Data-driven parcellation and graph theory analyses to study adolescent mood and anxiety symptoms

Adolescence is a period of rapid brain development when psychiatric symptoms often first emerge. Studying adolescents may therefore facilitate the identification of neural alterations early in the course of psychiatric conditions. Here, we sought to utilize new, high-quality brain parcellations and data-driven graph theory approaches to characterize associations between resting-state networks and the severity of depression, anxiety, and anhedonia symptoms-salient features across psychiatric conditions. As reward circuitry matures considerably during adolescence, we examined both Whole Brain and three task-derived reward networks. Subjects were 87 psychotropic-medication-free adolescents (age = 12-20) with diverse psychiatric conditions (n = 68) and healthy controls (n = 19). All completed diagnostic interviews, dimensional clinical assessments, and 3T resting-state fMRI (10 min/2.3 mm/TR = 1 s). Following high-quality Human Connectome Project-style preprocessing, multimodal surface matching (MSMAll) alignment, and parcellation via the Cole-Anticevic Brain-wide Network Partition, weighted graph theoretical metrics (Strength Centrality = C_Str; Eigenvector Centrality = C_Eig; Local Efficiency = E_Loc) were estimated within each network. Associations with symptom severity and clinical status were assessed non-parametrically (two-tailed p_FWE < 0.05). Across subjects, depression scores correlated with ventral striatum C_Str within the Reward Attainment network, while anticipatory anhedonia correlated with C_Str and E_Loc in the subgenual anterior cingulate, dorsal anterior cingulate, orbitofrontal cortex, caudate, and ventral striatum across multiple networks. Group differences and associations with anxiety were not detected. Using detailed functional and clinical measures, we found that adolescent depression and anhedonia involve increased influence and communication efficiency in prefrontal and limbic reward areas. Resting-state network properties thus reflect positive valence system anomalies related to discrete reward sub-systems and processing phases early in the course of illness.

A pilot resting-state functional connectivity study of the kynurenine pathway in adolescents with depression and healthy controls

BACKGROUND

The neuroimmunological kynurenine pathway (KP) has been hypothesized to play a role in depressive/anhedonic symptoms and related CNS disturbances. Indoleamine 2,3-dioxygenase (IDO) is the rate limiting enzyme which leads to neurotrophic [kynurenic acid (KA)] and neurotoxic [Quinolinic acid (QUIN)] branches. In this pilot, we sought to examine associations between blood KP neuro-toxic/trophic measures and anhedonia/depression associated networks in youth with major depression (MDD) and healthy controls (HC).

METHODS

Subjects were 14 psychotropic-medication free adolescents with MDD and 7 HC, ages 12-19 yo. All underwent resting-state functional magnetic resonance imagining (fMRI) scans. Voxel-wise maps were generated indicating correlation strengths among 4 bilateral seeds [(dorsal anterior cingulate cortex (dACC), perigenual ACC (pgACC), subgenual ACC (sgACC) and nucleus accumbens (NAc)] and remaining brain regions. FMRI analyses were family-wise error corrected. KP metabolites were measured using liquid chromatography-tandem mass spectrometry.

RESULTS

Connectivity between the right dACC and the right precuneus was positively correlated with KA levels. This same cluster demonstrated an inverse correlation with IDO activity. Exploratory analysis at a more liberal clustering threshold showed the KA/QUIN ratio was positively correlated with connectivity between the pgACC and the right medial prefrontal cortex. Lastly, connectivity between the pgACC and the left inferior temporal gyrus was positively correlated with QUIN levels.

LIMITATIONS

Findings are preliminary due to the small sample size.

CONCLUSIONS

This pilot study is the first report in depressed adolescents demonstrating associations between the KP and anhedonia/depression-associated brain networks. This pilot adds evidence to the putative role of the KP in MDD.

The hyper-sentient addict: an exteroception model of addiction

BACKGROUND

Exteroception involves processes related to the perception of environmental stimuli important for an organism's ability to adapt to its environment. As such, exteroception plays a critical role in conditioned response. In addiction, behavioral and neuroimaging studies show that the conditioned response to drug-related cues is often associated with alterations in brain regions including the precuneus/posterior cingulate cortex, an important node within the default mode network dedicated to processes such as self-monitoring.

OBJECTIVE

This review aimed to summarize the growing, but largely fragmented, literature that supports a central role of exteroceptive processes in addiction.

METHODS

We performed a systematic review of empirical research via PubMed and Google Scholar with keywords including 'addiction', 'exteroception', 'precuneus', and 'self-awareness', to identify human behavioral and neuroimaging studies that report mechanisms of self-awareness in healthy populations, and altered self-awareness processes, specifically exteroception, in addicted populations.

RESULTS

Results demonstrate that exteroceptive processes play a critical role in conditioned cue response in addiction and serve as targets for interventions such as mindfulness training. Further, a hub of the default mode network, namely, the precuneus, is (i) consistently implicated in exteroceptive processes, and (ii) widely demonstrated to have increased activation and connectivity in addicted populations.

CONCLUSION

Heightened exteroceptive processes may underlie cue-elicited craving, which in turn may lead to the maintenance and worsening of substance use disorders. An exteroception model of addiction provides a testable framework from which novel targets for interventions can be identified.

