Amygdala functional connectivity predicts pharmacotherapy outcome in pediatric bipolar disorder

Innovative Neuroimaging Biomarker Distinction of Major Depressive Disorder and Bipolar Disorder through Structural Connectome Analysis and Machine Learning Models

Major depressive disorder (MDD) and bipolar disorder (BD) share clinical features, which complicates their differentiation in clinical settings. This study proposes an innovative approach that integrates structural connectome analysis with machine learning models to discern individuals with MDD from individuals with BD. High-resolution MRI images were obtained from individuals diagnosed with MDD or BD and from HCs. Structural connectomes were constructed to represent the complex interplay of brain regions using advanced graph theory techniques. Machine learning models were employed to discern unique connectivity patterns associated with MDD and BD. At the global level, both BD and MDD patients exhibited increased small-worldness compared to the HC group. At the nodal level, patients with BD and MDD showed common differences in nodal parameters primarily in the right amygdala and the right parahippocampal gyrus when compared with HCs. Distinctive differences were found mainly in prefrontal regions for BD, whereas MDD was characterized by abnormalities in the left thalamus and default mode network. Additionally, the BD group demonstrated altered nodal parameters predominantly in the fronto-limbic network when compared with the MDD group. Moreover, the application of machine learning models utilizing structural brain parameters demonstrated an impressive 90.3% accuracy in distinguishing individuals with BD from individuals with MDD. These findings demonstrate that combined structural connectome and machine learning enhance diagnostic accuracy and may contribute valuable insights to the understanding of the distinctive neurobiological signatures of these psychiatric disorders.

Neuroimaging alterations associated with medication use in early-onset bipolar disorder: An updated review

BACKGROUND

Pediatric bipolar disorder (PBD) is a severe disorder characterized by mood fluctuations starting at a young age. Several neuroimaging studies revealed a specific biological signature of PBD involving alterations in the amygdala and prefrontal regions. Considering the growing concerns regarding the effects of PBD treatments on developing brains, this review aims to provide an overview of the studies investigating the effect of mood stabilizers, antipsychotics, and anticonvulsants on neuroimaging findings in PBD.

METHODS

We searched PubMed, Scopus, and Web of Science to identify all structural magnetic resonance imaging (sMRI), functional magnetic resonance imaging (fMRI), and diffusion tensor imaging (DTI) studies exploring the effects of medications on neuroimaging findings in PBD. A total of 18 studies met our inclusion criteria (fMRI n = 11, sMRI n = 6, DTI n = 1).

RESULTS

Although the findings varied highly across the studies, some investigations consistently indicated that medications primarily affect the prefrontal cortex and the amygdala. Moreover, despite some exceptions, the reported medication effects predominantly lean towards structural and functional normalization.

LIMITATIONS

The reviewed studies differ in methods, medications, and fMRI paradigms. Furthermore, most studies used observational approaches with small sample sizes, minimizing the statistical power.

CONCLUSIONS

Evidence suggests the potential of antipsychotics and mood stabilizers to modulate the neuroimaging findings in PBD patients, mostly normalizing brain structure and function in key mood-regulating regions.

Brain morphometric features predict medication response in youth with bipolar disorder: a prospective randomized clinical trial

BACKGROUND

Identification of treatment-specific predictors of drug therapies for bipolar disorder (BD) is important because only about half of individuals respond to any specific medication. However, medication response in pediatric BD is variable and not well predicted by clinical characteristics.

METHODS

A total of 121 youth with early course BD (acute manic/mixed episode) were prospectively recruited and randomized to 6 weeks of double-blind treatment with quetiapine (n = 71) or lithium (n = 50). Participants completed structural magnetic resonance imaging (MRI) at baseline before treatment and 1 week after treatment initiation, and brain morphometric features were extracted for each individual based on MRI scans. Positive antimanic treatment response at week 6 was defined as an over 50% reduction of Young Mania Rating Scale scores from baseline. Two-stage deep learning prediction model was established to distinguish responders and non-responders based on different feature sets.

RESULTS

Pre-treatment morphometry and morphometric changes occurring during the first week can both independently predict treatment outcome of quetiapine and lithium with balanced accuracy over 75% (all p < 0.05). Combining brain morphometry at baseline and week 1 allows prediction with the highest balanced accuracy (quetiapine: 83.2% and lithium: 83.5%). Predictions in the quetiapine and lithium group were found to be driven by different morphometric patterns.

CONCLUSIONS

These findings demonstrate that pre-treatment morphometric measures and acute brain morphometric changes can serve as medication response predictors in pediatric BD. Brain morphometric features may provide promising biomarkers for developing biologically-informed treatment outcome prediction and patient stratification tools for BD treatment development.

The association of genetic variation in CACNA1C with resting-state functional connectivity in youth bipolar disorder

BACKGROUND

CACNA1C rs1006737 A allele, identified as a genetic risk variant for bipolar disorder (BD), is associated with anomalous functional connectivity in adults with and without BD. Studies have yet to investigate the association of CACNA1C rs1006737 with resting-state functional connectivity (rsFC) in youth BD.

