Search results for: Ziad S. Saad

Items from 1 to 20 out of 23 results

article

Surface based electrode localization and standardized regions of interest for intracranial EEG

Michael S. Trotta, John Cocjin, Emily Whitehead, Srikanth Damera, more

Human Brain Mapping > 39 > 2 > 709 - 721

Intracranial recordings captured from subdural electrodes in patients with drug resistant epilepsy offer clinicians and researchers a powerful tool for examining neural activity in the human brain with high spatial and temporal precision. There are two major challenges, however, to interpreting these signals both within and across individuals. Anatomical distortions following implantation make accurately...

article

Brainhack: a collaborative workshop for the open neuroscience community

R. Cameron Craddock, Daniel S. Margulies, Pierre Bellec, B. Nolan Nichols, more

GigaScience > 2016 > 5 > 1 > 1-8

Brainhack events offer a novel workshop format with participant-generated content that caters to the rapidly growing open neuroscience community. Including components from hackathons and unconferences, as well as parallel educational sessions, Brainhack fosters novel collaborations around the interests of its attendees. Here we provide an overview of its structure, past events, and example projects...

article

Shifts in connectivity during procedural learning after motor cortex stimulation: A combined transcranial magnetic stimulation/functional magnetic resonance imaging study

Adam Steel, Sunbin Song, Devin Bageac, Kristine M. Knutson, more

Cortex > 2016 > 74 > C > 134-148

Inhibitory transcranial magnetic stimulation (TMS), of which continuous theta burst stimulation (cTBS) is a common form, has been used to inhibit cortical areas during investigations of their function. cTBS applied to the primary motor area (M1) depresses motor output excitability via a local effect and impairs procedural motor learning. This could be due to an effect on M1 itself and/or to changes...

article

DBSproc: An open source process for DBS electrode localization and tractographic analysis

Peter M. Lauro, Nora Vanegas‐Arroyave, Ling Huang, Paul A. Taylor, more

Human Brain Mapping > 37 > 1 > 422 - 433

Deep brain stimulation (DBS) is an effective surgical treatment for movement disorders. Although stimulation sites for movement disorders such as Parkinson's disease are established, the therapeutic mechanisms of DBS remain controversial. Recent research suggests that specific white‐matter tract and circuit activation mediates symptom relief. To investigate these questions, we have developed a patient‐specific...

article

Applications of multivariate modeling to neuroimaging group analysis: A comprehensive alternative to univariate general linear model

Gang Chen, Nancy E. Adleman, Ziad S. Saad, Ellen Leibenluft, more

NeuroImage > 2014 > 99 > C > 571-588

All neuroimaging packages can handle group analysis with t-tests or general linear modeling (GLM). However, they are quite hamstrung when there are multiple within-subject factors or when quantitative covariates are involved in the presence of a within-subject factor. In addition, sphericity is typically assumed for the variance–covariance structure when there are more than two levels in a within-subject...

article

Linear mixed-effects modeling approach to FMRI group analysis

Gang Chen, Ziad S. Saad, Jennifer C. Britton, Daniel S. Pine, more

NeuroImage > 2013 > 73 > Complete > 176-190

Conventional group analysis is usually performed with Student-type t-test, regression, or standard AN(C)OVA in which the variance–covariance matrix is presumed to have a simple structure. Some correction approaches are adopted when assumptions about the covariance structure is violated. However, as experiments are designed with different degrees of sophistication, these traditional methods can become...

article

Effects of image contrast on functional MRI image registration

Javier Gonzalez-Castillo, Kristen N. Duthie, Ziad S. Saad, Carlton Chu, more

NeuroImage > 2013 > 67 > Complete > 163-174

Lack of tissue contrast and existing inhomogeneous bias fields from multi-channel coils have the potential to degrade the output of registration algorithms; and consequently degrade group analysis and any attempt to accurately localize brain function. Non-invasive ways to improve tissue contrast in fMRI images include the use of low flip angles (FAs) well below the Ernst angle and longer repetition...

