The European journal of neuroscience
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Saccades are often directed toward a stimulus that provides useful information for observers to navigate the visual world. The quality of visual signals of a stimulus is influenced by global luminance, and the pupil constricts or dilates after a luminance increase or decrease, respectively, to optimize visual signals for further information processing. Although luminance level changes regularly in the real environment, saccades are mostly studied in the luminance-unchanged setup. ⋯ Moreover, the luminance condition modulated saccade kinematics, showing reduced performances in the light condition than in the control condition, particularly in pro-saccades. Modeling results further suggested that both pupil diameter and pupil size derivative significantly modulated saccade behavior, though effect sizes were small and mainly mediated by intersubject differences. Together, our results demonstrated the influence of pupillary luminance responses on the generation of pro- and anti-saccades.
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Recent research has shown that premature ejaculation (PE) is associated with negative psychological effects (e.g., depression) and the decline of control over ejaculation is accompanied by structural and functional abnormalities in specific brain areas and connections. However, little is known about the alterations of topological organization in the brain network of patients with PE and its relationship with depressive symptom. We acquired diffusion tensor images, sexual function and depression assessment in 16 lifelong PE patients with depressive symptom, 16 lifelong PE patients without depression and 32 age- and education-matched healthy controls (HC). ⋯ Different hubs were found among PE patients with and without depression and HC based on nodal degree, betweenness and participation; however, no significant group differences were found in the frequency distribution of high-degree hubs, high-betweenness hubs, provincial hubs and connector hubs. These findings demonstrated that PE was a brain disorder with altered structural connectivity pattern of brain network and depressive symptom, which suggested that altered structural connectivities of the fronto-cingulate-parietal control network were core neurobiological features associated with PE and depression. Together, these alterations could prove helpful for understanding the pathophysiological mechanisms of PE in depression.
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Previous work has shown that humans account for and learn novel properties or the arm's dynamics, and that such learning causes changes in both the predictive (i.e., feedforward) control of reaching and reflex (i.e., feedback) responses to mechanical perturbations. Here we show that similar observations hold in old-world monkeys (Macaca fascicularis). Two monkeys were trained to use an exoskeleton to perform a single-joint elbow reaching and to respond to mechanical perturbations that created pure elbow motion. ⋯ In addition, after releasing the shoulder joint again, we found evidence of kinematic aftereffects (i.e., reach errors) in the direction predicted if failing to compensate for normal arm dynamics. We also tested whether such learning transfers to feedback responses evoked by mechanical perturbations and found a reduction in shoulder feedback responses, as appropriate for these altered arm intersegmental dynamics. Demonstrating this learning and transfer in non-human primates will allow the investigation of the neural mechanisms involved in feedforward and feedback control of the arm's dynamics.