The longitudinal stability of fMRI activation during reward processing in adolescents and young adults

Longitudinal stability of mood-related resting-state networks in youth with symptomatic bipolar-I/II disorder

Bipolar disorder (BD) is characterized by temporal instability of mood and energy, but the neural correlates of this instability are poorly understood. In previous cross-sectional studies, mood state in BD has been associated with differential functional connectivity (FC) amongst several subcortical regions and ventromedial prefrontal cortex. Here, we assess whether BD is associated with longitudinal instability within this mood-related network of interest (NOI). Young people with BD-I/II were scanned 4-6 times and healthy controls (HC) were scanned 4 times over 9 months. Following preprocessing of 20-min resting-state scans, we assessed across-scan correlation of FC, focusing on FC between regions previously associated with BD mood state. Utilizing Bayesian models, we assessed the relationship between diagnostic group and within-person, across-scan correlation, adjusting for motion, time-of-day, and inter-scan interval; prediction intervals (PI) are reported. In a sample of 16 youth (11 BD, 5 HC; 16.3-23.3 years old) with 70 scans (50 BD, 20 HC), across-scan NOI stability was higher within- than between-person (0.70 vs. 0.54; p < 0.0001). BD (vs. HC) within-person scan-pairs showed lower NOI stability (mean -0.109; 95% PI -0.181, -0.038), distinguishing BD vs. HC with excellent accuracy (AUC = 0.95). NOI instability was more pronounced with manic symptoms (mean -0.012; 95% PI -0.023, -0.0002) and in BD-II (vs. BD-I; mean -0.071; 90% PI -0.136, -0.007). Results persisted after accounting for medications, comorbidity, and sleep/arousal measures. Within this pilot sample, BD is characterized by less within-person stability of a mood-related NOI. While preliminary, these results highlight a possible role for precision imaging approaches to elucidate neural mechanisms underlying BD.

Impact of clinical factors on reproducibility of dopamine transporter imaging: A 99mTc-TRODAT SPECT study with sufficient size

OBJECTIVE

Reproducible measurement of dopamine transporter (DAT) availability is crucial for research investigating group differences or within-subject changes. However, existing DAT imaging test-retest studies are limited by short between-session intervals, restricted participant representativeness, and small sample sizes.

METHODS

Fifty-seven healthy subjects (27 female, 30 male) underwent two 99mTc-TRODAT SPECT scans to assess DAT availability, with between-session intervals ranging from 18 to 129 days. We calculated intraclass correlation coefficient (ICC) for reliability, and within-subject coefficient of variation (WSCV) and absolute variability (absVAR) for repeatability. The influence of outliers, between-session intervals, participant characteristics, and sample size on these metrics was evaluated.

RESULTS

The ICC values ranged from 0.73 to 0.80 with good precision (± 0.11). The values of WSCV (%) and coefficient of variation (COV) (%) ranged from 5.7 % to 7.9 % and 12.8 % to 15.2 %, respectively. Reporting both WSCV and COV values is crucial for interpreting ICC values and their applications. Exclusion of six outliers slightly improved reliability but not statistically significant. Longer between-session intervals (using a 42-day cutoff) did not significantly reduce ICC values. Similarly, age, sex, and body mass index did not significantly impact reliability or repeatability. Importantly, small sample sizes were found to potentially overestimate ICC values.

CONCLUSION

This study demonstrates the robust reproducibility of 99mTc-TRODAT SPECT for measuring DAT availability, supporting its use in clinical research and addressing limitations of previous reproducibility studies of DAT imaging. These findings emphasize the importance of reporting appropriate repeatability and reliability indices and employing adequate sample sizes in future test-retest studies.

Relevance of Probabilistic Reversal Learning for Adolescent Drinking Trajectories

One of the many human capabilities acquired during adolescence is the adaptivity in changing environments. In this longitudinal study, we investigated this adaptivity, as measured by probabilistic reversal learning (PReL) tasks, in N = 143 adolescents at ages 14, 16 and 18. Computational modelling and functional magnetic resonance imaging were applied to identify the neurocognitive processes underlying reversal learning and its development. Previous studies have demonstrated a correlation between heavy alcohol use and impaired reversal learning. Our hypothesis was that PReL is negatively associated with current and future alcohol use and that alcohol use impairs PReL by altering neurocognitive processes. Behaviourally, PReL performance improved, which was associated with a lower probability of switching choices and was considered an adaptive process. Computationally, this was accounted for by higher learning rates, enhanced sensitivity to wins and reduced sensitivity to losses in older adolescents. Alcohol consumption increased but remained at a low level for most participants. More risky drinking was associated with less medial frontal activity elicited by reward prediction errors. These findings suggest that reversal learning may be more relevant for the maintenance or escalation of risky than for low-level drinking. Challenges and potential solutions for longitudinal studies such as reliability are discussed.

