[1] 8w Preschool and School-Age Irritability Predict Reward-Related Brain Function

[1] 234w Objective: Although chronic irritability in childhood is prevalent, impairing, and predictive of later maladjustment, its pathophysiology is largely unknown. Deficits in reward processing are hypothesized to play a role in irritability. The current study aimed to identify how the developmental timing of irritability during preschool and school-age relates to reward-related brain function during school-age.Method: Children's irritability was assessed during the preschool period (Wave 1; ages 3.0-5.9 years) and three years later (Wave 2; ages 5.9-9.6 years) using a clinical interview. At Wave 2, children (N=46; 28 females) performed a monetary incentive delay task in which they received rewards, if they successfully hit a target, or no reward regardless of performance, during fMRI acquisition. Results:Children with more vs. less severe preschool irritability, controlling for concurrent irritability, exhibited altered reward-related connectivity: right amygdala with insula and inferior parietal lobe as well as left ventral striatum with lingual gyrus, post-central gyrus, superior parietal lobe and culmen. Children with more vs. less severe concurrent irritability, controlling for preschool irritability, exhibited a similar pattern of altered connectivity between left and right amygdalae and superior frontal gyrus and between left ventral striatum and precuneus and culmen. Neural differences associated with irritability were most evident between reward and no reward conditions when participants missed the target. Conclusion:Preschool irritability and concurrent irritability were uniquely associated with aberrant patterns of reward-related connectivity, highlighting the importance of developmental timing of irritability for brain function.

[1] 52w Irritability, defined as low frustration tolerance characterized by anger and temper outbursts, is a common and impairing symptom in youth. Irritability is one of the most frequent reasons for treatment referral and is present across multiple emotional and behavioral disorders, 1,2 including as the cardinal feature of DSM-5 disruptive mood dysregulation disorder.

[2] 68w Chronic irritability in school-age children and adolescents predicts depressive and anxiety disorders, suicidality, and functional impairment in adulthood. 1,3,4 Emerging findings also support the significance of irritability in early childhood, demonstrating that preschool-age irritability predicts psychiatric disorders, functional impairment, and treatment use later in childhood, even after accounting for baseline psychopathology. 5,6 Despite its prevalence and central role in developmental psychopathology, the pathophysiology of irritability is largely unknown.

[3] 141w Aberrant reward processing may be a pathway to chronic irritability in youth. [7][8][9][10] Reward processing constitutes an interconnected neural network including the striatum, amygdala, anterior cingulate cortex, prefrontal cortex, and midbrain regions. [11][12][13] Although research is limited, some studies [14][15][16] have demonstrated that youth with chronic irritability evidence a lower threshold for experiencing frustration when they fail to receive a reward (i.e., frustrative nonreward 7,8 ) compared to non-irritable youth. This observation may be due to difficulties in instrumental learning and cognitive flexibility (i.e., learning when to expect rewards and how to adjust to different reward contingencies). 17,18 Prior studies have reported neural abnormalities, including decreased amygdala activation and aberrations in prefrontal recruitment, when irritable youths failed to receive a reward, 14,15,19,20 and some findings indicate differences in striatal activation. 14,19 However, no research has examined associations between irritability and reward-

[4] 291w This study sought to identify the unique effects of preschool irritability and concurrent irritability on reward-related neural processes during early school-age. Examining irritability across childhood may provide insight into how the developmental timing of irritability influences the nature of brain function. Etiological pathways involving reward processing may be similar or unique depending on the developmental timing of the youth's irritability. Moreover, previous research has demonstrated that preschool irritability predicts later psychological outcomes and functional impairment, 5,6 supporting the importance of identifying irritability early and intervening; however, no prior study has tested whether preschool irritability predicts later childhood neural outcomes, which will be an important step toward identifying neural The study's focus is network connectivity, i.e., correlation of different brain regions' activation as a function of reward/no-reward contexts, as brain regions form highly connected neural circuits. By adopting a network perspective, this study increases our understanding of how irritability relates to the functional organization of the brain during reward processing. Analyses focused on amygdala connectivity, as there have been findings in older irritable youth and adults pointing towards the involvement of amygdala recruitment in aberrant reward processing. 14,20 Moreover, abnormalities in amygdala activation across a variety of tasks have been the most consistent finding in the irritability literature. 7,8,27 At preschool and early school-age, it is expected that amygdala-prefrontal connectivity during reward processing will relate to irritability symptom severity. The current study also examined striatal connectivity; the striatum plays a key role in reward processing, 28 and abnormalities in striatal activation during reward processing have also been linked to youth irritability. 14,19 Finally, consistent with previous studies, 14,15,19,20 we conducted traditional activation analyses, both whole-brain and regions-of-interest (ROI), to examine associations between irritability and reward-related activation in the amygdala and ventral striatum.

