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Electroconvulsive therapy (ECT) is the most effective and fast acting therapy for treatment-resistant depression (TRD). Animal research has consistently pointed to neuroplasticity as a central mechanism of ECT action (1), however evidence in humans remains scarce (2; 3).
We assessed two independent samples of TRD patients referred for ECT. The Barcelona-sample included 13 subjects treated with bitemporal ECT and 10 healthy volunteers (HV). Four successive 3T structural MRIs were acquired: baseline, 24-48 hours after the 1st ECT session, 24-48 hours after the 9th ECT, and two weeks after ECT course completion. HV were scanned twice five weeks apart. Within the framework of the Barcelona-Sydney Clinical Imaging Collaboration, we also scanned 10 patients treated mainly with right unilateral ECT (Sydney-sample). Whole-brain longitudinal grey matter (GM) changes were measured using intra-subject diffeomorphic registration, within SPM12b.
In the Barcelona-sample, over the course of treatment bitemporal ECT produced a linear increase of GM volume in the limbic system (involving bilateral hippocampi and amygdalae). Additionally, volumetric increase within the right subgenual cortex was detected from baseline to the 9th ECT session. Such volume changes were not observed in HV. Furthermore, GM volume expansion correlated positively with depressive symptom improvement and neurocognitive performance (memory and executive function). Hippocampal and amygdalar volume increases were replicated in the Sydney-sample, although limited to the stimulated hemisphere.
ECT effects described here could be accounted for by the induction of regionally specific structural plasticity. Nevertheless, other mechanisms such as neurovascular changes should not be discarded.
Pathological worry is a hallmark feature of generalised anxiety disorder (GAD), associated with dysfunctional emotional processing. The ventromedial prefrontal cortex (vmPFC) is involved in the regulation of such processes, but the link between vmPFC emotional responses and pathological v. adaptive worry has not yet been examined.
To study the association between worry and vmPFC activity evoked by the processing of learned safety and threat signals.
In total, 27 unmedicated patients with GAD and 56 healthy controls (HC) underwent a differential fear conditioning paradigm during functional magnetic resonance imaging.
Compared to HC, the GAD group demonstrated reduced vmPFC activation to safety signals and no safety–threat processing differentiation. This response was positively correlated with worry severity in GAD, whereas the same variables showed a negative and weak correlation in HC.
Poor vmPFC safety–threat differentiation might characterise GAD, and its distinctive association with GAD worries suggests a neural-based qualitative difference between healthy and pathological worries.
The assessment of inter-regional functional connectivity (FC) has allowed for the description of the putative mechanism of action of treatments such as deep brain stimulation (DBS) of the nucleus accumbens in patients with obsessive–compulsive disorder (OCD). Nevertheless, the possible FC alterations of other clinically-effective DBS targets have not been explored. Here we evaluated the FC patterns of the subthalamic nucleus (STN) and the bed nucleus of the stria terminalis (BNST) in patients with OCD, as well as their association with symptom severity.
Eighty-six patients with OCD and 104 healthy participants were recruited. A resting-state image was acquired for each participant and a seed-based analysis focused on our two regions of interest was performed using statistical parametric mapping software (SPM8). Between-group differences in FC patterns were assessed with two-sample t test models, while the association between symptom severity and FC patterns was assessed with multiple regression analyses.
In comparison with controls, patients with OCD showed: (1) increased FC between the left STN and the right pre-motor cortex, (2) decreased FC between the right STN and the lenticular nuclei, and (3) increased FC between the left BNST and the right frontopolar cortex. Multiple regression analyses revealed a negative association between clinical severity and FC between the right STN and lenticular nucleus.
This study provides a neurobiological framework to understand the mechanism of action of DBS on the STN and the BNST, which seems to involve brain circuits related with motor response inhibition and anxiety control, respectively.
The size of particular sub-regions within the ventromedial prefrontal cortex (vmPFC) has been associated with fear extinction in humans. Exposure therapy is a form of extinction learning widely used in the treatment of obsessive-compulsive disorder (OCD). Here we investigated the relationship between morphometric measurements of different sub-regions of the vmPFC and exposure therapy outcome in OCD.
A total of 74 OCD patients and 86 healthy controls underwent magnetic resonance imaging (MRI). Cortical thickness and volumetric measurements were obtained for the rostral anterior cingulate cortex (rACC), the medial orbital frontal cortex and the subcallosal cortex. After MRI acquisition, patients were enrolled in an exposure therapy protocol, and we assessed the relationship between MRI-derived measurements and treatment outcome. Baseline between-group differences for such measurements were also assessed.
Compared with healthy controls, OCD patients showed a thinner left rACC (p = 0.008). Also, left rACC thickness was inversely associated with exposure therapy outcome (r – 0.32, p = 0.008), and this region was significantly thinner in OCD patients who responded to exposure therapy than in those who did not (p = 0.006). Analyses based on regional volumetry did not yield any significant results.
OCD patients showed cortical thickness reductions in the left rACC, and these alterations were related to exposure therapy outcome. The precise characterization of neuroimaging predictors of treatment response derived from the study of the brain areas involved in fear extinction may optimize exposure therapy planning in OCD and other anxiety disorders.
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