Longitudinal Stability of Mood-Related Resting-State Networks in Youth with Symptomatic Bipolar-I/II Disorder

Bipolar disorder (BD) is characterized by temporal instability of mood and energy, but the neural correlates of this instability are poorly understood. In previous cross-sectional studies, mood state in BD has been associated with differential functional connectivity (FC) amongst several subcortical regions and ventromedial prefrontal cortex. Here, we assess whether BD is associated with longitudinal instability within this mood-related network of interest (NOI). Young people with BD-I/II were scanned 4-6 times and healthy controls (HC) were scanned 4 times over 9 months. Following preprocessing of 20-minute resting-state scans, we assessed across-scan correlation of FC, focusing on FC between regions previously associated with BD mood state. Utilizing Bayesian models, we assessed the relationship between diagnostic group and within-person, across-scan correlation, adjusting for motion, time-of-day, and inter-scan interval; prediction intervals (PI) are reported. In a sample of 16 youth (11 BD, 5 HC; 16.3-23.3 years old) with 70 scans (50 BD, 20 HC), across-scan NOI stability was higher within-than between-person (0.70 vs. 0.54; p<.0001). BD (vs. HC) within-person scan-pairs showed lower NOI stability (mean -0.109; 95% PI -0.181, -0.038), distinguishing BD vs. HC with excellent accuracy (AUC=0.95). NOI instability was more pronounced with manic symptoms (mean -0.012; 95% PI -0.023, -0.0002) and in BD-II (vs. BD-I; mean -0.071; 90% PI -0.136, -0.007). Results persisted after accounting for medications, comorbidity, and sleep/arousal measures. Within this pilot sample, BD is characterized by less within-person stability of a mood-related NOI. While preliminary, these results highlight a possible role for precision imaging approaches to elucidate neural mechanisms underlying BD.

Sex-Specific Vulnerability to Externalizing Problems: Sensitivity to Early Stress and Nucleus Accumbens Activation Over Adolescence

BACKGROUND

Exposure and sensitivity to early-life stress (ELS) are related to increased risk for psychopathology in adolescence. While cross-sectional studies have reported blunted nucleus accumbens (NAcc) activation in the context of these associations, researchers have not yet assessed the effects of ELS on developmental trajectories of activation. We examined whether trajectories are affected by stress and the moderating role of biological sex in predicting vulnerability to symptoms of psychopathology.

METHODS

Adolescents (n = 173) completed 3 assessments at 2-year intervals across puberty (ages 9-18 years). At baseline, we assessed objective ELS and stress sensitivity using the Traumatic Events Screening Inventory for Children. At all time points, we assessed NAcc activation using the Monetary Incentive Delay task and externalizing, internalizing, and total problems using the Youth Self-Report. We examined correlations between NAcc trajectories (extracted using linear mixed-effects models) with ELS and stress sensitivity and conducted multivariate regression analysis to examine the interaction of NAcc trajectories and biological sex in predicting symptoms of psychopathology.

RESULTS

Symptoms increased over adolescence. Stress sensitivity, but not objective ELS, was associated with decreasing trajectories of NAcc activation. Biological sex interacted with NAcc trajectories to predict psychopathology; boys, but not girls, with decreasing NAcc activation had more severe externalizing problems in adolescence. These findings were replicated in the putamen and caudate but not in the medial prefrontal cortex or control brain regions.

CONCLUSIONS

NAcc activation may be a sex-specific marker of externalizing problems in adolescence. Efforts to reduce stress sensitivity may help to decrease symptoms of psychopathology in adolescent boys.

