Methodological approaches in developmental neuroimaging studies

Temporal Course of Interference Control from Early to Late Young Adulthood: An ERP Study

In the present study, we aimed to investigate the neural dynamics of interference control using event-related potentials (ERPs) to reveal time course of interference control from the beginning to the end of young adulthood. Three groups of participants aged 19-21, 23-27 and 28-44 performed a Stroop task. The results revealed age differences in both accuracy and ERP amplitudes during all aspects of interreference control processing that reflect selective attention (P2), conflict monitoring (N2), conflict evaluation (P3) and interference control (N450). Both younger groups made more errors on incongruent trials compared to participants in their early 30s. The presence of higher P2 and N2 amplitudes, diminished P3 and again higher N450 amplitudes in participants in their early 20s points to a shortage of available resources for top-down control at this age. These results are in accordance with structural and functional studies that show that development of the frontoparietal network, which underlies interference control, continues after adolescence. While brain mechanisms are still developing, the use of accompanying cognitive abilities is still not optimal. The findings that change in neural dynamics and related performance continues into early adulthood challenge current models of cognitive development and call for new directions in developmental theorizing.

Cortical representations of numbers and nonsymbolic quantities expand and segregate in children from 5 to 8 years of age

Number symbols, such as Arabic numerals, are cultural inventions that have transformed human mathematical skills. Although their acquisition is at the core of early elementary education in children, it remains unknown how the neural representations of numerals emerge during that period. It is also unclear whether these relate to an ontogenetically earlier sense of approximate quantity. Here, we used multivariate fMRI adaptation coupled with within- and between-format machine learning to probe the cortical representations of Arabic numerals and approximate nonsymbolic quantity in 89 children either at the beginning (age 5) or four years into formal education (age 8). Although the cortical representations of both numerals and nonsymbolic quantities expanded from age 5 to age 8, these representations also segregated with learning and development. Specifically, a format-independent neural representation of quantity was found in the right parietal cortex, but only for 5-year-olds. These results are consistent with the so-called symbolic estrangement hypothesis, which argues that the relation between symbolic and nonsymbolic quantity weakens with exposure to formal mathematics in children.

Key considerations for child and adolescent MRI data collection

Cognitive neuroimaging researchers' ability to infer accurate statistical conclusions from neuroimaging depends greatly on the quality of the data analyzed. This need for quality control is never more evident than when conducting neuroimaging studies with children and adolescents. Developmental neuroimaging requires patience, flexibility, adaptability, extra time, and effort. It also provides us a unique, non-invasive way to understand the development of cognitive processes, individual differences, and the changing relations between brain and behavior over the lifespan. In this discussion, we focus on collecting magnetic resonance imaging (MRI) data, as it is one of the more complex protocols used with children and youth. Through our extensive experience collecting MRI datasets with children and families, as well as a review of current best practices, we will cover three main topics to help neuroimaging researchers collect high-quality datasets. First, we review key recruitment and retention techniques, and note the importance for consistency and inclusion across groups. Second, we discuss ways to reduce scan anxiety for families and ways to increase scan success by describing the pre-screening process, use of a scanner simulator, and the need to focus on participant and family comfort. Finally, we outline several important design considerations in developmental neuroimaging such as asking a developmentally appropriate question, minimizing data loss, and the applicability of public datasets. Altogether, we hope this article serves as a useful tool for those wishing to enter or learn more about developmental cognitive neuroscience.

Nurturing the Mathematical Brain: Home Numeracy Practices Are Associated With Children's Neural Responses to Arabic Numerals

Disparities in home numeracy environments contribute to variations in children's mathematical skills. However, the neural mechanisms underlying the relation between home numeracy experiences and mathematical learning are unknown. Here, parents of 66 eight-year-olds completed a questionnaire assessing the frequency of home numeracy practices. Neural adaptation to the repetition of Arabic numerals and words was measured in children using functional MRI (n = 50) to assess how sensitive the brain is to the presentation of numerical and nonnumerical information. Disparities in home numeracy practices were related to differences in digit (but not word) processing in a region of the left intraparietal sulcus (IPS) that was also related to children's arithmetic fluency. Furthermore, digit-related processing in the IPS influenced the relation between home numeracy practices and arithmetic fluency. Results were consistent with a model hypothesizing that home numeracy practices may affect children's mathematical skills by modulating the IPS response to symbolic numerical information.

