133 research outputs found
Methods for cleaning the BOLD fMRI signal
Available online 9 December 2016
http://www.sciencedirect.com/science/article/pii/S1053811916307418?via%3Dihubhttp://www.sciencedirect.com/science/article/pii/S1053811916307418?via%3DihubBlood oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI) has rapidly become a popular technique for the investigation of brain function in healthy individuals, patients as well as in animal studies. However, the BOLD signal arises from a complex mixture of neuronal, metabolic and vascular processes, being therefore an indirect measure of neuronal activity, which is further severely corrupted by multiple non-neuronal fluctuations of instrumental, physiological or subject-specific origin. This review aims to provide a comprehensive summary of existing methods for cleaning the BOLD fMRI signal. The description is given from a methodological point of view, focusing on the operation of the different techniques in addition to pointing out the advantages and limitations in their application. Since motion-related and physiological noise fluctuations are two of the main noise components of the signal, techniques targeting their removal are primarily addressed, including both data-driven approaches and using external recordings. Data-driven approaches, which are less specific in the assumed model and can simultaneously reduce multiple noise fluctuations, are mainly based on data decomposition techniques such as principal and independent component analysis. Importantly, the usefulness of strategies that benefit from the information available in the phase component of the signal, or in multiple signal echoes is also highlighted. The use of global signal regression for denoising is also addressed. Finally, practical recommendations regarding the optimization of the preprocessing pipeline for the purpose of denoising and future venues of research are indicated. Through the review, we summarize the importance of signal denoising as an essential step in the analysis pipeline of task-based and resting state fMRI studies.This work was supported by the Spanish Ministry of Economy and
Competitiveness [Grant PSI 2013–42343 Neuroimagen Multimodal],
the Severo Ochoa Programme for Centres/Units of Excellence in R & D
[SEV-2015-490], and the research and writing of the paper were
supported by the NIMH and NINDS Intramural Research Programs
(ZICMH002888) of the NIH/HHS
Closing eyes during auditory memory retrieval modulates alpha rhythm but does not alter tau rhythm
Available online 20 April 2019The alpha power increase that occurs when the eyes are closed is one of the most well-known effects in human electrophysiology. In particular, previous psychological studies have investigated whether eye closure can boost memory performance under certain circumstances, providing contradictory evidence across sensory input modalities. Although alpha power is modulated during different phases of memory and these modulations are correlated with performance, few studies have reported on the relationship between eye closure, memory, and alpha-band power. The present study investigates the influence of eye closure while participants (n = 21) performed an auditory recognition memory task with spoken words during the recording of magnetoencephalography (MEG) data. Our results showed no evidence for a behavioural effect of eye closure in the performance of the task. In addition, electrophysiological responses to the stimuli showed the expected alpha event-related desynchronization (ERD) 0.5–1 s and a high-alpha/beta event-related synchronization (ERS) 1–2 s after word onset. The data showed the expected memory effect, i.e. remembered words elicited greater 10 Hz ERD than forgotten words in the brain regions typically associated with the language network, suggesting a modulation of tau rhythm. Eye closure modulated alpha rhythm only in posterior-parietal and occipital regions. The lack of interaction and the different localizations found for modulations of tau and classical alpha rhythms suggests that these rhythms play distinct functional roles in memory performance.This research was possible thanks to the support of the “Severo Ochoa Program
for Centres/Units of Excellence in R&D” (SEV-2015-490). AB was
supported by the Basque Government (Eusko Jaurlaritza) under the
program “Ikertzaile ez doktoreen doktoretza-aurreko formakuntza programa”
( PRE_2015_2_0208), CCG was supported by the Spanish Ministry
of Economy and Competitiveness through the Juan de la Cierva (IJCI-
2014-20821) and Ramon y Cajal (RYC-2017-21845) Fellowships
Effect of prewhitening in resting-state functional near-infrared spectroscopy data