Functional connectivity during facial and vocal emotion recognition: Preliminary evidence for dissociations in developmental change by nonverbal modality

The developmental trajectory of emotion recognition (ER) skills is thought to vary by nonverbal modality, with vocal ER becoming mature later than facial ER. To investigate potential neural mechanisms contributing to this dissociation at a behavioural level, the current study examined whether youth's neural functional connectivity during vocal and facial ER tasks showed differential developmental change across time. Youth ages 8-19 (n = 41) completed facial and vocal ER tasks while undergoing functional magnetic resonance imaging, at two timepoints (1 year apart; n = 36 for behavioural data, n = 28 for neural data). Partial least squares analyses revealed that functional connectivity during ER is both distinguishable by modality (with different patterns of connectivity for facial vs. vocal ER) and across time-with changes in connectivity being particularly pronounced for vocal ER. ER accuracy was greater for faces than voices, and positively associated with age; although task performance did not change appreciably across a 1-year period, changes in latent functional connectivity patterns across time predicted participants' ER accuracy at Time 2. Taken together, these results suggest that vocal and facial ER are supported by distinguishable neural correlates that may undergo different developmental trajectories. Our findings are also preliminary evidence that changes in network integration may support the development of ER skills in childhood and adolescence.

Neuroticism/Negative Emotionality Is Associated with Increased Reactivity to Uncertain Threat in the Bed Nucleus of the Stria Terminalis, Not the Amygdala

Neuroticism/negative emotionality (N/NE)-the tendency to experience anxiety, fear, and other negative emotions-is a fundamental dimension of temperament with profound consequences for health, wealth, and well-being. Elevated N/NE is associated with a panoply of adverse outcomes, from reduced socioeconomic attainment to psychiatric illness. Animal research suggests that N/NE reflects heightened reactivity to uncertain threat in the bed nucleus of the stria terminalis (BST) and central nucleus of the amygdala (Ce), but the relevance of these discoveries to humans has remained unclear. Here we used a novel combination of psychometric, psychophysiological, and neuroimaging approaches to test this hypothesis in an ethnoracially diverse, sex-balanced sample of 220 emerging adults selectively recruited to encompass a broad spectrum of N/NE. Cross-validated robust-regression analyses demonstrated that N/NE is preferentially associated with heightened BST activation during the uncertain anticipation of a genuinely distressing threat (aversive multimodal stimulation), whereas N/NE was unrelated to BST activation during certain-threat anticipation, Ce activation during either type of threat anticipation, or BST/Ce reactivity to threat-related faces. It is often assumed that different threat paradigms are interchangeable assays of individual differences in brain function, yet this has rarely been tested. Our results revealed negligible associations between BST/Ce reactivity to the anticipation of threat and the presentation of threat-related faces, indicating that the two tasks are nonfungible. These observations provide a framework for conceptualizing emotional traits and disorders; for guiding the design and interpretation of biobank and other neuroimaging studies of psychiatric risk, disease, and treatment; and for refining mechanistic research.

Impact of analytic decisions on test-retest reliability of individual and group estimates in functional magnetic resonance imaging: a multiverse analysis using the monetary incentive delay task

Empirical studies reporting low test-retest reliability of individual blood oxygen-level dependent (BOLD) signal estimates in functional magnetic resonance imaging (fMRI) data have resurrected interest among cognitive neuroscientists in methods that may improve reliability in fMRI. Over the last decade, several individual studies have reported that modeling decisions, such as smoothing, motion correction and contrast selection, may improve estimates of test-retest reliability of BOLD signal estimates. However, it remains an empirical question whether certain analytic decisions consistently improve individual and group level reliability estimates in an fMRI task across multiple large, independent samples. This study used three independent samples (Ns: 60, 81, 119) that collected the same task (Monetary Incentive Delay task) across two runs and two sessions to evaluate the effects of analytic decisions on the individual (intraclass correlation coefficient [ICC(3,1)]) and group (Jaccard/Spearman rho) reliability estimates of BOLD activity of task fMRI data. The analytic decisions in this study vary across four categories: smoothing kernel (five options), motion correction (four options), task parameterizing (three options) and task contrasts (four options), totaling 240 different pipeline permutations. Across all 240 pipelines, the median ICC estimates are consistently low, with a maximum median ICC estimate of .43 - .55 across the three samples. The analytic decisions with the greatest impact on the median ICC and group similarity estimates are the Implicit Baseline contrast, Cue Model parameterization and a larger smoothing kernel. Using an Implicit Baseline in a contrast condition meaningfully increased group similarity and ICC estimates as compared to using the Neutral cue. This effect was largest for the Cue Model parameterization; however, improvements in reliability came at the cost of interpretability. This study illustrates that estimates of reliability in the MID task are consistently low and variable at small samples, and a higher test-retest reliability may not always improve interpretability of the estimated BOLD signal.