Age Differences of the Hierarchical Cognitive Control and the Frontal Rostro-Caudal Functional Brain Activation

Age-related differences in the functional hierarchical organization of the frontal lobe remain unclear. We adopted task-related functional magnetic resonance imaging (fMRI) to investigate age differences in the functional hierarchical organization of the frontal lobe. Behavioral results report both reaction time and efficiency declined as the levels of abstraction increased in the selection of a set of stimulus–response mappings in older adults compared with young adults. fMRI findings suggest trends of the hierarchical organization along the rostro–caudal axis in both groups, and brain–behavior correlation further suggests neural dedifferentiation in older adults when performing at the highest level of control demands experiment. Behavioral performances and age difference overactivations at the highest level of control demands were both associated with working memory capacity, suggesting the working memory capacity is important for processing the highest task demands. Region-of-interest analysis revealed age differences in brain overactivation and common activation across experiments in the primary motor cortex, parietal lobule, and the fusiform gyrus may serve as shared mechanisms underlying tasks that are required for the selection of stimulus–response mapping sets. Overall, older adults reflect maladaptive overactivation in task-irrelevant regions that are detrimental to performance with the highest control demands.

Neurophysiological correlates of age differences in driving behavior during concurrent subtask performance

Driving is a complex cognitive-motor task that requires the continuous integration of multisensory information, cognitive processes, and motor actions. With higher age, driving becomes increasingly challenging as a result of naturally declining neurophysiological resources. Performing additional subtasks, such as conversations with passengers or interactions with in-vehicle devices (e.g., adjusting the radio), may further challenge neurocognitive resources that are required to maintain driving performance. Based on declining brain physiological resources and inferior neurocognitive functioning, older adults (OA) may show higher brain activation and larger performance decrements than younger adults (YA) when engaging in additional subtasks during driving. Age differences, however, may further vary for different neurocognitive task demands, such that driving performance of OA might be particularly affected by certain subtasks. In this study, we hence investigated the brain functional correlates of age differences in driving behavior during concurrent subtask performance in YA and OA. Our final sample consisted of thirty younger (21.80 ± 1.73y, 15 female) and thirty older (69.43 ± 3.30y, 12 female) regular drivers that drove along a typical rural road (25 - 30 min) in a driving simulator and performed three different concurrent subtasks that were presented auditorily or visually: typing a 3-digit number (TYPE), comparing traffic news and gas station prices (working memory, WM), and stating arguments (ARG). We measured variability in lateral car position, velocity, and following distance to a frontal lead car as the standard deviation from 0 to 15 s after subtask onset. Brain activity was continuously recorded using functional near-infrared spectroscopy over the dorsolateral prefrontal cortex. Both YA and OA particularly varied in their lateral position during TYPE with a more pronounced effect in OA. For YA, in contrast, ARG led to higher variability in velocity compared to TYPE and WM, whereas OA showed no task-specific differences. Substantiating our behavioral findings, OA revealed the largest brain functional response to TYPE, while YA demonstrated a very distinct activation during ARG and smaller hemodynamic responses to TYPE and WM. Brain activity in the DLPFC was, overall, not significantly, but small to moderately related to certain behavioral performance parameters (mainly lateral position). We conclude that both OA and YA are vulnerable to distractive subtasks while driving. Age differences, however, seem to largely depend on neurocognitive task demands. OA may be at higher risk for accidents when performing visuo-motor subtasks (e.g., interacting with navigational systems) during driving while YA may be more (cognitively) distracted when talking to passengers.

Minimizing noise in pediatric task-based functional MRI; Adolescents with developmental disabilities and typical development

Functional Magnetic Resonance Imaging (fMRI) represents a powerful tool with which to examine brain functioning and development in typically developing pediatric groups as well as children and adolescents with clinical disorders. However, fMRI data can be highly susceptible to misinterpretation due to the effects of excessive levels of noise, often related to head motion. Imaging children, especially with developmental disorders, requires extra considerations related to hyperactivity, anxiety and the ability to perform and maintain attention to the fMRI paradigm. We discuss a number of methods that can be employed to minimize noise, in particular movement-related noise. To this end we focus on strategies prior to, during and following the data acquisition phase employed primarily within our own laboratory. We discuss the impact of factors such as experimental design, screening of potential participants and pre-scan training on head motion in our adolescents with developmental disorders and typical development. We make some suggestions that may minimize noise during data acquisition itself and finally we briefly discuss some current processing techniques that may help to identify and remove noise in the data. Many advances have been made in the field of pediatric imaging, particularly with regard to research involving children with developmental disorders. Mindfulness of issues such as those discussed here will ensure continued progress and greater consistency across studies.