METHODS

Participants included 139 youth with BD-I, -II, or -not otherwise specified, ages 13-20 years, including 27 BD A-carriers, 41 BD non-carriers, 32 healthy controls (HC) A-carriers, and 39 HC non-carriers. Anterior cingulate cortex (ACC), amygdala, and orbitofrontal cortex (OFC) were examined as regions-of-interest in seed-to-voxel analyses. General linear models included main effects of diagnosis and rs1006737, and an interaction term, controlling for age, sex, and race.

RESULTS

We observed a main effect of BD diagnosis on rsFC between the right amygdala and the right occipital pole (p = 0.02), and a main effect of rs1006737 genotypes on rsFC between the right OFC and bilateral occipital cortex (p < 0.001). Two significant BD diagnosis-by-CACNA1C rs1006737 interactions were also identified. The A allele was associated with positive rsFC between the right ACC and right amygdala in BD but negative rsFC in HC (p = 0.01), and negative rsFC between the left OFC and left putamen in BD but positive rsFC in HC (p = 0.01).

CONCLUSION

This study found that the rs1006737 A allele, identified as a genetic risk variant for BD in adults, was differentially associated with rsFC in youth with BD in regions relevant to emotion, executive function, and reward. Future task-based approaches are warranted to better understand brain connectivity in relation to CACNA1C in BD.

Does the Brain Matter? Cortical Alterations in Pediatric Bipolar Disorder: A Critical Review of Structural and Functional Magnetic Resonance Studies

Pediatric bipolar disorder (PBD) is associated with significant psychosocial impairment, high use of mental health services and a high number of relapses and hospitalization. Neuroimaging techniques provide the opportunity to study the neurodevelopmental processes underlying PBD, helping to identify the endophenotypic markers of illness and early biological markers of PBD. The aim of the study is to review available studies assessing structural and functional brain correlates associated with PBD. PubMed, ISI Web of Knowledge and PsychINFO databases have been searched. Studies were included if they enrolled patients aged 0-18 years with a main diagnosis of PBD according to ICD or DSM made by a mental health professional, adopted structural and/or functional magnetic resonance as the main neuroimaging method, were written in English and included a comparison with healthy subjects. Of the 400 identified articles, 46 papers were included. Patients with PBD present functional and anatomic alterations in structures normally affecting regulations and cognition. Structural neuroimaging revealed a significant reduction in gray matter, with cortical thinning in bilateral frontal, parietal and occipital cortices. Functional neuroimaging studies reported a reduced engagement of the frontolimbic and hyperactivation of the frontostriatal circuitry. Available studies on brain connectivity in PBD patients potentially indicate less efficient connections between regions involved in cognitive and emotional functions. A greater functional definition of alteration in brain functioning of PBD patients will be useful to set up a developmentally sensitive targeted pharmacological and nonpharmacological intervention.

A graph theory neuroimaging approach to distinguish the depression of bipolar disorder from major depressive disorder in adolescents and young adults

BACKGROUND

Markers to differentiate depressions of bipolar disorder (BD-Dep) from depressions of major depressive disorder (MDD-Dep), and for more targeted treatments, are critically needed to decrease current high rates of misdiagnosis that can lead to ineffective or potentially deleterious treatments. Distinguishing, and specifically treating the depressions, during the adolescent/young adult epoch is especially important to decrease illness progression and improve prognosis, and suicide, as it is the epoch when suicide thoughts and behaviors often emerge. With differences in functional connectivity patterns reported when BD-Dep and MDD-Dep have been studied separately, this study used a graph theory approach aimed to identify functional connectivity differences in their direct comparison.

METHODS

Functional magnetic resonance imaging whole-brain functional connectivity (Intrinsic Connectivity Distribution, ICD) measures were compared across adolescents/young adults with BD-Dep (n = 28), MDD-Dep (n = 20) and HC (n = 111). Follow-up seed-based connectivity was conducted on regions of significant ICD differences. Relationships with demographic and clinical measures were assessed.

RESULTS

Compared to the HC group, both the BD-Dep and MDD-Dep groups exhibited left-sided frontal, insular, and medial temporal ICD increases. The BD-Dep group had additional right-sided ICD increases in frontal, basal ganglia, and fusiform areas. In seed-based analyses, the BD-Dep group exhibited increased interhemispheric functional connectivity between frontal areas not seen in the MDD-Dep group.

LIMITATIONS

Modest sample size; medications not studied systematically.

CONCLUSIONS

This study supports bilateral and interhemispheric functional dysconnectivity as features of BD-Dep that may differentiate it from MDD-Dep in adolescents/young adults and serve as a target for early diagnosis and treatment strategies.

