Neural correlates of symptom severity in obsessive-compulsive disorder using magnetization transfer and diffusion tensor imaging

Inflammation in obsessive-compulsive disorder: A literature review and hypothesis-based potential of transcranial photobiomodulation

Obsessive-compulsive disorder (OCD) is a disabling neuropsychiatric disorder that affects about 2%-3% of the global population. Despite the availability of several treatments, many patients with OCD do not respond adequately, highlighting the need for new therapeutic approaches. Recent studies have associated various inflammatory processes with the pathogenesis of OCD, including alterations in peripheral immune cells, alterations in cytokine levels, and neuroinflammation. These findings suggest that inflammation could be a promising target for intervention. Transcranial photobiomodulation (t-PBM) with near-infrared light is a noninvasive neuromodulation technique that has shown potential for several neuropsychiatric disorders. However, its efficacy in OCD remains to be fully explored. This study aimed to review the literature on inflammation in OCD, detailing associations with T-cell populations, monocytes, NLRP3 inflammasome components, microglial activation, and elevated proinflammatory cytokines such as TNF-α, CRP, IL-1β, and IL-6. We also examined the hypothesis-based potential of t-PBM in targeting these inflammatory pathways of OCD, focusing on mechanisms such as modulation of oxidative stress, regulation of immune cell function, reduction of proinflammatory cytokine levels, deactivation of neurotoxic microglia, and upregulation of BDNF gene expression. Our review suggests that t-PBM could be a promising, noninvasive intervention for OCD, with the potential to modulate underlying inflammatory processes. Future research should focus on randomized clinical trials to assess t-PBM's efficacy and optimal treatment parameters in OCD. Biomarker analyses and neuroimaging studies will be important in understanding the relationship between inflammatory modulation and OCD symptom improvement following t-PBM sessions.

Individuals with problem gambling and obsessive-compulsive disorder learn through distinct reinforcement mechanisms

Obsessive-compulsive disorder (OCD) and pathological gambling (PG) are accompanied by deficits in behavioural flexibility. In reinforcement learning, this inflexibility can reflect asymmetric learning from outcomes above and below expectations. In alternative frameworks, it reflects perseveration independent of learning. Here, we examine evidence for asymmetric reward-learning in OCD and PG by leveraging model-based functional magnetic resonance imaging (fMRI). Compared with healthy controls (HC), OCD patients exhibited a lower learning rate for worse-than-expected outcomes, which was associated with the attenuated encoding of negative reward prediction errors in the dorsomedial prefrontal cortex and the dorsal striatum. PG patients showed higher and lower learning rates for better- and worse-than-expected outcomes, respectively, accompanied by higher encoding of positive reward prediction errors in the anterior insula than HC. Perseveration did not differ considerably between the patient groups and HC. These findings elucidate the neural computations of reward-learning that are altered in OCD and PG, providing a potential account of behavioural inflexibility in those mental disorders.

Application of advanced magnetic resonance imaging in glaucoma: a narrative review

Glaucoma is a group of eye diseases characterized by progressive degeneration of the optic nerve head and retinal ganglion cells and corresponding visual field defects. In recent years, mounting evidence has shown that glaucoma-related damage may not be limited to the degeneration of retinal ganglion cells or the optic nerve head. The entire structure of the visual pathway may be degraded, and the degradation may even extend to some non-visual brain regions. We know that advanced morphological, functional, and metabolic magnetic resonance technologies provide a means to observe quantitatively and in real time the state of brain function. Advanced magnetic resonance imaging (MRI) techniques provide additional diagnostic markers for glaucoma, which are related to known potential histopathological changes. Many researchers in China and globally have conducted clinical and imaging studies on glaucoma. However, they are scattered, and we still need to systematically sort out the advanced MRI related to glaucoma. We reviewed literature published in any language and included all studies that were able to be translated into English from 1 January 1980 to 31 July 2021. Our literature search focused on emerging magnetic resonance neuroimaging techniques for the study of glaucoma. We then identified each functional area of the brain of glaucoma patients through the integration of anatomy, image, and function. The aim was to provide more information about the occurrence and development of glaucoma diseases. From the perspective of neuroimaging, our study provides a research basis to explain the possible mechanism of the occurrence and development of glaucoma. This knowledge gained from these techniques enables us to more clearly observe the damage glaucoma causes to the whole visual pathway. Our study provides new insights into glaucoma-induced changes to the brain. Our findings may enable the progress of these changes to be analyzed and inspire new neuroprotective therapeutic strategies for patients with glaucoma in the future.

Association between gray/white matter contrast and white matter microstructural alterations in medication-naïve obsessive–compulsive disorder

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Increased gray/white matter contrast (GWC) was found in patients with OCD.

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Decreased fractional anisotropy (FA) was found in patients with OCD.

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GWC and white matter FA were coupled in patients with OCD and healthy controls.

Intracortical myelin is involved in speeding and synchronizing neural activity of the cerebral cortex and has been found to be disrupted in various psychiatric disorders. However, its role in obsessive–compulsive disorder (OCD) has remained unknown. In this study, we investigated the alterations in intracortical myelin and their association with white matter (WM) microstructural abnormalities in OCD. T1-weighted and diffusion-weighted brain images were obtained for 51 medication-naïve patients with OCD and 26 healthy controls (HCs). The grey/white matter contrast (GWC) was calculated from T1-weighted signal intensities to characterize the intracortical myelin profile in OCD. Diffusion parameters, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD), were extracted from diffusion-weighted images to examine the WM microstructure in OCD. Compared with HCs, patients with OCD showed increased GWC in the bilateral orbitofrontal, cuneus, lingual and fusiform gyrus, left anterior cingulate, left superior parietal, right inferior parietal, and right middle frontal cortices, suggesting reduced intracortical myelin. Patients with OCD also showed decreased FA in several WM regions, with a topology corresponding to the GWC alterations. In both groups, the mean GWC of the significant clusters in between-group GWC analysis was correlated negatively with the mean FA of the significant clusters in between-group FA analysis. In patients with OCD, the FA of a cluster in the right cerebellum correlated negatively with the Yale-Brown obsessive–compulsive scale scores. Our results suggest that abnormal intracortical and WM myelination could be the microstructural basis for the brain connectivity alterations and disrupted inhibitory control in OCD.