Constructivist developmental theory is needed in developmental neuroscience

Neuroscience techniques provide an open window previously unavailable to the origin of thoughts and actions in children. Developmental cognitive neuroscience is booming, and knowledge from human brain mapping is finding its way into education and pediatric practice. Promises of application in developmental cognitive neuroscience rests however on better theory-guided data interpretation. Massive amounts of neuroimaging data from children are being processed, yet published studies often do not frame their work within developmental models-in detriment, we believe, to progress in this field. Here we describe some core challenges in interpreting the data from developmental cognitive neuroscience, and advocate the use of constructivist developmental theories of human cognition with a neuroscience interpretation.

Neural activation patterns of successful episodic encoding: Reorganization during childhood, maintenance in old age

The two-component framework of episodic memory (EM) development posits that the contributions of medial temporal lobe (MTL) and prefrontal cortex (PFC) to successful encoding differ across the lifespan. To test the framework’s hypotheses, we compared subsequent memory effects (SME) of 10–12 year-old children, younger adults, and older adults using functional magnetic resonance imaging (fMRI). Memory was probed by cued recall, and SME were defined as regional activation differences during encoding between subsequently correctly recalled versus omitted items. In MTL areas, children’s SME did not differ in magnitude from those of younger and older adults. In contrast, children’s SME in PFC were weaker than the corresponding SME in younger and older adults, in line with the hypothesis that PFC contributes less to successful encoding in childhood. Differences in SME between younger and older adults were negligible. The present results suggest that, among individuals with high memory functioning, the neural circuitry contributing to successful episodic encoding is reorganized from middle childhood to adulthood. Successful episodic encoding in later adulthood, however, is characterized by the ability to maintain the activation patterns that emerged in young adulthood.

Functional MRI, resting state fMRI, and DTI for predicting verbal fluency outcome following resective surgery for temporal lobe epilepsy

OBJECTIVE

Predicting cognitive function following resective surgery remains an important clinical goal. Each MRI neuroimaging technique can potentially provide unique and distinct insight into changes that occur in the structural or functional organization of "at-risk" cognitive functions. The authors tested for the singular and combined power of 3 imaging techniques (functional MRI [fMRI], resting state fMRI, diffusion tensor imaging) to predict cognitive outcome following left (dominant) anterior temporal lobectomy for intractable epilepsy. METHODS; The authors calculated the degree of deviation from normal, determined the rate of change in this measure across the pre- and postsurgical imaging sessions, and then compared these measures for their ability to predict verbal fluency changes following surgery.

RESULTS

The data show that the 3 neuroimaging techniques, in a combined model, can reliably predict cognitive outcome following anterior temporal lobectomy for medically intractable temporal lobe epilepsy.

CONCLUSIONS

These findings suggest that these 3 imaging modalities can be used effectively, in an additive fashion, to predict functional reorganization and cognitive outcome following anterior temporal lobectomy.

Revising the BIS/BAS Scale to study development: Measurement invariance and normative effects of age and sex from childhood through adulthood

