scholarly journals A Sensitivity Analysis of fMRI Balloon Model

2015 ◽  
Vol 2015 ◽  
pp. 1-11
Author(s):  
Chadia Zayane ◽  
Taous Meriem Laleg-Kirati
Keyword(s):  
Sensitivity Analysis ◽  
Blood Oxygenation ◽  
Model Parameters ◽  
Input Stimulus ◽  
Output Measurement ◽  
Oxygenation Level ◽  
Hemodynamic Model ◽  
The Brain ◽  
Selection Of

Functional magnetic resonance imaging (fMRI) allows the mapping of the brain activation through measurements of the Blood Oxygenation Level Dependent (BOLD) contrast. The characterization of the pathway from the input stimulus to the output BOLD signal requires the selection of an adequate hemodynamic model and the satisfaction of some specific conditions while conducting the experiment and calibrating the model. This paper, focuses on the identifiability of the Balloon hemodynamic model. By identifiability, we mean the ability to estimate accurately the model parameters given the input and the output measurement. Previous studies of the Balloon model have somehow added knowledge either by choosing prior distributions for the parameters, freezing some of them, or looking for the solution as a projection on a natural basis of some vector space. In these studies, the identification was generally assessed using event-related paradigms. This paper justifies the reasons behind the need of adding knowledge, choosing certain paradigms, and completing the few existing identifiability studies through a global sensitivity analysis of the Balloon model in the case of blocked design experiment.

scholarly journals Nuisance effects in inter-scan functional connectivity estimates before and after nuisance regression

2019 ◽  
Author(s):  
Alican Nalci ◽  
Wenjing Luo ◽  
Thomas T. Liu
Keyword(s):  
Functional Connectivity ◽  
Brain Regions ◽  
Blood Oxygenation ◽  
Bold Signal ◽  
Global Signal ◽  
Before And After ◽  
Oxygenation Level ◽  
Motion Measurements ◽  
The Brain

AbstractIn resting-state functional MRI, the correlation between blood-oxygenation-level-dependent (BOLD) signals across brain regions is used to estimate the functional connectivity (FC) of the brain. FC estimates are prone to the influence of nuisance factors including scanner-related artifacts and physiological modulations of the BOLD signal. Nuisance regression is widely performed to reduce the effect of nuisance factors on FC estimates on a per-scan basis. However, a dedicated analysis of nuisance effects on the variability of FC metrics across a collection of scans has been lacking. This work investigates the effects of nuisance factors on the variability of FC estimates across a collection of scans both before and after nuisance regression. Inter-scan variations in FC estimates are shown to be significantly correlated with the geometric norms of various nuisance terms, including head motion measurements, signals derived from white-matter and cerebrospinal regions, and the whole-brain global signal (GS) both before and after nuisance regression. In addition, it is shown that GS regression (GSR) can introduce GS norm-related fluctuations that are negatively correlated with inter-scan FC estimates. The empirical results are shown to be largely consistent with the predictions of a theoretical framework previously developed for the characterization of dynamic FC measures. This work shows that caution must be exercised when interpreting inter-scan FC measures across scans both before and after nuisance regression.

A NEW MATHEMATICAL APPROACH FOR DETECTION OF ACTIVE AREA IN HUMAN BRAIN fMRI USING NONLINEAR MODEL

2010 ◽  
Vol 22 (05) ◽  
pp. 409-418 ◽  
Author(s):  
Ali Taalimi ◽  
Emad Fatemizadeh
Keyword(s):  
Moving Average ◽  
Simulated Data ◽  
Nonlinear Behavior ◽  
Blood Oxygenation ◽  
Superior Performance ◽  
Model Parameters ◽  
Bold Signal ◽  
Mathematical Approach ◽  
Region Detection ◽  
Oxygenation Level

