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Tissue Structure and Function
Published in Joseph W. Freeman, Debabrata Banerjee, Building Tissues, 2018
Joseph W. Freeman, Debabrata Banerjee
The cerebrum is split into a right and left hemisphere. The hemispheres are joined by a dense bundle of nerve fibers called the corpus callosum. The corpus callosum allows signals to be sent from one hemisphere to the other. The cerebral cortex lies at the top layer of the cerebrum. This area coordinates cognition, learning, memory, sensory perception, volunteer movement, and motor planning.3,20 It has a wrinkled gray appearance (called gray matter). Beneath the cerebral cortex are connecting fibers between neurons called the white matter.20 The wrinkles of the cerebral cortex consist of sulci (small grooves), fissures (larger grooves), and gyri (bulges between grooves).20
A Short Tour of Mathematical Morphology on Edge and Vertex Weighted Graphs
Published in Olivier Lézoray, Leo Grady, Image Processing and Analysis with Graphs, 2012
In the medical context, Diffusion Tensor Images (DTIs) [52] provide a unique insight into oriented structures within tissues. A DTI T maps the set of voxels V⊆ℤ3 (i.e., V is a cuboid of ℤ3) into the set of 3 × 3 tensors (i.e., 3 × 3 symmetric positive definite matrices). The value T(υ) of a DTI T at a voxel υ∈V describes the diffusion of water molecules at υ. For instance, the first eigenvector of T(υ) (i.e., the one whose associated eigenvalue is maximal) provides the principal direction of water molecules diffusion at point x and its associated eigenvalue gives the magnitude of the diffusion along this direction. Since water molecules highly diffuse along fiber tracts and since the white matter of the brain is mainly composed of fiber tracts, DTIs are particularly adapted to the study of brain architecture. Figure 6.8a shows a representation of a cross-section of a brain DTI where the tensors are represented by ellipsoids. Indeed, the data of a tensor is equivalent to the one of an ellipsoid. In the brain, the corpus callosum is an important structure made of fiber tracts connecting homologous areas of each hemisphere. In order to track the fibers that pass through the corpus callosum, it is necessary to segment it first. The next paragraph briefly reviews how to reach this goal, thanks to watershed cuts [47].
Story of the Human Brain
Published in Junichi Takeno, Self-Aware Robots, 2022
The brain looks like a walnut and consists of two hemispheres: right and left. It consists of a cerebrum, cerebellum, and the brain stem, which is a bundle of nerves that hang downward. The hemispheres are connected by a bundle of nerve fibers called the corpus callosum. The right hemisphere on the right hand side is called the right brain and the one on the opposite side is the left brain (Fig. 3.2a,b).
A Functional BCI Model by the P2731 working group: Physiology
Published in Brain-Computer Interfaces, 2021
Ali Hossaini, Davide Valeriani, Chang S. Nam, Raffaele Ferrante, Mufti Mahmud
The hemispheres are divided by the great longitudinal fissure which runs from the front to the back of the head, but a thick tract of flesh called the corpus callosum crosses the fissure. The corpus callosum contains nerves and other tissues that facilitate inter-hemispheric communication, and it enables the seemingly symmetrical hemispheres to perform specialized functions. Defects in the corpus callosum usually cause pathological symptoms, but some individuals who lack one show few effects. Even more surprising are cases of people who live with only one hemisphere [11]. This situation reflects an important consideration for BCI design: brains are highly adaptable. The brain’s adaptability works to the advantage of BCI, for instance in human-machine teaming, but it also creates ambiguities in BCI system design because mental operations vary among individuals.
The effect of Tai Chi practice on brain white matter structure: a diffusion tensor magnetic resonance imaging study
Published in Research in Sports Medicine, 2019
Jian Yao, Qipeng Song, Kai Zhang, Youlian Hong, Weiping Li, Dewei Mao, Yan Cong, Jing Xian Li
This study examined the effect of regular long-term Tai Chi practice on brain white matter and whether or not the Tai Chi practice skill level and practicing experience are associated with the changes in brain white matter by using DTI. The results showed that Tai Chi group had significantly higher FA values than the control group, indicating better microstructure of the brain white matter in the region. The corpus callosum connects and enables the communication between the left and right cerebral hemispheres and is the largest white matter microstructure in the human brain (Luders, Thompson, & Toga, 2010). During aging, the volumes of total brain and total white matter decrease, whereas white matter lesion increases in both men and women (Ge et al., 2002; Ikram et al., 2008). These related microstructure changes in brain tissue are linked with functional decline, including that in memory, cognition, and diseases (Alzheimer’s disease) (Teipel et al., 2010).
Investigation of dynamic deformation of the midbrain in rear-end collision using human brain FE model
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
Noritoshi Atsumi, Masami Iwamoto, Yuko Nakahira, Yoshitaka Asano, Jun Shinoda
The brain stem is one of the most vulnerable sites in DAI histopathologically (Teasdale and Mathew 1996). Disconnection of the ascending arousal system in the brain stem has been demonstrated in the postmortem neuroimaging data of the autopsy brain of patients with severe TBI (Edlow et al. 2013). (Smith et al. 2000) also suggested that injury to axons in the brain stem plays a major role in the induction of immediate post-traumatic coma through an experimental study loading head rotational acceleration along the coronal or axial plane in pigs. In a concussion, the parts of the brain most affected by rotational forces are generally the midbrain and diencephalon (Ropper and Gorson 2007; Pearce 2008). Forces from the injury may disrupt normal cellular activities in the reticular activating system located in these areas and thereby cause loss of consciousness (Ropper and Gorson 2007). A study on the integrity of the brain stem in mild TBI by (Delano-Wood et al. 2015) showed that there was no significant difference in the fractional anisotropy (FA) maps of the brain stem between normal control and mild TBI groups. However, they also showed that the FA value of the corticospinal tracts was significantly negatively associated with the duration of loss of consciousness among the TBI group. Additionally, a lower FA value for certain tracts, especially the pontine tegmentum, was significantly associated with increased post-concussion symptoms (Delano-Wood et al. 2015). Hirad et al. (2019) showed that there were reductions in the midbrain white matter integrity due to a single season of collegiate football, and that the amount of reduction is related to the amount of rotational acceleration to which the brains of players are exposed. They also observed reduced midbrain white matter integrity in a retrospective cohort of subjects with concussions. These results suggest that there may be some relationship between the symptoms and damages in the brain stem, even in a mild TBI. On the other hand, the corpus callosum has been also known to be one of the most predominant sites where axonal retraction balls, axonal swelling, micro-bleeding, and aggregation of microglia can be observed histopathologically in DAI (Teasdale and Mathew 1996). Neuroradiologically, the disruption of the connectivity in the corpus callosum, as shown using diffusion tensor imaging (DTI), has been revealed to be also characteristic in patients with severe TBI (Nakayama et al. 2006). A review by (Narayana 2017) revealed that the corpus callosum is the most frequently affected white matter tract in mild TBI. Other parts of the brain that may be affected include the upper part of the brain stem, fornix, medial temporal lobe, and base of the frontal lobe (Bigler 2008). However, the detailed shearing dynamics of these brain regions in a concussion has not yet been clarified.