Carver and White's (1994) Behavioral Inhibition System/Behavioral Activation System (BIS/BAS) Scales have been useful tools for studying individual differences in reward-punishment sensitivity; however, their factor structure and invariance across development have not been well tested. In the current study, we examined the factor structure of the BIS/BAS Scales across 5 age groups: 6- to 10-year-old children (N = 229), 11- to 13-year-old early adolescents (N = 311), 14- to 16-year-old late adolescents (N = 353), 18- to 22-year-old young adults (N = 844), and 30- to 45-year-old adults (N = 471). Given poor fit of the standard 4-factor model (BIS, Reward Responsivity, Drive, Fun Seeking) in the literature, we conducted exploratory factor analyses in half of the participants and identified problematic items across age groups. The 4-factor model showed poor fit in our sample, whereas removing the BAS Fun Seeking subscale and problematic items from the remaining subscales improved fit in confirmatory factor analyses conducted with the second half of the participants. The revised model showed strict invariance across age groups and by sex, indicating consistent factor structure, item loadings, thresholds, and unique or residual variances. Additionally, in our cross-sectional data, we observed nonlinear relations between age and subscale scores, where scores tended to be higher in young adulthood than in childhood and later adulthood. Furthermore, sex differences emerged across development; adolescent and adult females had higher BIS scores than males in this age range, whereas sex differences were not observed in childhood. These differences may help us to understand the rise in internalizing psychopathology in adolescence, particularly in females. Future developmental studies are warranted to examine the impact of rewording problematic items.

Intrinsic brain indices of verbal working memory capacity in children and adolescents

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Digit span forward and backward performance has unique intrinsic neural correlates.

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Dorsal anterior cingulate gyrus plays distinctive roles in forward and backward span.

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Angular gyrus and subcallosum associated with forward digit span performance depending on age.

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Visual cortex and ventrolateral PFC linked to backward digit span performance depending on age.

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Age-related brain–behavior relationship changes are more robust for forward span.

Working memory (WM) is central to the acquisition of knowledge and skills throughout childhood and adolescence. While numerous behavioral and task-based functional magnetic resonance imaging (fMRI) studies have examined WM development, few have used resting-state fMRI (R-fMRI). Here, we present a systematic R-fMRI examination of age-related differences in the neural indices of verbal WM performance in a cross-sectional pediatric sample (ages: 7–17; n = 68), using data-driven approaches. Verbal WM capacity was measured with the digit span task, a commonly used educational and clinical assessment. We found distinct neural indices of digit span forward (DSF) and backward (DSB) performance, reflecting their unique neuropsychological demands. Regardless of age, DSB performance was related to intrinsic properties of brain areas previously implicated in attention and cognitive control, while DSF performance was related to areas less commonly implicated in verbal WM storage (precuneus, lateral visual areas). From a developmental perspective, DSF exhibited more robust age-related differences in brain–behavior relationships than DSB, and implicated a broader range of networks (ventral attention, default, somatomotor, limbic networks) – including a number of regions not commonly associated with verbal WM (angular gyrus, subcallosum). These results highlight the importance of examining the neurodevelopment of verbal WM and of considering regions beyond the “usual suspects”.

Effect of GABRA2 genotype on development of incentive-motivation circuitry in a sample enriched for alcoholism risk

Heightened reactivity of the incentive-motivation system has been proposed to underlie adolescent-typical risky behaviors, including problem alcohol involvement. However, even in adolescence considerable individual variation in these behaviors exists, which may have genetic underpinnings and be related to variations in risk for later alcohol use disorder (AUD). Variants in GABRA2 have been associated with adult alcohol dependence as well as phenotypic precursors, including impulsiveness and externalizing behaviors. We investigated the impact of GABRA2 on the developmental trajectory of nucleus accumbens (NAcc) activation during anticipation of monetary reward from childhood to young adulthood. Functional MRI during a monetary incentive delay task was collected in 175 participants, with the majority (n = 151) undergoing repeated scanning at 1- to 2-year intervals. One group entered the study at age 8-13 years (n = 76) and another entered at age 18-23 years (n = 99). Most participants were children of alcoholics (79%) and thus at heightened risk for AUD. A total of 473 sessions were completed, covering ages 8-27 years. NAcc activation was heightened during adolescence compared with childhood and young adulthood. GABRA2 genotype (SNP rs279858) was associated with individual differences in NAcc activation specifically during adolescence, with the minor allele (G) associated with greater activation. Furthermore, NAcc activation mediated an effect of genotype on alcohol problems (n = 104). This work demonstrates an impact of GABRA2 genotype on incentive-motivation neurocircuitry in adolescence, with implications for vulnerability to alcoholism. These findings represent an important step toward understanding the genetic and neural basis of individual differences in how risk for addiction unfolds across development.

