The Effect of Modular Degeneracy on Neuroimaging Data.

The concept of community structure, based on modularity, is widely used to address many systems-level queries. However, its algorithm, based on the maximization of the modularity index Q, suffers from degeneracy problem, which yields a set of different possible solutions. In this work, we explored the degeneracy effect of modularity principle on resting-state functional magnetic resonance imaging (rsfMRI) data, when it is used to parcellate the cingulate cortex using data from the Human Connectome Project.

Sex-difference in the association between social drinking, structural brain aging and cognitive function in older individuals free of cognitive impairment.

Background: We investigated a potential sex difference in the relationship between alcohol consumption, brain age gap and cognitive function in older adults without cognitive impairment from the population-based Mayo Clinic Study of Aging.

Methods: Self-reported alcohol consumption was collected using the food-frequency questionnaire. A battery of cognitive testing assessed performance in four different domains: attention, memory, language, and visuospatial.

Low frequency repetitive transcranial magnetic stimulation to the right dorsolateral prefrontal cortex engages thalamus, striatum, and the default mode network.

The positive treatment outcomes of low frequency (LF) repetitive transcranial magnetic stimulation (rTMS) when applied over the right dorsolateral prefrontal cortex (DLPFC) in treatment-refractory depression has been verified. However, the mechanism of action behind these results have not been well-explored. In this work we used simultaneous functional magnetic resonance imaging (fMRI) during TMS to explore the effect of LF rTMS on brain activity when applied to the right [RDLPFC1 (MNI: 50, 30, 36)] and left DLPFC sites [LDLPFC1 (MNI: -50, 30, 36), LDLPFC2 (MNI: -41, 16, 54)].

High-Frequency Transcranial Magnetic Stimulation Combined With Functional Magnetic Resonance Imaging Reveals Distinct Activation Patterns Associated With Different Dorsolateral Prefrontal Cortex Stimulation Sites.

Objectives: Transcranial magnetic stimulation (TMS) has been extensively used for the treatment of depression, obsessive-compulsive disorder, and certain neurologic disorders. Despite having promising treatment efficacy, the fundamental neural mechanisms of TMS remain understudied.

Materials And Methods: In this study, 15 healthy adult participants received simultaneous TMS and functional magnetic resonance imaging to map the modulatory effect of TMS when it was applied over three different sites in the dorsolateral prefrontal cortex.

Simultaneous Transcranial Magnetic Stimulation and Functional Magnetic Resonance Imaging: Aspects of Technical Implementation.

The simultaneous transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) offers a unique opportunity to non-invasively stimulate brain circuits while simultaneously monitoring changes in brain activity. However, to take advantage of this multimodal technique, some technical issues need to be considered/addressed. In this work, we evaluated technical issues associated with the setup and utilization of this multimodal tool, such as the use of a large single-channel radio frequency (rf) coil, and the artifacts induced by TMS when interleaved with the echo-planar imaging (EPI) sequence.

Short-term nicotine deprivation alters dorsal anterior cingulate glutamate concentration and concomitant cingulate-cortical functional connectivity.

Most cigarette smokers who wish to quit too often relapse within the first few days of abstinence, primarily due to the aversive aspects of the nicotine withdrawal syndrome (NWS), which remains poorly understood. Considerable research has suggested that the dorsal anterior cingulate cortex (dACC) plays a key role in nicotine dependence, with its functional connections between other brain regions altered as a function of trait addiction and state withdrawal. The flow of information between dACC and fronto-striatal regions is secured through different pathways, the vast majority of which are glutamatergic.

Subcortical surface morphometry in substance dependence: An ENIGMA addiction working group study.

While imaging studies have demonstrated volumetric differences in subcortical structures associated with dependence on various abused substances, findings to date have not been wholly consistent. Moreover, most studies have not compared brain morphology across those dependent on different substances of abuse to identify substance-specific and substance-general dependence effects. By pooling large multinational datasets from 33 imaging sites, this study examined subcortical surface morphology in 1628 nondependent controls and 2277 individuals with dependence on alcohol, nicotine, cocaine, methamphetamine, and/or cannabis.

Factors Affecting Detection Power of Blood Oxygen-Level Dependent Signal in Resting-State Functional Magnetic Resonance Imaging Using High-Resolution Echo-Planar Imaging.

