Maturation of widely distributed brain function subserves cognitive development

The neurobiological effects of stress on adolescent decision making

Relative to other developmental periods, adolescence is characterized by risky decision making, increased perceived stress and heightened reactivity to acute stress. It is also during this time that individuals undergo significant neurodevelopment in brain regions that process decision making and stress. In this review, we summarize what is currently known about stress during adolescence, how it impacts risky decision-making, and how acute stress may exert neurobiological effects on circuitry that subserves decision-making in the developing brain. We conclude by suggesting future research directions that may help the field gain traction on this important, but relatively understudied, question.

The development of creative cognition across adolescence: distinct trajectories for insight and divergent thinking

We examined developmental trajectories of creative cognition across adolescence. Participants (N = 98), divided into four age groups (12/13 yrs, 15/16 yrs, 18/19 yrs, and 25-30 yrs), were subjected to a battery of tasks gauging creative insight (visual; verbal) and divergent thinking (verbal; visuo-spatial). The two older age groups outperformed the two younger age groups on insight tasks. The 25-30-year-olds outperformed the two youngest age groups on the originality measure of verbal divergent thinking. No age-group differences were observed for verbal divergent thinking fluency and flexibility. On divergent thinking in the visuo-spatial domain, however, only 15/16-year-olds outperformed 12/13-year-olds; a model with peak performance for 15/16-years-old showed the best fit. The results for the different creativity processes are discussed in relation to cognitive and related neurobiological models. We conclude that mid-adolescence is a period of not only immaturities but also of creative potentials in the visuo-spatial domain, possibly related to developing control functions and explorative behavior.

Regional differences in the developmental trajectory of lateralization of the language network

The timing and developmental factors underlying the establishment of language dominance are poorly understood. We investigated the degree of lateralization of traditional frontotemporal and modulatory prefrontal-cerebellar regions of the distributed language network in children (n = 57) ages 4 to 12--a critical period for language consolidation. We examined the relationship between the strength of language lateralization and neuropsychological measures and task performance. The fundamental language network is established by four with ongoing maturation of language functions as evidenced by strengthening of lateralization in the traditional frontotemporal language regions; temporal regions were strongly and consistently lateralized by age seven, while frontal regions had greater variability and were less strongly lateralized through age 10. In contrast, the modulatory prefrontal-cerebellar regions were the least strongly lateralized and degree of lateralization was not associated with age. Stronger core language skills were significantly correlated with greater right lateralization in the cerebellum.

Distinct structural alterations independently contributing to working memory deficits and symptomatology in paranoid schizophrenia

Schizophrenia is considered a brain disease with a quite heterogeneous clinical presentation. Studies in schizophrenia have yielded a wide array of correlations between structural and functional brain changes and clinical and cognitive symptoms. Reductions of grey matter volume (GMV) in the prefrontal and temporal cortex have been described which are crucial for the development of positive and negative symptoms and impaired working memory (WM). Associations between GMV reduction and positive and negative symptoms as well as WM impairment were assessed in schizophrenia patients (symptomatology in 34, WM in 26) and compared to healthy controls (36 total, WM in 26). GMV was determined by voxel-based morphometry and its relation to positive and negative symptoms as well as WM performance was assessed. In schizophrenia patients, reductions of GMV were evident in anterior cingulate cortex, ventrolateral prefrontal cortex (VLPFC), superior temporal cortex, and insula. GMV reductions in the superior temporal gyrus (STG) were associated with positive symptom severity as well as WM impairment. Furthermore, the absolute GMV of VLPFC was strongly related to negative symptoms. These predicted WM performance as well as processing speed. The present results support the assumption of two distinct pathomechanisms responsible for impaired WM in schizophrenia: (1) GMV reductions in the VLPFC predict the severity of negative symptoms. Increased negative symptoms in turn are associated with a slowing down of processing speed and predict an impaired WM. (2) GMV reductions in the temporal and mediofrontal cortex are involved in the development of positive symptoms and impair WM performance, too.

Linking novelty seeking and harm avoidance personality traits to cerebellar volumes

Personality traits are multidimensional traits comprising cognitive, emotional, and behavioral characteristics, and a wide array of cerebral structures mediate individual variability. Differences in personality traits covary with brain morphometry in specific brain regions, and neuroimaging studies showed structural or functional abnormalities of cerebellum in subjects with personality disorders, suggesting a cerebellar role in affective processing and an effect on personality characteristics. To test the hypothesis that cerebellar [white matter (WM) and cortex] volumes are correlated with scores obtained in the four temperamental scales of the Temperament and Character Inventory (TCI) by Cloninger, a total of 125 healthy participants aged 18-67 years of both genders (males = 52) completed the TCI and underwent magnetic resonance imaging. The scores obtained in each temperamental scale were associated with the volumes of cerebellar WM and cortex of right and left hemispheres separately by using linear regression analyses. In line with our hypothesis, novelty seeking (NS) scores were positively associated with WM and cortex cerebellar volumes. Harm avoidance (HA) scores were negatively associated with WM and cortex cerebellar volumes. The range of individual differences in NS and HA scores reflects the range of variances of cerebellar volumes. The present data indicating a cerebellar substrate for some personality traits extend the relationship between personality and brain areas to a structure up to now thought to be involved mainly in motor and cognitive functions, much less in emotional processes and even less in personality individual differences.

Developmental changes in emotion recognition from full-light and point-light displays of body movement

To date, research on the development of emotion recognition has been dominated by studies on facial expression interpretation; very little is known about children's ability to recognize affective meaning from body movements. In the present study, we acquired simultaneous video and motion capture recordings of two actors portraying four basic emotions (Happiness Sadness, Fear and Anger). One hundred and seven primary and secondary school children (aged 4-17) and 14 adult volunteers participated in the study. Each participant viewed the full-light and point-light video clips and was asked to make a forced-choice as to which emotion was being portrayed. As a group, children performed worse than adults for both point-light and full-light conditions. Linear regression showed that both age and lighting condition were significant predictors of performance in children. Using piecewise regression, we found that a bilinear model with a steep improvement in performance until 8.5 years of age, followed by a much slower improvement rate through late childhood and adolescence best explained the data. These findings confirm that, like for facial expression, adolescents' recognition of basic emotions from body language is not fully mature and seems to follow a non-linear development. This is in line with observations of non-linear developmental trajectories for different aspects of human stimuli processing (voices and faces), perhaps suggesting a shift from one perceptual or cognitive strategy to another during adolescence. These results have important implications to understanding the maturation of social cognition.