Published: 24 October 2018Near-infrared spectroscopy (NIRS) offers the potential to characterize resting-state functional connectivity (RSFC) in populations that are not easily assessed otherwise, such as young infants. In addition to the advantages of NIRS, one should also consider that the RS-NIRS signal requires specific data preprocessing and analysis. In particular, the RS-NIRS signal shows a colored frequency spectrum, which can be observed as temporal autocorrelation, thereby introducing spurious correlations. To address this issue, prewhitening of the RS-NIRS signal has been recently proposed as a necessary step to remove the signal temporal autocorrelation and therefore reduce false-discovery rates. However, the impact of this step on the analysis of experimental RS-NIRS data has not been thoroughly assessed prior to the present study. Here, the results of a standard preprocessing pipeline in a RS-NIRS dataset acquired in infants are compared with the results after incorporating two different prewhitening algorithms. Our results with a standard preprocessing replicated previous studies. Prewhitening altered RSFC patterns and disrupted the antiphase relationship between oxyhemoglobin and deoxyhemoglobin. We conclude that a better understanding of the effect of prewhitening on RS-NIRS data is still needed before directly considering its incorporation to the standard preprocessing pipeline.This research was possible due to the support of the Basque Government predoctoral grant PRE_2016_2_0188 to Borja Blanco, as well as the support of the Spanish Ministry of Economy and Competitiveness through the project PSI 2014-54512-P, Juan de la Cierva Fellowship (IJCI-2014-20821) and the “Severo Ochoa” Programme for Centres/Units of Excellence in R & D (SEV-2015-490)
A LOW RANK AND SPARSE PARADIGM FREE MAPPING ALGORITHM FOR DECONVOLUTION OF FMRI DATA
Date Added to IEEE Xplore: 25 May 2021Current deconvolution algorithms for functional magnetic resonance
imaging (fMRI) data are hindered by widespread signal changes
arising from motion or physiological processes (e.g. deep breaths)
that can be interpreted incorrectly as neuronal-related hemodynamic
events. This work proposes a novel deconvolution approach that
simultaneously estimates global signal fluctuations and neuronalrelated
activity with no prior information about the timings of the
blood oxygenation level-dependent (BOLD) events by means of a
low rank plus sparse decomposition algorithm. The performance
of the proposed method is evaluated on simulated and experimental
fMRI data, and compared with state-of-the-art sparsity-based deconvolution
approaches and with a conventional analysis that is aware of
the temporal model of the neuronal-related activity. We demonstrate
that the novel low-rank and sparse paradigm free mapping algorithm
can estimate global signal fluctuations related to motion in our task,
while estimating the neuronal-related activity with high fidelity
Paradigm free mapping: detection and characterization of single trial fMRI BOLD responses without prior stimulus information
The increased contrast to noise ratio available at Ultrahigh (7T) Magnetic Resonance Imaging (MRI) allows mapping in space and time the brain's response to single trial events with functional MRI (fMRI) based on the Blood Oxygenation Level Dependent (BOLD) contrast. This thesis primarily concerns with the development of techniques to detect and characterize single trial event-related BOLD responses without prior paradigm information, Paradigm Free Mapping, and assess variations in BOLD sensitivity across brain regions at high field fMRI.
Based on a linear haemodynamic response model, Paradigm Free Mapping (PFM) techniques rely on the deconvolution of the neuronal-related signal driving the BOLD effect using regularized least squares estimators. The first approach, named PFM, builds on the ridge regression estimator and spatio-temporal t-statistics to detect statistically significant changes in the deconvolved fMRI signal. The second method, Sparse PFM, benefits from subset selection features of the LASSO and Dantzig Selector estimators that automatically detect the single trial BOLD responses by promoting a sparse deconvolution of the signal. The third technique, Multicomponent PFM, exploits further the benefits of sparse estimation to decompose the fMRI signal into a haemodynamical component and a baseline component using the morphological component analysis algorithm.
These techniques were evaluated in simulations and experimental fMRI datasets, and the results were compared with well-established fMRI analysis methods. In particular, the methods developed here enabled the detection of single trial BOLD responses to visually-cued and self-paced finger tapping responses without prior information of the events. The potential application of Sparse PFM to identify interictal discharges in idiopathic generalized epilepsy was also investigated. Furthermore, Multicomponent PFM allowed us to extract cardiac and respiratory fluctuations of the signal without the need of physiological monitoring.
To sum up, this work demonstrates the feasibility to do single trial fMRI analysis without prior stimulus or physiological information using PFM techniques
Paradigm free mapping: detection and characterization of single trial fMRI BOLD responses without prior stimulus information
The increased contrast to noise ratio available at Ultrahigh (7T) Magnetic Resonance Imaging (MRI) allows mapping in space and time the brain's response to single trial events with functional MRI (fMRI) based on the Blood Oxygenation Level Dependent (BOLD) contrast. This thesis primarily concerns with the development of techniques to detect and characterize single trial event-related BOLD responses without prior paradigm information, Paradigm Free Mapping, and assess variations in BOLD sensitivity across brain regions at high field fMRI.
