Neurostructural correlates of optimism: Gray matter density in the putamen predicts dispositional optimism in late adolescence.

Dispositional optimism reflects one's generalized positive expectancies for future outcomes and plays a crucial role in personal developmental outcomes and health (e.g., counteracting related mental disorders such as depression and anxiety). Increasing evidence has suggested that extraversion is an important personality factor contributing to dispositional optimism. However, less is known about the association between dispositional optimism and brain structure and the role of extraversion in this association. Here, we examined these issues in 231 healthy high school students aged 16 to 20 years (110 males, mean age = 18.48 years, SD = 0.54) by estimating regional gray matter density (rGMD) using a voxel-based morphometry method via structural magnetic resonance imaging. Whole-brain regression analyses revealed a significant positive correlation between dispositional optimism and the rGMD of the bilateral putamen after adjusting for age, sex, family socioeconomic status (SES), general intelligence, and total gray matter volume (TGMV). Moreover, prediction analyses using fourfold balanced cross-validation combined with linear regression confirmed a significant connection between dispositional optimism and putamen density after adjusting for age, sex, and family SES. More importantly, subsequent mediation analysis showed that extraversion may account for the association between putamen density and dispositional optimism after adjusting for age, sex, family SES, general intelligence, TGMV, and the other four Big Five personality traits. Taken together, the current study provides new evidence regarding the neurostructural basis underlying dispositional optimism in adolescents and underscores the importance of extraversion as an essential personality factor for dispositional optimism acquisition.

Altered cortical morphology of visual cortex in adults with monocular amblyopia.

BACKGROUND: The neural mechanism of amblyopia and its impact on the adult brain remain unclear. This hinders effective treatment for adults with this disease. PURPOSE: To investigate neuroanatomical differences in cortical morphometry between amblyopic adults and healthy controls, and to explore the structural covariance of abnormal morphometric changes. STUDY TYPE: Prospective. POPULATION: Twenty-one amblyopic adults and 34 healthy controls. FIELD STRENGTH/SEQUENCE: 3T MRI, T1 -weighted, MPRAGE sequence. ASSESSMENT: All participants completed ophthalmologic exams to confirm the diagnosis of amblyopia or its absence in the healthy controls, including tests of ocular motility and dilation, fundus exam, autorefraction and synoptophore tests. Cortical volume, thickness, and surface area measurements were obtained using FreeSurfer software. STATISTICAL TESTS: Statistical differences of MRI measures between amblyopic adults and healthy controls were identified using a general linear model with intracranial volume and age as covariates. Monte Carlo simulations were used to correct for multiple comparisons. The structural covariance of abnormal morphometric changes and the relationship between morphometric abnormalities and visual acuity of the amblyopic eye were examined. RESULTS: Compared with healthy controls, amblyopic adults showed reduced cortical volume in left lateral occipital cortex, and decreased cortical thickness in bilateral inferior temporal gyrus and left precentral gyrus (P < 0.05; Monte Carlo corrected). Structural covariance between cortical volume of left lateral occipital cortex and cortical thickness of right inferior temporal gyrus in amblyopic adults was significantly less than in healthy controls (z = 1.73; P < 0.05). DATA CONCLUSION: Our study identified morphological abnormalities in occipital cortex and in temporal and frontal cortex which are projection fields of visual cortex important for processing of visual form and object location information, and disrupted structural covariance of visual cortex with other brain regions in amblyopic patients. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:1405-1412.

Value of MRI in medicine: More than just another test?

There is increasing scrutiny from healthcare organizations towards the utility and associated costs of imaging. MRI has traditionally been used as a high-end modality, and although shown extremely important for many types of clinical scenarios, it has been suggested as too expensive by some. This editorial will try and explain how value should be addressed and gives some insights and practical examples of how value of MRI can be increased. It requires a global effort to increase accessibility, value for money, and impact on patient management. We hope this editorial sheds some light and gives some indications of where the field may wish to address some of its research to proactively demonstrate the value of MRI. Level of Evidence: 5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2019;49:e14-e25.

Assessment of Cortical Dysfunction in Patients with Intermittent Exotropia: An fMRI Study.

Neural imaging studies have found the connection between strabismus and brain cortex. However, the pathological mechanisms of intermittent exotropia are still not fully understood. In the present study, changes of binocular fusion related cortices in intermittent exotropia were investigated with blood oxygen level dependent functional magnetic resonance imaging. Activated cortices induced by fusion stimulus were found to be distributed in several regions such as bilateral middle occipital gyrus, bilateral middle temporal gyrus, left superior parietal lobule and so on. Compared with normal subjects, the increased activation intensity was observed in bilateral superior parietal lobule and inferior parietal lobule in subjects with intermittent exotropia. These findings indicate that binocular fusion involves a complicated brain network including several regions. And cortical activities of bilateral superior parietal lobule and inferior parietal lobule compensate for the binocular fusion dysfunction in intermittent exotropia.