[1] 84w ACCEPTED MANUSCRIPT childhood irritability symptoms. 5,23 Study exclusion criteria consisted of child developmental/physical disability, non-fluent in English, and a lifetime history of psychotic or bipolar disorder in either biological parent. Data on child psychological symptoms were collected at two time points (Wave 1: 3-5 years; Wave 2: ~3 years post-Wave 1), and child neuroimaging data were collected from a subset participating at Wave 2. Parents gave written informed consent, and minor participants (>7 years) gave assent. The University's Institutional Review Board approved study procedures.

[2] 188w At Wave 2, 64 children (ages 5.9-9.6 years), free of MRI contraindications, volunteered to participate in the neuroimaging assessment. Of the 64 volunteers, one child was not scanned due to claustrophobia, 17 were excluded due to issues with data collection (n=10 had incomplete scan data; n=3 had excessive head motion [see fMRI Data Preprocessing]; n=2 completed a different scan protocol; n=1 had inadequate neuroanatomical scan coverage; n=1 was missing behavioral data), leaving a final sample of 46 usable datasets. No children were taking psychotropic medications. The 46 children whose neuroimaging datasets were included versus those without usable data did not differ on any demographic or clinical variable included in the study. There were no differences between the scanned subsample and those who were not scanned at Wave 2 on any demographic or clinical variable with one exception: the MRI subsample had significantly higher irritability scores at Wave 2 (M=1.61, SD=1.61) than those who did not complete the MRI assessment at Wave 2 (M=0.94, SD=1.16, p=.023); there were no differences between the MRI subsample and children who only completed the Wave 1 assessment. See Table 1 for sample characteristics.

[3] 37w Irritability was not significantly associated with demographic characteristics. Consistent with large behavior studies of irritability, 5,23 the association between Waves 1 and 2 irritability was marginally significant in the scanned subsample (Spearman rho=.29, p=.05), demonstrating low stability.

[4] 93w Preschool irritability and school-age brain connectivity. Whole-brain corrected analyses showed that Wave 1 irritability, controlling for Wave 2, predicted degree of right amygdala connectivity with insula and inferior parietal lobule, dependent on whether the target was hit and whether there was a potential reward (Wave 1 Irritability [controlling for Wave 2] x Performance x Condition; Table 2). Children with more severe irritability at Wave 1 exhibited altered patterns of connectivity, compared to children with less severe irritability, when hitting and missing the target during reward and no reward conditions (Figure 1). Differences in

[5] 19w connectivity associated with preschool irritability were particularly evident between reward and no reward conditions when participants missed the target.

[6] 75w The three-way interaction was not significant for the ventral striatum, but Wave 1 Irritability (controlling for Wave 2) x Performance was significant in several clusters connected with the left ventral striatum, including lingual gyrus (Figure 1), postcentral gyrus, superior parietal lobule, and culmen (Table 2). Across all areas, and as illustrated for lingual gyrus (Figure 1), higher levels of preschool irritability were associated with greater connectivity during hit trials and less connectivity during miss trials.