Neurobiological Markers for Predicting Treatment Response in Patients with Bipolar Disorder

Predictive neurobiological markers for prognosis are essential but underemphasized for patients with bipolar disorder (BD), a neuroprogressive disorder. Hence, we developed models for predicting symptom and functioning changes. Sixty-one patients with BD were recruited and assessed using the Young Mania Rating Scale (YMRS), Montgomery−Åsberg Depression Rating Scale (MADRS), Positive and Negative Syndrome Scale (PANSS), UKU Side Effect Rating Scale (UKU), Personal and Social Performance Scale (PSP), and Global Assessment of Functioning scale both at baseline and after 1-year follow-up. The models for predicting the changes in symptom and functioning scores were trained using data on the brain morphology, functional connectivity, and cytokines collected at baseline. The correlation between the predicted and actual changes in the YMRS, MADRS, PANSS, and UKU scores was higher than 0.86 (q < 0.05). Connections from subcortical and cerebellar regions were considered for predicting the changes in the YMRS, MADRS, and UKU scores. Moreover, connections of the motor network were considered for predicting the changes in the YMRS and MADRS scores. The neurobiological markers for predicting treatment-response symptoms and functioning changes were consistent with the neuropathology of BD and with the differences found between treatment responders and nonresponders.

Pretreatment Alterations and Acute Medication Treatment Effects on Brain Task-Related Functional Connectivity in Youth With Bipolar Disorder: A Neuroimaging Randomized Clinical Trial

OBJECTIVE

Disruptions in cognition are a clinically significant feature of bipolar disorder (BD). The effects of different treatments on these deficits and the brain systems that support them remain to be established.

METHOD

A continuous performance test was administered to 55 healthy controls and 71 acutely ill youths with mixed/manic BD to assess vigilance and working memory during task-based functional magnetic resonance imaging studies. Patients, who were untreated for at least 7 days at baseline, and controls were scanned at pretreatment baseline and at weeks 1 and 6. After baseline testing, patients (n = 71) were randomly assigned to 6-week double-blind treatment with lithium (n = 26; 1.0-1.2 mEq/L) or quetiapine (n = 45; 400-600 mg). Weighted seed-based connectivity (wSBC) was used to assess regional brain interactions during the attention task compared with the control condition.

RESULTS

At baseline, youths with BD showed reduced connectivity between bilateral anterior cingulate cortex and both left ventral lateral prefrontal cortex and left insula and increased connectivity between left ventral lateral prefrontal cortex and left temporal pole, left orbital frontal cortex and right postcentral gyrus, and right amygdala and right occipital pole compared with controls. At 1-week follow-up, quetiapine, but not lithium, treatment led to a significant shift of connectivity patterns toward those of the controls. At week 6, compared with baseline, there was no difference between treatment conditions, at which time both patient groups showed significant normalization of brain connectivity toward that of controls.

CONCLUSION

Functional alterations in several brain regions associated with cognitive processing and the integration of cognitive and affective processing were demonstrated in untreated youths with BD before treatment. Treatment reduced several of these alterations, with significant effects at week 1 only in the quetiapine treatment group. Normalization of functional connectivity might represent a promising biomarker for early target engagement in youth with BD.

CLINICAL TRIAL REGISTRATION INFORMATION

Multimodal Neuroimaging of Treatment Effects in Adolescent Mania; https://clinicaltrials.gov/; NCT00893581.

Amygdala structure and function in paediatric bipolar disorder and high-risk youth: A systematic review of magnetic resonance imaging findings

OBJECTIVE

Converging evidence from structural and functional magnetic resonance imaging (MRI) studies points to amygdala alteration as crucial in the development of paediatric bipolar disorder (pBP). The high number of recent studies prompted us to comprehensively evaluate findings. We aimed to systematically review structural and functional MRI studies investigating the amygdala in patients with pBP and in youth at high-risk (HR) for developing pBP.

METHODS

We searched PubMed from any time to 25 September 2020 using: 'amygdala AND (MRI OR magnetic resonance imaging) AND bipolar AND (pediatr* OR child OR children OR childhood OR adolescent OR adolescents OR adolescence OR young OR familial OR at-risk OR sibling* OR offspring OR high risk)'. In this review, we adhered to the PRISMA statement.

RESULTS

Amygdala hyperactivity to emotional stimuli is the most commonly reported finding in youth with pBP and HR compared to healthy peers (HC), whereas findings from structural MRI studies are inconsistent.

CONCLUSIONS

Hyperactivation of the amygdala might be an endophenotype of pBP.

Changes in the brain structural connectome after a prospective randomized clinical trial of lithium and quetiapine treatment in youth with bipolar disorder

