Open-ended movements structure sensorimotor information in early human development.

Human behaviors, with whole-body coordination, involve large-scale sensorimotor interaction. Spontaneous bodily movements in the early developmental stage potentially lead toward acquisition of such coordinated behavior. These movements presumably contribute to the structuration of sensorimotor interaction, providing specific regularities in bidirectional information among muscle activities and proprioception. Whether and how spontaneous movements, despite being task-free, structure and organize sensorimotor interactions in the entire body during early development remain unknown. Herein, to address these issues, we gained insights into the structuration process of the sensorimotor interaction in neonates and 3-mo-old infants. By combining detailed motion capture and musculoskeletal simulation, sensorimotor information flows among muscle activities and proprioception throughout the body were obtained. Subsequently, we extracted spatial modules and temporal state in sensorimotor information flows. Our approach demonstrated that early spontaneous movements elicited body-dependent sensorimotor modules, revealing age-related changes in them, depending on the combination or direction. The sensorimotor interactions also displayed temporal non-random fluctuations analogous to those seen in spontaneous activities in the cerebral cortex and spinal cord. Furthermore, we found recurring state sequence patterns across multiple participants, characterized by a substantial increase in infants compared to the patterns in neonates. Therefore, early spontaneous movements induce the spatiotemporal structuration in sensorimotor interactions and subsequent developmental changes. These results implicated that early open-ended movements, emerging from a certain neural substrate, regulate the sensorimotor interactions through embodiment and contribute to subsequent coordinated behaviors. Our findings also provide a conceptual linkage between early spontaneous movements and spontaneous neuronal activity in terms of spatiotemporal characteristics.

Computational fluid dynamic analysis of the initiation of cerebral aneurysms.

OBJECTIVE: Relationships between aneurysm initiation and hemodynamic factors remain unclear since de novo aneurysms are rarely observed. Most previous computational fluid dynamics (CFD) studies have used artificially reproduced vessel geometries before aneurysm initiation for analysis. In this study, the authors investigated the hemodynamic factors related to aneurysm initiation by using angiographic images in patients with cerebral aneurysms taken before and after an aneurysm formation. METHODS: The authors identified 10 cases of de novo aneurysms in patients who underwent follow-up examinations for existing cerebral aneurysms located at a different vessel. The authors then reconstructed the vessel geometry from the images that were taken before aneurysm initiation. In addition, 34 arterial locations without aneurysms were selected as control cases. Hemodynamic parameters acting on the arterial walls were calculated by CFD analysis. RESULTS: In all de novo cases, the aneurysmal initiation area corresponded to the highest wall shear stress divergence (WSSD point), which indicated that there was a strong tensile force on the arterial wall at the initiation area. The other previously reported parameters did not show such correlations. Additionally, the pressure loss coefficient (PLc) was statistically significantly higher in the de novo cases (p < 0.01). The blood flow impact on the bifurcation apex, or the secondary flow accompanied by vortices, resulted in high tensile forces and high total pressure loss acting on the vessel wall. CONCLUSIONS: Aneurysm initiation may be more likely in an area where both tensile forces acting on the vessel wall and total pressure loss are large.

Decreased wall shear stress at high-pressure areas predicts the rupture point in ruptured intracranial aneurysms.

OBJECTIVE: Degenerative cerebral aneurysm walls are associated with aneurysm rupture and subarachnoid hemorrhage. Thin-walled regions (TWRs) represent fragile areas that may eventually lead to aneurysm rupture. Previous computational fluid dynamics (CFD) studies reported the correlation of maximum pressure (Pmax) areas and TWRs; however, the correlation with aneurysm rupture has not been established. This study aims to investigate this hemodynamic correlation. METHODS: The aneurysmal wall surface at the Pmax areas was intraoperatively evaluated using a fluid flow formula under pulsatile blood flow conditions in 23 patients with 23 saccular middle cerebral artery (MCA) bifurcation aneurysms (16 unruptured and 7 ruptured). The pressure difference (Pd) at the Pmax areas was calculated by subtracting the average pressure (Pave) from the Pmax and normalized by dividing this by the dynamic pressure at the aneurysm inlet side. The wall shear stress (WSS) was also calculated at the Pmax areas, aneurysm dome, and parent artery. These hemodynamic parameters were used to validate the correlation with TWRs in unruptured MCA aneurysms. The characteristic hemodynamic parameters at the rupture points in ruptured MCA aneurysms were then determined. RESULTS: In 13 of 16 unruptured aneurysms (81.2%), Pmax areas were identified that corresponded to TWRs. In 5 of the 7 ruptured cerebral aneurysms, the Pmax areas coincided with the rupture point. At these areas, the Pd values were not higher than those of the TWRs in unruptured cerebral aneurysms; however, minimum WSS, time-averaged WSS, and normalized WSS at the rupture point were significantly lower than those of the TWRs in unruptured aneurysms (p < 0.01). CONCLUSIONS: At the Pmax area of TWRs, decreased WSS appears to be the crucial hemodynamic parameter that indicates the risk of aneurysm rupture.

