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.

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 Nuisance Effects and the Limitations of Nuisance Regression in Dynamic Functional Connectivity fMRI

2018 ◽  
Author(s):  
Alican Nalci ◽  
Bhaskar D. Rao ◽  
Thomas T. Liu
Keyword(s):  
Functional Connectivity ◽  
Resting State Fmri ◽  
Brain Regions ◽  
Blood Oxygenation ◽  
Dynamic Functional Connectivity ◽  
Temporal Fluctuations ◽  
Before And After ◽  
The Difference ◽  
Time Courses ◽  
The Relationship

AbstractIn resting-state fMRI, dynamic functional connectivity (DFC) measures are used to characterize temporal changes in the brain’s intrinsic functional connectivity. A widely used approach for DFC estimation is the computation of the sliding window correlation between blood oxygenation level dependent (BOLD) signals from different brain regions. Although the source of temporal fluctuations in DFC estimates remains largely unknown, there is growing evidence that they may reflect dynamic shifts between functional brain networks. At the same time, recent findings suggest that DFC estimates might be prone to the influence of nuisance factors such as the physiological modulation of the BOLD signal. Therefore, nuisance regression is used in many DFC studies to regress out the effects of nuisance terms prior to the computation of DFC estimates. In this work we examined the relationship between DFC estimates and nuisance factors. We found that DFC estimates were significantly correlated with temporal fluctuations in the magnitude (norm) of various nuisance regressors, with significant correlations observed in the majority (76%) of the cases examined. Significant correlations between the DFC estimates and nuisance regressor norms were found even when the underlying correlations between the nuisance and fMRI time courses were relatively small. We then show that nuisance regression does not eliminate the relationship between DFC estimates and nuisance norms, with significant correlations observed in the majority (71%) of the cases examined after nuisance regression. We present theoretical bounds on the difference between DFC estimates obtained before and after nuisance regression and relate these bounds to limitations in the efficacy of nuisance regression with regards to DFC estimates.

scholarly journals The Exercising Brain: Changes in Functional Connectivity Induced by an Integrated Multimodal Cognitive and Whole-Body Coordination Training

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Traute Demirakca ◽  
Vita Cardinale ◽  
Sven Dehn ◽  
Matthias Ruf ◽  
Gabriele Ende
Keyword(s):  
Functional Connectivity ◽  
Brain Plasticity ◽  
Brain Regions ◽  
Posterior Cingulate Cortex ◽  
Whole Body ◽  
Before And After ◽  
Coordination Training ◽  
Brain Changes ◽  
The Impact ◽  
The Brain

This study investigated the impact of “life kinetik” training on brain plasticity in terms of an increased functional connectivity during resting-state functional magnetic resonance imaging (rs-fMRI). The training is an integrated multimodal training that combines motor and cognitive aspects and challenges the brain by introducing new and unfamiliar coordinative tasks. Twenty-one subjects completed at least 11 one-hour-per-week “life kinetik” training sessions in 13 weeks as well as before and after rs-fMRI scans. Additionally, 11 control subjects with 2 rs-fMRI scans were included. The CONN toolbox was used to conduct several seed-to-voxel analyses. We searched for functional connectivity increases between brain regions expected to be involved in the exercises. Connections to brain regions representing parts of the default mode network, such as medial frontal cortex and posterior cingulate cortex, did not change. Significant connectivity alterations occurred between the visual cortex and parts of the superior parietal area (BA7). Premotor area and cingulate gyrus were also affected. We can conclude that the constant challenge of unfamiliar combinations of coordination tasks, combined with visual perception and working memory demands, seems to induce brain plasticity expressed in enhanced connectivity strength of brain regions due to coactivation.