The goals of the current study were to determine whether topological organization of brain structural networks is altered in youth with bipolar disorder, whether such alterations predict treatment outcomes, and whether they are normalized by treatment. Youth with bipolar disorder were randomized to double-blind treatment with quetiapine or lithium and assessed weekly. High-resolution MRI images were collected from children and adolescents with bipolar disorder who were experiencing a mixed or manic episode (n = 100) and healthy youth (n = 63). Brain networks were constructed based on the similarity of morphological features across regions and analyzed using graph theory approaches. We tested for pretreatment anatomical differences between bipolar and healthy youth and for changes in neuroanatomic network metrics following treatment in the youth with bipolar disorder. Youth with bipolar disorder showed significantly increased clustering coefficient (Cp) (p = 0.009) and characteristic path length (Lp) (p = 0.04) at baseline, and altered nodal centralities in insula, inferior frontal gyrus, and supplementary motor area. Cp, Lp, and nodal centrality of the insula exhibited normalization in patients following treatment. Changes in these neuroanatomic parameters were correlated with improvement in manic symptoms but did not differ between the two drug therapies. Baseline structural network matrices significantly differentiated medication responders and non-responders with 80% accuracy. These findings demonstrate that both global and nodal structural network features are altered in early course bipolar disorder, and that pretreatment alterations in neuroanatomic features predicted treatment outcome and were reduced by treatment. Similar connectome normalization with lithium and quetiapine suggests that the connectome changes are a downstream effect of both therapies that is related to their clinical efficacy.

Cognitive correlates of impulsive aggression in youth with pediatric bipolar disorder and bipolar offspring

BACKGROUND

Youth with bipolar disorder (BD) and offspring of individuals with BD (BD-OFF) are characterized by higher levels of impulsive and overt aggression. The cognitive basis underlying these aggressive behaviors are not clarified in this population. The aim of this study was to investigate the relationship between cognitive alterations and aggressive behavior in youth with BD and BD-OFF.

METHODS

Forty-two youth with BD, 17 BD-OFF and 57 healthy controls (HCs) were administered the Modified Overt Aggression Scale (MOAS), the Cambridge Neuropsychological Test Automated Battery (CANTAB), the Young Mania Rating Scale (YMRS) and the Children's Depression Rating Scale (CDRS). Multiple linear regression analyses were performed in the three groups separately. In each group, tests scores from the CANTAB were predictors. MOAS subscale scores and MOAS total scores were dependent variables. Results are corrected for age, IQ and mood state.

RESULTS

Both youth with BD and BD-OFF showed positive correlations between impairment in executive functions and levels of verbal aggression. In youth with BD, altered processing of either positive and negative stimuli positively correlated with MOAS total scores, whereas in BD-OFF, such relationship was negative.

CONCLUSIONS

Impulsive aggressive behaviors in youth with BD arise from a combination of altered affective processing and executive dysfunction. The negative relationship between affective processing and aggression in BD-OFF suggested the presence of possible mechanisms of resilience in this population.

Imaging-Based Subtyping for Psychiatric Syndromes

Despite considerable research evidence demonstrating significant neurobiological alterations in psychiatric disorders, incorporating neuroimaging approaches into clinical practice remains challenging. There is an urgent need for biologically validated psychiatric disease constructs that can inform diagnostic algorithms and targeted treatment development. In this article, we present a conceptual review of the most robust and impactful findings from studies that use neuroimaging methods in efforts to define distinct disease subtypes, while emphasizing cross-diagnostic and dimensional approaches. In addition, we discuss current challenges in psychoradiology and outline potential future strategies for clinically applicable translation.

Early and late cortical reactivity to passively viewed emotional faces in pediatric bipolar disorder

BACKGROUND

We studied emotional information processing in youth with pediatric bipolar disorder (pBD) using the late positive potential (LPP), assessing automatic allocation of attentional resources to emotionally salient stimuli, and the occipital P1, assessing early sensory processing.

METHODS

Participants were 20 youth with pBD and 26 healthy controls (HC). Participants passively viewed faces with a fearful, neutral or happy expressions. Group differences were tested with general linear models. P1 was included to examine modulating effects on LPP. We calculated Bayes factor (BF) values to express strength of evidence for choosing one hypothesis over another.

RESULTS

A significant emotion by group interaction for LPP amplitude was associated with a larger amplitude for happy faces for pBD than HC (F[1,40] = 6.04, p = .018); this was not modulated by P1 amplitude or latency. P1 amplitude did not differ between groups, although P1 peaked earlier for HC (F[1,40] = 5.45, p = .025). BF for LPP was 2.93, suggesting moderate evidence favoring H₁. BF for P1 latency of 14.58 suggests strong evidence favoring H₁.

LIMITATIONS

Inclusion of children and adolescents prohibited careful control for neurodevelopmental effects.

CONCLUSIONS

Larger LPP amplitude for happy faces without change in P1 suggests enhanced automatic allocation of attentional resources to positive information in pBD. Delayed P1 latency in pBD suggests slower early processing of emotional information.

Fronto-subcortical functional connectivity in patients with schizophrenia and bipolar disorder during a verbal fluency task

OBJECTIVES

Impairments in language production are common of schizophrenia (SZ) and bipolar disorder (BD). Identifying distinct functional connectivity (FC) patterns in SZ and BD may provide biomarkers for their diagnoses.

METHODS

Forty-nine participants (15 SZ, 14 BD and 20 healthy controls (HC)) underwent a verbal fluency task consisting of mentally generating verbs in French, alternated with periods of silence. Functional network allowed identifying activation clusters: the medio-frontal cluster (MFC), the left subcortical cluster (LSCC) and the left fronto-lateral cluster (LFLC). FC was calculated between the average blood oxygen level-dependent signal time series in each cluster. Analyses of covariance were performed to test group differences on FC among the three paired-seed regions.

