The dorsal Anterior Cingulate Cortex (dACC) and the Supplementary Motor Area (SMA) are known to interact during motor coordination behavior. We previously discovered that the directional influences underlying this interaction in a visuo-motor coordination task are asymmetric, with the dACC→SMA influence being significantly greater than that in the reverse direction. To assess the specificity of this effect, here we undertook an analysis of the interaction between dACC and SMA in two distinct contexts. In addition to the motor coordination task, we also assessed these effects during a (n-back) working memory task. We applied directed functional connectivity analysis to these two task paradigms, and also to the rest condition of each paradigm, in which rest blocks were interspersed with task blocks. We report here that the previously known asymmetric interaction between dACC and SMA, with dACC→SMA dominating, was significantly larger in the motor coordination task than the memory task. Moreover the asymmetry between dACC and SMA was reversed during the rest condition of the motor coordination task, but not of the working memory task. In sum, the dACC→SMA influence was significantly greater in the motor task than the memory task condition, and the SMA→dACC influence was significantly greater in the motor rest than the memory rest condition. We interpret these results as suggesting that the potentiation of motor sub-networks during the motor rest condition supports the motor control of SMA by dACC during the active motor task condition.
In an effort to elucidate differences in functioning brain networks between youth with obsessive-compulsive disorder and controls, we used fMRI signals to analyze brain network interactions of the dorsal anterior cingulate cortex (dACC) during visually coordinated motor responses. Subjects made a uni-manual response to briefly presented probes, at periodic (allowing participants to maintain a “motor set”) or random intervals (demanding reactive responses). Network interactions were assessed using psycho-physiological interaction (PPI), a basic model of functional connectivity evaluating modulatory effects of the dACC in the context of each task condition. Across conditions, OCD were characterized by hyper-modulation by the dACC, with loci alternatively observed as both condition-general and condition-specific. Thus, dynamically driven task demands during simple uni-manual motor control induce compensatory network interactions in cortical-thalamic regions in OCD. These findings support previous research in OCD showing compensatory network interactions during complex memory tasks, but establish that these network effects are observed during basic sensorimotor processing. Thus, these patterns of network dysfunction may in fact be independent of the complexity of tasks used to induce brain network activity. Hypothesis-driven approaches coupled with sophisticated network analyses are a highly valuable approach in using fMRI to uncover mechanisms in disorders like OCD.
Fronto-limbic brain networks involved in regulation of impulsivity and aggression are abnormal in Borderline Personality Disorder (BPD). However, it is unclear whether, or to what extent, these personality traits actually modulate brain responses during cognitive processing. Using fMRI, we examined the effects of trait impulsivity, aggression, and depressed mood on regional brain responses in 31 female BPD and 25 control subjects during a Go No-Go task using Ekman faces as targets. First-level contrasts modeled effects of negative emotional context. Second-level regression models used trait impulsivity, aggression and depressed mood as predictor variables of regional brain activations. In BPD, trait impulsivity was positively correlated with activation in the dorsal anterior cingulate cortex, orbital frontal cortex (OFC), basal ganglia (BG), and dorsolateral prefrontal cortex, with no areas of negative correlation. In contrast, aggression was negatively correlated with activation in OFC, hippocampus, and BG, with no areas of positive correlation. Depressed mood had a generally dampening effect on activations. Effects of trait impulsivity on healthy controls differed from effects in BPD, suggesting a disorder-specific response. Negative emotional context and trait impulsivity, but not aggression or depression, diminished task performance across both groups. Negative emotional context may interfere with cognitive functioning in BPD through interaction with the neurobiology of personality traits.
Background.-Negative affective interference with executive cognition is associated with emotion dysregulation and behavioral dyscontrol in BPD, including a diathesis to suicidal and self-injurious behavior. While clinically well described, the neural basis of affective interference with central executive network function, and resulting suicidal behavior is poorly understood. Method.-In an fMRI study, 23 BPD suicide attempters completed an affectively modified Continuous Performance Task(X-CPT), in which targets and distractors were rendered on Negative, Positive and Neutral Ekman faces, with a Distorted image as a behavioral baseline. Responses to targets were contextualized by the affective context of the face. Lethality Rating Scale scores(LRS) were modeled as the primary regressor of interest on activation peaks, with HamD scores covaried. Results.-In the Negative vs. Neutral contrast, LRS scores were inversely related to activation in the ACC, parietal precuneus, BG and OFC, with no positive relationships. Results were similar in the Negative vs Positive contrast. In the Neutral vs. Positive contrast, activations were much less extensive, with mixed positive and negative relationships. Contextualizing responses based on the effects of valence decreased participant's ability to distinguish between targets and distracters; however, no differences were observed between valence contexts. fMRI-estimated effects were not confounded by differences in behavioral sensitivity across contexts. Limitations.-In this female-only sample, possible gender differences were not addressed.
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