Assessment of cortical dysfunction in infantile esotropia using fMRI.

PURPOSE: Functional magnetic resonance imaging (fMRI) is popular in the field of neuroimaging. The aim of this study was to explore the neural basis of infantile esotropia and locate the cortical region of fusion function defects using blood oxygen level-dependent fMRI (BOLD-fMRI). METHODS: Subjects (5 with infantile esotropia and 8 normal) were presented with a visual stimulus (letter E). The BOLD-fMRI was used to measure the visual cortex response as the distance between the E and the eyes changing from 20 to 100 cm using a block experimental design. Data were processed offline using statistical parametric mapping and compared between the 2 groups. RESULTS: Areas activated in the visual cortex of normal subjects were located in the bilateral frontal gyrus and left lingual visual cortex (p<0.001). The BOLD signal in the left cingulate gyrus, bilateral precuneus, and left angular gyrus was higher in the infantile esotropia group than in the controls (p<0.001). None of the visual cortical areas showed higher signal in the control individuals than in those with infantile esotropia (p<0.001). CONCLUSIONS: The bilateral frontal gyrus and left lingual visual cortex regulate normal fusion function in human eyes. In infantile esotropia, the left cingulate gyrus, bilateral precuneus, and left angular gyrus visual cortex may compensate for the fusion dysfunction. These insights may help improve the diagnosis and treatment of strabismus.

An fMRI study on sunk cost effect.

Sunk cost effect (also called escalation of commitment, etc) is a pervasive, interesting and famous decision bias, which has been intensively discussed in psychology, economics, management, political science, zoology, etc. To date, little has been known about the neural basis of this phenomenon. We investigated it by using functional magnetic resonance imaging (fMRI) to monitor healthy subjects' brain activities when they made decisions in a task wherein sunk cost and incremental cost were systematically manipulated. Higher sunk cost only increased activity of some brain areas (mainly lateral frontal and parietal cortices, which are involved in risk-taking), whereas lower incremental cost mainly increased activity of some brain areas (including striatum and medial prefrontal cortex, which are sensitive to rewards). No overlapping brain areas were found to respond to both sunk cost and incremental cost. These results favor certainty effect over self-justification or diminishing sensitivity as account of sunk cost effect.

The trade-off between wiring cost and network topology in white matter structural networks in health and migraine.

The human brain organization of cortical networks has optimized trade-off architecture for the economical minimization of connection distance and maximizing valuable topological properties; however, whether this network configuration is disrupted in chronic migraine remains unknown. Here, employing the diffusion tensor imaging and graph theory approaches to construct white matter networks in 26 patients with migraine (PM) and 26 gender-matched healthy controls (HC), we investigated relationships between structural connectivity, cortical network architecture and anatomical distance in the two groups separately. Compared with the HC group, the patients showed longer global distance connection in PM, with proportionally less short-distance and more medium-distance; correspondingly, the patients showed abnormal global topology in their structural networks, mainly presented as a higher clustering coefficient. Moreover, the abnormal association between these two network features was also found. Intriguingly, the network measure that combined the nodal anatomical distance and network topology could distinguish PM from HC with high accuracy of 90.4%. We also demonstrated a high reproducibility of our findings across different parcellation schemes. Our results demonstrated that long-term migraine may result in a abnormal optimization of a trade-off between wiring cost and network topology in white matter structural networks and highlights the potential for combining spatial and topological aspects as a network marker, which may provide valuable insights into the understanding of brain network reorganization that could be attributed to the underlying pathophysiology resulting from migraine.

Investigation of different boundary treatment methods in Monte-Carlo simulations of diffusion NMR.

PURPOSE: To enrich and develop more convenient and effective boundary treatment method in Monte-Carlo simulation of restricted diffusion nuclear magnetic resonance. METHODS: The conventional approach used in treating boundary behaviors of restricted diffusion is the elastic boundary reflection. Because random walk is not dynamic process, other boundary treatments such as inelastic reflection are acceptable and probably simplify the programming of diffusion nuclear magnetic resonance simulation. The present study simulated the pulse gradient spin echo nuclear magnetic resonance by employing three boundary models, i.e., the elastic boundary reflection, the non-elastic boundary reflection, and the equal-step-length random leap. Their effects on precision, convergence, and calculation efficiency were investigated, as well as the effects of non-fixed boundary reflection step-length drawn from a Gaussian distribution in barrier-crossing steps. RESULTS: The results show no obvious difference in convergences and precisions for different methods when the relative step-length is sufficiently small. Compared with the traditional approach, the required computation time of the latter two was reduced in some degree. CONCLUSION: Boundary treatments based on inelastic reflection are a feasible choice in Monte-Carlo simulation of nuclear magnetic resonance, and in comparison with the conventional approach, it not only renders programming more convenience but also possibly lead to higher calculating efficiency.

