Blue-Light Therapy Strengthens Resting-State Effective Connectivity within Default-Mode Network after Mild TBI

Background:

Emerging evidence suggests that post concussive symptoms, including mood changes, may be improved through morning blue-wavelength light therapy (BLT). However, the neurobiological mechanisms underlying these effects remain unknown. We hypothesize that BLT may influence the effective brain connectivity (EC) patterns within the default-mode network (DMN), particularly involving the medial prefrontal cortex (MPFC), which may contribute to improvements in mood.

Methods:

Resting-state functional MRI data were collected from 41 healthy-controls (HCs) and 28 individuals with mild traumatic brain injury (mTBI). Individuals with mTBI also underwent a diffusion-weighted imaging scan and were randomly assigned to complete either 6 weeks of daily morning BLT (N = 14) or amber light therapy (ALT; N = 14). Advanced spectral dynamic causal modeling (sDCM) and diffusion MRI connectometry were used to estimate EC patterns and structural connectivity strength within the DMN, respectively.

Results:

The sDCM analysis showed dominant connectivity pattern following mTBI (pre-treatment) within the hemisphere contralateral to the one observed for HCs. BLT, but not ALT, resulted in improved directional information flow (ie, EC) from the left lateral parietal cortex (LLPC) to MPFC within the DMN. The improvement in EC from LLPC to MPFC was accompanied by stronger structural connectivity between the 2 areas. For the BLT group, the observed improvements in function and structure were correlated (at a trend level) with changes in self-reported happiness.

Conclusions:

The current preliminary findings provide empirical evidence that morning short-wavelength light therapy could be used as a novel alternative rehabilitation technique for mTBI.

Trial registry:

The research protocols were registered in the ClinicalTrials.gov database (CT Identifiers NCT01747811 and NCT01721356).

Exposure to Blue Wavelength Light Is Associated With Increases in Bidirectional Amygdala-DLPFC Connectivity at Rest

Blue wavelength light has been used successfully as a treatment method for certain mood disorders, but, the underlying mechanisms behind the mood enhancing effects of light remain poorly understood. We investigated the effects of a single dose of 30 min of blue wavelength light (n = 17) vs. amber wavelength light (n = 12) exposure in a sample of healthy adults on subsequent resting-state functional and directed connectivity, and associations with changes in state affect. Individuals who received blue vs. amber wavelength light showed greater positive connectivity between the right amygdala and a region within the left dorsolateral prefrontal cortex (DLPFC). In addition, using granger causality, the findings showed that individuals who received blue wavelength light displayed greater bidirectional information flow between these two regions relative to amber light. Furthermore, the strength of amygdala-DLPFC functional connectivity was associated with greater decreases in negative mood for the blue, but not the amber light condition. Blue light exposure may positively influence mood by modulating greater information flow between the amygdala and the DLPFC, which may result in greater engagement of cognitive control strategies that are needed to perceive and regulate arousal and mood.

Individual associations of adolescent alcohol use disorder versus cannabis use disorder symptoms in neural prediction error signaling and the response to novelty

Two of the most commonly used illegal substances by adolescents are alcohol and cannabis. Alcohol use disorder (AUD) and cannabis use disorder (CUD) are associated with poorer decision-making in adolescents. In adolescents, level of AUD symptomatology has been negatively associated with striatal reward responsivity. However, little work has explored the relationship with striatal reward prediction error (RPE) representation and the extent to which any augmentation of RPE by novel stimuli is impacted. One-hundred fifty-one adolescents participated in the Novelty Task while undergoing functional magnetic resonance imaging (fMRI). In this task, participants learn to choose novel or non-novel stimuli to gain monetary reward. Level of AUD symptomatology was negatively associated with both optimal decision-making and BOLD response modulation by RPE within striatum and regions of prefrontal cortex. The neural alterations in RPE representation were particularly pronounced when participants were exploring novel stimuli. Level of CUD symptomatology moderated the relationship between novelty propensity and RPE representation within inferior parietal lobule and dorsomedial prefrontal cortex. These data expand on an emerging literature investigating individual associations of AUD symptomatology levels versus CUD symptomatology levels and RPE representation during reinforcement processing and provide insight on the role of neuro-computational processes underlying reinforcement learning/decision-making in adolescents.