Functional magnetic resonance imaging (fMRI) is widely-used for detection of the brain's neural activity. The signals and images acquired through this imaging technique demonstrate the human brain's response to pre-scheduled tasks. Several studies on blood oxygenation level-dependent (BOLD) signal responses demonstrate nonlinear behavior in response to a stimulus. In this paper we propose a new mathematical approach for modeling BOLD signal activity, which is able to model nonlinear and time variant behaviors of this physiological system. We employ the Nonlinear Auto Regressive Moving Average (NARMA) model to describe the mathematical relationship between output signals and predesigned tasks. The model parameters can be used to distinguish between rest and active states of a brain region. We applied our proposed method for active region detection on real as well as simulated data sets. The results show superior performance in comparison with existing methods.

scholarly journals Relationship of the BOLD Signal with VEP for Ultrashort Duration Visual Stimuli (0.1 to 5 ms) in Humans

2009 ◽  
Vol 30 (2) ◽  
pp. 449-458 ◽  
Author(s):  
Barış Yeşilyurt ◽  
Kevin Whittingstall ◽  
Kâmil Uğurbil ◽  
Nikos K Logothetis ◽  
Kâmil Uludağ
Keyword(s):  
Brain Function ◽  
Temporal Dynamics ◽  
Visual Stimulation ◽  
Impulse Response Function ◽  
Blood Oxygenation ◽  
Context Dependency ◽  
Oxygenation Level ◽  
Relationship Of ◽  
The Relationship ◽  
The Brain

There is currently a great interest to combine electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) to study brain function. Earlier studies have shown different EEG components to correlate well with the fMRI signal arguing for a complex relationship between both measurements. In this study, using separate EEG and fMRI measurements, we show that (1) 0.1 ms visual stimulation evokes detectable hemodynamic and visual-evoked potential (VEP) responses, (2) the negative VEP deflection at ∼80 ms (N2) co-varies with stimulus duration/intensity such as with blood oxygenation level-dependent (BOLD) response; the positive deflection at ∼120 ms (P2) does not, and (3) although the N2 VEP–BOLD relationship is approximately linear, deviation is evident at the limit of zero N2 VEP. The latter finding argues that, although EEG and fMRI measurements can co-vary, they reflect partially independent processes in the brain tissue. Finally, it is shown that the stimulus-induced impulse response function (IRF) at 0.1 ms and the intrinsic IRF during rest have different temporal dynamics, possibly due to predominance of neuromodulation during rest as compared with neurotransmission during stimulation. These results extend earlier findings regarding VEP–BOLD coupling and highlight the component- and context-dependency of the relationship between evoked potentials and hemodynamic responses.

scholarly journals A studyforrest extension, MEG recordings while watching the audio-visual movie "Forrest Gump"

2021 ◽  
Author(s):  
Xingyu Liu ◽  
Yuxuan Dai ◽  
Hailun Xie ◽  
Zonglei Zhen
Keyword(s):  
Neuronal Activity ◽  
Brain Function ◽  
Ecological Validity ◽  
Blood Oxygenation ◽  
Free Access ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Oxygenation Level ◽  
The Brain ◽  
The Magnetic Field

Naturalistic stimuli, such as movies, are being increasingly used to map brain function because of their high ecological validity. The pioneering studyforrest and other naturalistic neuroimaging projects have provided free access to multiple movie-watching functional magnetic resonance imaging (fMRI) datasets to prompt the community for naturalistic experimental paradigms. However, sluggish blood-oxygenation-level-dependent fMRI signals are incapable of resolving neuronal activity with the temporal resolution at which it unfolds. Instead, magnetoencephalography (MEG) measures changes in the magnetic field produced by neuronal activity and is able to capture rich dynamics of the brain at the millisecond level while watching naturalistic movies. Herein, we present the first public prolonged MEG dataset collected from 11 participants while watching the 2 h long audio-visual movie "Forrest Gump". Minimally preprocessed data was also provided to facilitate the use. As a studyforrest extension, we envision that this dataset, together with fMRI data from the studyforrest project, will serve as a foundation for exploring the neural dynamics of various cognitive functions in real-world contexts.