Based on a linear haemodynamic response model, Paradigm Free Mapping (PFM) techniques rely on the deconvolution of the neuronal-related signal driving the BOLD effect using regularized least squares estimators. The first approach, named PFM, builds on the ridge regression estimator and spatio-temporal t-statistics to detect statistically significant changes in the deconvolved fMRI signal. The second method, Sparse PFM, benefits from subset selection features of the LASSO and Dantzig Selector estimators that automatically detect the single trial BOLD responses by promoting a sparse deconvolution of the signal. The third technique, Multicomponent PFM, exploits further the benefits of sparse estimation to decompose the fMRI signal into a haemodynamical component and a baseline component using the morphological component analysis algorithm.
These techniques were evaluated in simulations and experimental fMRI datasets, and the results were compared with well-established fMRI analysis methods. In particular, the methods developed here enabled the detection of single trial BOLD responses to visually-cued and self-paced finger tapping responses without prior information of the events. The potential application of Sparse PFM to identify interictal discharges in idiopathic generalized epilepsy was also investigated. Furthermore, Multicomponent PFM allowed us to extract cardiac and respiratory fluctuations of the signal without the need of physiological monitoring.
To sum up, this work demonstrates the feasibility to do single trial fMRI analysis without prior stimulus or physiological information using PFM techniques
Phonatory and articulatory representations of speech production in cortical and subcortical fMRI responses
Speaking involves coordination of multiple neuromotor systems, including respiration, phonation and articulation. Developing non-invasive imaging methods to study how the brain controls these systems is critical for understanding the neurobiology of speech production. Recent models and animal research suggest that regions beyond the primary motor cortex (M1) help orchestrate the neuromotor control needed for speaking, including cortical and sub-cortical regions. Using contrasts between speech conditions with controlled respiratory behavior, this fMRI study investigates articulatory gestures involving the tongue, lips and velum (i.e., alveolars versus bilabials, and nasals versus orals), and phonatory gestures (i.e., voiced versus whispered speech). Multivariate pattern analysis (MVPA) was used to decode articulatory gestures in M1, cerebellum and basal ganglia. Furthermore, apart from confirming the role of a mid-M1 region for phonation, we found that a dorsal M1 region, linked to respiratory control, showed significant differences for voiced compared to whispered speech despite matched lung volume observations. This region was also functionally connected to tongue and lip M1 seed regions, underlying its importance in the coordination of speech. Our study confirms and extends current knowledge regarding the neural mechanisms underlying neuromotor speech control, which hold promise to study neural dysfunctions involved in motor-speech disorders non-invasively.Tis work was supported by the Spanish Ministry of Economy and Competitiveness through the Juan de la Cierva
Fellowship (FJCI-2015-26814), and the Ramon y Cajal Fellowship (RYC-2017- 21845), the Spanish State Research
Agency through the BCBL “Severo Ochoa” excellence accreditation (SEV-2015-490), the Basque Government
(BERC 2018- 2021) and the European Union’s Horizon 2020 research and innovation program under the Marie
Sklodowska-Curie grant (No 799554).info:eu-repo/semantics/publishedVersio
Enhanced top-down sensorimotor processing in somatic anxiety
Published: 25 July 2022Functional neuroimaging research on anxiety has traditionally focused on brain networks associated with the psychological aspects of anxiety. Here, instead, we target the somatic aspects of anxiety. Motivated by the growing appreciation that top-down cortical processing plays a crucial role in perception and action, we used resting-state functional MRI data from the Human Connectome Project and Dynamic Causal Modeling (DCM) to characterize effective connectivity among hierarchically organized regions in the exteroceptive, interoceptive, and motor cortices. In people with high (fear-related) somatic arousal, top-down effective connectivity was enhanced in all three networks: an observation that corroborates well with the phenomenology of anxiety. The anxiety-associated changes in connectivity were sufficiently reliable to predict whether a new participant has mild or severe somatic anxiety. Interestingly, the increase in top-down connections to sensorimotor cortex were not associated with fear affect scores, thus establishing the (relative) dissociation between somatic and cognitive dimensions of anxiety. Overall, enhanced top-down effective connectivity in sensorimotor cortices emerges as a promising and quantifiable candidate marker of trait somatic anxiety.This research was supported by the Basque Government through the BERC