Association between emotional intelligence and effective brain connectome: A large-scale spectral DCM study

INTRODUCTION

Emotional Intelligence (EI) is a well-documented aspect of social and interpersonal functioning, but the underlying neural mechanisms for this capacity remain poorly understood. Here we used advanced brain connectivity techniques to explore the associations between EI and effective connectivity (EC) within four functional brain networks.

METHODS

The Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT) was used to collect EI data from 55 healthy individuals (mean age = 30.56±8.3 years, 26 males). The MSCEIT comprises two area cores - experiential EI (T1) and strategic EI (T2). The T1 core included two sub-scales - perception of emotions (S1) and using emotions to facilitate thinking (S2), and the T2 core included two sub-scales - understanding of emotions (S3) and management of emotions (S4). All participants underwent structural and resting-state functional magnetic resonance imaging (rsfMRI) scans. The spectral dynamic causal modeling approach was implemented to estimate EC within four networks of interest - the default-mode network (DMN), dorsal attention network (DAN), control-execution network (CEN) and salience network (SN). The strength of EC within each network was correlated with the measures of EI, with correlations at p_FDR < 0.05 considered as significant.

RESULTS

There was no significant association between any of the measures of EI and EC strength within the DMN and DAN. For CEN, however, we found that there were significant negative associations between EC strength from the right anterior prefrontal cortex (RAPFC) to the left anterior prefrontal cortex (LAPFC) and both S2 and T1, and significant positive associations between EC strength from LAPFC to RAPFC and S2. EC strength from the right superior parietal cortex (SPC) to RAPFC also showed significant negative association with S4 and T2. For the SN, S3 showed significant negative association with EC strength from the right insula to RAPFC and significant positive association with EC strength from the left insula to dorsal anterior cingulate cortex (DACC).

CONCLUSIONS

We provide evidence that the negative ECs within the right hemisphere, and from the right to left hemisphere, and positive ECs within the left hemisphere and from the left to right hemisphere of CEN (involving bilateral frontal and right parietal region) and SN (involving right frontal, anterior cingulate and bilateral insula) play a significant role in regulating and processing emotions. These findings also suggest that measures of EC can be utilized as important biomarkers to better understand the underlying neural mechanisms of EI.

Callous-Unemotional Traits Moderate the Relationship Between Irritability and Threatening Responding

Background: Irritability and callous-unemotional (CU; reduced guilt/empathy) traits vary dimensionally in the typically developing population but may be particularly marked in youth with conduct disorder (CD). While these dimensional traits are positively correlated, they have been associated with divergent forms of dysfunction, particularly with respect to threat processing (i.e., irritability with increased, and CU traits with decreased, threat responsiveness). This suggests that interactions between these two dimensions may be complex at the neurobiological level. However, this issue has received minimal empirical attention. Methods: The study included 105 adolescents (typically developing and cases with CD; N = 59). They were scanned with fMRI during a looming threat task that involved images of threatening and neutral human faces or animals that appeared to be either looming or receding. Results: Significant irritability-by-CU traits-by-Direction-by-Emotion interactions were seen within right thalamus/PAG, left lingual gyrus and right fusiform gyrus; irritability was positively associated with the BOLD response for Looming Threatening vs. Receding Threatening trials, particularly for youth with low CU traits. In contrast, CU traits were negatively associated with the same differential BOLD response but particularly for youth showing higher levels of irritability. Similar findings were seen within left ventral anterior and posterior cingulate cortices, though the addition of the interaction with CU traits was only seen at slightly more lenient thresholds. Conclusions: The results support previous work linking irritability to increased, and CU traits to reduced, threat responsiveness. However, for adolescents with high irritability, if CU traits are also high, the underlying neuropathology appears to relate to reduced, rather than increased, threat responsiveness.

Alcohol Use Disorder and Cannabis Use Disorder Symptomatology in Adolescents and Aggression: Associations With Recruitment of Neural Regions Implicated in Retaliation

BACKGROUND

Alcohol and cannabis are commonly used by adolescents in the United States. Both alcohol use disorder (AUD) and cannabis use disorder (CUD) have been associated with an increased risk of aggression. One form of aggression seen during retaliation is reactive aggression to social provocation. This study investigated the association between AUD and CUD symptom severity and recruitment of neural regions implicated in retaliation.