Overcoming residual interference in mental set switching: neural correlates and developmental trajectory

Mental set switching is a key facet of executive control measured behaviorally through reaction time or accuracy (i.e., 'switch costs') when shifting among task types. One of several experimentally dissociable influences on switch costs is 'task set inertia', conceptualized as the residual interference conferred when a previous stimulus-response tendency interferes with subsequent stimulus processing on a new task. Task set inertia is thought to represent the passive decay of the previous stimulus-response set from working memory, and its effects decrease with increased interstimulus interval. Closely spaced trials confer high task set inertia, while sparsely spaced trials confer low task set inertia. This functional magnetic resonance imaging (fMRI) study characterized, for the first time, two opposing brain systems engaged to resolve task set inertia: 1) a frontoparietal 'cortical control' network for overcoming high task set inertia interference and 2) a subcortical-motor network more active during trials with low task set inertia. These networks were distinct from brain regions showing general switching effects (i.e., switch>non-switch) and from other previously characterized interference effects. Moreover, there were ongoing maturational effects throughout adolescence for the brain regions engaged to overcome high task set inertia not seen for generalized switching effects. These novel findings represent a new avenue of exploration of cognitive set switching neural function.

Investigating white matter development in infancy and early childhood using myelin water faction and relaxation time mapping

The elaboration of the myelinated white matter is essential for normal neurodevelopment, establishing and mediating rapid communication pathways throughout the brain. These pathways facilitate the synchronized communication required for higher order behavioral and cognitive functioning. Altered neural messaging (or ‘disconnectivity’) arising from abnormal white matter and myelin development may underlie a number of neurodevelopmental psychiatric disorders. Despite the vital role myelin plays, few imaging studies have specifically examined its maturation throughout early infancy and childhood. Thus, direct investigations of the relationship(s) between evolving behavioral and cognitive functions and the myelination of the supporting neural systems have been sparse. Further, without knowledge of the ‘normative’ developmental time-course, identification of early abnormalities associated with developmental disorders remains challenging. In this work, we examined the use of longitudinal (T₁) and transverse (T₂) relaxation time mapping, and myelin water fraction (MWF) imaging to investigate white matter and myelin development in 153 healthy male and female children, 3 months through 60 months in age. Optimized age-specific acquisition protocols were developed using the DESPOT and mcDESPOT imaging techniques; and mean T₁, T₂ and MWF trajectories were determined for frontal, temporal, occipital, parietal and cerebellar white matter, and genu, body and splenium of the corpus callosum. MWF results provided a spatio-temporal pattern in-line with prior histological studies of myelination. Comparison of T₁, T₂ and MWF measurements demonstrates dissimilar sensitivity to tissue changes associated with neurodevelopment, with each providing differential but complementary information.

Functional connectivity in brain networks underlying cognitive control in chronic cannabis users

The long-term effect of regular cannabis use on brain function underlying cognitive control remains equivocal. Cognitive control abilities are thought to have a major role in everyday functioning, and their dysfunction has been implicated in the maintenance of maladaptive drug-taking patterns. In this study, the Multi-Source Interference Task was employed alongside functional magnetic resonance imaging and psychophysiological interaction methods to investigate functional interactions between brain regions underlying cognitive control. Current cannabis users with a history of greater than 10 years of daily or near-daily cannabis smoking (n=21) were compared with age, gender, and IQ-matched non-using controls (n=21). No differences in behavioral performance or magnitude of task-related brain activations were evident between the groups. However, greater connectivity between the prefrontal cortex and the occipitoparietal cortex was evident in cannabis users, as compared with controls, as cognitive control demands increased. The magnitude of this connectivity was positively associated with age of onset and lifetime exposure to cannabis. These findings suggest that brain regions responsible for coordinating behavioral control have an increased influence on the direction and switching of attention in cannabis users, and that these changes may have a compensatory role in mitigating cannabis-related impairments in cognitive control or perceptual processes.

Considerations for imaging the adolescent brain

In recent years the number of functional neuroimaging studies on adolescence has exploded. These studies have led to important new insights about the relation between functional brain development and behavior. However, special consideration is warranted when working with adolescents. In this review, we review variables, including pubertal stage, sleep patterns and pregnancy, which are particularly relevant for developmental cognitive neuroscience studies involving adolescents. Consideration of the unique challenges associated with adolescence will help the growing field of developmental neuroimaging standardize procedures and will eventually facilitate interpretation across studies.

Neural substrates of childhood anxiety disorders: a review of neuroimaging findings

The development of fear is a normative process, and significant progress has been made in identifying fear neurocircuitry. The normal development of fear goes awry in children who develop anxiety disorders, and dysfunction in fear circuitry is likely. In this article, the authors present current knowledge about the neural basis of normal fear development and reviews findings from structural and functional neuroimaging studies of childhood anxiety disorders.

Executive dysfunction in pediatric posterior fossa tumor survivors: a systematic literature review of neurocognitive deficits and interventions

Improved medical therapies have increased survivorship rates for children with posterior fossa tumors; resultantly, morbidities associated with survivorship, such as executive function deficits, have become increasingly important to identify and address. Executive dysfunction can impact academic achievement as well as functional outcomes. We summarize studies describing executive functioning deficits in pediatric posterior fossa tumor survivors who received cranial radiation therapy and intervention studies that have targeted executive functioning deficits. Previous theoretical models describing the etiology of these deficits are reviewed, and a new, more comprehensive model is proposed. Future research should move toward incorporating neuroimaging, longitudinal designs, and multiple informants.