[7] 162w analyses revealed that Wave 2 irritability, controlling for Wave 1, was associated with degree of left and right amygdala connectivity with superior frontal gyrus, depending on whether the target was hit and presence of potential reward (Wave 2 Irritability [controlling for Wave 1] x Performance x Condition; Table 2). This three-way interaction with Wave 2 irritability was driven by similar patterns as the three-way interactions at Wave 1: children with greater vs. lesser concurrent irritability showed altered patterns of connectivity, particularly when they missed targets with and without rewards (Figure 2). Whole-brain corrected connectivity analyses with the left ventral striatum seed also indicated a significant Wave 2 Irritability (controlling for Wave 1) x Performance x Condition interaction for left ventral striatum-right precuneus and -culmen connectivity (Table 2). Similar to the pattern found with amygdalae connectivity, the interaction for ventral striatal connectivity was driven by differences in connectivity between reward and no reward conditions when participants missed the target (Table 2; Figure 2).

[8] 9w activation analyses survived a conservative Type I error correction.

[9] 178w No significant main effect of Wave 2 irritability. Figure 1. More severe preschool-age irritability predicts atypical modulation of amygdala and ventral striatal connectivity in school-age, controlling for concurrent irritability. Note: (A) Right amygdala-right inferior parietal lobule and (B) right amygdala-right insula connectivity clusters with significant Wave 1 Irritability x Performance x Condition interactions during feedback period; (C) left ventral striatum-right lingual gyrus connectivity cluster with significant Wave 1 Irritability x Performance interaction during feedback period. Brain images represent axial sections (left=left) with threshold set at whole-brain corrected p<.05. Interaction effects were estimated using simple slopes analyses 50 at the maximum level of youth irritability ("high" irritability), at the mean level of youth irritability, and at the minimum level of youth irritability ("low" irritability). Values from clusters were extracted and averaged for plots. more severe school age irritability, above and beyond preschool age irritability. Note: (A) Right amygdala-and (B) left amygdala-superior frontal gyrus and (C) left striatumright precuneus connectivity clusters with significant Wave 2 Irritability x Performance x Condition interactions during feedback period. Brain images represent axial sections (left=left)

[1] 88w This study investigated the unique effects of early and concurrent irritability on rewardrelated brain function in school-age children. We observed that children with more vs. less severe preschool-age irritability, controlling for concurrent irritability, exhibited aberrant patterns of connectivity between right amygdala and insula and inferior parietal lobe depending on whether the target was hit/missed and presence of potential reward. In addition, preschool irritability was associated with greater connectivity between left ventral striatum and lingual gyrus, postcentral gyrus, superior parietal lobule and culmen when hitting vs. missing the target.

[2] 90w Children with more vs. less severe concurrent irritability, controlling for preschool irritability, exhibited similar aberrant patterns of left and right amygdalae connectivity with superior frontal gyrus and left ventral striatum with precuneus and culmen when hitting or missing the target during reward and no-reward conditions. Results held after controlling for maternal depression and child internalizing and externalizing scores, suggesting that links between irritability and brain function are not primarily driven by related constructs. These findings highlight how reward-related neural circuits observed in school-age children may be altered in children with

[1] 42w Participants were recruited from a larger study investigating biological risk factors for depression. 29,30 Families were recruited via flyers and a commercial mailing list and oversampled for offspring with maternal depression; thus, the sample is enriched to achieve a wider range of

[2] 41w Participating children underwent an fMRI scan using a 3T Siemens scanner equipped with a 12-channel head coil. During task acquisition, blood oxygen level dependent (BOLD) images were acquired as 36 contiguous axial slices parallel to the AC-PC line, with whole brain

[3] 88w Neurological processes related to reward processing were assessed using a child-friendly monetary incentive delay task. 13,30 We previously reported that this task is effective at eliciting neural responses of reward processing in this sample. 30 During fMRI acquisition, children were given the opportunity to win stars by pressing a button to hit a target; stars translated into money earned (<$15). The task consisted of cue (2000ms) period, during which the child was informed of whether or not they would earn a reward (50% reward condition, 50% no-reward condition).