METHODS

In this study, 102 youths aged 13-18 years (67 male; 84 in residential care) completed self-report measures of aggression-related constructs and participated in a retaliation task during functional magnetic resonance imaging to investigate the association between relative severity of AUD/CUD and atypical recruitment of regions implicated in retaliation.

RESULTS

AUD Identification Test scores were positively associated with irritability and reactive aggression scores. CUD Identification Test scores were positively associated with callous-unemotional traits and both proactive and reactive aggression scores. In functional magnetic resonance imaging analyses, only AUD Identification Test (not CUD Identification Test) scores were associated with an exaggerated recruitment of regions implicated in retaliation (dorsomedial frontal, anterior insula cortices, caudate, and, to a lesser extent, periaqueductal gray).

CONCLUSIONS

These data suggest that relative severity of AUD is associated with a disinhibited, exaggerated retaliation response that relates to an increased risk for reactive aggression. Similar findings were not related to severity of CUD.

Worry and insomnia as risk factors for depression during initial stages of COVID-19 pandemic in India

The biggest nationwide COVID-19 pandemic lockdown worldwide was enforced in India for an initial period of 21-days. Emerging evidence suggests that pandemic situations and associated lockdowns have an adverse impact on sleep and mental health. However, prediction of sleep health from sociodemographic characteristics and the public’s worry during the initial stages of the COVID-19 pandemic has not been extensively explored so far. It’s also unclear whether sleep outcomes mediate the association between worry and mental health during pandemic situations. A web-survey (N = 391) on sociodemographic characteristics, COVID-19 related worry, sleep health (insomnia and daytime sleepiness), and depression was conducted during the initial 21-days of the COVID-19 stringent lockdown in India. Multiple regression analyses showed that variables, including sex, age, income level, and worry score, contributed to the significant regression equation for insomnia but not for daytime sleepiness. Specifically, the female, younger, lower income, and highly worried populations contributed significantly more than the male, elderly, higher income, and less worried populations, respectively, to the prediction of insomnia. Mediation analyses showed that insomnia, but not daytime sleepiness, fully mediated the relationship between worry score and severity of depressive symptoms. We provide evidence that the female, younger, lower income, and worried populations may be at higher risk for insomnia during pandemic situations. Current evidence gives hope that improving sleep may reduce depressive symptoms during a pandemic situation. This underscores the importance of the implementation of effective public health policies in conjunction with strategical responses to the COVID-19 pandemic.

Physician Health in the Times of COVID-19

BACKGROUND AND OBJECTIVES

A virtual registry study evaluating real world evidence on physicians' use of prophylactic regimens for protection against SARS-CoV-2. This paper summarizes the interim results.

METHODS

Asymptomatic physicians at risk of acquiring SARS-CoV-2 responded to online questions at baseline and 7 weeks post-baseline. Baseline data included demographics, prophylaxis regimen (including "no prophylaxis") and start date. Participants who provided complete week-7 data (information on type of health facility [COVID/Non-COVID], number of presumed/confirmed cases exposed to, PPE use, SARS-CoV-2 testing and symptoms, regimen adherence and intercurrent illness) comprised the Completer population. Limited data (regimen adherence, SARS-CoV-2 testing) was collected for participants who failed to provide complete week7 data. Those providing limited/complete information comprised the Evaluable population.

RESULTS

Of 369 enrolled participants, 182 (mean age 42±11.05 years) comprised the Evaluable population. They showed a male preponderance (67.6%). Practitioners from Maharashtra (59.9%) and specialties of Pediatrics, Internal Medicine, Anesthesiology and Critical Care (63.2%) accounted for the majority. ICMR's HCQ prophylaxis regimen was initiated by 125 (68.7%) participants with 31 (17%) initiating 'No prophylaxis'. The highest adherence was for the ICMRregimen (87.2%). In the Completer population comprising 150 participants, 87 were exposed to presumed (81) and/or confirmed cases (60). Most exposures to confirmed cases (49, 81.7%) were high-risk. PPE use was generally high (75-100%). Most participants (94.7%) did not report an AE. The proportions with an AE was similar with ICMR regimen (5.9%) and no prophylaxis (6.5%).