A developmental study of the neural circuitry mediating motor inhibition in bipolar disorder

OBJECTIVE

Despite increased interest in the developmental trajectory of the pathophysiology mediating bipolar disorder, few studies have compared adults and youths with bipolar disorder. Deficits in motor inhibition are thought to play an important role in the pathophysiology of the illness across the age spectrum. The authors compared the neural circuitry mediating this process in bipolar youths relative to bipolar adults and in healthy volunteers.

METHOD

Participants were pediatric (N=16) and adult (N=23) patients with bipolar disorder and healthy child (N=21) and adult (N=29) volunteers. Functional MRI (fMRI) data were acquired while participants performed the stop-signal task.

RESULTS

During failed inhibition, an age group-by-diagnosis interaction manifested in the anterior cingulate cortex, with bipolar youths exhibiting hypoactivation relative to both healthy youths and bipolar adults, and bipolar adults exhibiting hyperactivation relative to healthy adults. During successful inhibition, a main effect of diagnosis emerged in the right nucleus accumbens and the left ventral prefrontal cortex, with bipolar patients in both age groups showing less activation than healthy subjects.

CONCLUSIONS

Anterior cingulate cortex dysfunction during failed motor inhibition was observed in both bipolar youths and adults, although the nature of this dysfunction differed between the two groups. Adults and youths with bipolar disorder exhibited similar deficits in activation of the nucleus accumbens and the ventral prefrontal cortex during successful inhibition. Therefore, while subcortical and ventral prefrontal cortex hypoactivation was present in bipolar patients across the lifespan, anterior cingulate cortex dysfunction varied developmentally, with reduced activation in youths and increased activation in adults during failed inhibition. Longitudinal fMRI studies of the developmental trajectory of the neural circuitry mediating motor inhibition in bipolar disorder are warranted.

The neglected role of positive emotion in adolescent psychopathology

Adolescence is a developmental period characterized by elevated stress, heightened risky behaviors, and increases in psychopathology. Emotion dysregulation is a hypothesized contributor to negative outcomes and to the onset of psychopathology during adolescence. However, the dysregulation of negative emotion has been the focus of research while the literature on positive emotion in adolescent psychopathology is limited. This review highlights both the development of normative and dysregulated positive emotion during adolescence. First, the literature on normative adolescent emotional development and on negative emotional regulation is briefly reviewed, followed by a discussion of current theories of positive emotion, which are grounded in the adult literature. From a developmental perspective, the dimension of approach motivation within positive emotion is emphasized throughout and frames the review. This conceptualization guides organization of literatures on normative experiences of positive emotion in adolescence and the role of dysregulated positive emotion in adolescent psychopathology, specifically adolescent depression, anxiety, bipolar disorder, externalizing disorders and eating disorders. Last, future directions in the study of adolescent positive emotion and its regulation and the implications of highlighting approach motivation in normative and dysregulated positive emotion in adolescence are detailed.

Impulsivity and the modular organization of resting-state neural networks

Impulsivity is a complex trait associated with a range of maladaptive behaviors, including many forms of psychopathology. Previous research has implicated multiple neural circuits and neurotransmitter systems in impulsive behavior, but the relationship between impulsivity and organization of whole-brain networks has not yet been explored. Using graph theory analyses, we characterized the relationship between impulsivity and the functional segregation ("modularity") of the whole-brain network architecture derived from resting-state functional magnetic resonance imaging (fMRI) data. These analyses revealed remarkable differences in network organization across the impulsivity spectrum. Specifically, in highly impulsive individuals, regulatory structures including medial and lateral regions of the prefrontal cortex were isolated from subcortical structures associated with appetitive drive, whereas these brain areas clustered together within the same module in less impulsive individuals. Further exploration of the modular organization of whole-brain networks revealed novel shifts in the functional connectivity between visual, sensorimotor, cortical, and subcortical structures across the impulsivity spectrum. The current findings highlight the utility of graph theory analyses of resting-state fMRI data in furthering our understanding of the neurobiological architecture of complex behaviors.

Functional connectivity of the frontal eye fields in humans and macaque monkeys investigated with resting-state fMRI

Although the frontal eye field (FEF) has been identified in macaque monkeys and humans, practical constraints related to invasiveness and task demands have limited a direct cross-species comparison of its functional connectivity. In this study, we used resting-state functional MRI data collected from both awake humans and anesthetized macaque monkeys to examine and compare the functional connectivity of the FEF. A seed region analysis revealed consistent ipsilateral functional connections of the FEF with fronto-parietal cortical areas across both species. These included the intraparietal sulcus, dorsolateral prefrontal cortex, anterior cingulate cortex, and supplementary eye fields. The analysis also revealed greater lateralization of connectivity with the FEF in both hemispheres in humans than in monkeys. Cortical surface-based transformation of connectivity maps between species further corroborated the remarkably similar organization of the FEF functional connectivity. The results support an evolutionarily preserved fronto-parietal system and provide a bridge for linking data from monkey and human studies.

Developmental effects of incentives on response inhibition

Inhibitory control and incentive processes underlie decision making, yet few studies have explicitly examined their interaction across development. Here, the effects of potential rewards and losses on inhibitory control in 64 adolescents (13- to 17-year-olds) and 42 young adults (18- to 29-year-olds) were examined using an incentivized antisaccade task. Notably, measures were implemented to minimize age-related differences in reward valuation and potentially confounding motivation effects. Incentives affected antisaccade metrics differently across the age groups. Younger adolescents generated more errors than adults on reward trials, but all groups performed well on loss trials. Adolescent saccade latencies also differed from adults across the range of reward trials. Overall, results suggest persistent immaturities in the integration of reward and inhibitory control processes across adolescence.