RESULTS

SZ presented a significant reduced FC compared to HC within two paired-seed regions between the LFLC and the LSCC and between the MFC and the LSCC while BD were not significantly different from HC. SZ compared to BD exhibited a reduced FC within one paired-seed region between the MFC and the LSCC. There was no group effect between the MFC and the LFLC.

CONCLUSIONS

A specific medio-prefronto-striato-thalamic functional dysconnectivity may be implicated in the pathophysiology of schizophrenia. This reduced fronto-subcortical FC could be a functional brain biomarker of schizophrenia.

Discrete patterns of cortical thickness in youth with bipolar disorder differentially predict treatment response to quetiapine but not lithium

The need for treatment response predictive biomarkers is being increasingly recognized in children and adolescents with psychiatric disorders. Structural gray matter abnormalities as a predictor of treatment outcome in pediatric bipolar disorder have not been systematically investigated, especially early in the illness course. With a prospective longitudinal study design, the present study enrolled 52 bipolar adolescents with no history of treatment with mood stabilizers or a therapeutic dose of antipsychotic drugs and 31 healthy controls. Patients were randomly assigned to treatment with quetiapine or lithium after pretreatment data collection. A hierarchical cluster analysis was performed using pretreatment cortical thickness data that identified two discrete patient subgroups. Compared to healthy subjects, patients in subgroup 1 (n = 16) showed widespread greater cortical thickness mainly across heteromodal cortex but also involving some regions of unimodal cortex, while those in subgroup 2 (n = 36) showed regional cortical thinning mainly in superior temporal and superior parietal regions. Patients within subgroup 1 showed a significantly higher response rate to quetiapine than those in subgroup 2 (100% vs 53%). No statistically significant difference was found in lithium response rate between the patient subgroups (63% vs 53%). Pretreatment clinical ratings and neuropsychological data did not differ across subgroups. Our findings suggest the existence of distinct and clinically relevant subgroups of pediatric bipolar patients, as defined by pattern of cortical thickness. These groups appear to differentially respond to antipsychotic treatment-notably with greater cortical thickness relative to controls predicting better treatment response.

The International Society for Bipolar Disorders Task Force report on pediatric bipolar disorder: Knowledge to date and directions for future research

OBJECTIVES

Over the past two decades, there has been tremendous growth in research regarding bipolar disorder (BD) among children and adolescents (ie, pediatric BD [PBD]). The primary purpose of this article is to distill the extant literature, dispel myths or exaggerated assertions in the field, and disseminate clinically relevant findings.

METHODS

An international group of experts completed a selective review of the literature, emphasizing areas of consensus, identifying limitations and gaps in the literature, and highlighting future directions to mitigate these gaps.

RESULTS

Substantial, and increasingly international, research has accumulated regarding the phenomenology, differential diagnosis, course, treatment, and neurobiology of PBD. Prior division around the role of irritability and of screening tools in diagnosis has largely abated. Gold-standard pharmacologic trials inform treatment of manic/mixed episodes, whereas fewer data address bipolar depression and maintenance/continuation treatment. Adjunctive psychosocial treatment provides a forum for psychoeducation and targets primarily depressive symptoms. Numerous neurocognitive and neuroimaging studies, and increasing peripheral biomarker studies, largely converge with prior findings from adults with BD.

CONCLUSIONS

As data have accumulated and controversy has dissipated, the field has moved past existential questions about PBD toward defining and pursuing pressing clinical and scientific priorities that remain. The overall body of evidence supports the position that perceptions about marked international (US vs elsewhere) and developmental (pediatric vs adult) differences have been overstated, although additional research on these topics is warranted. Traction toward improved outcomes will be supported by continued emphasis on pathophysiology and novel therapeutics.

Brain functional effects of psychopharmacological treatments in bipolar disorder

Functional magnetic resonance imaging (fMRI) studies have contributed to the understanding of bipolar disorder. However the effect of medication on brain activation remains poorly understood. We conducted an extensive literature review on PubMed and ScienceDirect to investigate the influence of medication in fMRI studies, including both longitudinal and cross-sectional studies, which aimed at assessing this influence. Although we reported all reviewed studies, we gave greater emphasis to studies with the most robust methodology. One hundred and forty studies matched our inclusion criteria and forty-seven studies demonstrated an effect of pharmacological treatment on fMRI blood oxygen level dependent (BOLD) signal in adults and children with bipolar disorder. Out of these studies, nineteen were longitudinal. Most of cross-sectional studies suffered from methodological bias, due to post-hoc analyses performed on a limited number of patients and did not find any effect of medication. However, both longitudinal and cross-sectional studies showing an impact of treatment tend to suggest that medication prescribed to patients with bipolar disorder mostly influenced brain activation in prefrontal regions, when measured by tasks involving emotional regulation and processing as well as non-emotional cognitive tasks. FMRI promises to elucidate potential new biomarkers in bipolar disorder and could be used to evaluate the effect of new therapeutic compounds. Further research is needed to disentangle the effect of medication and the influence of the changes in mood state on brain activation in patients with bipolar disorder.