[4] 146w Across both conditions, there was a variable anticipation period in which they waited to hit the target (2500-5500ms) and feedback (1500ms) on whether they hit or missed the target. During reward conditions only, they were given feedback that hits resulted in monetary reward and misses resulted in no monetary reward. The task was projected onto a screen that participants viewed via a mirror attached to the head coil. Time was automatically adjusted (+/-50ms) based on the participant's performance during the task. Task runs spanned 4 minutes 52 seconds, and each child completed 3 runs with a total 60 trials across all runs (30 trials reward, 30 no-reward conditions). One child completed two of the three runs; all available data were included in the analyses. Because past findings in this sample 30 were in the feedback period, the connectivity analyses reported below focused on the feedback period.

[5] 19w To identify the role that preschool and school-age irritability symptoms played in reward-related brain connectivity, second-level analyses were conducted

[1] 36w related network connectivity, despite that brain regions do not act in isolation. Connectivity studies addressing this important gap would provide insight into the neural circuitry underlying irritability, which could inform the development of mechanistic treatment targets.

[2] 87w With the exception of Perlman et al., 19 all prior studies have been in adolescents, even though irritability in early childhood is common and impairing. 5,6,21,22 Although trajectories of irritability across childhood demonstrate considerable variability, 23 normatively, irritability decreases from preschool-to school-age, 22,23 as children's regulatory capacities to inhibit temper outbursts increase; thus, children who demonstrate steady or increasing irritability across childhood become more atypical compared to peers. 23 Little work has been done, however, to examine neural correlates of irritability symptoms during preschool-age and early school-age.

[3] 30w Identifying neural mechanisms is important because irritability during childhood is a potent predictor of later maladjustment 8 and reward-related neural circuits undergo significant development from early childhood into adulthood. [24][25][26]

[4] 255w At Waves 1 and 2, primary caregivers were interviewed with the Preschool Age Psychiatric Assessment (PAPA 31 ). A 6-item measure of chronic irritability symptoms was derived from the PAPA (Wave 1: ICC=.97; α=.71; Wave 2: ICC=.96; α=.64). See 5,6 for a complete description of the scale. Items included: irritable mood, feelings of anger under minor provocation, displays of anger under minor provocation, feelings of frustration under minor provocation, episodes of temper without violence, and episodes of excessive temper, manifested by shouting, crying, or stomping, and/or involving violence/damage. PAPA items were rated for intensity, frequency, and duration. The intensity rating indicates whether a symptom was absent/present and the extent to which it was intrusive, interfering, and generalizable across activities. A rating of two or higher on a two or three-point scale indicates that the symptom was present at a threshold level of intensity. Frequency items reflect the number of occurrences during the last three months. Following guidelines for chronic irritability, 1,32 items were coded as present if a child engaged in the behavior at least 45 times in the past three months. The duration criterion was coded as present if the child was rated as having at least a 30-minute duration on irritable mood, prone to frustration, annoyance or anger, or difficulty recovering from temper tantrums. The total irritability scale consisted of the sum of symptoms coded as present according to the intensity, frequency, and duration criteria. The PAPA has been shown to have acceptable psychometric properties when used in children through age 8. 33

[5] 55w coverage, using an echo planar single-shot gradient echo pulse sequence (matrix size=64x64, TR=2000ms, TE=25ms, flip angle=70°, FOV=192mm, voxel size=3x3x3mm, 438 images across all runs). Anatomical images (T1-weighted MPRAGE) were acquired at high resolution for anatomical localization and spatial normalization (176 1.0mm sagittal slices, flip angle=9°, matrix size=256x256, FOV=250mm, voxel size=1x1x1mm). See 30 for additional information.

[6] 70w fMRI data preprocessing. Standard fMRI data preprocessing protocols were implemented, using Analysis of Functional NeuroImages (AFNI; https://afni.nimh.nih.gov/afni/) to perform slice-time correction, realignment of functional images, spatial smoothing at 4mm, and non-linear registration for spatial standardization to the Talairach template. TR pairs with frame-wise displacement exceeding 1mm were censored from participant-level analysis, and participants with mean framewise head displacement ≥.30mm or censoring of ≥35% of TRs were excluded from all analyses.