Executive functions and social skills in survivors of pediatric brain tumor

Medical advances have resulted in increased survival rates for children with brain tumors. Consequently, issues related to survivorship have become more critical. The use of multimodal treatment, in particular cranial radiation therapy, has been associated with subsequent cognitive decline. Specifically, deficits in executive functions have been reported in survivors of various types of pediatric brain tumor. Survivors are left with difficulties, particularly in self-monitoring, initiation, inhibition, and planning, to name a few. Another domain in which survivors of pediatric brain tumor have been reported to show difficulty is that of social skills. Parents, teachers, and survivors themselves have reported decreased social functioning following treatment. Deficits in executive functions and social skills are likely interrelated in this population, as executive skills are needed to navigate various aspects of social interaction; however, this has yet to be studied empirically. Twenty-four survivors of pediatric brain tumor were assessed using a computerized task of executive functions, as well as paper-and-pencil measures of social skills and real-world executive skills. Social functioning was related to a specific aspect of executive functions, that is, the survivors' variability in response time, such that inconsistent responding was associated with better parent-reported and survivor-reported social skills, independent of intellectual abilities. Additionally, parent-reported real-world global executive abilities predicted parent-reported social skills. The implications of these findings for social skills interventions and future research are discussed.

Having to identify a target reduces antisaccade latencies in mixed saccadic paradigms: A top-down effect released by tonic prefrontal activation?

Instructing participants to "identify a target" dramatically reduces saccadic reaction times in prosaccade tasks (PS). However, it has been recently shown that this effect disappears in antisaccade tasks (AS). The instruction effect observed in PS may result from top-down processes, mediated by pathways connecting the prefrontal cortex (PFC) to the superior colliculus. In AS, the PFC's prior involvement is in competition with the instruction process, annulling its effect. This study aims to discover whether the instruction effect persists in mixed paradigms. According to Dyckman's fMRI study (2007), the difficulty of mixed tasks leads to PFC involvement. The antisaccade-related PFC activation observed on comparison of blocked AS and PS therefore disappears when the two are compared in mixed paradigms. However, we continued to observe the instruction effect for both PS and AS. We therefore posit different types of PFC activation: phasic during blocked AS, and tonic during mixed saccadic experiments.

Incentive effect on inhibitory control in adolescents with early-life stress: an antisaccade study

OBJECTIVE

Early-life stress (ES) such as adoption, change of caregiver, or experience of emotional neglect may influence the way in which affected individuals respond to emotional stimuli of positive or negative valence. These modified responses may stem from a direct alteration of how emotional stimuli are coded, and/or the cognitive function implicated in emotion modulation, such as self-regulation or inhibition. These ES effects have been probed on tasks either targeting reward and inhibitory function. Findings revealed deficits in both reward processing and inhibitory control in ES youths. However, no work has yet examined whether incentives can improve automatic response or inhibitory control in ES youths.

METHOD

To determine whether incentives would only improve self-regulated voluntary actions or generalize to automated motoric responses, participants were tested on a mixed eye movement task that included reflex-like prosaccades and voluntary controlled antisaccade eye movements. Seventeen adopted children (10 females, mean age 11.3 years) with a documented history of neglect and 29 typical healthy youths (16 females, mean age 11.9 years) performed the mixed prosaccade/antisaccade task during monetary incentive conditions or during no-incentive conditions.

RESULTS

Across both saccade types, ES adolescents responded more slowly than controls. As expected, control participants committed fewer errors on antisaccades during the monetary incentive condition relative to the no-incentive condition. By contrast, ES youths failed to show this incentive-related improvement on inhibitory control. No significant incentive effects were found with prepotent prosaccades trials in either group. Finally, co-morbid psychopathology did not modulate the findings.

CONCLUSIONS

These data suggest that youths with experience of early stress exhibit deficient modulation of inhibitory control by reward processes, in tandem with a reward-independent deficit in preparation for both automatic and controlled responses. These data may be relevant to interventions in ES youths.

Developmental changes in human dopamine neurotransmission: cortical receptors and terminators

Background

Dopamine is integral to cognition, learning and memory, and dysfunctions of the frontal cortical dopamine system have been implicated in several developmental neuropsychiatric disorders. The dorsolateral prefrontal cortex (DLPFC) is critical for working memory which does not fully mature until the third decade of life. Few studies have reported on the normal development of the dopamine system in human DLPFC during postnatal life. We assessed pre- and postsynaptic components of the dopamine system including tyrosine hydroxylase, the dopamine receptors (D1, D2 short and D2 long isoforms, D4, D5), catechol-O-methyltransferase, and monoamine oxidase (A and B) in the developing human DLPFC (6 weeks -50 years).

Results

Gene expression was first analysed by microarray and then by quantitative real-time PCR. Protein expression was analysed by western blot. Protein levels for tyrosine hydroxylase peaked during the first year of life (p < 0.001) then gradually declined to adulthood. Similarly, mRNA levels of dopamine receptors D2S (p < 0.001) and D2L (p = 0.003) isoforms, monoamine oxidase A (p < 0.001) and catechol-O-methyltransferase (p = 0.024) were significantly higher in neonates and infants as was catechol-O-methyltransferase protein (32 kDa, p = 0.027). In contrast, dopamine D1 receptor mRNA correlated positively with age (p = 0.002) and dopamine D1 receptor protein expression increased throughout development (p < 0.001) with adults having the highest D1 protein levels (p ≤ 0.01). Monoamine oxidase B mRNA and protein (p < 0.001) levels also increased significantly throughout development. Interestingly, dopamine D5 receptor mRNA levels negatively correlated with age (r = -0.31, p = 0.018) in an expression profile opposite to that of the dopamine D1 receptor.

Conclusions

We find distinct developmental changes in key components of the dopamine system in DLPFC over postnatal life. Those genes that are highly expressed during the first year of postnatal life may influence and orchestrate the early development of cortical neural circuitry while genes portraying a pattern of increasing expression with age may indicate a role in DLPFC maturation and attainment of adult levels of cognitive function.

