A specific neural substrate predicting current and future impulsivity in young adults

Impulsivity (rash action with deleterious outcomes) is common to many psychiatric disorders. While some studies indicate altered amygdala and prefrontal cortical (PFC) activity associated with impulsivity, it remains unclear whether these patterns of neural activity are specific to impulsivity or common to a range of affective and anxiety symptoms. To elucidate neural markers specific to impulsivity, we aimed to differentiate patterns of amygdala-PFC activity and functional connectivity associated with impulsivity from those associated with affective and anxiety symptoms, and identify measures of this circuitry predicting future worsening of impulsivity. Using a face emotion processing task that reliably activates amygdala-PFC circuitry, neural activity and connectivity were assessed in a transdiagnostically-recruited sample of young adults, including healthy (N = 47) and treatment-seeking individuals (N = 67). Relationships were examined between neural measures and impulsivity, anhedonia, and affective and anxiety symptoms at baseline (N = 114), and at 6 months post scan (N = 30). Impulsivity, particularly negative urgency and lack of perseverance, was related to greater amygdala activity (beta = 0.82, p = 0.003; beta = 0.68, p = 0.004; respectively) and lower amygdala-medial PFC functional connectivity (voxels = 60, tpeak = 4.45, pFWE = 0.017; voxels = 335, tpeak = 5.26, pFWE = 0.001; respectively) to facial fear. Left vlPFC, but not amygdala, activity to facial anger was inversely associated with mania/hypomania (beta = -2.08, p = 0.018). Impulsivity 6 months later was predicted by amygdala activity to facial sadness (beta = 0.50, p = 0.017). There were no other significant relationships between neural activity and 6-month anhedonia, affective, and anxiety symptoms. Our findings are the first to associate amygdala-PFC activity and functional connectivity with impulsivity in a large, transdiagnostic sample, providing neural targets for future interventions to reduce predisposition to impulsivity and related future mental health problems in young adults.

Changes in functional connectivity of the amygdala during cognitive reappraisal predict symptom reduction during trauma-focused cognitive-behavioral therapy among adolescent girls with post-traumatic stress disorder

BACKGROUND

While trauma-focused cognitive-behavioral therapy (TF-CBT) is the 'gold standard' treatment for pediatric post-traumatic stress disorder (PTSD), little is known about the neural mechanisms by which TF-CBT produces clinical benefit. Here, we test the hypothesis that PTSD symptom reduction during TF-CBT among adolescent girls with PTSD is associated with changes in patterns of brain functional connectivity (FC) with the amygdala during cognitive reappraisal.

METHOD

Adolescent girls with PTSD related to physical or sexual assault (n = 34) were enrolled in TF-CBT, delivered in an approximately 12-session format, in an open trial. Before and after treatment, they were engaged in a cognitive reappraisal task, probing neural mechanisms of explicit emotion regulation, during 3 T functional magnetic resonance imaging.

RESULTS

Among adolescent girls completing TF-CBT with usable pre- and post-treatment scans (n = 20), improvements in self-reported emotion from pre- to post-treatment were positively related to improvements in PTSD symptoms. Adolescent girls with greater post-treatment symptom reduction were also able to suppress amygdala-insula FC while re-appraising, which was not evident in girls with less symptom reduction. Pre- to post-treatment changes in right amygdala to left insula FC that scaled with PTSD symptom reduction also scaled with improvements in emotion regulation.

CONCLUSIONS

These preliminary results suggest the neurocircuitry mechanisms through which TF-CBT produces clinical outcomes, providing putative brain targets for augmenting TF-CBT response.

Brain and behavioral evidence for altered social learning mechanisms among women with assault-related posttraumatic stress disorder

Current neurocircuitry models of PTSD focus on the neural mechanisms that mediate hypervigilance for threat and fear inhibition/extinction learning. Less focus has been directed towards explaining social deficits and heightened risk of revictimization observed among individuals with PTSD related to physical or sexual assault. The purpose of the present study was to foster more comprehensive theoretical models of PTSD by testing the hypothesis that assault-related PTSD is associated with behavioral impairments in a social trust and reciprocity task and corresponding alterations in the neural encoding of social learning mechanisms. Adult women with assault-related PTSD (n = 25) and control women (n = 15) completed a multi-trial trust game outside of the MRI scanner. A subset of these participants (15 with PTSD and 14 controls) also completed a social and non-social reinforcement learning task during 3T fMRI. Brain regions that encoded the computationally modeled parameters of value expectation, prediction error, and volatility (i.e., uncertainty) were defined and compared between groups. The PTSD group demonstrated slower learning rates during the trust game and social prediction errors had a lesser impact on subsequent investment decisions. PTSD was also associated with greater encoding of negative expected social outcomes in perigenual anterior cingulate cortex and bilateral middle frontal gyri, and greater encoding of social prediction errors in the left temporoparietal junction. These data suggest mechanisms of PTSD-related deficits in social functioning and heightened risk for re-victimization in assault victims; however, comorbidity in the PTSD group and the lack of a trauma-exposed control group temper conclusions about PTSD specifically.