[7] 102w Generalized PPI. The current study used generalized psychophysiological interaction analysis (gPPI 34 ) to calculate connectivity between brain areas during the feedback period of the reward task. gPPI calculates change in correlations between a seed region of interest and all other regions in each condition compared to implicit baseline. Generalized methods 34 are advantageous as they allow for the evaluation of more than two task conditions in a single model. Given past work on this task 13,30 and prior fMRI work strongly implicating amygdala dysfunction in irritability, 14,27 the current study focused on left and right amygdala as seeds for gPPI analyses.

[8] 97w We also examined ventral striatum (i.e., nucleus accumbens) as the seed. Masks for seeds and other masks (see secondary analyses below) were created using the Talairach daemon atlas in AFNI 35 (left amygdala=756mm 3 ; right amygdala=972mm 3 ; ventral striatum [nucleus accumbens]=108mm 3 ). The end product is a set of voxel-wise images that represent connectivity between the seed region and the rest of the brain in each condition (reward/hit, reward/miss, noreward/hit, no-reward/miss). Estimated head motion in x, y, z, roll, pitch, yaw directions and third-degree polynomials to model low-frequency drift were included in the model.

[9] 164w with the gPPI images (reward/hit, reward/miss, no-reward/hit, no-reward/miss for each individual) using a whole-brain, group-level ANCOVA via AFNI's 3dMVM program, including Wave 1 and 2 Irritability as quantitative, between-subjects variables, and Performance (hit, miss) and Condition (no reward, reward) as within-subject variables. Significant clusters in contrasts with Wave 1 Irritability thus represent brain function at Wave 2 predicted by preschool irritability, above and beyond concurrent irritability. Contrasts with Wave 2 Irritability represent contributions of concurrent irritability to brain function at Wave 2 above and beyond preschool irritability. We report the Wave 1 Irritability (controlling for Wave 2) x Performance x Condition and Wave 2 Irritability (controlling for Wave 1) x Performance x Condition interactions, which examined whether irritability severity relates to brain connectivity, depending on whether participants successfully hit the target, and whether a reward was received. Where 3-way interactions were not significant, we report lower-order interactions (Irritability x Performance, Irritability x Condition, Irritability main effect) to identify other connectivity disparities related to irritability.

[10] 119w Results were corrected for multiple comparisons, employing a whole-brain corrected threshold (p<.05). The cluster threshold was calculated by 3dClustSim using the updated mixedmodel spatial autocorrelation function (-acf) and the NN1 bisided option; bisided allows both positive and negative voxels above threshold to be clustered separately and both sets of clusters to be retained. The group mask used in the 3dClustSim calculation represented brain regions where 90% of participants had valid data. Model parameters were calculated by 3dFWHMx for each run separately, were averaged over runs for each participant, and then averaged across participants (left amygdala: .66, 3.02, 11.15; right amygdala: .66, 3.02, 11.19; left ventral striatum: .65, 3.03, 11.15; right ventral striatum: .65, 3.03, 11.16). The cluster extent threshold

[11] 118w across all models was k≥28 voxels (756 mm 3 ) with a conservative height threshold of p<.005, which is appropriate for event-related designs. 36,37 This correction method addresses issues raised by Eklund and colleagues 36 regarding cluster correction methods. 37 Secondary analyses. We conducted traditional activation analyses, both whole-brain and ROI, as described in prior work 30 . Whole brain analyses were corrected using the same method as described above. The secondary ROI analyses probed differences in irritability in the amygdala and ventral striatum, regions utilized in the gPPI analyses, and reported to show altered responses in previous reward and irritability studies. 38 Average ROI responses were extracted for each condition in each individual using ANOVA in SPSS.

[12] 63w Additional Analyses. To investigate the impact of other variables, analyses were repeated separately with the following covariates: child age, maternal depression, child internalizing and externalizing symptoms at Waves 1 and 2, and time between Waves. All findings remained significant after including these covariates, supporting the impact of irritability on brain functioning, independent of other constructs (see Supplement 1 and Tables S1-S3, available online).