The effects of pediatric traumatic brain injury on verbal and visual-spatial working memory

The purpose of this study was to investigate the effects of pediatric traumatic brain injury (TBI) on verbal and visual-spatial working memory (WM). WM tasks examined memory span through recall of the last item of a series of stimuli. Additionally, both verbal and visual-spatial tests had a dual-task condition assessing the effect of increasing demands on the central executive (CE). Inhibitory control processes in verbal WM were examined through intrusion errors. The TBI group (n = 73) performed more poorly on verbal and visual-spatial WM tasks than orthopedic-injured children (n = 30) and non-injured children (n = 40). All groups performed more poorly on the dual-task conditions, reflecting an effect of increasing CE load. This effect was not greater for the TBI group. There were no group differences in intrusion errors on the verbal WM task, suggesting that problems in WM experienced by children with TBI were not primarily due to difficulties in inhibitory control. Finally, injury-related characteristics, namely days to follow commands, accounted for significant variance in WM performance, after controlling for relevant demographic variables. Findings suggest that WM impairments in TBI are general rather than modality-specific and that severity indices measured over time are better predictors of WM performance than those taken at a single time point.

Neural activation during inhibition predicts initiation of substance use in adolescence

BACKGROUND

Problems inhibiting non-adaptive behaviors have been linked to an increased risk for substance use and other risk taking behaviors in adolescence. This study examines the hypothesis that abnormalities in neural activation during inhibition in early adolescence may predict subsequent substance involvement.

METHODS

Thirty eight adolescents from local area middle schools, ages 12-14, with very limited histories of substance use, underwent functional magnetic resonance imaging (fMRI) as they performed a go/no-go task of response inhibition and response selection. Adolescents and their parents were then followed annually with interviews covering substance use and other behaviors. Based on follow-up data, youth were classified as transitioning to heavy use of alcohol (TU; n=21), or as healthy controls (CON; n=17).

RESULTS

At baseline, prior to the onset of use, youth who later transitioned into heavy use of alcohol showed significantly less activation than those who went on to remain non to minimal users throughout adolescence. Activation reductions in TU at baseline were seen on no-go trials in 12 brain regions, including right inferior frontal gyrus, left dorsal and medial frontal areas, bilateral motor cortex, cingulate gyrus, left putamen, bilateral middle temporal gyri, and bilateral inferior parietal lobules (corrected p<.01, each cluster ≥32 contiguous voxels).

CONCLUSIONS

These results support the hypothesis that less neural activity during response inhibition demands predicts future involvement with problem behaviors such as alcohol and other substance use.

Functional development of fronto-striato-parietal networks associated with time perception

Compared to our understanding of the functional maturation of executive functions, little is known about the neurofunctional development of perceptive functions. Time perception develops during late adolescence, underpinning many functions including motor and verbal processing, as well as late maturing higher order cognitive skills such as forward planning and future-related decision making. Nothing, however, is known about the neurofunctional changes associated with time perception from childhood to adulthood. Using functional magnetic resonance imaging we explored the effects of age on the brain activation and functional connectivity of 32 male participants from 10 to 53 years of age during a time discrimination task that required the discrimination of temporal intervals of seconds differing by several hundred milliseconds. Increasing development was associated with progressive activation increases within left lateralized dorsolateral and inferior fronto-parieto-striato-thalamic brain regions. Furthermore, despite comparable task performance, adults showed increased functional connectivity between inferior/dorsolateral interhemispheric fronto-frontal activation as well as between inferior fronto-parietal regions compared with adolescents. Activation in caudate, specifically, was associated with both increasing age and better temporal discrimination. Progressive decreases in activation with age were observed in ventromedial prefrontal cortex, limbic regions, and cerebellum. The findings demonstrate age-dependent developmentally dissociated neural networks for time discrimination. With increasing age there is progressive recruitment of later maturing left hemispheric and lateralized fronto-parieto-striato-thalamic networks, known to mediate time discrimination in adults, while earlier developing brain regions such as ventromedial prefrontal cortex, limbic and paralimbic areas, and cerebellum subserve fine-temporal processing functions in children and adolescents.

Brain functional domains inform therapeutic interventions in attention-deficit/hyperactivity disorder and pediatric bipolar disorder

A deeper understanding of how the relationships between impulsivity, reward systems and executive function deficits may be similar or different in attention-deficit/hyperactivity disorder (ADHD) and pediatric bipolar disorder (PBD) is fundamental for better defining phenotypy in these two developmental illnesses, and moving towards improved treatment and intervention. We focus our article on recent neurocognitive and neuroimaging data examining the behavioral and neural aspects of poor behavior regulation, response inhibition and reward systems in ADHD and PBD. In light of recent research evidence, we propose that the common behavioral manifestations of impulsivity in ADHD and PBD may indeed originate from different neural mechanisms mediated by altered reward systems. In order to define and differentiate these mechanisms, unlike previous approaches, our theoretical model examines the interface of the dorsal frontostriatal circuit, involved in behavior regulation, and the ventral frontostriatal circuit, which is involved in reward-related and affect processes. Preliminary evidence suggests that the neural systems involved in impulsivity, reward systems and executive function engage differently in the two illnesses. In PBD, 'emotional impulsivity' is predominantly 'bottom-up' and emotionally/motivationally driven, and stems from ventral frontostriatal circuitry dysfunction. By contrast, in ADHD 'cognitive impulsivity' is predominantly 'top-down' and more 'cognitively driven', and stems from dorsal frontostriatal dysfunction. We discuss this evidence in view of clinically relevant questions and implications for illness-based intervention. We conclude that the reward-related mechanisms underlying the interactions between executive function, behavior regulation and impulsivity in PBD and ADHD may be differentially compromised, and in accordance differently shape the clinical symptoms of impulsivity and goal-directed behavior.