Attenuated behavioral and brain responses to trust violations among assaulted adolescent girls

Physical and sexual assault during adolescence is a potent risk factor for mental health and psychosocial problems, as well as revictimization, especially among female victims. To better understand this conferred risk, we conducted an exploratory study comparing assaulted and non-assaulted girls׳ behavioral and brain responses during a trust learning task. Adolescent girls (14 assaulted, 16 non-assaulted) performed a functional magnetic resonance imaging task that manipulated the percentages of which three different faces delivered positive and negative outcomes. Analyses focused on comparing unexpected to expected outcomes. We found that assaulted adolescent girls demonstrated less behavioral slowing in response to unexpected negative social outcomes, or trust violations (i.e., when a presumably trustworthy face delivered a negative outcome), relative to control girls. Trust violations were also associated with less activation in anterior insular and anterior cingulate regions among the assaulted group compared to the control group. Furthermore, we found that the severity of participants׳ exposure to assaultive events scaled negatively with recruitment of these regions. These preliminary results suggest that assault victims may engage differential learning processes upon unexpected negative social outcomes. These findings have implications for understanding impaired trust learning and social functioning among assault victims.

Functional reorganization of neural networks during repeated exposure to the traumatic memory in posttraumatic stress disorder: an exploratory fMRI study

BACKGROUND

Repeated exposure to the traumatic memory (RETM) is a common component of treatments for posttraumatic stress disorder (PTSD). This treatment is based on a fear extinction model; however, the degree to which this treatment actually engages and modifies neural networks mediating fear extinction is unknown. Therefore, the purpose of the current exploratory study was to define the dynamic changes in neural processing networks while participants completed a novel adaptation of RETM.

METHOD

Participants were adult women (N = 16) with PTSD related to physical or sexual assault. Prior to scanning, participants provided written narratives of a traumatic event related to their PTSD as well as a neutral control event. RETM during fMRI consisted of 5 sequential presentations of the blocked narrative types, lasting three minutes each. Self-reported anxiety was assessed after each presentation.

RESULTS

Relative to changes in functional connectivity during the neutral control script, RETM was associated with strengthened functional connectivity of the right amygdala with the right hippocampus and right anterior insular cortex, left amygdala with the right insular cortex, medial PFC with right anterior insula, left hippocampus with striatum and dorsal cingulate cortex, and right hippocampus with striatum and orbitofrontal cortex. Greater PTSD severity generally led to less changes in functional connectivity with the right insular cortex.

CONCLUSIONS

These results provide evidence that RETM engages and modifies functional connectivity pathways with neural regions implicated in fear extinction. The results also implicate the engagement of the right insular cortex and striatum during RETM and suggest their importance in human fear extinction to trauma memories. However, comorbidity in the sample and the lack of a control group limit inferences regarding RETM with PTSD populations specifically.

Neural processing correlates of assaultive violence exposure and PTSD symptoms during implicit threat processing: a network-level analysis among adolescent girls

Assaultive violence exposure during childhood is a significant risk factor for posttraumatic stress disorder (PTSD). The purpose of the present study was to characterize the relationships of assault and PTSD severity with the organization of large-scale networks identified during emotion processing. Adolescent girls aged 12-16 with (N=15) and without (N=15) histories of assault underwent functional magnetic resonance imaging (fMRI) while engaged in a task that presented images of fearful or neutral facial expressions. Independent component analysis (ICA) identified a frontocingulate network, a frontoparietal network, and a default mode network. Assault exposure was associated with significantly greater activation of the frontocingulate network for fear versus neutral faces. Within the frontocingulate network, Posttraumatic stress disorder (PTSD) severity was associated with weakened functional connectivity between the left amygdala and the perigenual anterior cingulate. Within the frontoparietal network, assaulted girls demonstrated weakened connectivity of the premotor cortex with the right middle frontal gyrus. Within the default mode network, assault exposure and PTSD severity were associated with strengthening functional connectivity of the parahippocampus with the medial and lateral prefrontal cortex, respectively. Individual differences in functional connections within the frontocingulate network and frontoparietal network among the assaulted group were strongly associated with caregiver-rated family disengagement. These results demonstrate associations between assault and PTSD symptoms with the functional organization of large-scale frontoparietal, frontocingulate, and default mode networks during emotion processing. The relationship with caregiver-rated family disengagement suggests the impact of family support on the neural processing correlates of assault and PTSD symptoms.