Functional maturation of the executive system during adolescence

Adolescence is characterized by rapid development of executive function. Working memory (WM) is a key element of executive function, but it is not known what brain changes during adolescence allow improved WM performance. Using a fractal n-back fMRI paradigm, we investigated brain responses to WM load in 951 human youths aged 8-22 years. Compared with more limited associations with age, WM performance was robustly associated with both executive network activation and deactivation of the default mode network. Multivariate patterns of brain activation predicted task performance with a high degree of accuracy, and also mediated the observed age-related improvements in WM performance. These results delineate a process of functional maturation of the executive system, and suggest that this process allows for the improvement of cognitive capability seen during adolescence.

Different developmental trajectories for anticipation and receipt of reward during adolescence

Typical adolescent behaviour such as increased risk-taking and novelty-seeking is probably related to developmental changes in the brain reward system. This functional MRI study investigated how brain activation related to two components of reward processing (Reward Anticipation and Reward Outcome) changes with age in a sample of 39 children, adolescents and young adults aged 10-25. Our data revealed age-related changes in brain activity during both components of reward processing. Activation related to Reward Anticipation increased with age, while activation related to Reward Outcome decreased in various regions of the reward network. This shift from outcome to anticipation was confirmed by subsequent analyses showing positive correlations between age and the difference in activation between Reward Anticipation and Reward Outcome. The shift was predominantly present in striatal regions and was accompanied by a significant effect of age on behaviour, with older participants showing more response speeding on potentially rewarding trials than younger participants. This study provides evidence for functional changes in the reward system which may underlie typical adolescent behaviour.

Contributions of neuroscience to the study of socioeconomic health disparities

Socioeconomic disadvantage confers risk for ill health. Historically, the pathways by which socioeconomic disadvantage may affect health have been viewed from epidemiological perspectives emphasizing environmental, behavioral, and biopsychosocial risk factors. Such perspectives, however, have yet to integrate findings from emerging neuroscience studies demonstrating that indicators of socioeconomic disadvantage relate to patterns of brain morphology and functionality that have been associated with aspects of mental, physical, and cognitive health over the lifecourse. This commentary considers findings from one such study appearing in the current issue of Psychosomatic Medicine. It reports that an area-level indicator of socioeconomic disadvantage relates to cortical morphology in brain regions important for language, executive control, and other cognitive and behavioral functions-possibly via a systemic inflammatory pathway. These findings are put into context by discussing broader questions and challenges that need to be addressed in order for neuroscience approaches to a) become better integrated with existing epidemiological perspectives and b) more fully advance our understanding of the pathways by which socioeconomic disadvantage becomes embodied by the brain in relation to health.

A balancing act of the brain: activations and deactivations driven by cognitive load

The majority of neuroimaging studies focus on brain activity during performance of cognitive tasks; however, some studies focus on brain areas that activate in the absence of a task. Despite the surge of research comparing these contrasted areas of brain function, their interrelation is not well understood. We systematically manipulated cognitive load in a working memory task to examine concurrently the relation between activity elicited by the task versus activity during control conditions. We presented adults with six levels of task demand, and compared those with three conditions without a task. Using whole-brain analysis, we found positive linear relations between cortical activity and task difficulty in areas including middle frontal gyrus and dorsal cingulate; negative linear relations were found in medial frontal gyrus and posterior cingulate. These findings demonstrated balancing of activation patterns between two mental processes, which were both modulated by task difficulty. Frontal areas followed a graded pattern more closely than other regions. These data also showed that working memory has limited capacity in adults: an upper bound of seven items and a lower bound of four items. Overall, working memory and default-mode processes, when studied concurrently, reveal mutually competing activation patterns.

Enhanced striatal sensitivity to aversive reinforcement in adolescents versus adults

Neurodevelopmental changes in mesolimbic regions are associated with adolescent risk-taking behavior. Numerous studies have shown exaggerated activation in the striatum in adolescents compared with children and adults during reward processing. However, striatal sensitivity to aversion remains elusive. Given the important role of the striatum in tracking both appetitive and aversive events, addressing this question is critical to understanding adolescent decision-making, as both positive and negative factors contribute to this behavior. In this study, human adult and adolescent participants performed a task in which they received squirts of appetitive or aversive liquid while undergoing fMRI, a novel approach in human adolescents. Compared with adults, adolescents showed greater behavioral and striatal sensitivity to both appetitive and aversive stimuli, an effect that was exaggerated in response to delivery of the aversive stimulus. Collectively, these findings contribute to understanding how neural responses to positive and negative outcomes differ between adolescents and adults and how they may influence adolescent 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.

