尤物视频

Abstract: Central cord syndrome, a type of spinal cord injury (SCI) resulting from cervical spine hyperextension, is becoming increasingly prevalent among older adults. This is concerning because these incidents stem from low-energy impacts, such as ground-level falls, which are generally inconsequential in younger individuals yet disrupt upper motor function in the elderly due to spinal degeneration. Degenerative changes in the spine, which leads to a narrowing of the spinal canal (known as stenosis), plays a critical role in altering the injury mechanism and increasing vulnerability. However, the variability in degenerative patterns, tissue damage, and functional outcomes indicates that some individuals may be more predisposed to SCI from falls. Retrospective clinical studies have identified pre-injury cord compression exceeding 40% to be a risk factor for SCIs. Biomechanical investigations have demonstrated that an ossified ligamentum flavum and disc-osteophyte complexes exacerbate spinal cord stresses during neck hyperextension. Our retrospective MRI studies show that these SCIs can even occur in individuals with cord compression as low as 15%, aging does not uniformly result in ligament ossification, and there is significant variability in the nature of degeneration. Therefore, there is a need to comprehensively identify the patient profile most at risk of this SCI. This study adopts a biomechanical approach by integrating retrospective MRI data with computational models to comprehensively evaluate patient-specific risk factors for SCI in older adults under hyperextension loading conditions.

Abstract: The brain exhibits spontaneous dynamics at both local and global levels. Understanding how external perturbations influence these dynamics is essential for understanding brain function, including the coordination of local information flow and large-scale synchronization. Although focal stimulation, like single-pulse transcranial magnetic stimulation (TMS), significantly affects local brain oscillations and phase dynamics, its effects on global network dynamics remain less understood. This study uses electroencephalography (EEG) microstate analysis to explore TMS effects on global brain dynamics.

Single-pulse TMS was applied to the left dorsolateral prefrontal cortex (DLPFC) and left primary motor cortex (M1) while recording EEG from 34 healthy participants. Five canonical microstates (A, B, C, D, E) and their dynamics were extracted. T-tests with cluster-based permutations were used to assess changes in microstate occurrences and transitions post-TMS. Paired t-tests with cluster-based permutations assessed how changes in microstate features following TMS differed between the DLPFC and M1. These analyses were replicated in 22 participants who underwent repeated testing.

TMS to both sites significantly induced changes in microstate occurrences and transitions. DLPFC stimulation increased occurrences of microstates C, D, and E, while decreasing A and B, with bidirectional transitions A-B and A-E decreasing, and C-D and D-E increasing. M1 stimulation increased occurrence of microstates A and D, and their transitions, while decreasing B and E. Comparison between stimulation sites revealed microstates A, C, and E exhibited opposite changes following DLPFC vs M1 stimulation. Moreover, microstate B decreased more, and microstate D increased more after DLPFC stimulation than after M1. These statistically significant findings were replicated in a repeated session.

The observed changes in microstates post-TMS likely result from temporary heightened activation of the stimulated network, providing new insights into the neural mechanisms of TMS and cortical excitability. This could further our understanding of how focal perturbations influence global brain dynamics.