Neuroimaging in concussion
Brian Sindelar, Julian E. Bailes in Sports-Related Concussion, 2017
Functional MRI (fMRI) is a noninvasive study that can assess regional brain activity while performing or not performing a specific task (resting state fMRI or task-based fMRI), which is achieved indirectly by imaging the regional differences in cerebral blood flow using blood oxygenation level dependent (BOLD) imaging. Under normal physiologic conditions, regional blood flow in the brain is tightly linked to oxygen and carbon dioxide. When a specific part of the brain cortex is activated, the increased metabolic need leads to increased extraction of oxygen from the local capillaries with an initial drop in oxyhemoglobin levels. After a short lag of 26 seconds, the regional blood flow increases providing a surplus of oxyhemoglobin and leading to deoxyhemoglobin washout. This physiologic response of decreased levels of deoxyhemoglobin is what is imaged in fMRI. Because deoxygenated hemoglobin is paramagnetic whereas oxygenated hemoglobin is not, the relative decrease in the deoxyhemoglobin in the activated cortex leads to proton dephasing by inducing local magnetic field inhomogeneities and a net minimal but measurable decrease in signal on a heavily T2* weighted sequence such as BOLD imaging.
Mapping the Injured Brain
Yu Chen, Babak Kateb in Neurophotonics and Brain Mapping, 2017
Functional MRI (fMRI) is a valuable tool as it can identify the deficits in neural networks associated with various cognitive processes. Specifically, fMRI provides an indirect measure of large-scale neural activation and is based on the MR signal differences between deoxygenated blood and oxygenated blood. When individual neurons that are recruited for a given task produce an axon potential, there is an increase in freshly oxygenated blood to the local tissue to keep up with the increased neuronal demand. This change in the ratio of deoxygenated blood to oxygenated blood in the activated region causes a change in the tissue signal as the local tissue changes from a predominantly paramagnetic state to diamagnetic state. It is this MR signal change that is measured in fMRI and is called the blood-oxygen-level-dependent (BOLD) signal (Figure 14.3a). Currently fMRI data are acquired in one of two ways using a task-based fMRI paradigm and a resting-state fMRI (rs-fMRI) paradigm (Figure 14.3b and c).
Brain Insulin Action in the Control of Metabolism in Humans
André Kleinridders in Physiological Consequences of Brain Insulin Action, 2023
Thanks to neuroimaging techniques, brain insulin action can be spatially localized by evaluating the brain’s response to cognitive demanding tasks such as, for example, the investigation of the role of insulin in memory or reward-related processes. Since the brain is active even in the absence of external cues, spontaneous BOLD fluctuations are located in all brain regions. Brain activity can therefore be evaluated under the so-called “resting-state” or “intrinsic condition”. To this end, subjects lie in the MRI scanner with their eyes open or closed without performing any task. Resting-state fMRI thus greatly enhances the translation of fMRI into clinical care (for review, see (59)).
Altered resting-state cerebellar-cerebral functional connectivity in patients with end-stage renal disease
Published in Renal Failure, 2023
Jie Fang, Yingying Miao, Fan Zou, Yarui Liu, Jiangle Zuo, Xiangming Qi, Haibao Wang
Resting-state fMRI is a method that indirectly infers information about brain activity by measuring Blood-Oxygen-Level Dependent (BOLD) signal. The temporal correlations of BOLD signals in different brain regions can be used to reflect brain FC [30]. The abnormalities in resting-state fMRI connectivity reflect alterations in the interactions among different brain regions [31]. Considering that DMN, ECN, ALN, and SMN are abnormal in ESRD, and that cerebellar sub-regions can identify the cerebellar-cerebral DMN, ECN, ALN, and SMN, we hypothesized that the cerebellum-cerebral FC is abnormal and related to cognitive impairment in ESRD patients. Therefore, the present study aimed to explore whether the cerebellar-cerebral FC is altered in ESRD patients with cerebellar sub-regions as seeds using resting-state fMRI, and further investigate the relationship between the altered FC, neuropsychological function, and clinical parameters in patients with ESRD.
Deep brain stimulation in essential tremor: targets, technology, and a comprehensive review of clinical outcomes
Published in Expert Review of Neurotherapeutics, 2020
Joshua K. Wong, Christopher W. Hess, Leonardo Almeida, Erik H. Middlebrooks, Evangelos A. Christou, Erin E. Patrick, Aparna Wagle Shukla, Kelly D. Foote, Michael S. Okun
Connectivity profiling has been increasingly used to assist with DBS targeting [55]. One study created connectivity profiles using structural and functional connectivity data of a normative connectome database to predict ‘optimal connectivity.’ Structural connectivity profiles were created by utilizing MRI diffusion tensor imaging (DTI) data and reconstructing approximations of axonal connections using computational tractography algorithms. Functional connectivity profiles were created by analyzing the real-time fluctuations of oxygen simultaneously throughout the brain in the absence of external stimuli via a technique known as blood-oxygen-level dependent resting state fMRI (BOLD rs-fMRI) [56]. Connectivity data from the entire brain network were mapped into a statistical model and correlated with clinical outcomes. The statistical model was combined with volume of tissue activation (VTA) analysis to map tremor suppression with brain tissue and somatotopy between the hand and head. VTA analysis involves approximating the electric field from the DBS electrode based on the specific input of programming parameters [57]. This technique, when combined with 3D imaging data of the brain, can estimate the region of neuronal tissue stimulated by the DBS system. The authors identified optimal connectivity for tremor suppression at the region of the inferior-posterior border of the VIM and the dorsal border of the ZI.
Patterns of brain regional functional coherence in cognitive impaired ALS
Published in International Journal of Neuroscience, 2020
Tao Hu, Yanbing Hou, Qianqian Wei, Jing Yang, Chunyan Luo, Yongping Chen, Qiyong Gong, Huifang Shang
Noninvasive neuroimaging methods of the structural and functional MRI (fMRI) allowing to investigate an extent of neurological system degeneration in vivo, have been broadly applied in the studies on ALS [14]. Resting state fMRI, based on blood oxygenation level dependent (BOLD) contrast, could offer a novel non-invasive method to assess the brain regional and neural circuitry function without potential performance confounds associated with variable tasks. The regional homogeneity (ReHo) method can characterize the local synchronization of spontaneous BOLD signals in fMRI between a given voxel and the nearest neighboring voxels (typically 26 voxels) using Kendells coefficient of concordance (KCC) [15]. It reflects the coherence of spontaneous neuronal activity, and its contribution to task activation is due to the amplitude of low frequency fluctuations, which in part influences the neuronal activity during a task. The meaning of ReHo is consistent with the functional activity of a specific region of the brain. The decreased or increased ReHo suggests that the functional activity in certain regions is poorly or highly synchronized compared to controls [15]. This method has been successfully used to detect alterations of the local synchronization of spontaneous neural activity in patients with ALS [16].
Related Knowledge Centers
- Brain Mapping
- Cerebral Circulation
- Default Mode Network
- Electroencephalography
- Functional Magnetic Resonance Imaging
- Neurological Disorder
- Brain
- Blood-Oxygen-Level-Dependent Imaging
- Mental Disorder
- Magnetic Resonance Imaging