article

Effects of alcohol dependence on cortical thickness as determined by magnetic resonance imaging

Reza Momenan, Leah E. Steckler, Ziad S. Saad, Stefanie van Rafelghem, more

Psychiatry Research: Neuroimaging > 2012 > 204 > 2-3 > 101-111

Alterations of brain structures have been seen in patients suffering from drug abuse or mental disorders like schizophrenia. Similar changes in volume of brain structures have been observed in both alcoholic men and women. We examined the thickness of gray matter in the cerebral cortex in control men and women (n=69, 47 men) and alcohol-dependent subjects (n=130, 83 men) to test the hypothesis that...

article

SUMA

Ziad S. Saad, Richard C. Reynolds

NeuroImage > 2012 > 62 > 2 > 768-773

Surface-based brain imaging analysis offers the advantages of preserving the topology of cortical activation, increasing statistical power of group-level statistics, estimating cortical thickness, and visualizing with ease the pattern of activation across the whole cortex. SUMA is an open-source suite of programs for performing surface-based analysis and visualization. It was designed since its inception...

article

FMRI group analysis combining effect estimates and their variances

Gang Chen, Ziad S. Saad, Audrey R. Nath, Michael S. Beauchamp, more

NeuroImage > 2012 > 60 > 1 > 747-765

Conventional functional magnetic resonance imaging (FMRI) group analysis makes two key assumptions that are not always justified. First, the data from each subject is condensed into a single number per voxel, under the assumption that within-subject variance for the effect of interest is the same across all subjects or is negligible relative to the cross-subject variance. Second, it is assumed that...

article

Vector autoregression, structural equation modeling, and their synthesis in neuroimaging data analysis

Gang Chen, Daniel R. Glen, Ziad S. Saad, J. Paul Hamilton, more

Computers in Biology and Medicine > 2011 > 41 > 12 > 1142-1155

Vector autoregression (VAR) and structural equation modeling (SEM) are two popular brain-network modeling tools. VAR, which is a data-driven approach, assumes that connected regions exert time-lagged influences on one another. In contrast, the hypothesis-driven SEM is used to validate an existing connectivity model where connected regions have contemporaneous interactions among them. We present the...

article

Segmentation priors from local image properties: Without using bias field correction, location-based templates, or registration

Andrej Vovk, Robert W. Cox, Janez Stare, Dusan Suput, more

NeuroImage > 2011 > 55 > 1 > 142-152

We present a novel approach for generating information about a voxel's tissue class membership based on its signature—a collection of local image textures estimated over a range of neighborhood sizes. The approach produces a form of tissue class priors that can be used to initialize and regularize image segmentation. The signature-based approach is a departure from current location-based methods,...

article

Mapping sources of correlation in resting state FMRI, with artifact detection and removal

Hang Joon Jo, Ziad S. Saad, W. Kyle Simmons, Lydia A. Milbury, more

NeuroImage > 2010 > 52 > 2 > 571-582

Many components of resting-state (RS) FMRI show non-random structure that has little to do with neural connectivity but can covary over multiple brain structures. Some of these signals originate in physiology and others are hardware-related. One artifact discussed herein may be caused by defects in the receive coil array or the RF amplifiers powering it. During a scan, this artifact results in small...

article

Defining functional SMA and pre-SMA subregions in human MFC using resting state fMRI: Functional connectivity-based parcellation method

Jae-Hun Kim, Jong-Min Lee, Hang Joon Jo, Sook Hui Kim, more

NeuroImage > 2010 > 49 > 3 > 2375-2386

Noninvasive parcellation of the human cerebral cortex is an important goal for understanding and examining brain functions. Recently, the patterns of anatomical connections using diffusion tensor imaging (DTI) have been used to parcellate brain regions. Here, we present a noninvasive parcellation approach that uses “functional fingerprints” obtained by correlation measures on resting state functional...

article

Functional but not structural changes associated with learning: An exploration of longitudinal Voxel-Based Morphometry (VBM)