Blood Flow Analysis in Coil Embolized Aneurysms: Difference between Porous Media and Real Coil Geometry Model.

To clarify the mechanism of aneurysmal recanalization, it is necessary to understand the characteristics of the blood flow inside the aneurysm in particular the flow resistance generated by the coil. In studies using computational fluid dynamics (CFD), mainly two approaches have been used to model the coil embolized aneurysm; modeling the coils as porous media or by real coil geometries. In this study, we calculated the pressure drop along a vessel through a coiled region modeled as porous media or by real coil geometry and compared the pressure drop generated by the two coil models. The porous media model was described by Darcy's law and Ergun's equation, while the real coil geometry was generated using finite element method (FEM) structural analysis. We calculated the pressure drop for inlet velocities from 0.1 m/s to 1.0 m/s in steps of 0.1 m/s. Our results indicated that the porous media model may produce larger pressure drops than the real coil geometry model under low packing density. The value of the pressure drop was also changed due to the difference of coil distribution even if the packing density was the same.

Multivariate Analysis For Predicting Internal Carotid (IC) And Middle Cerebral (MC) Aneurysmal Rupture By Hemodynamic Parameters.

Currently, aneurysmal rupture can hardly be predicted and the search for an objective and precise indicator is ongoing. The objective of this study was to find a rupture prediction indicator (RPI) based on hemodynamic parameters of unruptured aneurysms focusing on the internal carotid (IC) and middle cerebral (MC) arteries. Computational fluid dynamics simulations were performed and hemodynamic parameters were calculated using three-dimensional C-arm computed tomography (3D C-arm CT) images of a total of 137 unruptured aneurysms (69 IC and 68 MC artery aneurysms) with known outcomes of rupture or unrupture. Multivariate analysis was applied to build an RPI model. The final RPI models contained the pressure-loss coefficient at the time maximum (TMAXPLc). Ruptured aneurysms were found to have lower TMAXPLc than unruptured aneurysms. The mean values were 1.002 (95%CI 0.827 to 1.177) and 1.466 (95%CI 1.352 to 1.579), respectively (P=0.002). TMAXPLc may thus be a useful parameter for rupture prediction of IC and MC artery aneurysms.

Hemodynamic Change In A Cerebral Aneurysm Treated By Double Stenting Technique.

Rupture of cerebral aneurysms often causes subarachnoid hemorrhage which is a life-threatening condition with high mortality rates. Larger aneurysms are believed to be more likely to rupture and should therefore be treated. Recently, flow diverters (FDs) are widely used to treat large or wide neck aneurysms. However, it can be difficult to treat them by deployment of a single FD because of its insufficient flow disturbance. To overcome this problem, double stenting technique is sometimes applied with the aim to improve the effect of blood velocity reduction. In this study, we used computational fluid dynamics (CFD) to investigate the hemodynamic changes in an aneurysm when deploying virtual FDs. The results showed that the characteristics of the blood flow field inside the aneurysm did not changed much after the deployment of a single FD but underwent a large change after the deployment of two FDs. Furthermore, the velocity reduction in the aneurysm sac at a plane away from the parent artery increased from 25.9% to 92.8% when two FDs were deployed instead of one compared to no stenting. Double stenting was effective to decrease blood velocity in large or wide neck aneurysms.

Relationship between hemodynamic parameters and cerebral aneurysm initiation.

Research on the relationship between cerebralaneurysm initiation and hemodynamic parameters, but several open questions remain on initiation and growth mechanisms of cerebral aneurysms. If factors contributing to initiation were identified, it would be possible to predict the initiation of aneurysms. The purpose of this study is to investigate the relationship between cerebral aneurysm initiation and hemodynamic factors. Blood flow simulations in aneurysms of three patients were performed using computational fluid dynamics (CFD) based on the cerebral blood vessel geometry before aneurysm initiation. We evaluated pressure, wall shear stress (WSS), wall shear stress gradient (WSSG), oscillatory shear index (OSI) and gradient oscillatory number (GON) since these factors are known to be associated with aneurysmal initiation. We also focused on the wall shear stress divergence (WSSD) in particular on the direction of WSS. Our results indicated that only high WSSD regions corresponded to the initiation regions, and the value of WSSD was remarkably high. Stretching force to the vessel wall may be related to the initiation of cerebral aneurysms.