INTERPRETATION AND CONCLUSIONS

Physicians in India preferred ICMR's HCQ regimen. The regimen appears to be safe and associated with a high level of adherence.

Fixed-dose combination in management of type 2 diabetes mellitus: Expert opinion from an international panel

Type 2 diabetes mellitus (T2DM) is a progressive disease with multifactorial etiology. The first-line therapy includes monotherapy (with metformin), which often fails to provide effective glycemic control, necessitating the addition of add-on therapy. In this regard, multiple single-dose agents formulated as a single-dose form called fixed-dose combinations (FDCs) have been evaluated for their safety, efficacy, and tolerability. The primary objective of this review is to develop practice-based expert group opinion on the current status and the causes of concern regarding the irrational use of FDCs, in Indian settings. After due discussions, the expert group analyzed the results from several clinical evidence in which various fixed combinations were used in T2DM management. The panel opined that FDCs (double or triple) improve patient adherence, reduce cost, and provide effective glycemic control and, thereby, play an important role in the management of T2DM. The expert group strongly recommended that the irrational metformin FDC's, banned by Indian government, should be stopped and could be achieved through active participation from the government, regulatory bodies, and health ministry, and through continuous education of primary care physicians and pharmacists. In T2DM management, FDCs play a crucial role in achieving glycemic targets effectively. However, understanding the difference between rational and irrational FDC combinations is necessary from the safety, efficacy, and tolerability perspective. In this regard, primary care physicians will have to use a multistep approach so that they can take informed decisions.

0070 The Effects of Acute Blue Wavelength Light Exposure on Functional Brain Connectivity and Mood

Introduction

Blue wavelength light is an effective treatment for delayed sleep phase syndrome, seasonal affective disorder and bipolar depression. The role of blue light in regulating melatonin production has been extensively studied, but other potential neurophysiological effects remain poorly understood. Some studies have suggested that daily blue light exposure may modulate functional brain responses within the amygdala and prefrontal cortex (PFC), potentially explaining blue light’s antidepressant effect. In this study we investigated the effects of a single 30-minute session of blue light exposure on functional resting state connectivity between the amygdala and PFC.

Methods

Twenty-nine healthy 18–32 year olds were randomly assigned to either receive 30 minutes of blue (n=17) or non-blue (amber) light (n=12) exposure followed by a 7-minute resting state scan. Pre- and post light exposure, participants completed the Positive and Negative Affect Scale, as a measure of state affect.

Results

Individuals who received blue versus amber light showed greater positive connectivity between the right amygdala and the left dorsolateral prefrontal cortex (DLPFC) (x=-24, y=46, z=18, k=90, volume p-FDR corrected, p&lt;0.001). Increased amygdala-DLFC connectivity correlated with greater decreases in negative mood for the blue (ρ=-.55, p=0.03), but not the amber group. Using Granger Causality, we found that the directionality of information flow between these two areas was bidirectional (p&lt;0.0025).

Conclusion

Blue light exposure appears to facilitate greater information flow between the amygdala and the DLPFC at rest, potentially enhancing cognitive processes that regulate arousal and mood. As blue light exposure has been shown to enhance attention and learning, using blue light exposure during practice of emotional regulation strategies, such as reappraisal, may further increase the beneficial effects of blue light on mood. In order to use blue light exposure in a more targeted manner for sleep and mood disorders, further research into the underlying neurophysiological mechanisms is needed.

Support

This research was supported by a USAMRAA grant to WDSK (W81XWH-14-1-0571) as well as by an Arizona Health Education Centers (AHEC) Research Grant to AA.

Unravelling the utility of modern sulfonylureas from cardiovascular outcome trials and landmark trials: expert opinion from an international panel

AIM

The primary objective of this review is to develop practice-based expert group opinions on the cardiovascular (CV) safety and utility of modern sulfonylureas (SUs) in cardiovascular outcome trials (CVOTs).

