged by the need to select among competing response alternatives. These findings support the idea that parietal cortex is involved in activating possible responses on the basis of learned stimulus-response associations, and that prefrontal cortex is recruited when there is a need to select between competing responses.

How we use rules to select actions: A review of evidence from cognitive neuroscience

Much of our behavior is guided by rules, or prescribed guides for action. In this review, I consider the current state of knowledge of how rules are learned, stored in the brain, and retrieved and used as the need arises. The focus is primarily on studies in humans, but the review is informed by relevant studies in nonhuman primates. Ventrolateral prefrontal cortex (VLPFC) has been implicated in rule learning, retrieval from long-term memory, and on-line maintenance during task preparation. Interactions between VLPFC and temporal cortex are required for rule retrieval in nonhuman primates, and brain imaging findings in humans suggest that rule knowledge is stored in the posterior middle temporal gyrus. Dorsolateral PFC appears to be more closely related to rule-based response selection than to rule retrieval. An important task for the future is to explain how PFC, basal ganglia, and temporal, parietal, and motor cortices interact to produce rule-guided behavior.

Neurodevelopmental changes in working memory and cognitive control

One of the most salient ways in which our behavior changes during childhood and adolescence is that we get better at working towards long-term goals, at ignoring irrelevant information that could distract us from our goals, and at controlling our impulses - in other words, we exhibit improvements in cognitive control. Several recent magnetic resonance imaging studies have examined the developmental changes in brain structure and function that underlie improvements in working memory and cognitive control. Increased recruitment of task-relevant regions in the prefrontal cortex, parietal cortex and striatum over the course of development is associated with better performance in a range of cognitive tasks. Further work is needed to assess the role of experience in shaping the neural circuitry that underlies cognitive control.

A Brain-Based Account of the Development of Rule Use in Childhood:

The ability to follow explicit rules improves dramatically during the course of childhood, but relatively little is known about the changes in brain structure and function that underlie this behavioral improvement. Drawing from neuroscientific studies in human adults and other animals, as well as from an emerging literature in developmental cognitive neuroscience, we propose a brain-based account of the development of rule use in childhood. This account focuses on four types of rules represented in different parts of the prefrontal cortex: simple rules for reversing stimulus–reward associations, pairs of conditional stimulus–response rules (both univalent and bivalent), and higher-order stimulus–response rules for selecting among task sets. It is hypothesized that the pattern of developmental changes in rule use reflects the different rates of development of specific regions within the prefrontal cortex.

Prefrontal and hippocampal contributions to visual associative recognition: interactions between cognitive control and episodic retrieval.

The ability to recover episodic associations is thought to depend on medial-temporal lobe mnemonic mechanisms and frontal lobe cognitive control processes. The present study examined the neural circuitry underlying non-verbal associative retrieval, and considered the consequences of successful retrieval on cognitive control demands. Event-related fMRI data were acquired while subjects retrieved strongly or weakly associated pairs of novel visual patterns in a two-alternative forced choice associative recognition paradigm. Behaviorally, successful retrieval of strongly associated relative to weakly associated pairs was more likely to be accompanied by conscious recollection of the pairs prior co-occurrence. At the neural level, right ventrolateral prefrontal cortex (VLPFC) and hippocampus were more active during successful retrieval of Strong than of Weak associations, consistent with a role in visual associative recollection. By contrast, Weak trials elicited greater activation in right anterior cingulate cortex (ACC), which may detect conflict between the similarly familiar target and foil stimuli in the absence of recollection. Consistent with this interpretation, stronger ACC activity was associated with weaker hippocampal and stronger right dorsolateral PFC (DLPFC) responses. Thus, recollection of relevant visual associations (hippocampus and VLPFC) results in lower levels of mnemonic conflict (ACC) and decreased familiarity-based monitoring demands (DLPFC). These findings highlight the interplay between cognitive control and episodic retrieval.

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.

The Role of the Prefrontal Cortex in the Maintenance of Verbal Working Memory: An Event-Related fMRI Analysis.

Neuroimaging studies have been inconclusive in characterizing the role of the prefrontal cortex (PFC) for maintaining increasingly larger amounts of information in working memory (WM). To address this question, the authors collected event-related functional MRI data while participants performed an item-recognition task in which the number of to-be-remembered letters was parametrically modulated. During maintenance of information in WM, the dorsolateral and the ventrolateral PFC exhibited linearly increasing activation in response to increasing WM load. Prefrontal regions could not be distinguished from one another on the basis of load sensitivity, but the dorsolateral PFC had stronger functional connectivity with the parietal and motor cortex than the ventrolateral PFC. These results suggest an increasingly important role for the PFC in actively maintaining information as the amount of that information increases.

Developmental Differences in Medial Temporal Lobe Function during Memory Encoding

The ability to recollect details about past events improves during childhood. Most researchers favor the view that this improvement depends largely on the development of the prefrontal cortex, which is thought to have a protracted course of development relative to the medial temporal lobes (MTL). The primary goal of the present study was to test the hypothesis that the development of detail recollection is also associated with changes in MTL function. We collected functional magnetic resonance imaging data during an incidental encoding task in 80 participants, divided equally across four age groups: 8-year-olds, 10- to 11-year-olds, 14-year-olds, and young adults. Developmental differences in MTL activation profiles were observed. Fourteen-year-olds and adults engaged regions of the hippocampus and posterior parahippocampal gyrus selectively for subsequent detail recollection, whereas 8- and 10- to 11-year-olds did not. In 8-year-olds, these regions were recruited indiscriminately for detail recollection and item recognition; in 10- to 11-year-olds, activation in these regions did not consistently predict subsequent memory. These results suggest there are changes in the functional organization of the MTL, such that the hippocampus and posterior parahippocampal gyrus become increasingly specialized for recollection; these changes may be in part responsible for long-term memory improvements during childhood.