Representations of fabric hand attributes in the cerebral cortices based on the Automated Anatomical Labeling atlas

2018 ◽  
Vol 89 (18) ◽  
pp. 3768-3778 ◽  
Author(s):  
Qicai Wang ◽  
Yuan Tao ◽  
Zhongwei Zhang ◽  
Jie Yuan ◽  
Zuowei Ding ◽  
...  
Keyword(s):  
Brain Regions ◽  
Blood Oxygenation ◽  
Brain Areas ◽  
Cognitive Mechanism ◽  
Fabric Hand ◽  
Promising Tool ◽  
Two Samples ◽  
Oxygenation Level ◽  
The Relationship ◽  
The Brain

Fabric hand is most frequently used by consumers and researchers to evaluate the touch feeling of textiles. Academically, many methods have been developed to characterize it psychologically and physically, and the relationship between the hand attributes of fabrics and their physical properties are well understood. However, in physiological terms, the cognitive mechanism of the brain on different attributes of fabric hand is not clear. Previous studies have shown that the sensory or discrimination information from fabric touch can be detected by the technology of functional magnetic resonance imaging (fMRI). In this study, further fMRI experiments were carried out, attempting to find the relationship between the cerebral cortices of various brain areas and different hand attributes of fabrics. The subtle atlas of Automated Anatomical Labeling (AAL) was used to display and analyze the blood oxygenation level dependent signals completely and conveniently. The results showed that when the subjects touched two samples with distinct fabric hand in a specified way, activation information and the index of the mean signal in every related brain areas can distinguish them, and several brain regions in the AAL atlas are linked to different fabric hand attributes. The technology of fMRI was proved again to be a promising tool for studying the cognitive mechanism of the brain on fabric touch.

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 Feedback to distal dendrites links fMRI signals to neural receptive fields in a spiking network model of the visual cortex

2015 ◽  
Vol 114 (1) ◽  
pp. 57-69 ◽  
Author(s):  
Hanna Heikkinen ◽  
Fariba Sharifian ◽  
Ricardo Vigario ◽  
Simo Vanni
Keyword(s):  
Visual Cortex ◽  
Feedback Loop ◽  
Receptive Fields ◽  
Blood Oxygenation ◽  
High Fidelity ◽  
Bold Signal ◽  
Bold Response ◽  
Spiking Network ◽  
Oxygenation Level ◽  
The Brain

The blood oxygenation level-dependent (BOLD) response has been strongly associated with neuronal activity in the brain. However, some neuronal tuning properties are consistently different from the BOLD response. We studied the spatial extent of neural and hemodynamic responses in the primary visual cortex, where the BOLD responses spread and interact over much longer distances than the small receptive fields of individual neurons would predict. Our model shows that a feedforward-feedback loop between V1 and a higher visual area can account for the observed spread of the BOLD response. In particular, anisotropic landing of inputs to compartmental neurons were necessary to account for the BOLD signal spread, while retaining realistic spiking responses. Our work shows that simple dendrites can separate tuning at the synapses and at the action potential output, thus bridging the BOLD signal to the neural receptive fields with high fidelity.

scholarly journals Brain functional connectivity in headache disorders: A narrative review of MRI investigations

2017 ◽  
Vol 39 (4) ◽  
pp. 650-669 ◽  
Author(s):  
Catherine D Chong ◽  
Todd J Schwedt ◽  
Anders Hougaard
Keyword(s):  
Functional Connectivity ◽  
Resting State ◽  
Medication Overuse Headache ◽  
Headache Disorder ◽  
Brain Regions ◽  
Brain Network ◽  
Blood Oxygenation ◽  
Headache Disorders ◽  
Default Mode ◽  
Oxygenation Level

Resting-state functional magnetic resonance imaging (rs-fMRI) is used to interrogate the functional connectivity and network organization amongst brain regions. Functional connectivity is determined by measuring the extent of synchronization in the spontaneous fluctuations of blood oxygenation level dependent (BOLD) signal. Here, we review current rs-fMRI studies in headache disorders including migraine, trigeminal autonomic cephalalgias, and medication overuse headache. We discuss (1) brain network alterations that are shared amongst the different headache disorders and (2) network abnormalities distinct to each headache disorder. In order to focus the section on migraine, the headache disorder that has been most extensively studied, we chose to include articles that interrogated functional connectivity: (i) during the attack phase; (ii) in migraine patients with aura compared to migraine patients without aura; and (iii) of regions within limbic, sensory, motor, executive and default mode networks and those which participate in multisensory integration. The results of this review show that headache disorders are associated with atypical functional connectivity of regions associated with pain processing as well as atypical functional connectivity of multiple core resting state networks such as the salience, sensorimotor, executive, attention, limbic, visual, and default mode networks.