BACKGROUND

The United States Food and Drug Administration issued new guidance to the pharmaceutical industry in 2008 regarding the development of new antihyperglycemic drugs. The guidance expanded the scope for the approval of novel antihyperglycemic drugs by mandating CVOTs for safety. A few long-term CVOTs on dipeptidyl peptidase 4 inhibitors, glucagon-like peptide 1 receptor agonists, and sodium-glucose cotransporter 2 inhibitors have been completed, while others are ongoing. SUs, which constitute one of the key antihyperglycemic agents used for the management of type 2 diabetes mellitus (T2DM), have been used as comparator agents in several CVOTs. However, the need for CVOTs on modern SUs remains debatable. In this context, a multinational group of endocrinologists convened for a meeting and discussed the need for CVOTs of modern SUs to evaluate their utility in the management of patients with T2DM. At the meeting, CVOTs of modern SUs conducted to date and the hypotheses derived from the results of these trials were discussed.

REVIEW RESULTS

The expert group analyzed the key trials emphasizing the CV safety of modern SUs and also reviewed the results of various CVOTs in which modern SUs were used as comparators. Based on literature evidence and individual clinical insights, the expert group opined that modern SUs are cardiosafe and that since they have been used as comparators in other CVOTs, CVOTs of SUs are not required.

CONCLUSION

Modern SUs can be considered a cardiosafe option for the management of patients with diabetes mellitus and CV disease; thus CVOTs among individuals with T2DM are not required.

Expert Group Consensus Opinion: Role of Anti-inflammatory Agents in the Management of Type-2 Diabetes (T2D)

Diabetes is a major public health emergency of the 21st century. Results of the Indian Council of Medical Research-INdia DIABetes (ICMR-INDIAB) study have found prevalence of diabetes and prediabetes in India to be as high as 7.3% and 10.3%, respectively with nation-wide projection of 77.2 million people with prediabetes and 69.2 million with diabetes. It is well established that insulin resistance (IR) and islet β-cell failure are the two major features of T2D Multiple mechanisms including glucotoxicity, lipotoxicity, oxidative stress, endoplasmic reticulum stress, formation of amyloid deposits in the islets, etc. have been hypothesized to participate in the pathology of the disease. In the concluding decade of the last century, numerous studies - prospective and cross-sectional, have confirmed the role of chronic low-grade inflammation as a pathogenetic factor of T2D. It has been shown that increased levels of various inflammatory markers and mediators including fundamental markers like white blood cell count, C-reactive protein (CRP) to the more specific circulating cytokines like, interleukin-6 (IL-6), IL-1β, plasminogen activator inhibitor-1 (PAI-1), etc. correlate with incident T2D. Based on the robust evidence implying the role of inflammation in T2D pathogenesis, several studies have proven that the proinflammatory cytokines play a central role in the development of microvascular diabetic complications such as nephropathy, retinopathy, and neuropathy. Inflammation in T2D causes accelerated atherosclerosis which predisposes to CVD, the leading cause of mortality in these patients. Recently there is a considerable increase in the interest among the researchers about anti-inflammatory therapies in the setting of chronic disorders such as T2D and CV diseases. In a multi-country study conducted in Asia, approximately 50% of Indian respondents had poor diabetes control. Most patients initially respond to sulfonylurea and/or metformin, and later these agents lose their effectiveness with time. Therapeutic option in patients uncontrolled on two-drug combination therapy is either to add third oral drug or insulin. However, use of insulin is limited due to its high cost and poor compliance. Majority of new treatment options like GLP1 agonists, insulin analogs and SGLT2 inhibitors are costly considering they are still under patent. The thiazolidinedione class of drugs is associated with adverse effects like fluid retention and weight gain that may result in or exacerbate edema and congestive heart failure. Thus there is a need for a safe and inexpensive treatment option for the management of uncontrolled T2D. Considering the role of inflammation in T2D pathogenesis, the drug should not only have antihyperglycemic effects but also reduce inflammatory burden thus reducing the progression and complications of T2D. The current interest is apparently directed towards drugs targeting inflammation acting at different stages of the inflammatory cascade. In the recently published CANTOS study, canakinumab, a selective, high-affinity, fully human monoclonal antibody which inhibits IL-1β, has no consistent long-term benefits on HbA1c. Other selective inhibitors like anakinra (IL-1 receptor antagonist) and etanercept (TNF inhibitor) too have yielded modest effects on glycemic parameters and insulin sensitivity. However, hydroxychloroquine (HCQ), a broad anti-inflammatory agent has been shown to reduce HbA1c by 0.87%. Hydroxychloroquine (HCQ) is considered as one of the safest disease modifying anti-rheumatic drug, used widely for the treatment of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). The effect of HCQ in preventing development of diabetes in patients with chronic inflammatory diseases was highlighted in a prospective observational study of 4905 adults with rheumatoid arthritis and no diabetes with 21.5 years of follow-up. Patients who took HCQ for more than 4 years had a significant 77% lower risk of diabetes compared with non users of HCQ (RR, 0.23; 95% CI, 0.11-0.50). Taking cue from this study highlighting the anti-diabetic effect of HCQ, pioneering research studies evaluating these effects of HCQ were conducted in India. In 2014, hydroxychloroquine 400 mg got DCGI approval as an adjunct to diet and exercise to improve glycemic control of patients on metformin, sulfonylurea combination in Type 2 diabetes.