Latest developments in magnetic resonance imaging (MRI) hardware and software have significantly improved image acquisition for functional MRI (fMRI) techniques, including resting-state fMRI (rsfMRI). Specifically, with improvements in gradient and radiofrequency coils and advances in pulse sequence designs, functional images with higher spatiotemporal resolution can be achieved. However, while smaller voxel size has the benefit of resolving finer brain structures, it also decreases voxel-wise signal-to-noise ratio (SNR) and, subsequently, temporal SNR (tSNR), which is critical for the sensitivity of fMRI.

Mega-Analysis of Gray Matter Volume in Substance Dependence: General and Substance-Specific Regional Effects.

Objective: Although lower brain volume has been routinely observed in individuals with substance dependence compared with nondependent control subjects, the brain regions exhibiting lower volume have not been consistent across studies. In addition, it is not clear whether a common set of regions are involved in substance dependence regardless of the substance used or whether some brain volume effects are substance specific. Resolution of these issues may contribute to the identification of clinically relevant imaging biomarkers.

Effect of combined naltrexone and bupropion therapy on the brain's functional connectivity.

Background: The control of food intake in environments with easy access to highly rewarding foods is challenging to most modern societies. The combination of sustained release (SR) naltrexone and SR bupropion (NB32) has been used in weight-loss and obesity management. However, the effects of NB32 on the brain circuits implicated in the regulation of food intake are unknown.

Graph theory reveals amygdala modules consistent with its anatomical subdivisions.

Similarities on the cellular and neurochemical composition of the amygdaloid subnuclei suggests their clustering into subunits that exhibit unique functional organization. The topological principle of community structure has been used to identify functional subnetworks in neuroimaging data that reflect the brain effective organization. Here we used modularity to investigate the organization of the amygdala using resting state functional magnetic resonance imaging (rsfMRI) data.

Overlapping patterns of brain activation to food and cocaine cues in cocaine abusers: association to striatal D2/D3 receptors.

Cocaine, through its activation of dopamine (DA) signaling, usurps pathways that process natural rewards. However, the extent to which there is overlap between the networks that process natural and drug rewards and whether DA signaling associated with cocaine abuse influences these networks have not been investigated in humans. We measured brain activation responses to food and cocaine cues with fMRI, and D2/D3 receptors in the striatum with [11C]raclopride and Positron emission tomography in 20 active cocaine abusers.

Cytotoxicity, cytocompatibility, cell-labeling efficiency, and in vitro cellular magnetic resonance imaging of gadolinium-catalyzed single-walled carbon nanotubes.

Cell tracking by magnetic resonance imaging (MRI) is an emerging technique that typically requires the use of MRI contrast agents (CAs). A MRI CA for cellular imaging should label cells efficiently at potentially safe concentrations, have high relaxivity, and not affect the cellular machinery. In this article, we report the cytotoxicity, cytocompatibility, and cell labeling efficiency in NIH/3T3 fibroblasts of novel, single-walled carbon nanotubes synthesized using gadolinium nanoparticles as catalysts (Gd-SWCNTs).

Computerized MRS voxel registration and partial volume effects in single voxel 1H-MRS.

Partial volume effects in proton magnetic resonance spectroscopy in the brain have been studied previously in terms of proper water concentration calculations, but there is a lack of disclosure in terms of voxel placement techniques that would affect the calculations. The purpose of this study is to facilitate a fully automated MRS voxel registration method which is time efficient, accurate, and can be extended to all imaging modalities. A total of thirteen healthy adults underwent single voxel 1H-MRS scans in 3.

Induced magnetic force in human heads exposed to 4 T MRI.

Purpose: To map the distribution of the magnetic force induced in the human head during magnetic resonance imaging (MRI) at 4 T for a large group of healthy volunteers.

Materials And Methods: The magnetic field distribution in the head of 100 men and 18 women was mapped using phase mapping techniques. Statistical parametric mapping methods using a family-wise error (FWE) corrected threshold P < 0.

Effects of low-field magnetic stimulation on brain glucose metabolism.

Echo planar imaging (EPI), the gold standard technique for functional MRI (fMRI), is based on fast magnetic field gradient switching. These time-varying magnetic fields induce electric (E) fields in the brain that could influence neuronal activity; but this has not been tested. Here we assessed the effects of EPI on brain glucose metabolism (marker of brain function) using PET and 18F 2-fluoro-2-deoxy-D-glucose ((18)FDG).

Thalamo-cortical dysfunction in cocaine abusers: implications in attention and perception.