[13] 17w increased concurrent irritability and in children with early preschool-age irritability, suggesting possible mechanisms underlying impairing mood dysregulation.

[14] 257w Children with higher levels of preschool-age irritability demonstrated alterations in brain connectivity during reward processing compared to children with lower levels of early irritability. Although children with lower levels of preschool irritability showed little to no modulation of amygdala connectivity with insula and inferior parietal lobule between the various trial types, children with higher levels of preschool irritability evidenced decreased amygdala connectivity with these regions on miss vs. hit trials during reward conditions and increased connectivity on miss vs. hit trials during non-reward conditions. These differences in connectivity in relation to preschool irritability level were particularly evident between reward and no-reward conditions when participants missed the target. The aberrant connectivity patterns observed in children with greater preschool irritability during miss vs. hit trials as a function of reward may reflect that irritable youth show inappropriate modulation following both reward attainment and non-attainment. 7,8 Furthermore, although children with lower levels of preschool irritability did not show differences in left ventral striatum connectivity with lingual gyrus, postcentral gyrus, superior parietal lobule, and culmen between hits and misses, children with higher levels of preschool irritability evidenced greater connectivity between these regions during hit trials and decreased connectivity between these regions during miss trials. This finding suggests that early irritability predicts aberrant connectivity in response to performance success and failure, regardless of reward, which may contribute to greater frustration and outbursts in response to failures in irritable youth. 7,8 Concurrent irritability was similarly associated with altered patterns of connectivity after accounting for preschool irritability. Children with lower levels of school-age irritability

[15] 135w evidenced greater connectivity between both left and right amygdalae and superior frontal gyrus on miss vs. hit trials during reward conditions and decreased connectivity between these regions on miss vs. hit trials during non-reward conditions. In contrast, children with greater school-age irritability showed the opposite pattern, and the differences were most pronounced on misses during reward trials. Amygdala and prefrontal cortex, including superior frontal gyrus, have been implicated in the neural circuity supporting reward processing, emotion processing, attention, and inhibition/cognitive control. 7,8,10,39 Given research supports the coupling of amygdala and frontal regions in both bottom-up emotion generation systems and top-down emotion regulation systems, 10 it is possible that abnormalities in their connectivity during reward processing may contribute to heightened experiences of frustrative non-reward, particularly as observed differences were most notable when children missed the target.

[16] 159w A similar altered pattern of connectivity between the left ventral striatum and right precuneus and culmen was observed for children with greater concurrent irritability. Children with greater school-age irritability evidenced an opposite pattern of connectivity between these regions compared to children with lower levels of concurrent irritability on reward trials. While children with lower levels of school-age irritability demonstrated decreased connectivity between left ventral striatum and precuneus and culmen on miss vs. hit trials during reward, children with greater school-age irritability demonstrated greater connectivity on miss vs. hit trials during reward. During non-reward trials, children with high and low irritability showed similar connectivity patterns on miss and hit trials. The striatum is a key brain region involved in the anticipation and receipt of both reward and punishment, 28 and the precuneus is considered a hub in the default mode network, a network hypothesized to be involved in self-referential processing, affective decision making, and emotion regulation. 40 Resting state functional

[17] 245w connectivity studies have linked connectivity between these regions to depression, 41,42 and a recent study 43 reported a similarly aberrant pattern of ventral striatum-precuneus connectivity in depressed adults vs. controls during loss vs. reward trials. Taken together, these findings suggest that irritable youth evidence aberrant connectivity during reward processing, similar to what is observed in depressed adults, which may explain links between youth irritability and adult depression. 1,3,4 In contrast to previous findings examining irritability, primarily in adolescence, 14,15,19,20 irritability in preschool-age and school-age was not associated with brain activation differences, when participants failed to receive a reward. These divergent findings may be due to differences in age (childhood vs. adolescence), particularly as this neural circuitry undergoes developmental changes across childhood and into adulthood. 39,44,45 Furthermore, the tasks used in these studies varied widely, and reward and non-reward outcomes have not always been isolated. In addition, all prior irritability and reward studies employed extreme group designs, typically comparing youth with clinical levels of severe irritability to healthy comparison children. Although our sample was enriched for risk, given that we did not recruit a clinical sample, we did not have many children with extremely high levels of irritability. It is possible that activation differences are most evident in severe cases of irritability only, whereas connectivity differences may be more sensitive to individual differences in irritability using a dimensional approach. As this is the first study to examine reward-related functional connectivity and activation, this requires further investigation.