Rare disease heralded by pulmonary manifestations: Avoiding pitfalls of an "asthma" label

Pulmonary manifestations are seldom recognized as symptoms of storage disorders. The report describes the diagnostic journey in a 30-month-old male infant, born of a third-degree consanguineous marriage referred to our institute as severe persistent asthma. History revealed that the child had progressively worsening breathlessness and persistent dry cough not associated with fever but accompanied by weight loss. On physical examination, there was growth failure, respiratory distress, clubbing, hepatosplenomegaly, and occasional rhonchi. Blood gas revealed hypoxemia which improved with oxygen administration. Plain X-rays and high-resolution computed tomography of the chest showed perihilar alveolar infiltrates and patchy consolidation. The clinicoradiological features did not support a diagnosis of asthma but favored interstitial lung disease (ILD). Bronchoalveolar lavage was performed as a first-tier investigation. It showed periodic acid-Schiff-negative foamy macrophages. The clues of consanguinity, visceromegaly, ILD, and foamy macrophages in the bronchoalveolar fluid prompted consideration of lysosomal storage disorders as the likely etiology. Gaucher disease and Niemann-Pick disease A/B were ruled out by enzyme estimation. Niemann-Pick disease type C was suspected and confirmed by detecting a homozygous mutation in the NPC2 gene. This case serves to caution physicians against labeling breathlessness in every toddler as asthma. It emphasizes the importance of searching for tell-tale signs such as clubbing and extrapulmonary clues which point to a systemic disease such as lysosomal storage disorders as a primary etiology of chronic respiratory symptoms.

Vulnerability to mood degradation during sleep deprivation is influenced by white-matter compactness of the triple-network model

Sleep deprivation (SD) is often associated with significant shifts in mood state relative to baseline functioning. Prior work suggests that there are consistent trait-like differences among individuals in the degree to which their mood and performances are affected by sleep loss. The goal of this study was to determine the extent to which trait-like individual differences in vulnerability/resistance to mood degradation during a night of SD are dependent upon region-specific white and grey matter (WM/GM) characteristics of a triple-network model, including the default-mode network (DMN), control-execution network (CEN) and salience network (SN). Diffusion-weighted and anatomical brain data were collected from 45 healthy individuals several days prior to a 28-h overnight SD protocol. During SD, a visual analog mood scale was administered every hour from 19:15 (time point1; TP1) to 11:15 (TP17) the following morning to measure two positive and six negative mood states. Four core regions within the DMN, five within the CEN, and seven within the SN were used as regions of interest (ROIs). An index of mood resistance (IMR) was defined as the averaged differences between positive and negative mood states over 12 TPs (TP5 to TP16) relative to baseline (TP1 to TP4). For each ROI, characteristics of WM - quantitative anisotropy (QA) and mean curvature index (WM-MCI), and GM - cortical volume (CV) and GM-MCI were estimated, and used to predict IMR. WM characteristics, particularly QA, of all of regions within the DMN, and most of the regions within the CEN and SN predicted IMR during SD. In contrast, most ROIs did not show significant association between IMR and any of the GM characteristics (CV and MCI) or WM MCI. Our findings suggest that greater resilience to mood degradation induced by total SD appears to be associated with more compact axonal pathways within the DMN, CEN and SN.