Annual Research Review: Puberty and the development of anhedonia - considering childhood adversity and inflammation

Anhedonia, or diminished pleasure and motivation, is a symptom of severe mental illness (e.g., depressive disorder, bipolar disorder, schizophrenia) that emerges during adolescence. Anhedonia is a pernicious symptom that is related to social impairments, treatment resistance, and suicide. As the mechanisms of anhedonia are postulated to include the frontostriatal circuitry and the dopamine neuromodulatory system, the development and plasticity of these systems during the vulnerable period of adolescence, as well as their sensitivity to pubertal hormones, suggest that pubertal maturation could play a role in the development of anhedonia. This review takes a developmental perspective, considering the possibility that anhedonia emerges in the context of pubertal maturation and adolescent development, with childhood adversity and chronic inflammation influencing neural reward systems to accelerate anhedonia's progression. Here, we review the relevant extant literature on the components of this model and suggest directions for future research.

Anhedonia in adolescents at transdiagnostic familial risk for severe mental illness: Clustering by symptoms and mechanisms of association with behavior

BACKGROUND

Anhedonia is a transdiagnostic symptom of severe mental illness (SMI) and emerges during adolescence. Possible subphenotypes and neural mechanisms of anhedonia in adolescents at risk for SMI are understudied.

METHODS

Adolescents at familial risk for SMI (N = 81) completed anhedonia (e.g., consummatory, anticipatory, social), demographic, and clinical measures and one year prior, a subsample (N = 46) completed fMRI scanning during a monetary reward task. Profiles were identified using k-means clustering of anhedonia type and differences in demographics, suicidal ideation, impulsivity, and emotional processes were examined. Moderation analyses were conducted to investigate whether levels of brain activation of reward regions moderated the relationships between anhedonia type and behaviors.

RESULTS

Two-clusters emerged: a high anhedonia profile (high-anhedonia), characterized by high levels of all types of anhedonia, (N = 32) and a low anhedonia profile (low-anhedonia), characterized by low levels of anhedonia types (N = 49). Adolescents in the high-anhedonia profile reported more suicidal ideation and negative affect, and less positive affect and desire for emotional closeness than low-anhedonia profile. Furthermore, more suicidal ideation, less positive affect, and less desire for emotional closeness differentiated the familial high-risk, high-anhedonia profile adolescents from the familial high-risk, low-anhedonia profile adolescents. Across anhedonia profiles, moderation analyses revealed that adolescents with high dmPFC neural activation in response to reward had positive relationships between social, anticipatory, and consummatory anhedonia and suicidal ideation.

LIMITATIONS

Small subsample with fMRI data.

CONCLUSION

Profiles of anhedonia emerge transdiagnostically and vary on clinical features. Anhedonia severity and activation in frontostriatal reward areas have value for clinically important outcomes such as suicidal ideation.

From Classical Methods to Generative Models: Tackling the Unreliability of Neuroscientific Measures in Mental Health Research

Advances in computational statistics and corresponding shifts in funding initiatives over the past few decades have led to a proliferation of neuroscientific measures being developed in the context of mental health research. Although such measures have undoubtedly deepened our understanding of neural mechanisms underlying cognitive, affective, and behavioral processes associated with various mental health conditions, the clinical utility of such measures remains underwhelming. Recent commentaries point toward the poor reliability of neuroscientific measures to partially explain this lack of clinical translation. Here, we provide a concise theoretical overview of how unreliability impedes clinical translation of neuroscientific measures; discuss how various modeling principles, including those from hierarchical and structural equation modeling frameworks, can help to improve reliability; and demonstrate how to combine principles of hierarchical and structural modeling within the generative modeling framework to achieve more reliable, generalizable measures of brain-behavior relationships for use in mental health research.