[18] 37w Our findings suggest that early and concurrent symptoms of chronic irritability are related to unique reward-related neural circuits. In addition, results pose that irritability-connectivity associations involving the amygdala may be more lateralized in early childhood and "spread"

[19] 107w bilaterally as children age. Moreover, these brain circuits mature considerably across childhood, resulting in improved regulatory capacities in executive functioning and emotion regulation. 46,47 Thus, aberrations in this circuitry may contribute to poorer regulatory capacities to inhibit frustration in response to blocked rewards, which is particularly problematic as age-matched peers are developing strategies to inhibit frustration successfully. Lastly, establishing links between childhood irritability and reward-related neural processes could explain links between childhood irritability and depression and externalizing psychopathology, which have also been linked to reward processing deficits. Thus, reward-related processing deficits may be a common underlying factor, perhaps increasing risk for each, as well as their co-occurrence.

[20] 23w This study had several strengths. First, whereas prior studies typically focused on adolescents, our sample included children assessed from preschool-age to early school-age.

[21] 104w Examining neural correlates of irritability at younger ages allows us to map the developmental timing of impairing and chronic mood dysregulation and its mechanisms. Next, our study uniquely examined network connectivity as a function of reward context. A network approach examines the interconnectedness of brain regions and contributes to our understanding of the functional organization of brain activity in relation to irritability. This is important as activation analyses failed to detect effects that were evident in connectivity analyses. Lastly, unlike previous studies, we used a dimensional construct of youth irritability, as the boundaries between clinically significant irritability and normative irritability continue to be investigated.

[22] 54w The study also had limitations. First, although our sample size was comparable to previous studies, 14,15,19,20 our sample size was modest (n=46) and not sufficient to examine how the developmental trajectory of irritability relates to reward-related brain function. Second, the ventral striatum mask encompassed a small region (nucleus accumbens; k=4 voxels, 108mm 3 ).

[23] 119w Replication with higher resolution scans (e.g., using stronger magnetic fields, although 7T scans are not currently indicated in children due to their possible side effects) with individually traced nucleus accumbens will be necessary to confirm results. Lastly, although our study used a longitudinal design, MRI scans only took place at one assessment; therefore, we do not know whether these reward-related aberrations are present earlier in development. Ideally, future research would scan children at the earlier time-point in childhood (~age 4); however, this would require a reward task that is developmentally appropriate for both 4-and 7-year-olds to compare brain activation over time and would additionally require overcoming challenges inherent in scanning young children (i.e., remaining still while completing a task).

[24] 129w Our findings support hypotheses that irritable youth show impairments in reward processing and point to how coordinated neural networks may be altered in youth with higher levels of early and concurrent irritability. Future work should incorporate a multi-method assessment, involving assessments of multiple behavioral and neural facets of reward learning, as well connectivity at rest, to characterize reward-related mechanisms involved in irritability. This research has important clinical implications. Specifically, identifying the neural architecture of irritability may be used to characterize irritability and its associations with other forms of psychopathology, which could refine how we classify and treat mental health problems. Lastly, this research may lead to earlier identification of at-risk individuals and inform the development of targeted mechanistic approaches to intervention. No significant main effect of Wave 1 irritability.

[25] 42w with threshold set at whole-brain corrected p<.05. Interaction effects were estimated using simple slopes analyses 50 at the maximum level of youth irritability ("high" irritability), at the mean level of youth irritability, and at the minimum level of youth irritability ("low" irritability).

[26] 9w Values from clusters were extracted and averaged for plots.