Adam G. Thomas, Sean Marrett, Ziad S. Saad, Douglas A. Ruff, more

NeuroImage > 2009 > 48 > 1 > 117-125

Voxel-Based Morphometry (VBM) has been used for several years to study differences in brain structure between populations. Recently, a longitudinal version of VBM has been used to show changes in gray matter associated with relatively short periods of training. In the present study we use fMRI and three different standard implementations of longitudinal VBM: SPM2, FSL, and SPM5 to assess functional...

article

A new method for improving functional-to-structural MRI alignment using local Pearson correlation

Ziad S. Saad, Daniel R. Glen, Gang Chen, Michael S. Beauchamp, more

NeuroImage > 2009 > 44 > 3 > 839-848

Accurate registration of Functional Magnetic Resonance Imaging (FMRI) T2⁎-weighted volumes to same-subject high-resolution T1-weighted structural volumes is important for Blood Oxygenation Level Dependent (BOLD) FMRI and crucial for applications such as cortical surface-based analyses and pre-surgical planning. Such registration is generally implemented by minimizing a cost functional, which measures...

article

Functional neuroanatomy of human voluntary cough and sniff production

Kristina Simonyan, Ziad S. Saad, Torrey M.J. Loucks, Christopher J. Poletto, more

NeuroImage > 2007 > 37 > 2 > 401-409

Cough and sniff are both spontaneous respiratory behaviors that can be initiated voluntarily in humans. Disturbances of cough may be life threatening, while inability to sniff impairs the sense of smell in neurological patients. Cortical mechanisms of voluntary cough and sniff production have been predicted to exist; however, the localization and function of supramedullary areas responsible for these...

article

The spatial extent of the BOLD response

Ziad S. Saad, Kristina M. Ropella, Edgar A. DeYoe, Peter A. Bandettini

NeuroImage > 2003 > 19 > 1 > 132-144

Functional magnetic resonance imaging is routinely used to localize brain function, with multiple brain scans averaged together to reveal activation volumes. In this study, we examine the seldom-studied effect of multiple scan averaging on the extent of activation volume. Using restricted visual field stimulation, we obtained a large number of scan repetitions and analyzed changes in activation volume...

article

Estimation of FMRI response delays

Ziad S. Saad, Edgar A. DeYoe, Kristina M. Ropella

NeuroImage > 2003 > 18 > 2 > 494-504

We present an efficient algorithm using the Hilbert Transform for estimating the delay of the BOLD response to neuronal stimulation. With minimal additional computations, the algorithm estimates parameters generated in the widely used cross-correlation method and simplifies the interpolation required to estimate the response delay from the cross-correlation function. We examined errors in the Hilbert-based...

article

Dynamic nonlinearities in BOLD contrast: neuronal or hemodynamic?

Peter A. Bandettini, Rasmus M. Birn, Dan Kelley, Ziad S. Saad

International Congress Series > 2002 > 1235 > Complete > 73-85

A primary goal of the functional MRI (fMRI) methods development is to characterize the relationship between the blood oxygenation level-dependent (BOLD) signal changes and neuronal activation. Recent studies of blood oxygenation level-dependent (BOLD) signal responses have demonstrated nonlinear behavior with respect to stimulus duration. Specifically, shorter duration stimuli produce larger signal...

