Neuroscience
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Traumatic brain injury (TBI) is a major risk factor for dementia. Recently, TBI has also been suggested as a risk factor for frontotemporal dementia (FTD), and plasma immunoreactivity to the TAR-DNA binding protein 43 (TDP-43) has been observed in both patients with acute TBI and long-term survivors of this condition. We used a population-based study to estimate and compare the risk of FTD in individuals with and without TBI. ⋯ Further, the behavioral impairments were likely associated with TDP-43 short fragment mislocalization and accumulation. Our findings suggest that in humans, TBI is associated with a greater occurrence of FTD. Moreover, clinical FTD manifestations may be associated with TDP-43 proteolysis, since impaired behaviors in TBI rats were reminiscent of those in humans with FTD.
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Convergent evidence suggests that the lateral frontal cortex is at the heart of a brain network subserving cognitive control. Recent theories assume a functional segregation along the rostro-caudal axis of the lateral frontal cortex based on differences in the degree of complexity of cognitive control. However, the functional contribution of specific rostral and caudal sub-regions remains elusive. ⋯ Participants performed three different task-switching conditions that assessed differences in the degree of complexity of cognitive control processes, after temporally disrupting rostral, or caudal target regions, or a control region. Disrupting the rostral lateral frontal region specifically impaired behavioral performance of the most complex task-switching condition, in comparison to the caudal target region and the control region. These novel findings shed light on the neuroanatomical architecture supporting control over goal-directed behavior.
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Assessment of awareness in patients with disorders of consciousness such as patients in a vegetative state (unresponsive wakefulness syndrome, UWS) and patients in a minimally conscious state (MCS) remains difficult, with a high rate of misdiagnosis (around 40%). While patients with UWS have no awareness, patients with MCS have partial preservation of conscious awareness. To improve the assessment of awareness in these patients, recent functional neuroimaging protocols have been developed. ⋯ The correlation-based method obtained the best results with an error rate of 4.2%. The results of this study demonstrate that fMRI-based communication paradigms may not be robust enough to reliably detect awareness in all aware patients. There is still a need to develop new statistical and analytical methods before considering their generalization in clinical routine.
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Survivin, a unique member of the inhibitor of the apoptosis protein (IAP) family, has been suggested to play a crucial role in promoting the cell cycle and mediates mitosis during embryonic development. However, the role of survivin following traumatic brain injury (TBI) in adult neurogenesis and apoptosis in the mouse dentate gyrus (DG) remains only partially understood. We adopted adenovirus-mediated RNA interference (RNAi) as a means of suppressing the expression of survivin and observed its effects on adult regeneration and neurological function in mice after brain injury. ⋯ Furthermore, downregulation of survivin results in a significant increase in programmed cell death in the DG, as assessed using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and 4',6-diamidino-2-phenylindole (DAPI) double staining. The Morris water maze (MWM) test was adopted to evaluate neurological function, which confirmed that knockdown of survivin worsened the memory capacity that was already compromised following TBI. Survivin in adult mice brains after TBI can be successfully down-regulated by RNAi, which inhibited adult hippocampal neurogenesis, promoted apoptotic cell death, and resulted in a negative role in the recovery of dysfunction following injury.
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Updating the position of an earth-fixed target during whole-body rotation seems to rely on cognitive processes such as the utilization of external feedback. According to perceptual learning models, improvement in performance can also occur without external feedback. The aim of this study was to assess spatial updating improvement in the absence and in the presence of external feedback. ⋯ However, no group difference was observed for the untrained direction (p=0.22). We demonstrated that spatial updating improved without external feedback but less than when external feedback was given. These observations are explained by a mixture of calibration processes and supervised vestibular learning.