Clinical neuroimaging markers of response to treatment in mood disorders

Mood disorders (MD) are important and frequent psychiatric illness. The management of patients affected by these conditions represents an important factor of disability as well as a significant social and economic burden. The "in-vivo" studies can help researchers to understand the first developmental events of the pathology and to identify the molecular and non-molecular targets of therapies. However, they have strong limitations due to the fact that human brain circuitry can not be reproduced in animal models. In addition, these neural pathways are difficult to be selectively studied with the modern imaging (such as Magnetic Resonance and Positron Emitted Tomography/Computed Tomography) and non-imaging (such as electroencephalography, magnetoencephalography, transcranial magnetic stimulation and evoked potentials) methods. In comparison with other methods, the "in-vivo" imaging investigations have higher temporal and spatial resolution compared to the "in-vivo" non-imaging techniques. All these factors make difficult to fully understand the aetiology and pathophysiology of these disorders, and consequently hinder the analysis of the effects of pharmacological and non-pharmacological therapies, which have been demonstrated effective in clinical settings. In this review, we will focus our attention on the current state of the art of imaging in the assessment of treatment efficacy in MD. We will analyse briefly the actual classification of MD; then we will focus on the "in vivo" imaging methods used in research and clinical activity, the current knowledge about the neural models at the base of MD. Finally the last part of the review will focus on the analysis of the main markers of response to treatment.

Amygdala functional connectivity as a longitudinal biomarker of symptom changes in generalized anxiety

Generalized anxiety disorder (GAD) is characterized by excessive worry, autonomic dysregulation and functional amygdala dysconnectivity, yet these illness markers have rarely been considered together, nor their interrelationship tested longitudinally. We hypothesized that an individual’s capacity for emotion regulation predicts longer-term changes in amygdala functional connectivity, supporting the modification of GAD core symptoms. Sixteen patients with GAD (14 women) and individually matched controls were studied at two time points separated by 1 year. Resting-state fMRI data and concurrent measurement of vagally mediated heart rate variability were obtained before and after the induction of perseverative cognition. A greater rise in levels of worry following the induction predicted a stronger reduction in connectivity between right amygdala and ventromedial prefrontal cortex, and enhanced coupling between left amygdala and ventral tegmental area at follow-up. Similarly, amplified physiological responses to the induction predicted increased connectivity between right amygdala and thalamus. Longitudinal shifts in a distinct set of functional connectivity scores were associated with concomitant changes in GAD symptomatology over the course of the year. Results highlight the prognostic value of indices of emotional dysregulation and emphasize the integral role of the amygdala as a critical hub in functional neural circuitry underlying the progression of GAD symptomatology.

The underlying neurobiology of key functional domains in young people with mood and anxiety disorders: a systematic review

BACKGROUND

Mood and anxiety disorders are leading causes of disability and mortality, due largely to their onset during adolescence and young adulthood and broader impact on functioning. Key factors that are associated with disability and these disorders in young people are social and economic participation (e.g. education, employment), physical health, suicide and self-harm behaviours, and alcohol and substance use. A better understanding of the objective markers (i.e. neurobiological parameters) associated with these factors is important for the development of effective early interventions that reduce the impact of disability and illness persistence.

METHODS

We systematically reviewed the literature for neurobiological parameters (i.e. neuropsychology, neuroimaging, sleep-wake and circadian biology, neurophysiology and metabolic measures) associated with functional domains in young people (12 to 30 years) with mood and/or anxiety disorders.

RESULTS

Of the one hundred and thirty-four studies selected, 7.6 % investigated social and economic participation, 2.1 % physical health, 15.3 % suicide and self-harm behaviours, 6.9 % alcohol and substance use, whereas the majority (68.1 %) focussed on clinical syndrome.

CONCLUSIONS

Despite the predominance of studies that solely examine the clinical syndrome of young people the literature also provides evidence of distinct associations among objective measures (indexing various aspects of brain circuitry) and other functional domains. We suggest that a shift in focus towards characterising the mechanisms that underlie and/or mediate multiple functional domains will optimise personalised interventions and improve illness trajectories.

Can neuroimaging disentangle bipolar disorder?

BACKGROUND

Bipolar disorder heterogeneity is large, leading to difficulties in identifying neuropathophysiological and etiological mechanisms and hindering the formation of clinically homogeneous patient groups in clinical trials. Identifying markers of clinically more homogeneous groups would help disentangle BD heterogeneity. Neuroimaging may aid in identifying such groups by highlighting specific biomarkers of BD subtypes or clinical dimensions.

METHODS

We performed a systematic literature search of the neuroimaging literature assessing biomarkers of relevant BD phenotypes (type-I vs. II, presence vs. absence of psychotic features, suicidal behavior and impulsivity, rapid cycling, good vs. poor medication response, age at onset, cognitive performance and circadian abnormalities).

