Heritability of cerebral blood flow in adolescent and young adult twins: an arterial spin labeling perfusion imaging study.

Blood perfusion is a fundamental physiological property of all organs and is closely linked to brain metabolism. Genetic factors were reported to have important influences on cerebral blood flow. However, the profile of genetic contributions to cerebral blood flow in adolescents or young adults was underexplored. In this study, we recruited a sample of 65 pairs of same-sex adolescent or young adult twins undergoing resting arterial spin labeling imaging to conduct heritability analyses. Our findings indicate that genetic factors modestly affect cerebral blood flow in adolescents or young adults in the territories of left anterior cerebral artery and right posterior cerebral artery, with the primary contribution being to the frontal regions, cingulate gyrus, and striatum, suggesting a profile of genetic contributions to specific brain regions. Notably, the regions in the left hemisphere demonstrate the highest heritability in most regions examined. These results expand our knowledge of the genetic basis of cerebral blood flow in the developing brain and emphasize the importance of regional analysis in understanding the heritability of cerebral blood flow. Such insights may contribute to our understanding of the underlying genetic mechanism of brain functions and altered cerebral blood flow observed in youths with brain disorders.

Genetic contribution to the phenotypic correlation between trait impulsivity and resting-state functional connectivity of the amygdala and its subregions.

Trait impulsivity, a predisposition to respond to stimuli without regard for the potentially negative consequences, contributes to many maladaptive behaviors. Studies have shown that both genetic factors and interregional functional interactions underlie trait impulsivity. However, whether common genes contribute to both trait impulsivity and its neural basis is still unknown. This study investigated the phenotypic correlations between trait impulsivity and the resting-state functional connectivity (rsFC) of the amygdala as well as its subregions and the genetic contribution to the phenotypic correlations. By recruiting a sample of 292 twins in late adolescence and young adulthood, we found that trait impulsivity was positively correlated with the rsFC between the left full amygdala and the right dorsolateral prefrontal cortex (DLPFC). Further analyses on the subregions of the amygdala showed that trait impulsivity was positively correlated with the rsFCs between the left basolateral (BL) amygdala and both the right DLPFC and the right inferior frontal gyrus and with the rsFCs between the right superficial (SF) amygdala and both the dorsal anterior cingulate cortex and right anterior insula. Bivariate genetic modelling analyses found genetic overlaps between trait impulsivity and the rsFC of the left full amygdala or the left BL amygdala with the right DLPFC. The proportions of phenotypic associations accounted for by overlapping genes were 82% and 60%, respectively. These results provide evidence for the genetic overlap between trait impulsivity and the intrinsic brain functional connectivity centered at the amygdala and especially at its BL subregion.

Genetic Contribution to Variation in Risk Taking: A Functional MRI Twin Study of the Balloon Analogue Risk Task.

Excessive risk-taking behaviors have been implicated as a potential endophenotype for substance use disorders and psychopathological gambling. However, the genetic and environmental influences on risk taking and the risk-related brain activations remain unclear. This study investigated the heritability of risk taking and the genetic influence on individual variation in risk-related brain activation. The Balloon Analogue Risk Task was used to assess individuals' risk-taking behavior. In a sample of 244 pairs of young adult twins, we found that there was a moderate heritability (41%) of risk taking. Using voxel-level analysis, we found a moderate genetic influence on risk-related brain activation. We also found a moderate genetic correlation between risk-taking behavior and risk-related brain activation in the left insula, right striatum, and right superior parietal lobule in the active-choice condition. The present study provides important evidence for the genetic correlation between risk-taking behavior and risk-related brain activation.

Born for fairness: evidence of genetic contribution to a neural basis of fairness intuition.

Human beings often curb self-interest to develop and enforce social norms, such as fairness, as exemplified in the ultimatum game (UG). Inspired by the dual-system account for the responder's choice during the UG, we investigated whether the neural basis of psychological process induced by fairness is under genetic control using a twin fMRI study (62 monozygotic, 48 dizygotic; mean age: 19.32 ± 1.38 years). We found a moderate genetic contribution to the rejection rate of unfair proposals (24%-35%), independent of stake size or proposer type, during the UG. Using a voxel-level analysis, we found that genetic factors moderately contributed to unfairness-evoked activation in the bilateral anterior insula (AI), regions representing the intuition of fairness norm violations (mean heritability: left 37%, right 40%). No genetic contributions were found in regions related to deliberate, controlled processes in the UG. This study provides the first evidence that evoked brain activity by unfairness in the bilateral AI is influenced by genes and sheds light on the genetic basis of brain processes underlying costly punishment.

Abnormalities within and beyond the cortico-striato-thalamo-cortical circuitry in medication-free patients with OCD revealed by the fractional amplitude of low-frequency fluctuations and resting-state functional connectivity.

Neuroimaging studies of obsessive-compulsive disorder (OCD) often focus on the cortico-striato-thalamo-cortical (CSTC) circuitry, but recent studies have found abnormal spontaneous brain activity in regions outside the CSTC circuitry in patients with OCD using resting-state functional magnetic resonance imaging. Researchers have not clearly determined whether changes in spontaneous brain activity within and beyond the CSTC circuitry coexist in medication-free patients with OCD. To address this question, we recruited 64 medication-free patients with OCD and 60 matched healthy controls (HCs) to investigate their spontaneous brain activity by measuring the fractional amplitude of low-frequency fluctuation (fALFF) and resting-state functional connectivity. Patients with OCD showed increased fALFF values in the left dorsolateral prefrontal cortex (DLPFC) and decreased fALFF values in the right rolandic operculum compared with HCs. Furthermore, patients with OCD exhibited significantly increased functional connectivity between the left DLPFC and the left cerebellum and reduced negative functional connectivity between the right rolandic operculum and the left precuneus. These findings provided new insights into the pathophysiological model of OCD, which may include CSTC circuitry and regions outside this circuitry.

Disrupted resting-state functional architecture of the brain after 45-day simulated microgravity.

Long-term spaceflight induces both physiological and psychological changes in astronauts. To understand the neural mechanisms underlying these physiological and psychological changes, it is critical to investigate the effects of microgravity on the functional architecture of the brain. In this study, we used resting-state functional MRI (rs-fMRI) to study whether the functional architecture of the brain is altered after 45 days of -6° head-down tilt (HDT) bed rest, which is a reliable model for the simulation of microgravity. Sixteen healthy male volunteers underwent rs-fMRI scans before and after 45 days of -6° HDT bed rest. Specifically, we used a commonly employed graph-based measure of network organization, i.e., degree centrality (DC), to perform a full-brain exploration of the regions that were influenced by simulated microgravity. We subsequently examined the functional connectivities of these regions using a seed-based resting-state functional connectivity (RSFC) analysis. We found decreased DC in two regions, the left anterior insula (aINS) and the anterior part of the middle cingulate cortex (MCC; also called the dorsal anterior cingulate cortex in many studies), in the male volunteers after 45 days of -6° HDT bed rest. Furthermore, seed-based RSFC analyses revealed that a functional network anchored in the aINS and MCC was particularly influenced by simulated microgravity. These results provide evidence that simulated microgravity alters the resting-state functional architecture of the brains of males and suggest that the processing of salience information, which is primarily subserved by the aINS-MCC functional network, is particularly influenced by spaceflight. The current findings provide a new perspective for understanding the relationships between microgravity, cognitive function, autonomic neural function, and central neural activity.