Reduced gray matter volume in the anterior cingulate, orbitofrontal cortex and thalamus as a function of mild depressive symptoms: a voxel-based morphometric analysis.

BACKGROUND: Studies investigating structural brain abnormalities in depression have typically employed a categorical rather than dimensional approach to depression [i.e., comparing subjects with Diagnostic and Statistical Manual of Mental Disorders (DSM)-defined major depressive disorder (MDD) v. healthy controls]. The National Institute of Mental Health, through their Research Domain Criteria initiative, has encouraged a dimensional approach to the study of psychopathology as opposed to an over-reliance on categorical (e.g., DSM-based) diagnostic approaches. Moreover, subthreshold levels of depressive symptoms (i.e., severity levels below DSM criteria) have been found to be associated with a range of negative outcomes, yet have been relatively neglected in neuroimaging research. METHOD: To examine the extent to which depressive symptoms--even at subclinical levels--are linearly related to gray matter volume reductions in theoretically important brain regions, we employed whole-brain voxel-based morphometry in a sample of 54 participants. RESULTS: The severity of mild depressive symptoms, even in a subclinical population, was associated with reduced gray matter volume in the orbitofrontal cortex, anterior cingulate, thalamus, superior temporal gyrus/temporal pole and superior frontal gyrus. A conjunction analysis revealed concordance across two separate measures of depression. CONCLUSIONS: Reduced gray matter volume in theoretically important brain regions can be observed even in a sample that does not meet DSM criteria for MDD, but who nevertheless report relatively elevated levels of depressive symptoms. Overall, these findings highlight the need for additional research using dimensional conceptual and analytic approaches, as well as further investigation of subclinical populations.

Differential influence of safe versus threatening facial expressions on decision-making during an inhibitory control task in adolescence and adulthood.

Social cognition matures dramatically during adolescence and into early adulthood, supported by continued improvements in inhibitory control. During this time, developmental changes in interpreting and responding to social signals such as facial expressions also occur. In the present study, subjects performed a Go No-Go task that required them to respond or inhibit responding based on threat or safety cues present in facial expressions. Subjects (N = 112) were divided into three age groups: adolescent (12-15 years), emerging adult (18-25 years) and adult (26-44 years). Analyses revealed a significant improvement in accuracy on No-Go trials, but not Go trials, during both safe and threat face conditions, with changes evident through early adulthood. In order to better identify the decision-making processes responsible for these changes in inhibitory control, a drift diffusion model (DDM) was fit to the accuracy and reaction time data, generating measures of caution, response bias, nondecision time (encoding + motor response), and drift rate (face processing efficiency). Caution and nondecision time both increased significantly with age while bias towards the Go response decreased. Drift rate analyses revealed significant age-related improvements in the ability to map threat faces to a No-Go response while drift rates on all other trial types were equivalent across age groups. These results suggest that both stimulus-independent and stimulus-dependent processes contribute to improvements in inhibitory control in adolescence with processing of negative social cues being specifically impaired by self-regulatory demands. Findings from this novel investigation of emotional responsiveness integrated with inhibitory control may provide useful insights about healthy development that can be applied to better understand adolescent risk-taking behavior and the elevated incidence of related forms of psychopathology during this period of life.

Cortico-limbic responsiveness to high-calorie food images predicts weight status among women.

OBJECTIVES: Excessive weight gain and obesity are currently among the world's major threats to health. Women show significantly higher rates of obesity and eating disorders relative to men, but the factors contributing to these gender differences remain uncertain. We examined the correlations between regional brain responses to images of high-calorie versus low-calorie foods and self-reported motivational status, including ratings of general appetite, overeating propensity, state hunger and desire for specific foods. SUBJECTS: Thirty-eight healthy right-handed adults (22 male; 16 female) ages 18-45 participated. There were no differences between males and females with regard to age or body mass index (BMI). RESULTS: Overall, motivational status correlated significantly with activation within the amygdala, insula and orbitofrontal cortex. Regional activation was then used to predict BMI, an indicator of long-term food consumption and energy expenditure. The combined model was significant, accounting for 76% of the variance in BMI for women, whereas the same regions were not predictive of weight status among men. CONCLUSIONS: Findings suggest that long-term weight status is related to visual responsiveness to calorie-dense food imagery among women.