RESULTS

Consistent biomarkers were associated with suicidal behavior, i.e. frontal/anterior alterations (prefrontal and cingulate grey matter, prefrontal white matter) in patients with a history of suicide attempts; and with cognitive performance, i.e. involvement of frontal and temporal regions, superior and inferior longitudinal fasciculus, right thalamic radiation, and corpus callosum in executive dysfunctions. For the other dimensions and sub-types studied, no consistent biomarkers were identified.

LIMITATIONS

Studies were heterogeneous both in methodology and outcome.

CONCLUSIONS

Though theoretically promising, neuroimaging has not yet proven capable of disentangling subtypes and dimensions of bipolar disorder, due to high between-study heterogeneity. We issue recommendations for future studies.

Intrinsic Amygdala Functional Connectivity in Youth With Bipolar I Disorder

OBJECTIVE

Bipolar disorder (BD) commonly begins during adolescence and may continue into adulthood. Studies in adults with BD suggest that disruptions in amygdalar neural circuitry explain the pathophysiology underlying the disorder. Importantly, however, amygdala subregion networks have not yet been examined in youth close to mania onset. The goal of this study was to compare resting state functional connectivity patterns in amygdala subregions in youth with bipolar I disorder with patterns in healthy controls.

METHOD

Centromedial, laterobasal, and superficial amygdala subdivisions were assessed during rest and examined in relation to clinical measures of mania in youth (14-20 years old) with bipolar I disorder who experienced only a single episode of mania (BD; n = 20) and age-matched healthy comparison youth without any personal or family history of DSM-IV Axis I disorders (HC; n = 23).

RESULTS

Relative to HC youth, youth with BD exhibited decreased connectivity between the laterobasal subdivision of the amygdala and the hippocampus and precentral gyrus, and increased connectivity between the laterobasal subdivision and the precuneus. Connectivity between the right laterobasal amygdala and right hippocampus was positively correlated with levels of anxiety in BD but not in HC youth, and connectivity between the right laterobasal amygdala and right precuneus was negatively correlated with insight about bipolar illness.

CONCLUSION

Youth with BD have abnormal amygdala resting state network connections to regions that are critical for emotional processing and self-awareness. Longitudinal studies are needed to determine whether these aberrant patterns in youth with BD can be altered with intervention and can influence the course of disorder.

Using neuroimaging to evaluate and guide pharmacological and psychotherapeutic treatments for mood disorders in children

Mood disorders are increasing in childhood, and often require multimodal and comprehensive treatment plans to address a complex array of symptoms and associated morbidities. Pharmacotherapy, in combination with psychotherapeutic interventions, is essential for treatment and stabilization. Current evidence supports the use of a number of interventions in children and adolescents diagnosed with DSM-5 mood spectrum disorders, which are associated with impairments in prefrontal-striatal-limbic networks, which are key for emotional functioning and regulation. Yet, little is known about the neurobiological effects of interventions on the developing brain. This chapter provides a synopsis of the literature demonstrating the neural effects of psychotropic medications and psychotherapy in youth with depressive or bipolar spectrum disorders. Additional longitudinal and biological studies are warranted to characterize the effects of these interventions on all phases and stages of mood illness development in children and adolescents.

Facial emotion recognition in childhood-onset bipolar I disorder: an evaluation of developmental differences between youths and adults

OBJECTIVES

Bipolar disorder (BD) is a severe mental illness with high healthcare costs and poor outcomes. Increasing numbers of youths are diagnosed with BD, and many adults with BD report that their symptoms started in childhood, suggesting that BD can be a developmental disorder. Studies advancing our understanding of BD have shown alterations in facial emotion recognition both in children and adults with BD compared to healthy comparison (HC) participants, but none have evaluated the development of these deficits. To address this, we examined the effect of age on facial emotion recognition in a sample that included children and adults with confirmed childhood-onset type-I BD, with the adults having been diagnosed and followed since childhood by the Course and Outcome in Bipolar Youth study.

METHODS

Using the Diagnostic Analysis of Non-Verbal Accuracy, we compared facial emotion recognition errors among participants with BD (n = 66; ages 7-26 years) and HC participants (n = 87; ages 7-25 years). Complementary analyses investigated errors for child and adult faces.

RESULTS

A significant diagnosis-by-age interaction indicated that younger BD participants performed worse than expected relative to HC participants their own age. The deficits occurred both for child and adult faces and were particularly strong for angry child faces, which were most often mistaken as sad. Our results were not influenced by medications, comorbidities/substance use, or mood state/global functioning.

CONCLUSIONS

Younger individuals with BD are worse than their peers at this important social skill. This deficit may be an important developmentally salient treatment target - that is, for cognitive remediation to improve BD youths' emotion recognition abilities.

Neurocognitive impairments among youth with pediatric bipolar disorder: a systematic review of neuropsychological research

BACKGROUND

Pediatric bipolar disorder (PBD) has emerged as a field of research in which neuropsychological studies are continuously providing new empirical findings. Despite this, a comprehensive framework for neurocognitive impairments is still lacking, and most of the evidence remains unconnected. We addressed this question through a systematic review of neuropsychological research, with the aim of elucidating the main issues concerning this topic.