An improved framework for confound regression and filtering for control of motion artifact in the preprocessing of resting-state functional connectivity data

Several recent reports in large, independent samples have demonstrated the influence of motion artifact on resting-state functional connectivity MRI (rsfc-MRI). Standard rsfc-MRI preprocessing typically includes regression of confounding signals and band-pass filtering. However, substantial heterogeneity exists in how these techniques are implemented across studies, and no prior study has examined the effect of differing approaches for the control of motion-induced artifacts. To better understand how in-scanner head motion affects rsfc-MRI data, we describe the spatial, temporal, and spectral characteristics of motion artifacts in a sample of 348 adolescents. Analyses utilize a novel approach for describing head motion on a voxelwise basis. Next, we systematically evaluate the efficacy of a range of confound regression and filtering techniques for the control of motion-induced artifacts. Results reveal that the effectiveness of preprocessing procedures on the control of motion is heterogeneous, and that improved preprocessing provides a substantial benefit beyond typical procedures. These results demonstrate that the effect of motion on rsfc-MRI can be substantially attenuated through improved preprocessing procedures, but not completely removed.

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.

Functional neuroimaging of treatment effects in psychiatry: methodological challenges and recommendations

Functional magnetic resonance imaging (fMRI) has helped to elucidate the neurobiological bases of psychiatric and neurodevelopmental disorders by localizing etiologically-relevant aberrations in brain function. Functional MRI also has shown great promise to help understand potential mechanisms of action of effective treatments for a range of psychiatric and neurodevelopmental disorders, including mood and anxiety disorders, schizophrenia, and autism. However, the use of fMRI to probe intervention effects in psychiatry is associated with unique methodological considerations, including the psychometric properties of repeated fMRI scans, how to assess potential relations between the effects of an intervention on symptoms and on specific brain activation patterns, and how to best make causal inferences about intervention effects on brain function. Additionally, the study of treatment effects in neurodevelopmental disorders presents additional unique challenges related to brain maturation, analysis methods, and the potential for motion artifacts. We review these methodological considerations and provide recommendations for best practices for each of these topics.

Training the developing brain: a neurocognitive perspective

Developmental training studies are important to increase our understanding of the potential of the developing brain by providing answers to questions such as: “Which functions can and which functions cannot be improved as a result of practice?,” “Is there a specific period during which training has more impact?,” and “Is it always advantageous to train a particular function?”In addition, neuroimaging methods provide valuable information about the underlying mechanisms that drive cognitive plasticity. In this review, we describe how neuroscientific studies of training effects inform us about the possibilities of the developing brain, pointing out that childhood is a special period during which training may have different effects. We conclude that there is much complexity in interpreting training effects in children. Depending on the type of training and the level of maturation of the individual, training may influence developmental trajectories in different ways. We propose that the immature brain structure might set limits on how much can be achieved with training, but that the immaturity can also have advantages, in terms of flexibility for learning.

Being right is its own reward: load and performance related ventral striatum activation to correct responses during a working memory task in youth

The ventral striatum (VS) is a critical brain region for reinforcement learning and motivation. Intrinsically motivated subjects performing challenging cognitive tasks engage reinforcement circuitry including VS even in the absence of external feedback or incentives. However, little is known about how such VS responses develop with age, relate to task performance, and are influenced by task difficulty. Here we used fMRI to examine VS activation to correct and incorrect responses during a standard n-back working memory task in a large sample (n=304) of healthy children, adolescents and young adults aged 8-22. We found that bilateral VS activates more strongly to correct than incorrect responses, and that the VS response scales with the difficulty of the working memory task. Furthermore, VS response was correlated with discrimination performance during the task, and the magnitude of VS response peaked in mid-adolescence. These findings provide evidence for scalable intrinsic reinforcement signals during standard cognitive tasks, and suggest a novel link between motivation and cognition during adolescent development.

