A growing body of evidence suggests that engagement in episodic future thinking (EFT) could reduce delay discounting rates. However, little is known about whether individual differences in the ability of EFT are associated with differences in delay discounting in young adults. In the present study, this association was tested in healthy college students ( n = 106, 19.98 ± 1.56 years), and the neural basis underlying this association was also examined using voxel-based morphometry (VBM) method. Behavioral analysis indicated that individual differences in EFT ability can significantly negatively predict discounting rates. VBM analysis first revealed that the EFT score positively correlated with gray matter volume (GMV) of a cluster in hippocampus, while negatively correlated with GMV of a cluster in rostral anterior cingulate cortex. We also found the GMV of a cluster in the mPFC was positively correlated with delay discounting. ROI analysis further revealed that individual differences in delay discounting could be reliably predicted by the GMV in the hippocampus and mPFC. The final mediation analysis showed that the GMV of the hippocampus plays a significant mediating role in the association between EFT and delay discounting, and the indirect effect of the hippocampal GMV accounts for 33.2% of the total effect. Our results suggest that individuals’ EFT ability may be an important determinant of differences in delay discounting, and highlight the hippocampal structure as a neural biomarker for explaining the association between EFT ability and delay discounting.
Abstract Delay discounting (DD) refers to a phenomenon that humans tend to choose small-sooner over large-later rewards during intertemporal choices. Steep discounting of delayed outcome is related to a variety of maladaptive behaviors and is considered as a transdiagnostic process across psychiatric disorders. Previous studies have investigated the association between brain structure (e.g. gray matter volume) and DD; however, it is unclear whether the intracortical myelin (ICM) influences DD. Here, based on a sample of 951 healthy young adults drawn from the Human Connectome Project, we examined the relationship between ICM, which was measured by the contrast of T1w and T2w images, and DD and further tested whether the identified associations were mediated by the regional homogeneity (ReHo) of brain spontaneous activity. Vertex-wise regression analyses revealed that steeper DD was significantly associated with lower ICM in the left temporoparietal junction (TPJ) and right middle-posterior cingulate cortex. Region-of-interest analysis revealed that the ReHo values in the left TPJ partially mediated the association of its myelin content with DD. Our findings provide the first evidence that cortical myelination is linked with individual differences in decision impulsivity and suggest that the myelin content affects cognitive performances partially through altered local brain synchrony.
Abstract Background The lateral hypothalamus (LHA) is an evolutionarily conserved structure that regulates basic functions of an organism, particularly wakefulness. To clarify the function of LHA GABA neurons and their projections on regulating general anesthesia is crucial for understanding the excitatory and inhibitory effects of anesthetics on the brain. The aim of the present study is to investigate whether LHA GABA neurons play either an inhibitory or a facilitatory role in sevoflurane‐induced anesthetic arousal regulation. Methods We used fiber photometry and immunofluorescence staining to monitor changes in neuronal activity during sevoflurane anesthesia. Opto‐/chemogenetic modulations were employed to study the effect of neurocircuit modulations during the anesthesia. Anterograde tracing was used to identify a GABAergic projection from the LHA to a periaqueductal gray (PAG) subregion. Results c‐Fos staining showed that LHA GABA activity was inhibited by induction of sevoflurane anesthesia. Anterograde tracing revealed that LHA GABA neurons project to multiple arousal‐associated brain areas, with the lateral periaqueductal gray (LPAG) being one of the dense projection areas. Optogenetic experiments showed that activation of LHA GABA neurons and their downstream target LPAG reduced the burst suppression ratio (BSR) during continuous sevoflurane anesthesia. Chemogenetic experiments showed that activation of LHA GABA and its projection to LPAG neurons prolonged the anesthetic induction time and promoted wakefulness. Conclusions In summary, we show that an inhibitory projection from LHA GABA to LPAG GABA neurons promotes arousal from sevoflurane‐induced loss of consciousness, suggesting a complex control of wakefulness through intimate interactions between long‐range connections.
Abstract Background Subjective cognitive decline (SCD) and amnestic mild cognitive impairment (aMCI) are considered as the spectrum of preclinical Alzheimer's disease (AD), with abnormal brain network connectivity as the main neuroimaging features. Repetitive transcranial magnetic stimulation (rTMS) has been proven to be an effective non-invasive technique for neuropsychiatric disorders. This article aims to explore whether precuneus (PCUN)-targeted rTMS can regulate the effective connectivity of the default mode network (DMN) and the executive control network (CEN), thereby improving cognitive function. Methods This study included 86 healthy controls (HCs), 72 SCDs, and 86 aMCIs. Among them, 10 SCDs and 11 aMCIs received a 2-week rTMS course of 5-day, once-daily. Cross-sectional analysis with the spectral dynamic causal model (spDCM) was used to analyze the DMN and CEN effective connectivity patterns of the three groups. Afterwards, longitudinal analysis was conducted on the changes in effective connectivity patterns and cognitive function before and after rTMS for SCD and aMCI, and the correlation between them was analyzed. Results Cross-sectional analysis showed that there were different effective connectivity patterns in the DMN and CEN in the three groups. Longitudinal analysis showed that the effective connectivity pattern of the SCD changed, accompanied by episodic memory improved. Correlation analysis showed that effective connectivity from the left angular gyrus (ANG) to the anterior cingulate gyrus (ACG) and the ANG.R to the right middle frontal gyrus (MFG) was negatively correlated with visuospatial and executive function, respectively. In the aMCI, episodic memory and executive function improved, while the effective connectivity pattern remained unchanged. Conclusions This study demonstrates that PCUN-targeted rTMS of SCD regulating the abnormal effective connectivity patterns of DMN and CEN improves cognition function, while in aMCI possibly through other mechanisms. Our findings further suggest that rTMS are more effective at preventing or delaying disease progression earlier in the AD spectrum. Trial registration CCTR, ChiCTR2000034533. Registered 9 July 2020 - Retrospectively registered, http://www.chictr.org.cn
Medicine is one of the subjects with the features of strong applicability and practice.The clinical operational skill plays an important part in the knowledge structure of the medical talents,and the clinical teaching practice is the critical stage for the realization of the training objective of the medical students.But the present grave employment situation makes the medical college graduates have to be faced with such pressures as preparing for master entrance examination and finding jobs during their clinical practice.To solve such problems,not only should colleges and teaching hospitals enhance the guidance and the management,but also the graduates should improve their awareness and change their idear.
Key words:
Medical science; Clinical practice; Prepare for master entrance examination; Find jobs
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