METHOD

A comprehensive search of databases (PubMed, PsycINFO) was performed. Published manuscripts between 1990 and January 2014 were identified. Overall, 124 studies fulfilled inclusion criteria. Methodological differences between studies required a descriptive review of findings.

RESULTS

Evidence indicates that verbal/visual-spatial memory, processing speed, working memory, and social cognition are neurocognitive domains impaired in PBD youth. Furthermore, these deficits are greater among those who suffer acute affective symptoms, PBD type I, and/or attention deficit hyperactivity disorder (ADHD) comorbidity. In addition, several neurocognitive deficits imply certain changes in prefrontal cortex activity and are somewhat associated with psychosocial and academic disabilities. Strikingly, these deficits are consistently similar to those encountered in ADHD as well as severe mood dysregulation (SMD). Besides, some neurocognitive impairments appear before the onset of the illness and tend to maintain stable across adolescence. Finally, any therapy has not yet demonstrated to be effective on diminishing these neurocognitive impairments.

LIMITATIONS

More prolonged follow-up studies aimed at delineating the course of treatment and the response to it are warranted.

CONCLUSIONS

Despite noteworthy research on the neurocognitive profile of PBD, our knowledge is still lagging behind evidence from adult counterparts.

Time course of recovery showing initial prefrontal cortex changes at 16 weeks, extending to subcortical changes by 3 years in pediatric bipolar disorder

OBJECTIVE

Activation changes at the interface of affective and cognitive systems are examined over a 3 year period in pediatric bipolar disorder (PBD).

METHODS

Thirteen participants with PBD and 10 healthy controls (HC) matched on demographics and IQ were scanned at baseline, at 16 weeks, and after 3 years. All patients received pharmacotherapy based on a medication algorithm. A pediatric affective color matching paradigm was used to probe cognitive processing under emotional challenge.

RESULTS

At baseline, in response to emotional vs. neutral words, patients with PBD showed greater activation than HC in the right dorsal lateral prefrontal cortex (DLPFC) and amygdala, ventral lateral prefrontal cortex (VLPFC), bilateral anterior cingulate cortex (ACC), and ventral striatum. Increased activation in DLPFC in the PBD group normalized by 16 weeks. By 3 years, normalization was observed in VLPFC, ACC, amygdala, and striatum.

LIMITATIONS

Small sample size renders the present findings preliminary.

CONCLUSIONS

Greater activation in fronto-striatal and fronto-limbic circuits were observed in unmedicated patients with PBD. Present findings suggest the possibility that DLPFC is most malleable to pharmacological intervention with systematic pharmacotherapy leading to immediate response, which extended to amygdalostriatal and ventral cortical regions at 3 years. The seminal observation from this study is the prolonged length of recovery time in the normalization of subcortical activity along with their interfacing cortical regions. Findings from this proof of concept study need to be replicated in a larger sample.

Altered affective, executive and sensorimotor resting state networks in patients with pediatric mania

BACKGROUND

The aim of the present study was to map the pathophysiology of resting state functional connectivity accompanying structural and functional abnormalities in children with bipolar disorder.

METHODS

Children with bipolar disorder and demographically matched healthy controls underwent resting-state functional magnetic resonance imaging. A model-free independent component analysis was performed to identify intrinsically interconnected networks.

RESULTS

We included 34 children with bipolar disorder and 40 controls in our analysis. Three distinct resting state networks corresponding to affective, executive and sensorimotor functions emerged as being significantly different between the pediatric bipolar disorder (PBD) and control groups. All 3 networks showed hyperconnectivity in the PBD relative to the control group. Specifically, the connectivity of the dorsal anterior cingulate cortex (ACC) differentiated the PBD from the control group in both the affective and the executive networks. Exploratory analysis suggests that greater connectivity of the right amygdala within the affective network is associated with better executive function in children with bipolar disorder, but not in controls.

LIMITATIONS

Unique clinical characteristics of the study sample allowed us to evaluate the pathophysiology of resting state connectivity at an early state of PBD, which led to the lack of generalizability in terms of comorbid disorders existing in a typical PBD population.

CONCLUSION

Abnormally engaged resting state affective, executive and sensorimotor networks observed in children with bipolar disorder may reflect a biological context in which abnormal task-based brain activity can occur. Dual engagement of the dorsal ACC in affective and executive networks supports the neuroanatomical interface of these networks, and the amygdala's engagement in moderating executive function illustrates the intricate interplay of these neural operations at rest.

The Neural Effects of Psychotropic Medications in Children and Adolescents

Little is known about the neurobiological effects of psychotropic medications used in the treatment of children and adolescents diagnosed with a psychiatric disorder. This review provides a synopsis of the literature demonstrating the neural effects associated with exposure to psychotropic medication in youth using multimodal neuroimaging. The article concludes by illustrating how, taken together, these studies suggest that pharmacological interventions during childhood do indeed affect brain structure and function in a detectable manner, and the effects appear to be ameliorative.