Maturation of task-induced brain activation and long range functional connectivity in adolescence revealed by multivariate pattern classification

The present study uses multivariate pattern classification analysis to examine maturation in task-induced brain activation and in functional connectivity during adolescence. The multivariate approach allowed accurate discrimination of adolescent boys of respectively 13, 17 and 21years old based on brain activation during a gonogo task, whereas the univariate statistical analyses showed no or only very few, small age-related clusters. Developmental differences in task activation were spatially distributed throughout the brain, indicating differences in the responsiveness of a wide range of task-related and default mode regions. Moreover, these distributed age-distinctive patterns generalized from a simple gonogo task to a cognitively and motivationally very different gambling task, and vice versa. This suggests that functional brain maturation in adolescence is driven by common processes across cognitive tasks as opposed to task-specific processes. Although we confirmed previous reports of age-related differences in functional connectivity, particularly for long range connections (>60mm), these differences were not specific to brain regions that showed maturation of task-induced responsiveness. Together with the task-independency of brain activation maturation, this result suggests that brain connectivity changes in the course of adolescence affect brain functionality at a basic level. This basic change is manifest in a range of tasks, from the simplest gonogo task to a complex gambling task.

Developmental change in regional brain structure over 7 months in early adolescence: comparison of approaches for longitudinal atlas-based parcellation

Early adolescence is a time of rapid change in neuroanatomy and sexual development. Precision in tracking changes in brain morphology with structural MRI requires image segmentation with minimal error. Here, we compared two approaches to achieve segmentation by image registration with an atlas to quantify regional brain structural development over a 7-month interval in normal, early adolescent boys and girls. Adolescents were scanned twice (average interval=7.3 months), yielding adequate data for analysis in 16 boys (baseline age 10.9 to 13.9 years; Tanner Stage=1 to 4) and 12 girls (baseline age=11.2 to 13.7 years; Tanner Stage=3 to 4). Brain volumes were derived from T1-weighted (SPGR) images and dual-echo Fast Spin-Echo (FSE) images collected on a GE 3T scanner with an 8-channel phased-array head coil and analyzed by registration-based parcellation using the SRI24 atlas. The "independent" method required two inter-subject registrations: both baseline (MRI 1) to atlas and follow-up (MRI 2) to the atlas. The "sequential" method required one inter-subject registration, which was MRI 1 to the atlas, and one intra-subject registration, which was MRI 2 to MRI 1. Gray matter/white matter/CSF were segmented in both MRI-1 and MRI-2 using FSL FAST with tissue priors also based on the SRI24 atlas. Gray matter volumes were derived for 10 cortical regions, gray+white matter volumes for 5 subcortical structures, and CSF volumes for 4 ventricular regions and the cortical sulci. Across the 15 tissue regions, the coefficient of variation (CV) of change scores across individuals was significantly lower for the sequential method (CV=3.02), requiring only one inter-subject registration, than for the independent method (CV=9.43), requiring two inter-subject registrations. Volume change based on the sequential method revealed that total supratentorial and CSF volumes increased, while cortical gray matter volumes declined significantly (p<0.01) in anterior (lateral and medial frontal, anterior cingulate, precuneus, and parietal) but not posterior (occipital, calcarine) cortical regions. These volume changes occurred in all boys and girls who advanced a step in Tanner staging. Subcortical structures did not show consistent changes. Thus, longitudinal MRI assessment using robust registration methods is sufficiently sensitive to identify significant regional brain changes over a 7-month interval in boys and girls in early adolescence. Increasing the temporal resolution of the retest interval in longitudinal developmental studies could increase accuracy in timing of peak growth of regional brain tissue and refine our understanding of the neural mechanisms underlying the dynamic changes in brain structure throughout adolescence.

Practical aspects of running developmental studies in the MEG

Developmental neuroimaging studies offer a unique opportunity to gain insight into the underpinnings of various cognitive functions by examining age-related changes in brain structure and function. There is an increasing body of neuroimaging literature discussing issues related to testing children in developmental studies (Crone et al. Human Brain Mapping 31:835-837, 2010). These deal with fMRI developmental studies and discuss methods (Luna et al. Human Brain Mapp 31:863-871, 2010), data interpretation (Poldrack Human Brain Mapp 31:872-878, 2010), and theoretical approaches (Karmiloff-Smith Human Brain Mapp 31:934-941, 2010). There has not yet been an equivalent discussion for MEG developmental studies. This paper will address issues specific to data acquisition, analysis, and interpretation for MEG developmental studies.