Neuroscience
-
Insulin-like growth factors (IGF) are potent neurotrophic and neurorepair factors that were recently proposed as biomarkers of traumatic brain injury (TBI) and associated psychiatric comorbidities, in particular post-traumatic stress disorder (PSTD). We tested the hypothesis that the IGF system is differentially deregulated in the acute and early chronic stages of TBI, and under acute stress. Plasma and brain IGF1 and IGF2 levels were evaluated in mice 3 weeks and 3 days after a controlled cortical impact (CCI)-induced mild-to-moderate TBI. ⋯ It also dampened the effects of TBI on brain IGF systems, but brain IGF1 level and IGF2 tissue distribution remained statistically different from controls under these conditions. In co-exposed animals, DNA methylation increased at the hippocampal Igf1 gene promoter. These results show that blood IGF1 and IGF2 are most reduced in the early chronic phase of TBI and after exposure to a stressful event, and that the brain IGF system is up-regulated after TBI, and more so in the acute phase.
-
Neighborhood disadvantage and community violence are common in poor, urban communities and are risk factors for emotional dysfunction. Emotional processes are supported by neural circuitry that includes the prefrontal cortex (PFC), hippocampus, amygdala, and hypothalamus. These brain regions are connected by white matter pathways that include the cingulum bundle, uncinate fasciculus, stria terminalis, and fornix. ⋯ The QA of the cingulum bundle, uncinate fasciculus, and stria terminalis/fornix varied negatively with neighborhood disadvantage such that the QA of these white matter tracts decreased as neighborhood disadvantage increased. Violence exposure was not related to QA in any tract (i.e., cingulum bundle, uncinate fasciculus, and stria terminalis/fornix) after correction for multiple comparisons. These results suggest that an adolescent's neighborhood may play an important role in the microstructure (i.e., QA) of white matter pathways that connect brain regions that support emotional function.
-
The precuneus, involved in various cognitive processes, is considered to form the midline core of the default mode network (DMN), while the medial temporal lobe (MTL) is a subsystem of the DMN. Until now, the anatomical study of the precuneus-MTL connection is limited in humans. One possible reason is the precuneus' territory of the posteromedial cortex (PMC) is inconsistent across studies. ⋯ Although the SC-rsFC correlation was scarce on the whole, the posterior precuneus (POS2, 7Pm, 7m) showed a relatively high correlation (r = 0.38349, p < 0.05) with the posterior MTL (PreS, H, ProS, PHA1, PHA2). Our findings suggest the posterior precuneus is highly connected to MTL structurally, which could have an effect on the resting-state functional connectivity. In addition, the precuneus might consist of the heterogeneous connectivity-based subdivisions.
-
Proprioception in old age is thought to be poorer due to degeneration of the central (CNS) and peripheral nervous systems (PNS). We tested whether community-dwelling older adults (65-83 years) make larger proprioceptive errors than young adults (18-22 years) using a natural reaching task. Subjects moved the right arm to touch the index fingertip to the stationary or moving left index fingertip. ⋯ Variable errors were small and similar in the two groups (p > 0.35). Importantly, clearly larger errors were observed for reaching to the stationary than to the moving index fingertip in both groups, demonstrating that dynamic proprioceptive information during movement permits more accurate localization of the endpoint of the moving arm. This novel finding demonstrates the importance of dynamic proprioceptive information in movement guidance and bimanual coordination.
-
Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that may improve motor learning. However, the long-term effects of tDCS have not been explored, and the ecological validity of the evaluated tasks was limited. To determine whether 20 sessions of tDCS over the primary motor cortex (M1) would enhance the performance of a complex life motor skill, i.e., typing, in healthy young adults. ⋯ Between the 10th and 20th tDCS sessions, the number of typing errors increased significantly in all groups. While anodal tDCS reduced typing errors marginally, such performance-enhancing effects plateaued after 10 sessions without any further improvements in typing speed. These findings suggest that long-term tDCS may not have functionally relevant effects on healthy young adults' typing performance.