Contribution of the central thalamus to the generation of volitional saccades

Lesions in the motor thalamus can cause deficits in somatic movements. However, the involvement of the thalamus in the generation of eye movements has only recently been elucidated. In this article, we review recent advances into the role of the thalamus in eye movements. Anatomically, the anterior group of the intralaminar nuclei and paralaminar portion of the ventrolateral, ventroanterior and mediodorsal nuclei of the thalamus send massive projections to the frontal eye field and supplementary eye field. In addition, these parts of the thalamus, collectively known as the 'oculomotor thalamus', receive inputs from the cerebellum, the basal ganglia and virtually all stages of the saccade-generating pathways in the brainstem. In their pioneering work in the 1980s, Schlag and Schlag-Rey found a variety of eye movement-related neurons in the oculomotor thalamus, and proposed that this region might constitute a 'central controller' playing a role in monitoring eye movements and generating self-paced saccades. This hypothesis has been evaluated by recent experiments in non-human primates and by clinical observations of subjects with thalamic lesions. In addition, several recent studies have also addressed the involvement of the oculomotor thalamus in the generation of anti-saccades and the selection of targets for saccades. These studies have revealed the impact of subcortical signals on the higher-order cortical processing underlying saccades, and suggest the possibility of future studies using the oculomotor system as a model to explore the neural mechanisms of global cortico-subcortical loops and the neural basis of a local network between the thalamus and cortex.

Developmental changes of prefrontal activation in humans: a near-infrared spectroscopy study of preschool children and adults

Previous morphological studies indicated that development of the human prefrontal cortex (PFC) appears to continue into late adolescence. Although functional brain imaging studies have sought to determine the time course of functional development of the PFC, it is unclear whether the developmental change occurs after adolescence to adulthood and when it achieves a peak because of the narrow or discontinuous range in the participant's age. Moreover, previous functional studies have not focused on the anterior frontal region, that is, the frontopolar regions (BA9/10). Thus, the present study investigated the developmental change in frontopolar PFC activation associated with letter fluency task by using near-infrared spectroscopy (NIRS), in subjects from preschool children to adults. We analyzed the relative concentration of hemoglobin (ΔHb) in the prefrontal cortex measured during the activation task in 48 typically-developing children and adolescents and 22 healthy adults. Consistent with prior morphological studies, we found developmental change with age in the children/adolescents. Moreover, the average Δoxy-Hb in adult males was significantly larger than that in child/adolescent males, but was not true for females. These data suggested that functional development of the PFC continues into late adolescence. Although the developmental change of the frontopolar PFC was independent of gender from childhood to adolescence, in adulthood a gender difference was shown.

The development of memory efficiency and value-directed remembering across the life span: a cross-sectional study of memory and selectivity

Although attentional control and memory change considerably across the life span, no research has examined how the ability to strategically remember important information (i.e., value-directed remembering) changes from childhood to old age. The present study examined this in different age groups across the life span (N = 320, 5-96 years old). A selectivity task was used in which participants were asked to study and recall items worth different point values in order to maximize their point score. This procedure allowed for measures of memory quantity/capacity (number of words recalled) and memory efficiency/selectivity (the recall of high-value items relative to low-value items). Age-related differences were found for memory capacity, as young adults recalled more words than the other groups. However, in terms of selectivity, younger and older adults were more selective than adolescents and children. The dissociation between these measures across the life span illustrates important age-related differences in terms of memory capacity and the ability to selectively remember high-value information.

A unified framework for inhibitory control

Inhibiting unwanted thoughts, actions and emotions figures centrally in daily life, and the prefrontal cortex (PFC) is widely viewed as a source of this inhibitory control. We argue that the function of the PFC is best understood in terms of representing and actively maintaining abstract information, such as goals, which produces two types of inhibitory effects on other brain regions. Inhibition of some subcortical regions takes a directed global form, with prefrontal regions providing contextual information relevant to when to inhibit all processing in a region. Inhibition within neocortical (and some subcortical) regions takes an indirect competitive form, with prefrontal regions providing excitation of goal-relevant options. These distinctions are crucial for understanding the mechanisms of inhibition and how they can be impaired or improved.

The development of the ventral prefrontal cortex and social flexibility

Over the last several years a number of studies in both humans and animals have suggested that the orbitofrontal and ventrolateral prefrontal cortices play an important role in generating flexible behavior. We suggest that input from these brain regions contribute to three functions involved in generating flexible behavior within social contexts: valuation, inhibition, and rule use. Recent studies have also demonstrated that the prefrontal cortex undergoes a prolonged course of maturation that extends well after puberty. Here, we review evidence that the prolonged development of these prefrontal regions parallels a slowly emerging ability for flexible social behavior. We also speculate on the possibility that sensitive periods for organizing social behavior may be embedded within this developmental time-fame. Finally, we discuss the role of prefrontal cortex in adolescent mood and anxiety disorders, particularly as orbitofrontal and ventrolateral prefrontal cortices are engaged in a social context.

Working memory and attention deficits in adolescent offspring of schizophrenia or bipolar patients: comparing vulnerability markers

BACKGROUND

Working memory deficits abound in schizophrenia and attention deficits have been documented in schizophrenia and bipolar disorder. Adolescent offspring of patients may inherit vulnerabilities in brain circuits that subserve these cognitive domains. Here we assess impairments in offspring of schizophrenia (SCZ-Offspring) or bipolar (BP-Offspring) patients compared to controls (HC) with no family history of mood or psychotic disorders to the second degree.

METHODS

Three groups (n=100 subjects; range: 10-20 yrs) of HC, SCZ-Offspring and BP-Offspring gave informed consent. Working memory was assessed using a delayed spatial memory paradigm with two levels of delay (2s & 12s); sustained attention processing was assessed using the Continuous Performance Task-Identical Pairs version.

RESULTS

SCZ-Offspring (but not BP-Offspring) showed impairments in working memory (relative to HC) at the longer memory delay indicating a unique deficit. Both groups showed reduced sensitivity during attention but only BP-Offspring significantly differed from controls.