scholarly journals Resting state functional connectivity in the human spinal cord

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Robert L Barry ◽  
Seth A Smith ◽  
Adrienne N Dula ◽  
John C Gore
Keyword(s):  
Spinal Cord ◽  
Functional Connectivity ◽  
Resting State ◽  
Low Frequency ◽  
Blood Oxygenation ◽  
Resting State Functional Connectivity ◽  
Human Spinal Cord ◽  
Oxygenation Level ◽  
Left And Right ◽  
The Brain

Functional magnetic resonance imaging using blood oxygenation level dependent (BOLD) contrast is well established as one of the most powerful methods for mapping human brain function. Numerous studies have measured how low-frequency BOLD signal fluctuations from the brain are correlated between voxels in a resting state, and have exploited these signals to infer functional connectivity within specific neural circuits. However, to date there have been no previous substantiated reports of resting state correlations in the spinal cord. In a cohort of healthy volunteers, we observed robust functional connectivity between left and right ventral (motor) horns, and between left and right dorsal (sensory) horns. Our results demonstrate that low-frequency BOLD fluctuations are inherent in the spinal cord as well as the brain, and by analogy to cortical circuits, we hypothesize that these correlations may offer insight into the execution and maintenance of sensory and motor functions both locally and within the cerebrum.

scholarly journals Neural Basis of the Sound-Symbolic Crossmodal Correspondence Between Auditory Pseudowords and Visual Shapes

2021 ◽  
pp. 1-50
Author(s):  
Kelly McCormick ◽  
Simon Lacey ◽  
Randall Stilla ◽  
Lynne C. Nygaard ◽  
K. Sathian
Keyword(s):  
Phonological Processing ◽  
Imaging Study ◽  
Blood Oxygenation ◽  
Sound Symbolism ◽  
Neural Basis ◽  
Oxygenation Level ◽  
Crossmodal Correspondence ◽  
Study Participants ◽  
The Brain ◽  
Left Middle

Abstract Sound symbolism refers to the association between the sounds of words and their meanings, often studied using the crossmodal correspondence between auditory pseudowords, e.g., ‘takete’ or ‘maluma’, and pointed or rounded visual shapes, respectively. In a functional magnetic resonance imaging study, participants were presented with pseudoword–shape pairs that were sound-symbolically congruent or incongruent. We found no significant congruency effects in the blood oxygenation level-dependent (BOLD) signal when participants were attending to visual shapes. During attention to auditory pseudowords, however, we observed greater BOLD activity for incongruent compared to congruent audiovisual pairs bilaterally in the intraparietal sulcus and supramarginal gyrus, and in the left middle frontal gyrus. We compared this activity to independent functional contrasts designed to test competing explanations of sound symbolism, but found no evidence for mediation via language, and only limited evidence for accounts based on multisensory integration and a general magnitude system. Instead, we suggest that the observed incongruency effects are likely to reflect phonological processing and/or multisensory attention. These findings advance our understanding of sound-to-meaning mapping in the brain.

scholarly journals Neural Basis of the Sound-Symbolic Crossmodal Correspondence Between Auditory Pseudowords and Visual Shapes

2018 ◽  
Author(s):  
Kelly McCormick ◽  
Simon Lacey ◽  
Randall Stilla ◽  
Lynne C. Nygaard ◽  
K. Sathian
Keyword(s):  
Phonological Processing ◽  
Imaging Study ◽  
Blood Oxygenation ◽  
Sound Symbolism ◽  
Neural Basis ◽  
Oxygenation Level ◽  
Crossmodal Correspondence ◽  
Underlying Mechanisms ◽  
Study Participants ◽  
The Brain