Sex differences in emotion- and reward-related neural responses predicting increases in substance use in adolescence

Adolescent substance use is a significant public health problem and there is a need for effective substance use preventions. To develop effective preventions, it is important to identify neurobiological risk factors that predict increases in substance use in adolescence and to understand potential sex differences in risk mechanisms. The present study used functional magnetic resonance imaging and hierarchical linear modeling to examine negative emotion- and reward-related neural responses in early adolescence predicting growth in substance use to middle adolescence in 81 youth, by sex. Adolescent neural responses to negative emotional stimuli and monetary reward receipt were assessed at age 12-14. Adolescents reported on substance use at age 12-14 and at 6 month, and 1, 2, and 3 year follow-ups. Adolescent neural responses did not predict initiation of substance use (yes/no), but, among users, neural responses predicted growth in substance use frequency. For girls, heightened right amygdala responses to negative emotional stimuli in early adolescence predicted growth in substance use frequency through middle adolescence. For boys, blunted left nucleus accumbens and bilateral ventromedial prefrontal cortex responses to monetary reward predicted growth in substance use frequency. Findings suggest different emotion and reward-related predictors of the development of substance use for adolescent girls versus boys.

Splitting the reward: Differences in inflammatory marker associations with neural connectivity between reward anticipation and reward outcome in adolescents at high risk for depression

BACKGROUND

Adolescent depression is associated with both dysfunction in neural reward processing and peripheral inflammatory markers (PIMs), such as interleukin-6 (IL-6), C-reactive-protein (CRP), and tumor-necrosis factor alpha (TNFα). Few adolescent studies have examined neural-inflammatory marker associations and associated behavioral correlates, which would contribute to a better understanding of developmental processes linked to depression.

METHODS

36 adolescents at high risk of depression completed an fMRI reward task (during anticipation and outcome), blood draw for PIMs (IL-6, CRP, and TNFα), and a behavioral task assessing motivation to expend effort. Analyses examined associations of task-dependent functional connectivity (FC; ventral striatum to frontal and default mode network brain regions), and if the interaction of PIMs and task-dependent FC predicted motivation to expend effort.

RESULTS

For anticipation contrast, TNFα was associated with increased task-dependent FC between the LVS and PCC/vmPFC. In moderation analyses, for anticipation contrasts, the combination of higher IL-6 and stronger FC (LVS-precuneus/PCC) was associated with lower motivation to expend effort, while for outcome contrasts, the combination of higher IL-6 and stronger FC (VS-precuneus/PCC) was associated with greater motivation to expend effort.

CONCLUSIONS

Our findings in adolescents during an important developmental time period suggest that PIMs are directly linked to greater FC between the VS and DMN brain regions during win anticipation, consistent with prior studies. Effects of PIMs on motivation to expend effort may vary the strength/type of neural reward processing (anticipation or outcome), which could guide better understanding how inflammatory markers and neural reward substrates contribute to development of depression in high-risk adolescents.

Adolescent to young adult longitudinal development across 8 years for matching emotional stimuli during functional magnetic resonance imaging

We investigated development from adolescence to young adulthood of neural bottom-up and top-down processes using a functional magnetic resonance imaging task on emotional attention. We followed 249 participants from age 14-22 in up to four waves resulting in 687 total scans of a matching task in which participants decided whether two pictures were the same including distracting emotional or neutral scenes. We applied generalized additive mixed models and a reliability approach for longitudinal analysis. Reaction times and error rates decreased longitudinally. For top-down processing, we found a longitudinal increase for the bilateral inferior frontal gyrus (IFG) for negative stimuli and in the left IFG also for positive and neutral stimuli. For bottom-up activation in the bilateral amygdala, we found a relative stability for negative and neutral stimuli. For positive stimuli, there was an increase starting in the twenties. Results show ongoing behavioral and top-down prefrontal development relatively independent from emotional valence. Amygdala bottom-up activation remained stable except for positive stimuli. Current findings add to the sparse literature on longitudinal top-down and bottom-up development into young adulthood and emphasize the role of reliability. These findings might help to characterize healthy in contrast to dysfunctional development of emotional attention.