Longitudinal ¹H MRS assessment of the thalamus in a Coriaria lactone-induced rhesus monkey status epilepticus model.

Neurophysiological, biochemical and anatomical evidence implicates the thalamus as playing a role in epileptic seizures. Until recently, however, longitudinal characterization of in vivo thalamus dynamics had not been reported. In this study, we investigated the metabolism in the thalamus to identify the changes that occur following Coriaria lactone (CL)-induced status epilepticus (SE) and to observe whether the epileptiform discharges could present a difference between the left and right thalami. Five rhesus monkeys underwent whole-brain MRI and single-voxel MRS on a Siemens Trio Tim 3-T MR scanner with a 12-channel head coil. Spectra were processed using LCModel. Scans were performed in five animals before SE and at 1, 7, 21 and 42 days after the onset of SE. Statistical analysis of the data obtained demonstrated no significant difference in the bilateral thalamus of healthy macaques. Our MRS data showed symmetrical distributions of N-acetylaspartate in the right and left thalami after SE (p = 0.003). In addition, this longitudinal study demonstrated elevated glutamate/glutamine (p < 0.05) and reduced myo-inositol (p < 0.05) in the bilateral thalamus 1 day after SE, and all metabolites approached their baseline levels by the fifth scan. Our results demonstrate that metabolic changes occur in the thalamus during CL-induced SE in rhesus monkeys. The various metabolic changes may indicate that the left thalamus is more vulnerable to epileptic strike.

Assessment of white matter abnormalities in paranoid schizophrenia and bipolar mania patients.

White matter abnormalities have been repeatedly reported in both schizophrenia and bipolar disorder (BD) in diffusion tensor imaging (DTI) studies, but the empirical evidence about the diagnostic specificity of white matter abnormalities in these disorders is still limited. This study sought to investigate the alterations in fractional anisotropy (FA) in white matter throughout the entire brain of patients from Chengdu, China with paranoid schizophrenia and bipolar mania. For this purpose, DTI was used to assess white matter integrity in patients with paranoid schizophrenia (n=25) and psychotic bipolar mania (n=18) who had been treated with standard pharmacotherapy for fewer than 5 days at the time of study, as well as in normal controls (n=30). The differences in FA were measured by use of voxel-based analysis. The results show that reduced FA was found in the left posterior corona radiata (PCR) in patients with psychotic bipolar mania and paranoid schizophrenia compared to the controls. Patients with psychotic bipolar mania also showed a significant reduction in FA in right posterior corona radiata and in right anterior thalamic radiation (ATR). A direct comparison between the two patient groups found no significant differences in any regions, and none of the findings were associated with illness duration. Correlation analysis indicated that FA values showed a significant negative correlation with positive symptom scores on the Positive and Negative Syndrome Scale in the left frontal-parietal lobe in the paranoid schizophrenia. It was concluded that common abnormalities in the left PCR might imply an overlap in white matter pathology in the two disorders and might be related to shared risk factors for the two disorders.

Diffusion tensor MRI for the assessment of cerebral ischemia/reperfusion injury in the penumbra of non-human primate stroke model.

OBJECTIVES: The purpose of this study is to use diffusion tensor imaging (DTI) parameters to evaluate cerebral ischemia/reperfusion injury in the infarct core (IC) and ischemic penumbra (IP) in a rhesus transient middle cerebral artery occlusion (MCAO) model. METHODS: Seven rhesus monkeys were used to construct the MCAO model. The temporal evolution of the relative apparent diffusion coefficient (rADC) and the relative fractional anisotropy (rFA) in the IC area, infarct growth area (IG), and reversible penumbra area (RP) were investigated. RESULTS: The rADC increased in the three areas in the early stage of reperfusion (1 hour after the reperfusion). However, the rate of rADC improvement was significantly slower in IG than in IC and RP. Different temporal evolutions of rFA were observed in the three areas in the following stage of reperfusion (3-24 hours after the reperfusion), which continued to decline in IG but slightly elevated in IC and RP. DISCUSSION: These findings suggest that the evolution of DTI parameters can help in the assessment of cerebral ischemia/reperfusion injury in the penumbra and predict the growth of the infarction area after stroke.