ABSTRACTSound symbolism refers to the association between the sounds of words and their meanings, often studied using the crossmodal correspondence between auditory pseudowords, e.g. ‘takete’ or ‘maluma’, and pointed or rounded visual shapes, respectively. In a functional magnetic resonance imaging study, participants were presented with pseudoword-shape pairs that were sound-symbolically congruent or incongruent. We found no significant congruency effects in the blood oxygenation level-dependent (BOLD) signal when participants were attending to visual shapes. Rather, during attention to auditory pseudowords, we observed greater BOLD activity for incongruent compared to congruent audiovisual pairs bilaterally in the intraparietal sulcus and supramarginal gyrus, and in the left middle frontal gyrus. We compared this activity to independent functional contrasts designed to test potential underlying mechanisms, but found no evidence for semantic mediation, and only limited evidence for multisensory integration and magnitude estimation. Instead, we suggest that the observed incongruency effects are likely to reflect phonological processing and/or multisensory attention. These findings advance our understanding of sound-to-meaning mapping in the brain.

Computational model of an infant brain subjected to periodic motion simplified modelling and bayesian sensitivity analysis

2011 ◽  
Vol 225 (11) ◽  
pp. 1036-1049 ◽  
Author(s):  
D C Batterbee ◽  
N D Sims ◽  
W Becker ◽  
K Worden ◽  
J Rowson
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Shaken Baby Syndrome ◽  
Human Head ◽  
Element Model ◽  
Model Parameters ◽  
Lack Of Information ◽  
Eulerian Mesh ◽  
Model Geometry ◽  
The Brain

Non-accidental head injury in infants, or shaken baby syndrome, is a highly controversial and disputed topic. Biomechanical studies often suggest that shaking alone cannot cause the classical symptoms, yet many medical experts believe the contrary. Researchers have turned to finite element modelling for a more detailed understanding of the interactions between the brain, skull, cerebrospinal fluid (CSF), and surrounding tissues. However, the uncertainties in such models are significant; these can arise from theoretical approximations, lack of information, and inherent variability. Consequently, this study presents an uncertainty analysis of a finite element model of a human head subject to shaking. Although the model geometry was greatly simplified, fluid-structure-interaction techniques were used to model the brain, skull, and CSF using a Eulerian mesh formulation with penalty-based coupling. Uncertainty and sensitivity measurements were obtained using Bayesian sensitivity analysis, which is a technique that is relatively new to the engineering community. Uncertainty in nine different model parameters was investigated for two different shaking excitations: sinusoidal translation only, and sinusoidal translation plus rotation about the base of the head. The level and type of sensitivity in the results was found to be highly dependent on the excitation type.

scholarly journals Intraoperative BOLD-fMRI Cerebrovascular Reactivity Assessment

2021 ◽  
pp. 139-143
Author(s):  
Giovanni Muscas ◽  
Christiaan Hendrik Bas van Niftrik ◽  
Martina Sebök ◽  
Giuseppe Esposito ◽  
Luca Regli ◽  
...  
Keyword(s):  
Cerebrovascular Diseases ◽  
Blood Oxygenation ◽  
Cerebrovascular Reactivity ◽  
Hemodynamic State ◽  
Neurosurgical Patients ◽  
Blood Oxygenation Level ◽  
Oxygenation Level ◽  
Ischemic Cerebrovascular Diseases ◽  
Brain Gliomas ◽  
The Brain

AbstractBlood oxygenation-level dependent cerebrovascular reactivity (BOLD-CVR) has gained attention in recent years as an effective way to investigate CVR, a measure of the hemodynamic state of the brain, with high spatial and temporal resolution. An association between impaired CVR and diverse pathologies has been observed, especially in ischemic cerebrovascular diseases and brain gliomas. The ability to obtain this information intraoperatively is novel and has not been widely tested. We report our first experience with this intraoperative technique in vascular and oncologic neurosurgical patients, discuss the results of its feasibility, and the possible developments of the intraoperative employment of BOLD-CVR.

Sign in / Sign up

Export Citation Format

Share Document