CONCLUSIONS

These results suggest unique (working memory/dorsal frontal cortex) and potentially overlapping (attention/fronto-striatal cortex) vulnerability pathways in adolescent offspring of patients with schizophrenia and bipolar disorder. Working memory and attention assessments in these offspring may assist in the clinical characterization of the adolescents vulnerable to SCZ or BP.

Cognitive control in adolescence: neural underpinnings and relation to self-report behaviors

BACKGROUND

Adolescence is commonly characterized by impulsivity, poor decision-making, and lack of foresight. However, the developmental neural underpinnings of these characteristics are not well established.

METHODOLOGY/PRINCIPAL FINDINGS

To test the hypothesis that these adolescent behaviors are linked to under-developed proactive control mechanisms, the present study employed a hybrid block/event-related functional Magnetic Resonance Imaging (fMRI) Stroop paradigm combined with self-report questionnaires in a large sample of adolescents and adults, ranging in age from 14 to 25. Compared to adults, adolescents under-activated a set of brain regions implicated in proactive top-down control across task blocks comprised of difficult and easy trials. Moreover, the magnitude of lateral prefrontal activity in adolescents predicted self-report measures of impulse control, foresight, and resistance to peer pressure. Consistent with reactive compensatory mechanisms to reduced proactive control, older adolescents exhibited elevated transient activity in regions implicated in response-related interference resolution.

CONCLUSIONS/SIGNIFICANCE

Collectively, these results suggest that maturation of cognitive control may be partly mediated by earlier development of neural systems supporting reactive control and delayed development of systems supporting proactive control. Importantly, the development of these mechanisms is associated with cognitive control in real-life behaviors.

Exercise improves executive function and achievement and alters brain activation in overweight children: a randomized, controlled trial

OBJECTIVE

This experiment tested the hypothesis that exercise would improve executive function.

DESIGN

Sedentary, overweight 7- to 11-year-old children (N = 171, 56% girls, 61% Black, M ± SD age = 9.3 ± 1.0 years, body mass index [BMI] = 26 ± 4.6 kg/m², BMI z-score = 2.1 ± 0.4) were randomized to 13 ± 1.6 weeks of an exercise program (20 or 40 min/day), or a control condition.

MAIN OUTCOME MEASURES

Blinded, standardized psychological evaluations (Cognitive Assessment System and Woodcock-Johnson Tests of Achievement III) assessed cognition and academic achievement. Functional MRI measured brain activity during executive function tasks.

RESULTS

Intent to treat analysis revealed dose-response benefits of exercise on executive function and mathematics achievement. Preliminary evidence of increased bilateral prefrontal cortex activity and reduced bilateral posterior parietal cortex activity attributable to exercise was also observed.

CONCLUSION

Consistent with results obtained in older adults, a specific improvement on executive function and brain activation changes attributable to exercise were observed. The cognitive and achievement results add evidence of dose-response and extend experimental evidence into childhood. This study provides information on an educational outcome. Besides its importance for maintaining weight and reducing health risks during a childhood obesity epidemic, physical activity may prove to be a simple, important method of enhancing aspects of children's mental functioning that are central to cognitive development. This information may persuade educators to implement vigorous physical activity.

Neural correlates of pediatric obesity

OBJECTIVE

Childhood obesity rates have increased over the last 40 years and have a detrimental impact on public health. While the causes of the obesity epidemic are complex, obesity ultimately arises from chronic imbalances between energy intake and expenditure. An emerging area of research in obesity has focused on the role of the brain in evaluating the rewarding properties of food and making decisions about what and how much to eat.

METHOD

This article reviews recent scientific literature regarding the brain's role in pediatric food motivation and childhood obesity.

RESULTS

The article will begin by reviewing some of the recent literature discussing challenges associated with neuroimaging in children and the relevant developmental brain changes that occur in childhood and adolescence. The article will then review studies regarding neural mechanisms of food motivation and the ability to delay gratification in children and how these responses differ in obese compared to healthy weight children.

CONCLUSION

Increasing our understanding about how brain function and behavior may differ in children will inform future research, obesity prevention, and interventions targeting childhood obesity.

The world looks small when you only look through a telescope: The need for a broad and developmental study of reasoning

If the target article represents the summary findings of the field, reasoning research is deeply flawed. The vision is too narrow and seems to fall into biological determinism. Humans use reasoning in effective ways apparently not studied by researchers, such as reasoning for action. Moreover, as the brain develops through adulthood and from experience so do reasoning capabilities.

The developing brain: from theory to neuroimaging and back

Surprisingly little headway has been made towards understanding how brain growth maps onto mental growth during child development. This review aims at bridging and integrating recent human neuroscientific brain maturation findings with the conceptual thinking of theorists in the behavioural tradition of studying cognitive development. Developmental research in the field of internal control and self-regulation serves as a reference point for understanding the relation between brain maturation and mental growth. Using several recent neuroimaging findings as points in case, we show how a deeper appreciation of structural and functional neural development can be obtained from considering the traditional conceptual frameworks, and vice versa. We conclude that paradigmatic progress in developmental neuroscience can rely more on knowledge from developmental experimental psychology, and that developmental models of cognitive development can be constrained and articulated with more precision on the basis of knowledge of differential structural and functional brain maturation.

Why do children lack the flexibility to innovate tools?

Despite being proficient tool users, young children have surprising difficulty in innovating tools (making novel tools to solve problems). Two experiments found that 4- to 7-year-olds had difficulty on two tool innovation problems and explored reasons for this inflexibility. Experiment 1 (N=51) showed that children's performance was unaffected by the need to switch away from previously correct strategies. Experiment 2 (N=92) suggested that children's difficulty could not easily be explained by task pragmatics or permission issues. Both experiments found evidence that some children perseverated on a single incorrect strategy, but such perseveration was insufficient to explain children's tendency not to innovate tools. We suggest that children's difficulty lies not with switching, task pragmatics, or behavioral perseveration but rather with solving the fundamentally "ill-structured" nature of tool innovation problems.