Reliability and stability challenges in ABCD task fMRI data

Trait stability of measures is an essential requirement for individual differences research. Functional MRI has been increasingly used in studies that rely on the assumption of trait stability, such as attempts to relate task related brain activation to individual differences in behavior and psychopathology. However, recent research using adult samples has questioned the trait stability of task-fMRI measures, as assessed by test-retest correlations. To date, little is known about trait stability of task fMRI in children. Here, we examined within-session reliability and long-term stability of individual differences in task-fMRI measures using fMRI measures of brain activation provided by the adolescent brain cognitive development (ABCD) Study Release v4.0 as an individual's average regional activity, using its tasks focused on reward processing, response inhibition, and working memory. We also evaluated the effects of factors potentially affecting reliability and stability. Reliability and stability (quantified as the ratio of non-scanner related stable variance to all variances) was poor in virtually all brain regions, with an average value of 0.088 and 0.072 for short term (within-session) reliability and long-term (between-session) stability, respectively, in regions of interest (ROIs) historically-recruited by the tasks. Only one reliability or stability value in ROIs exceeded the 'poor' cut-off of 0.4, and in fact rarely exceeded 0.2 (only 4.9%). Motion had a pronounced effect on estimated reliability/stability, with the lowest motion quartile of participants having a mean reliability/stability 2.5 times higher (albeit still 'poor') than the highest motion quartile. Poor reliability and stability of task-fMRI, particularly in children, diminishes potential utility of fMRI data due to a drastic reduction of effect sizes and, consequently, statistical power for the detection of brain-behavior associations. This essential issue urgently needs to be addressed through optimization of task design, scanning parameters, data acquisition protocols, preprocessing pipelines, and data denoising methods.

Editorial: Toward Neurobiological-Based Treatments of Depression and Anxiety: A Potential Case for the Nucleus Accumbens

Depression and anxiety disorders together account for the majority of mental health disorders in childhood and adolescence, and are often comorbid.¹ The frequent co-occurrence of these disorders has motivated clinicians and researchers to consider dimensional taxonomy models that focus on neurobiological substrates that explain transdiagnostic constructs of functioning (eg, reward processing abnormalities). Such an approach would redefine not only depression and anxiety disorders but could also revolutionize clinical care, as such biobehavioral targets, rather than a traditional primary diagnosis, could serve as the basis for treatment planning. In this issue of the Journal, Auerbach et al.² examined whether and how a key structure involved in reward processing, the nucleus accumbens (NAcc), is altered in adolescents aged 14 to 17 years with depression and/or anxiety (including generalized anxiety, separation anxiety, social anxiety, specific phobia, agoraphobia, and panic) disorders, and whether NAcc morphometry and function would improve prediction of 6-month symptomatology. As part of the Boston Adolescent Neuroimaging of Depression and Anxiety (BANDA) initiative,³ the researchers compared 129 adolescents with primary diagnoses of depression and/or anxiety and 64 psychiatrically healthy controls on gray matter volumes of the NAcc and on functional activation of the NAcc during a monetary incentive delay task using magnetic resonance imaging (MRI) protocols harmonized with the Human Connectome project (http://www.humanconnectomeproject.com/). Compared to healthy adolescents, depressed/anxious adolescents exhibited significantly smaller volumes of the NAcc and blunted NAcc responses to reward receipt. Among the 88 depressed/anxious adolescents and 57 healthy controls who provided symptom data 6 months later, the researchers also found that inclusion of NAcc volumes, but not reward-related responses of the NAcc on the task, significantly improved statistical prediction of subsequent depression symptoms.

Peer Connectedness and Pre-Existing Social Reward Processing Predicts U.S. Adolescent Girls' Suicidal Ideation During COVID-19

There is major concern about the impact of the COVID-19 pandemic on adolescent suicidal ideation (SI) and peer relationships. We investigated (1) rates of SI and (2) the extent to which peer connectedness and pre-existing neural activation to social reward predicted SI during the initial stay-at-home orders of the pandemic (April-May 2020) in a longitudinal sample of adolescent girls (N = 93; Mage  = 15.06; 69% White non-Hispanic). Daily diary and fMRI methods were used to assess peer connectedness and neural activation to social reward, respectively. Nearly 40% of girls endorsed SI during the initial stay-at-home orders. Greater peer connectedness and neural responsivity to anticipated social reward were associated with a reduced odds of SI during the pandemic among girls.