2018–2021 program, by the Spanish Ministry of Science, Innovation, and Universities
(BCBL Severo Ochoa excellence accreditation SEV- 2015–0490 and BCAM Severo
Ochoa accreditation SEV-2017–0718), the Spanish Ministry of Economy and
Competitiveness (Ramon y Cajal Fellowship, RYC-2017–21845) and the project
MTM2017–82379- R(AEI/FEDER,UE) (principal investigator: Dr. Maria Xose Rodriguez,
BCAM). KJF was supported by funding for the Wellcome Centre for Human
Neuroimaging (Ref: 205103/Z/16/Z), a Canada-UK Artificial Intelligence Initiative (Ref:
ES/T01279X/1) and the European Union’s Horizon 2020 Framework Programme for
Research and Innovation under the Specific Grant Agreement No. 945539 (Human
Brain Project SGA3)
Hemodynamic Deconvolution Demystified: Sparsity-Driven Regularization at Work
Deconvolution of the hemodynamic response is an important step to access
short timescales of brain activity recorded by functional magnetic resonance
imaging (fMRI). Albeit conventional deconvolution algorithms have been around
for a long time (e.g., Wiener deconvolution), recent state-of-the-art methods
based on sparsity-pursuing regularization are attracting increasing interest to
investigate brain dynamics and connectivity with fMRI. This technical note
revisits the main concepts underlying two main methods, Paradigm Free Mapping
and Total Activation, in the most accessible way. Despite their apparent
differences in the formulation, these methods are theoretically equivalent as
they represent the synthesis and analysis sides of the same problem,
respectively. We demonstrate this equivalence in practice with their
best-available implementations using both simulations, with different
signal-to-noise ratios, and experimental fMRI data acquired during a motor task
and resting-state. We evaluate the parameter settings that lead to equivalent
results, and showcase the potential of these algorithms compared to other
common approaches. This note is useful for practitioners interested in gaining
a better understanding of state-of-the-art hemodynamic deconvolution, and aims
to answer questions that practitioners often have regarding the differences
between the two methods.Comment: 18 pages, 6 figures, submitted to Apertur
Lag-Optimized Blood Oxygenation Level Dependent Cerebrovascular Reactivity Estimates Derived From Breathing Task Data Have a Stronger Relationship With Baseline Cerebral Blood Flow
Published: 15 June 2022Cerebrovascular reactivity (CVR), an important indicator of cerebrovascular health,
is commonly studied with the Blood Oxygenation Level Dependent functional MRI
(BOLD-fMRI) response to a vasoactive stimulus. Theoretical and empirical evidence
suggests that baseline cerebral blood flow (CBF) modulates BOLD signal amplitude
and may influence BOLD-CVR estimates. We address how acquisition and modeling
choices affect the relationship between baseline cerebral blood flow (bCBF) and
BOLD-CVR: whether BOLD-CVR is modeled with the inclusion of a breathing task,
and whether BOLD-CVR amplitudes are optimized for hemodynamic lag effects. We
assessed between-subject correlations of average GM values and within-subject spatial
correlations across cortical regions. Our results suggest that a breathing task addition to
a resting-state acquisition, alongside lag-optimization within BOLD-CVR modeling, can
improve BOLD-CVR correlations with bCBF, both between- and within-subjects, likely
because these CVR estimates are more physiologically accurate. We report positive
correlations between bCBF and BOLD-CVR, both between- and within-subjects. The
physiological explanation of this positive correlation is unclear; research with larger
samples and tightly controlled vasoactive stimuli is needed. Insights into what drives
variability in BOLD-CVR measurements and related measurements of cerebrovascular
function are particularly relevant when interpreting results in populations with altered
vascular and/or metabolic baselines or impaired cerebrovascular reserve.This work was supported by the Center for Translational Imaging
at Northwestern University. The authors disclosed receipt of
the following financial support for the research, authorship,
and/or publication of this article: This research was supported by
the Eunice Kennedy Shriver National Institute of Child Health
and Human Development of the National Institutes of Health
[K12HD073945]. KZ was supported by an NIH-funded training
program [T32EB025766]. SM was supported by the European
Union’s Horizon 2020 research and innovation program [Marie
Skłodowska-Curie grant agreement No. 713673] and a fellowship
from La Caixa Foundation [ID 100010434, fellowship code
LCF/BQ/IN17/11620063]. CC-G was supported by the Spanish
Ministry of Economy and Competitiveness [Ramon y Cajal
Fellowship, RYC2017-21845], the Basque Government [BERC
2018-2021 and PIBA_2019_104], and the Spanish Ministry
of Science, Innovation and Universities [MICINN; PID2019-
105520GB-100]
- …