Developing connections for affective regulation: age-related changes in emotional brain connectivity

The regulation of affective arousal is a critical aspect of children's social and cognitive development. However, few studies have examined the brain mechanisms involved in the development of this aspect of "hot" executive functioning. This process has been conceptualized as involving prefrontal control of the amygdala. Here, using functional magnetic resonance imaging (fMRI), we investigated the brain mechanisms involved in the development of affective regulation in typically developing 5- to 11-year-olds and an adult comparison sample. Children and adults displayed differing patterns of increased anterior cingulate cortex and decreased amygdala activation during episodes in which emotion regulation was required. Specifically, amygdala activation increased in adults but decreased in children during recovery from a frustrating episode. In addition, we used effective connectivity analyses to investigate differential correlations between key emotional brain areas in response to the regulatory task demands. We found reliable increases in effective connectivity between the anterior cingulate cortex and the amygdala during periods of increased demand for emotion regulation. This effective connectivity increased with age.

Braking and Accelerating of the Adolescent Brain

Adolescence is a developmental period often characterized as a time of impulsive and risky choices leading to increased incidence of unintentional injuries and violence, alcohol and drug abuse, unintended pregnancy and sexually transmitted diseases. Traditional neurobiological and cognitive explanations for such suboptimal choices and actions have failed to account for nonlinear changes in behavior observed during adolescence, relative to childhood and adulthood. This review provides a biologically plausible conceptualization of the mechanisms underlying these nonlinear changes in behavior, as an imbalance between a heightened sensitivity to motivational cues and immature cognitive control. Recent human imaging and animal studies provide a biological basis for this view, suggesting differential development of subcortical limbic systems relative to top-down control systems during adolescence relative to childhood and adulthood. This work emphasizes the importance of examining transitions into and out of adolescence and highlights emerging avenues of future research on adolescent brain development.

Top-down control of visual sensory processing during an ocular motor response inhibition task

The study addressed whether top-down control of visual cortex supports volitional behavioral control in a novel antisaccade task. The hypothesis was that anticipatory modulations of visual cortex activity would differentiate trials on which subjects knew an anti- versus a pro-saccade response was required. Trials consisted of flickering checkerboards in both peripheral visual fields, followed by brightening of one checkerboard (target) while both kept flickering. Neural activation related to checkerboards before target onset (bias signal) was assessed using electroencephalography. Pretarget visual cortex responses to checkerboards were strongly modulated by task demands (significantly lower on antisaccade trials), an effect that may reduce the predisposition to saccade generation instigated by visual capture. The results illustrate how top-down sensory regulation can complement motor preparation to facilitate adaptive voluntary behavioral control.

Developmental effects of reward on sustained attention networks

Adolescence is typified by significant maturation in higher-level attention functions coupled with less developed control over motivation, and enhanced sensitivity to novelty and reward. This study used event-related functional magnetic resonance imaging (fMRI) in seventy male and female participants aged between 10 and 43 years to identify age-related linear changes in cognitive sustained attention systems and the impact of reward on these systems, using a sustained attention task with and without a rewarded condition. For the non-rewarded sustained attention contrast, increasing age was associated with activation increases in typical regions of sustained attention including right inferior frontal, superior temporo-parietal and cerebellar cortices. Age-related activation decreases were observed within more posterior regions including posterior cingulate, insula and posterior cerebellar cortices, presumably mediating visual-spatial saliency detection. The effect of reward on sustained attention networks was associated with increased activation with age in regions associated with both executive attention control and reward processing, including dorsolateral, inferior and ventromedial prefrontal cortices (PFC), striatum, and temporo-parietal regions, suggestive of greater integration and executive control of motivation and cognition with maturity. Activation in paralimbic posterior cingulate and inferior temporal brain regions of visual-spatial saliency processing was progressively reduced in activation with increasing development. Thus, with increasing development between adolescence and adulthood, reward appears to enhance maturing cognitive sustained attention and executive reward-processing networks, whilst reducing paralimbic regions of saliency detection. These findings may be the neural underpinnings for the progressive maturation of motivational control over risk taking behaviours between adolescence and adulthood.

Deficits in oculomotor performance in pediatric epilepsy

PURPOSE

Given evidence of limitations in neuropsychological performance in epilepsy, we probed the integrity of components of cognition--including speed of processing, response inhibition, and spatial working memory--supporting executive function in pediatric epilepsy patients and matched controls.

METHODS

A total of 44 pairs of controls and medically treated pediatric epilepsy patients with no known brain pathology completed cognitive oculomotor tasks, computerized neuropsychological testing, and psychiatric assessment.

KEY FINDINGS

Patients showed slower reaction time to initiate a saccadic response compared to controls but had intact saccade accuracy. Cognitively driven responses including response inhibition were impaired in the patient group. Patients had increased incidence of comorbid psychopathology, but comorbidity did not predict worse functioning compared to patients with no Attention Deficit Hyperactivity Disorder (ADHD). Epilepsy type and medication status were not predictive of outcome. More complex neuropsychological performance was impaired in tasks requiring visual memory and sequential processing, which was correlated with inhibitory control and antisaccade accuracy.

SIGNIFICANCE

Pediatric epilepsy may be associated with vulnerabilities that specifically undermine speed of processing and response inhibition but not working memory, and may underlie known neuropsychological performance limitations. This particular profile of abnormalities may be associated with seizure-mediated compromises in brain maturation early in development.

Development of the action observation network during early adolescence: a longitudinal study

Adolescence places high demands on inter-personal interactions and, hence, on the extraction and processing of social cues. Here we assess longitudinally the development of brain activity within a network implicated in social cognition--the action observation network. We performed activation likelihood estimation meta-analyses to define regions of interest based upon the mature action observation network of adults. Using functional magnetic resonance imaging, we then examined developmental trajectories of functional brain activity within these brain regions. Using this approach, we reveal quadratic trajectories within a fronto-parietal network previously shown to demonstrate correlated morphological development.