Preliminary findings demonstrating latent effects of early adolescent marijuana use onset on cortical architecture

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Early onset MJ use was associated with different patterns of cortical architecture.

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Early vs. late onset divergence was in brain regions underlying higher-order cognition.

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Findings were above and beyond effects of alcohol and current age.

Background

As the most commonly used illicit substance during early adolescence, long-term or latent effects of early adolescent marijuana use across adolescent developmental processes remain to be determined.

Methods

We examined cortical thickness, gray/white matter border contrast (GWR) and local gyrification index (LGI) in 42 marijuana (MJ) users. Voxelwise regressions assessed early-onset (age <16) vs. late-onset (≥16 years-old) differences and relationships to continued use while controlling for current age and alcohol use.

Results

Although groups did not differ by onset status, groups diverged in their correlations between cannabis use and cortical architecture. Among early-onset users, continued years of MJ use and current MJ consumption were associated with thicker cortex, increased GWR and decreased LGI. Late-onset users exhibited the opposite pattern. This divergence was observed in all three morphological measures in the anterior dorsolateral frontal cortex (p < .05, FWE-corrected).

Conclusions

Divergent patterns between current MJ use and elements of cortical architecture were associated with early MJ use onset. Considering brain development in early adolescence, findings are consistent with disruptions in pruning. However, divergence with continued use for many years thereafter suggests altered trajectories of brain maturation during late adolescence and beyond.

Adolescent risk-taking and resting state functional connectivity

The existing literature on the role of emotion regulation circuits (amygdala-prefrontal cortex) in the adolescent brain yields mixed results, particularly on the role of these regions in the context of reward sensitivity and risk-taking behavior sensitivity and risk-taking behavior. Here, we examined functional connectivity in the resting state in 18 risk-taking (RT) adolescents compared with 18 non-risk-taking (NRT) adolescents as defined by the Youth Risk Behavior Surveillance Survey. Separate seed-based correlations with bilateral amygdala and bilateral nucleus accumbens used as the seed were performed to determine functional connectivity using functional magnetic resonance imaging (fMRI). The results showed greater connectivity between the amygdala (seed region) and the right middle frontal gyrus, left cingulate gyrus, left precuneus and right inferior parietal lobule in RT adolescents than in NRT adolescents. Likewise, there was greater connectivity between the nucleus accumbens (seed region) and the right middle frontal gyrus in RT adolescents compared with NRT adolescents. These findings suggest that risk-taking behavior in adolescents is associated with hyperconnectivity during the resting state in networks associated with emotion regulation, reward sensitivity, executive control, and the default mode.

Cannabis cue-elicited craving and the reward neurocircuitry

Cue-elicited craving or the intense desire to consume a substance following exposure to a conditioned drug cue is one of the primary behavioral symptoms of substance use disorders (SUDs). While the concept of cue-elicited craving is well characterized in alcohol and other substances of abuse, only recently has it been described in cannabis. A review of the extant literature has established that cue-elicited craving is a powerful reinforcer that contributes to drug-seeking for cannabis. Further, emergent research has begun to identify the neurobiological systems and neural mechanisms associated with this behavior. What research shows is that while theories of THC's effects on the dopaminergic-reward system remain divergent, cannabis cues elicit neural activation in the brain's reward network.

Physical growth of low birthweight infants in the first year of life: impact of maternal behaviors

Physical growth of preterm infants relates to many medical factors, such as birthweight, severity of medical illnesses, and nutritional status. We previously reported that maternal behaviors influence developmental outcomes in low birthweight infants (birthweight < 1600 g); we now hypothesize that maternal behaviors also influence physical somatic growth in low birthweight (LBW) infants. We serially followed 218 mother-infant pairs from birth through 12 months of age. One-hundred thirteen LBW infants were categorized based on severity of early medical complications. Low Risk infants (LR, n = 71) had acute respiratory distress and/or grade 1-2 intraventricular hemorrhage (IVH), or grade 3 IVH without hydrocephalus. High Risk infants (HR, n = 42) had chronic lung disease, grade 3 IVH with hydrocephalus or grade 4 IVH, and/or periventricular leukomalacia. We also studied 105 socioeconomic (SES) matched Full Term (FT) controls. Maternal behaviors were assessed during home visits with global ratings of Warm Sensitivity and Punitiveness. Infant weight was measured at birth and at 38 weeks, 6 months and 12 months corrected gestational age. We examined alternative expressions of weight growth across the three groups by developing the Weight Quotient (WQ), which is the ratio of actual measured weight to the median weight for age. For each infant the regression of the WQ ratio against correct gestational age was analyzed. We used a General Linear Model to compare the relation of the maternal variables to the weight quotients for the three groups. We determined the catch up growth as the slope of each regression. Results indicated that higher levels of maternal Punitiveness were related to slower rates of growth for High Risk (R2 = 0.36), but not Low Risk or Full Term. For maternal Warm Sensitivity (R2 = 0.36), there were significant (P < 0.05) inverse relations with weight gain growth for the Full Term infants. These data suggest that some maternal behaviors are related to the growth of term and premature infants, although the mechanisms through which this occurs is unclear.