Coherent Spontaneous Activity Identifies a Hippocampal-Parietal Memory Network

2006 ◽  
Vol 96 (6) ◽  
pp. 3517-3531 ◽  
Author(s):  
Justin L. Vincent ◽  
Abraham Z. Snyder ◽  
Michael D. Fox ◽  
Benjamin J. Shannon ◽  
Jessica R. Andrews ◽  
...  
Keyword(s):  
Parietal Cortex ◽  
Hippocampal Formation ◽  
Normal Subjects ◽  
Blood Oxygenation Level Dependent ◽  
Retrosplenial Cortex ◽  
Blood Oxygenation ◽  
Bold Signal ◽  
Inferior Parietal Lobule ◽  
Oxygenation Level ◽  
Memory Network

Despite traditional theories emphasizing parietal contributions to spatial attention and sensory-motor integration, functional MRI (fMRI) experiments in normal subjects suggest that specific regions within parietal cortex may also participate in episodic memory. Here we examined correlations in spontaneous blood-oxygenation-level-dependent (BOLD) signal fluctuations in a resting state to identify the network associated with the hippocampal formation (HF) and determine whether parietal regions were elements of that network. In the absence of task, stimuli, or explicit mnemonic demands, robust correlations were observed between activity in the HF and several parietal regions (including precuneus, posterior cingulate, retrosplenial cortex, and bilateral inferior parietal lobule). These HF-correlated regions in parietal cortex were spatially distinct from those correlated with the motion-sensitive MT+ complex. Reanalysis of event-related fMRI studies of recognition memory showed that the regions spontaneously correlated with the HF (but not MT+) were also modulated during directed recollection. These regions showed greater activity to successfully recollected items as compared with other trial types. Together, these results associate specific regions of parietal cortex that are sensitive to successful recollection with the HF.

scholarly journals Functional Connectivity within Brain Networks of Long Term and Short term Meditators

2019 ◽  
Vol 9 (2S) ◽  
pp. 29-34
Keyword(s):  
Functional Connectivity ◽  
Temporal Correlation ◽  
Brain Regions ◽  
Invasive Technique ◽  
Long Term Effects ◽  
Short Term ◽  
Statistical Concept ◽  
The Brain ◽  
Meditative Practices

Meditation refers to a state of mind of relaxation and concentration, where generally the mind and body is at rest. The process of meditation reflects the state of the brain which is distinct from sleep or typical wakeful states of consciousness. Meditative practices usually involve regulation of emotions and monitoring of attention. Over the past decade there has been a tremendous increase in an interest to study the neural mechanisms involved in meditative practices. It could also be beneficial to explore if the effect of meditation is altered by the number of years of meditation practice. Functional Magnetic Resonance Imaging (fMRI) is a very useful imaging technique which can be used to perform this analysis due to its inherent benefits, mainly it being a non-invasive technique. Functional activation and connectivity analysis can be performed on the fMRI data to find the active regions and the connectivity in the brain regions. Functional connectivity is defined as a simple temporal correlation between anatomically separate, active neural regions. Functional connectivity gives the statistical dependencies between regional time series. It is a statistical concept and is quantified using metrics like Correlation. In this study, a comparison is made between functional connectivity in the brain regions of long term meditation practitioners (LTP) and short-term meditation practitioners (STP) to see the differences and similarities in the connectivity patterns. From the analysis, it is evident that in fact there is a difference in connectivity between long term and short term practitioners and hence continuous practice of meditation can have long term effects.

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