Ego- and allo-network disconnection underlying spatial disorientation in subjective cognitive decline.

Patients with Alzheimer's disease (AD) related dementia and mild cognitive impairment experience difficulties with spatial navigation (SN). However, SN has rarely been investigated in individuals with subjective cognitive decline (SCD), a preclinical stage with elevated progression rate to symptomatic AD. In this study, 30 SCD subjects and 30 controls underwent cognitive scale (CS) evaluation, a 2D computerized SN test, and resting-state functional magnetic resonance imaging scanning. Two SN brain networks (ego-network and allo-network), each with 10 selected spherical regions, were defined. We calculated the average network functional connectivity (FC) and region-to-region FC within the two networks and evaluated correlations with SN performance. Compared with the controls, the SCD group performed worse in the SN test and showed decreased FC between the right retrosplenial and right prefrontal cortices in the ego-network, and between the right retrosplenial cortex and right hippocampus in the allo-network. The logistic regression model based on SN and FC measures revealed a high area under the curve of .880 in differentiating SCD individuals from controls. These results suggest that SN network disconnection contributes to spatial deficits in SCD, and SN and FC measures could benefit the preclinical detection of subjects with incipient AD dementia.

Brain Cortical Complexity and Subcortical Morphometrics in Lifelong Premature Ejaculation.

Premature ejaculation (PE) is the most common male sexual dysfunction. The brain disturbances that cause this disorder remain poorly understood. This study aimed to investigate how the morphology of cortical and subcortical brain structures differed in PE, how these morphologic differences were associated with severity measures of PE, such as intravaginal ejaculatory latency time (IELT), and how these cortical and subcortical structures were causally connected through mediation analysis. Anatomical MRI scans were acquired from 39 male participants, 23 with PE (28.78 ± 4.32 years), and 16 without PE (27.88 ± 3.65 years). We used a subcortical analysis package within FSL to perform subcortical shape segmentation and statistical analysis. The PE group was compared with the normal control (NC) group in the shapes of 15 subcortical structures with general linear models [p < 0.05, family-wise error (FWE)-corrected]. We analyzed the cortical complexity revealed by the gyrification index using the Computational Anatomy Toolbox (CAT12). Vertex-wise shape analyses revealed outward shape deformations (expansions) in the left hippocampus and bilateral thalamus. Gyrification index analyses revealed that the right orbital frontal cortex and the right nucleus accumbens had greater complexity in PE patients. The shape deformations were positively correlated with the IELTs in the NC group, while this relationship was interrupted in the PE group. PE is associated with outward deformations of the subcortical surfaces and more complexity of the cortical structures. These morphological differences may be the basis of the brain functional alterations underlying PE.