Sex differences in limbic network and risk-taking propensity in healthy individuals

Little is known about the structural neural substrates that may contribute to sex differences in risk-taking propensity (RTP). A close association between risk-seeking behavior and the emotional-regulation network led us to hypothesize that the sex differences in RTP would be associated with sex differences in brain morphometry of the limbic network (LN). We collected RTP scores using the bubble sheet version of the evaluation of risk (EVAR) scale and neuroanatomical data from 57 healthy individuals (29 males). The EVAR scale included sub-scales measuring recklessness/impulsivity, self-confidence, and need for control (NFC). We observed significant sex differences in NFC showing greater desire for control and dominance in males than females (multivariate analysis of covariance, MANCOVAN: p = .01). Morphometry analysis showed that it was only the right LN, which showed significant sex differences in normalized surface area, normalized cortical volume, and adjusted mean curvature index (females > males) at p < .01 (MANCOVAN, corrected for multiple comparisons). Correlation analysis showed that greater curvature of the right LN was significantly associated with lower desire for control in high-risk events (r = -.31, p = .02 at 95% CI of [-0.53, -0.05]). Our findings suggest that the normalized cortical measures could indicate specific sex differences in brain morphometry, particularly within the LN. The curvature index was the only differentiating factor for greater/lower propensity for risk-taking behavior in overall sample. Therefore, the LN and the curvature measures could be key biomarkers, which play an important role in predicting risk-taking behavior.

The Role of Prefrontal Cortical Surface Area and Volume in Preclinical Suicidal Ideation in a Non-Clinical Sample

Suicidal ideation (SUI) can occur in the absence of concomitant psychiatric diagnoses, and even normal levels can be problematic among individuals experiencing excess stress or lack of social support. The objective of this study was to investigate the neuroanatomical basis of SUI in non-clinical human populations who are within the normal limits of SUI, after accounting for elevated stress and perceived lack of social support. Neuroanatomical data were collected from 55 healthy individuals (mean age 30.9 ± 8.1 years, 27 females) whose depression severity levels were below the Diagnostic and Statistical Manual of Mental Disorders criteria. Measures of SUI, aggression, stress, non-support, and treatment rejection were collected from the treatment-consideration scales (TCS) of the Personality Assessment Inventory (PAI). Correlations between standardized SUI scores and three brain morphometry measures, including vertex wise cortical thickness (CT), cortical surface area (CSA), and cortical volume (CV), were estimated for each participant, controlling for age, sex, intracranial volume, and the remaining TCS measures. We observed a significant negative association between scores on SUI and both CSA and CV (cluster-forming threshold of p < 0.005, clusterwise threshold of p < 0.05, FDR corrected for multiple comparisons) within the left rostral middle frontal gyrus. Our findings suggest that greater CSA and CV within the dorsolateral prefrontal cortex are associated with reduced SUI in a non-clinical population with mild levels of stress and perceived lack of social support. Because the dorsolateral prefrontal cortex has been broadly linked to cognitive reappraisal, self-critical thoughts, and emotional regulation, greater CSA and CV within these regions may lead to better mental health by protecting healthy individuals from engaging in SUI during periods of stress and perceived insufficient social support. As our data consisted of only healthy individuals with non-clinical levels of SUI, further investigation will be necessary to explore the neural basis of SUI in populations who may be at greater risk of future suicidal behavior.

The Relationship Between General Intelligence and Cortical Structure in Healthy Individuals

Considerable work in recent years has examined the relationship between cortical thickness (CT) and general intelligence (IQ) in healthy individuals. It is not known whether specific IQ variables (i.e., perceptual reasoning [PIQ], verbal comprehension IQ [VIQ], and full-scale IQ [FSIQ]) are associated with multiple cortical measures (i.e., CT, cortical volume (CV), cortical surface area (CSA) and cortical gyrification (CG)) within the same individuals. Here we examined the association between these neuroimaging metrics and IQ in 56 healthy adults. At a cluster-forming threshold (CFT) of p < 0.05, we observed significant positive relationships between CT and all three IQ variables in regions within the posterior frontal and superior parietal lobes. Regions within the temporal and posterior frontal lobes exhibited positive relationships between CV and two IQ variables (PIQ and FSIQ) and regions within the inferior parietal lobe exhibited positive relationships between CV and PIQ. Additionally, CV was positively associated with VIQ in the left insula and with FSIQ within the inferior frontal gyrus. At a more stringent CFT (p < 0.01), the CT-PIQ, CT-VIQ, CT-FSIQ, and CV-PIQ relationships remained significant within the posterior frontal lobe, as did the CV-PIQ relationship within the temporal and inferior parietal lobes. We did not observe statistically significant relationships between IQ and either CSA or CG. Our findings suggest that the neural basis of IQ extends beyond previously observed relationships with fronto-parietal regions. We also conclude that CT and CV may be more useful metrics than CSA or CG in the study of intellectual abilities.