A comparison of statistical methods for detecting context-modulated functional connectivity in fMRI

Many cognitive and clinical neuroscience research studies seek to determine how contextual factors modulate cognitive processes. In fMRI, hypotheses about how context modulates distributed patterns of information processing are often tested by comparing functional connectivity between neural regions A and B as a function of task conditions X and Y, which is termed context-modulated functional connectivity (FC). There exist two exploratory statistical approaches to testing context-modulated FC: the beta-series method and psychophysiological interaction (PPI) analysis methods. While these approaches are commonly used, their relative power for detecting context-modulated FC is unknown, especially with respect to real-world experimental parameters (e.g., number of stimulus repetitions, inter-trial-interval, stimulus duration). Here, we use simulations to compare power for detecting context-modulated FC between the standard PPI formulation (sPPI), generalized PPI formulation (gPPI), and beta series methods. Simulation results demonstrate that gPPI and beta series methods are generally more powerful than sPPI. Whether gPPI or beta series methods performed more powerfully depended on experiment parameters: block designs favor the gPPI, whereas the beta series method was more powerful for designs with more trial repetitions and it also retained more power under conditions of hemodynamic response function variability. On a real dataset of adolescent girls, the PPI methods appeared to have greater sensitivity in detecting task-modulated FC when using a block design and the beta series method appeared to have greater sensitivity when using an event-related design with many trial repetitions. Implications of these performance results are discussed.

Plasma apolipoprotein (a) is increased in type 2 (non-insulin-dependent) diabetic patients with microalbuminuria

Patients with Type 2 (non-insulin-dependent) diabetes mellitus complicated by microalbuminuria or albuminuria, have an increased risk of developing macrovascular disease and of early mortality. Because lipoprotein abnormalities have been associated with diabetic nephropathy, this study tested the hypothesis that levels of apolipoprotein (a) are elevated in patients with Type 2 diabetes and increased levels of urinary albumin loss. Levels of apolipoprotein (a) in diabetic patients with microalbuminuria (n = 26, geometric mean 195 U/l, 95% confidence interval 117-324) and albuminuria (n = 19, 281 U/l, 165-479) were higher than in non-diabetic control subjects (n = 140, 107 U/l, 85-134, p < 0.05), and in the albuminuric group than diabetic patients without urinary albumin loss (n = 58, 114 U/l, 76-169, p < 0.05). Patients with microalbuminuria and albuminuria had levels comparable with patients undergoing elective coronary artery graft surgery (n = 40, 193 U/l, 126-298). Apolipoprotein (a) levels were higher in diabetic patients with macrovascular disease than in those without (n = 49, 209 U/l, 143-306 vs n = 54, 116 U/l, 78-173, p < 0.05). These preliminary results suggest that raised apolipoprotein (a) levels of Type 2 diabetic patients with microalbuminuria and albuminuria may contribute to their propensity to macrovascular disease and early mortality.

Increased plasma apolipoprotein(a) levels in IDDM patients with microalbuminuria

Patients with insulin-dependent diabetes mellitus (IDDM) have a significantly increased risk of macrovascular disease, particularly if they have persistent proteinuria. To determine whether altered levels of apolipoprotein(a) [apo(a)], the plasminogenlike glycoprotein of the potentially atherogenic lipoprotein(a); contribute to the increased risk of atherosclerosis, apo(a) levels were measured in 107 patients with IDDM and compared with nondiabetic control subjects and male elective coronary artery graft patients. Apo(a) levels were increased in diabetic patients with microalbuminuria (geometric mean 245 U/L, 95% confidence interval [CI] 142-427, n = 30) and albuminuria (mean 196 U/L, 95% CI 97-397, n = 18) with levels comparable to patients with coronary artery disease (mean 193 U/L, 95% CI 126-298, n = 40), which were higher than in the control group (mean 107 U/L, 95% CI 85-134, n = 140; P = 0.016). Apo(a) levels in diabetic patients without microalbuminuria (mean 86 U/L, 95% CI 63-116, n = 59) were comparable with the control population and less than in those with microalbuminuria (P less than 0.001) and albuminuria (P = 0.014). The elevated apo(a) levels found in patients with IDDM and increased urinary albumin loss may contribute to their heightened risk of macrovascular disease.