Cocaine affects sensory perception and attention, but little is known about the neural substrates underlying these effects in the human brain. We used functional magnetic resonance imaging (fMRI) and a sustained visuospatial attention task to assess if the visual attention network is dysfunctional in cocaine abusers (n=14) compared to age-, gender-, and education-matched controls (n=14). Compared with controls, cocaine abusers showed (1) hypo-activation of the thalamus, which may reflect noradrenergic and/or dopaminergic deficits; (2) hyper-activation in occipital and prefrontal cortices, which may reflect increased visual cortical processing to compensate for inefficient visual thalamic processing; and (3) larger deactivation of parietal and frontal regions possibly to support the larger hemodynamic supply to the hyper-activated brain regions.

Is decreased prefrontal cortical sensitivity to monetary reward associated with impaired motivation and self-control in cocaine addiction?

Objective: This study attempted to examine the brain's sensitivity to monetary rewards of different magnitudes in cocaine abusers and to study its association with motivation and self-control.

Method: Sixteen cocaine abusers and 13 matched healthy comparison subjects performed a forced-choice task under three monetary value conditions while brain activation was measured with functional magnetic resonance imaging. Objective measures of state motivation were assessed by reaction time and accuracy, and subjective measures were assessed by self-reports of task engagement.

Macrovascular contribution in activation patterns of working memory.

Brain activation maps of blood oxygenation level dependent (BOLD) signals during functional magnetic resonance imaging (fMRI) are sensitive to unwanted contributions from large vessels. Most BOLD-fMRI studies are based on a stimulus-correlated modulation of the MRI signal amplitude that is sensitive to desired microvascular effects and unwanted macrovascular effects. Aiming to suppress macrovascular effects in activation patterns, this BOLD-fMRI study evaluates brain activation during a verbal working memory task (2-back) in healthy volunteers (n=18) using the amplitude and phase components of the MRI signal.

Common deactivation patterns during working memory and visual attention tasks: an intra-subject fMRI study at 4 Tesla.

This parametric functional magnetic resonance imaging (fMRI) study investigates the balance of negative and positive fMRI signals in the brain. A set of visual attention (VA) and working memory (WM) tasks with graded levels of difficulty was used to deactivate separate but overlapping networks that include the frontal, temporal, occipital, and limbic lobes; regions commonly associated with auditory and emotional processing. Brain activation (% signal change and volume) was larger for VA tasks than for WM tasks, but deactivation was larger for WM tasks.

Magnetic field shift due to mechanical vibration in functional magnetic resonance imaging.

Mechanical vibrations of the gradient coil system during readout in echo-planar imaging (EPI) can increase the temperature of the gradient system and alter the magnetic field distribution during functional magnetic resonance imaging (fMRI). This effect is enhanced by resonant modes of vibrations and results in apparent motion along the phase encoding direction in fMRI studies. The magnetic field drift was quantified during EPI by monitoring the resonance frequency interleaved with the EPI acquisition, and a novel method is proposed to correct the apparent motion.

The effect of small rotations on R2* measured with echo planar imaging.

Several modern MRI techniques, such as functional MRI (fMRI), rely on the detection of microscopic changes in magnetic susceptibility. However, differences in magnetic susceptibility between brain tissue, bone, and air also produce local magnetic field gradients that may interfere with the contrast of interest, particularly at high field strengths. Since the magnetic field distribution depends on the orientation of the human head in the MRI scanner, head rotations can change the effective transverse relaxation rate (R(2)*) and confound fMRI studies.

Adaptation of the attention network in human immunodeficiency virus brain injury.

Human immunodeficiency virus (HIV)-positive patients commonly have attention and concentration problems. However, it remains unclear how HIV infection affects the attention network. Therefore, blood oxygenation level dependent functional magnetic resonance imaging (BOLD-fMRI) was performed in 36 subjects (18 HIV and 18 seronegative [SN] controls) during a set of visual attention tasks with increasing levels of attentional load.

k-Space based summary motion detection for functional magnetic resonance imaging.

Functional MRI studies are very sensitive to motion; head movements of as little as 1-mm translations or 1 degrees rotations may cause spurious signals. An algorithm was developed that uses k-space MRI data to monitor subject motion during functional MRI time series. A k-space weighted average of squared difference between the initial scan and subsequent scans is calculated, which summarizes subject motion in a single quality parameter; however, the quality parameter cannot be used for motion correction.