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Keywords

FUNCTIONAL MAGNETIC RESONANCE IMAGING (3)
AFNI (2)
BOLD FMRI (2)
FMRI GROUP ANALYSIS (2)
LINEARITY (2)
MOTOR (2)
STIMULUS DURATION (2)
VISUAL (2)
ACTIVATION LATENCY (1)
ACTIVATION VOLUME (1)
ALCOHOLISM (1)
AN(C)OVA (1)
ARTIFACT CORRECTION (1)
BALLOON MODEL (1)
BIAS FIELD (1)
BIOMARKER (1)
CEREBRAL CORTEX (1)
CLASSIFICATION (1)
COLLABORATION (1)
CONNECTIVITY ANALYSIS (1)
CONTINUOUS THETA BURST STIMULATION (1)
CORTICAL SURFACE MODELS (1)
CORTICAL THICKNESS (1)
DATA SHARING (1)
DEEP BRAIN STIMULATION (DBS) (1)
DIFFUSION TENSOR IMAGING (DTI) (1)
EFFECT ESTIMATE PRECISION OR RELIABILITY (1)
ELECTROCORTICOGRAPHY (1)
FEATURES (1)
FMRI RETINOTOPY (1)
FREESURFER (1)
FUNCTIONAL CONNECTIVITY (1)
FUNCTIONAL MRI (1)
GLM (1)
GRAY MATTER (1)
HACKATHON (1)
HIGH GAMMA‐BAND ACTIVITY (1)
HILBERT TRANSFORM (1)
HUMAN BRAIN (1)
ICC (1)
INTERACTIVE FMRI RESTING STATE ANALYSIS (1)
LME (1)
MAGNETIC RESONANCE IMAGING (MRI) (1)
MIXED-EFFECTS MULTILEVEL ANALYSIS (MEMA) (1)
MRI (1)
MRI METHODS/TECHNIQUES (1)
MULTIVARIATE CLASSIFICATION (1)
NETWORKING (1)
NEUROSCIENCE (1)
NEUROSTIMULATION (1)
NOISE REDUCTION (1)
OPEN SCIENCE (1)
OUTLIERS (1)
PARKINSON'S DISEASE (PD) (1)
PHASE ESTIMATION (1)
PRIMARY MOTOR CORTEX (1)
PRIORS (1)
PROBABILISTIC SEQUENCE LEARNING (1)
PROCEDURAL LEARNING (1)
R (1)
RESPIRATORY CONTROL (1)
RESTING STATE (1)
RESTRICTED MAXIMUM LIKELIHOOD (REML) (1)
SEGMENTATION (1)
SPECTRAL LEAKAGE (1)
STRUCTURAL EQUATION MODELING (SEM) (1)
STRUCTURAL VECTOR AUTOREGRESSION (SVAR) (1)
SUBDURAL ELECTRODES (1)
SUPPORT VECTOR MACHINES (1)
SURFACE ROI DRAWING (1)
SURFACE-BASED GROUP ANALYSIS (1)
SURFACE-BASED SMOOTHING (1)
SURFACE‐BASED NORMALIZATION (1)
TEXTURE (1)
UNCONFERENCE (1)
VECTOR AUTOREGRESSION (VAR) (1)
VISUAL CORTEX (1)
WEIGHTED LEAST SQUARES (WLS) (1)
more

Data set

Elsevier (20)
Wiley (2)
Springer (1)

INFONA - science communication portal

Search results for: Ziad S. Saad

Surface based electrode localization and standardized regions of interest for intracranial EEG

Brainhack: a collaborative workshop for the open neuroscience community

Shifts in connectivity during procedural learning after motor cortex stimulation: A combined transcranial magnetic stimulation/functional magnetic resonance imaging study

DBSproc: An open source process for DBS electrode localization and tractographic analysis

Applications of multivariate modeling to neuroimaging group analysis: A comprehensive alternative to univariate general linear model

Linear mixed-effects modeling approach to FMRI group analysis

Effects of image contrast on functional MRI image registration

Effects of alcohol dependence on cortical thickness as determined by magnetic resonance imaging

SUMA

FMRI group analysis combining effect estimates and their variances

Vector autoregression, structural equation modeling, and their synthesis in neuroimaging data analysis

Segmentation priors from local image properties: Without using bias field correction, location-based templates, or registration

Mapping sources of correlation in resting state FMRI, with artifact detection and removal

Defining functional SMA and pre-SMA subregions in human MFC using resting state fMRI: Functional connectivity-based parcellation method

Functional but not structural changes associated with learning: An exploration of longitudinal Voxel-Based Morphometry (VBM)

A new method for improving functional-to-structural MRI alignment using local Pearson correlation

Functional neuroanatomy of human voluntary cough and sniff production

The spatial extent of the BOLD response

Estimation of FMRI response delays

Dynamic nonlinearities in BOLD contrast: neuronal or hemodynamic?

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