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Neuroimaging in the Evaluation of Neurogenic Bladder Dysfunction
Published in Jacques Corcos, Gilles Karsenty, Thomas Kessler, David Ginsberg, Essentials of the Adult Neurogenic Bladder, 2020
Functional assessments have been primarily performed using blood-oxygen-level-dependent (BOLD)-MRI during a paradigm of repetitive tasks of LUT and/or pelvic floor stimulation, such as bladder filling/emptying through a catheter, voiding, and pelvic floor muscle contractions/relaxations. The BOLD signal is based on a hemodynamic response driven by the need of active neurons for (more) energy. This results in a regional change of blood oxygenation that can be detected using MRI due to the different magnetic properties of oxy- and deoxyhemoglobin. Thus, BOLD-MRI displays neuronal activity indirectly through changes in reginal blood oxygenation levels. Due to the relatively small signal amplitude, several repetitions and statistical analyses are required to detect those neuronal structures that show the most activity during the investigated task compared to a control condition (i.e., rest or another task).58
Substance misuse and young people: Reward mechanisms
Published in Ilana B. Crome, Richard Williams, Roger Bloor, Xenofon Sgouros, Substance Misuse and Young People, 2019
Functional magnetic resonance imaging (fMRI) exploits the magnetic property of blood changes as oxygen is removed. This can be detected using a magnetic resonance imaging (MRI) measure known as the blood oxygen level dependent (BOLD) signal, as a person engages in some behavioural task (e.g., responding for rewards) while in an MRI scanner. The BOLD response observed in the brain is the change in the oxyhaemoglobin to the deoxyhaemoglobin ratio in venous blood. The strength of this signal in a brain region (e.g., NAc/VS), therefore, indicates the relative level of oxygenated to deoxygenated blood at that location when processing rewards. As neuronal activity in response to processing demands requires more oxygen, the BOLD signal indirectly reflects neuronal activity at that location. The BOLD signal, therefore, can be used as a proxy measure of neuronal functioning in the brain.
Physical Principles of BOLD fMRI—What Is Important for the Clinician
Published in Andrei I. Holodny, Functional Neuroimaging, 2019
When interpreting BOLD fMRI studies, it is crucial to appreciate that an area of activation may actually represent a large draining vein rather than a capillary bed near the site of neuronal activation. The BOLD signal is only an indirect measure of neural activity and is therefore susceptible to influence by nonneural changes in the oxygenation of hemoglobin. Hence, it is indispensable to review the high-resolution study to exclude the presence of a large draining vein.
Complexity and Cognitive Engagement in the Rorschach Task: An fMRI Study
Published in Journal of Personality Assessment, 2021
Enrico Vitolo, Luciano Giromini, Donald J. Viglione, Franco Cauda, Alessandro Zennaro
BOLD signal fluctuations are often used as a means to measure neural activity because of their presumed relationship with neural activity itself. As firstly argued by Ogawa (Ogawa et al., 1990; Ogawa & Lee, 1990), they reflect differences in metabolic activity in brain regions involving cerebral blood flow (CBF) fluctuations. During any motor or “mental” action (such as viewing or processing a stimulus, feeling emotions, remembering facts or ideas, and so forth) the CBF increases as indicator of the functioning of those brain regions involved in the specific action (Fox et al., 1988; Fox & Raichle, 1986). The BOLD signal detects these hemodynamic fluctuations, thereby reflecting the neural activity – albeit not measuring it directly (Vul et al., 2009). Said differently, hemodynamic responses are markers of local field potentials’ activity, thereby implying a link between brain activation and local processing in that given brain region (Logothetis, 2003). Thus, the BOLD signal detection is deemed to be good measure of the strength of the neural responses elicited by a perceptual task, such as that posed by the Rorschach.
The effects of Alzheimer's disease related striatal pathologic changes on the fractional amplitude of low-frequency fluctuations
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
The hemodynamic model coupling synaptic activity and BOLD response presented by Friston et al. (2000) is used to make a relation between neuronal activities and the generated BOLD signal. In the literature, the fired neurons are generally considered for obtaining the BOLD signal, (Plenz and Kitai 1998; Yamanishi et al. 2013). The change in BOLD signal reflects the change in demand of energy and oxygen caused by neural activity. This neuronal activation signal must be related to all the activities of individual neuron. Considering only spiking neurons in the computation of total neuronal activity can be insufficient since the other neurons near spiking threshold will also spend energy. This assumption is consistent with the conclusions in (Logothetis and Wandell 2004) stated that there is a strong correlation between local field potentials and BOLD response. Therefore, the neuronal activity used in the computation of BOLD signal is taken as the summation of all neurons membrane potentials, not only the fired ones.
Utilizing wavelet deep learning network to classify different states of task-fMRI for verifying activation regions
Published in International Journal of Neuroscience, 2020
The task functional magnetic resonance imaging (fMRI) allows the volunteer subjects to complete the relevant tasks during scanning. It can be used for nondestructive detect of changes of human being brain in the blood-oxygen-level dependent (BOLD). The study of brain structure and function has received great attentions and develops very rapidly [1–5]. The BOLD signal obtained by fMRI is interfered by many complicated noises [6,7], such as: nuclear magnetic resonance environmental noises, instrument equipment electronic noises, human respiratory heartbeat noises and other biological noises. There are many differences among different subjects [8]. The methods of biological statistic analysis are usually used for processing the fMRI data. The analysis software named the SPM12 [9] is utilized to obtain statistical information on BOLD signal in the brain during completing the corresponding task by the T-test method.