Elevated Aggression and Reduced White Matter Integrity in Mild Traumatic Brain Injury: A DTI Study

Mild traumatic brain injury (mTBI) remains the most commonly reported head injury in the United States, and is associated with a wide range of post-concussive symptoms including physical, cognitive and affective impairments. Elevated aggression has been documented in mTBI; however, the neural mechanisms associated with aggression at the chronic stage of recovery remain poorly understood. In the present study, we investigated the association between white matter integrity and aggression in mTBI using diffusion tensor imaging (DTI). Twenty-six age-matched adults participated in the study, including 16 healthy controls (HCs) and 10 individuals in the chronic stage of recovery (either 6-months or 12 months post-mTBI). Psychological measures of aggression included the Buss-Perry Aggression Questionnaire and the Personality Assessment Inventory (PAI). Axonal pathways implicated in affective processing were studied, including the corpus callosum, anterior thalamic radiation, cingulum and uncinate fasciculus, and measures of white matter integrity included fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD). We found that adults with mTBI in the chronic stage of recovery had higher levels aggression. Individuals with mTBI also had greater RD in the corpus callosum compared to HCs, indicating reduced fiber integrity. Furthermore, we observed a significant association between reduced white matter integrity in the corpus callosum and greater aggression. Our findings provide additional evidence for underlying neuroanatomical mechanisms of aggression, although future research will be necessary to characterize the specific relationship between aggression and the white matter pathways we identified.

Diffusion Tensor Imaging (DTI) Correlates of Self-Reported Sleep Quality and Depression Following Mild Traumatic Brain Injury

Background: Mild traumatic brain injuries (mTBIs) are a significant social, sport, and military health issue. In spite of advances in the clinical management of these injuries, the underlying pathophysiology is not well-understood. There is a critical need to advance objective biomarkers, allowing the identification and tracking of the long-term evolution of changes resulting from mTBI. Diffusion-weighted imaging (DWI) allows for the assessment of white-matter properties in the brain and shows promise as a suitable biomarker of mTBI pathophysiology. Methods: 34 individuals within a year of an mTBI (age: 24.4 ± 7.4) and 18 individuals with no history of mTBI (age: 23.2 ± 3.4) participated in this study. Participants completed self-report measures related to functional outcomes, psychological health, post-injury symptoms, and sleep, and underwent a neuroimaging session that included DWI. Whole-brain white matter was skeletonized using tract-based spatial statistics (TBSS) and compared between groups as well as correlated within-group with the self-report measures. Results: There were no statistically significant anatomical differences between the two groups. After controlling for time since injury, fractional anisotropy (FA) demonstrated a negative correlation with sleep quality scores (higher FA was associated with better sleep quality) and increasing depressive symptoms in the mTBI participants. Conversely, mean (MD) and radial diffusivity (RD) demonstrated positive correlations with sleep quality scores (higher RD was associated with worse sleep quality) and increasing depressive symptoms. These correlations were observed bilaterally in the internal capsule (anterior and posterior limbs), corona radiata (anterior and superior), fornix, and superior fronto-occipital fasciculi. Conclusion: The results of this study indicate that the clinical presentation of mTBI, particularly with respect to depression and sleep, is associated with reduced white-matter integrity in multiple areas of the brain, even after controlling for time since injury. These areas are generally associated not only with sleep and emotion regulation but also cognition. Consequently, the onset of depression and sleep dysfunction as well as cognitive impairments following mTBI may be closely related to each other and to white-matter integrity throughout the brain.