PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-25 (50)
 

Clipboard (0)
None

Select a Filter Below

Journals
more »
Year of Publication
Document Types
1.  Early Postnatal Respiratory Viral Infection Induces Structural and Neurochemical Changes in the Neonatal Piglet Brain 
Brain, behavior, and immunity  2015;48:326-335.
Infections that cause inflammation during the postnatal period are common, yet little is known about their impact on brain development in gyrencephalic species. To address this issue, we investigated brain development in domestic piglets which have brain growth and morphology similar to human infants, after experimentally infecting them with porcine reproductive and respiratory syndrome virus (PRRSV) to induce an interstitial pneumonia Piglets were inoculated with PRRSV on postnatal day (PD) 7 and magnetic resonance imaging (MRI) was used to assess brain macrostructure (voxel-based morphometry), microstructure (diffusion tensor imaging) and neurochemistry (MR-spectroscopy) at PD 29 or 30. PRRSV piglets exhibited signs of infection throughout the post-inoculation period and had elevated plasma levels of TNFα at the end of the study. PRRSV infection increased the volume of several components of the ventricular system including the cerebral aqueduct, fourth ventricle, and the lateral ventricles. Group comparisons between control and PRRSV piglets defined 8 areas where PRRSV piglets had less gray matter volume; 5 areas where PRRSV piglets had less white matter volume; and 4 relatively small areas where PRRSV piglets had more white matter. Of particular interest was a bilateral reduction in gray and white matter in the primary visual cortex. PRRSV piglets tended to have reduced fractional anisotropy in the corpus callosum. Additionally, N-acetylaspartate, creatine, and myo-inositol were decreased in the hippocampus of PRRSV piglets suggesting disrupted neuronal and glial health and energy imbalances. These findings show in a gyrencephalic species that early-life infection can affect brain growth and development.
doi:10.1016/j.bbi.2015.05.001
PMCID: PMC4508213  PMID: 25967923
Magnetic Resonance Imaging; Infection; Neonatal; Pig; Development; Brain
2.  High-Resolution Dynamic Speech Imaging with Joint Low-Rank and Sparsity Constraints 
Purpose
To enable dynamic speech imaging with high spatiotemporal resolution and full-vocal-tract spatial coverage, leveraging recent advances in sparse sampling.
Methods
An imaging method is developed to enable high-speed dynamic speech imaging exploiting low-rank and sparsity of the dynamic images of articulatory motion during speech. The proposed method includes: a) a novel data acquisition strategy that collects navigators with high temporal frame rate, and b) an image reconstruction method that derives temporal subspaces from navigators and reconstructs high-resolution images from sparsely sampled data with joint low-rank and sparsity constraints.
Results
The proposed method has been systematically evaluated and validated through several dynamic speech experiments. A nominal imaging speed of 102 frames per second (fps) was achieved for a single-slice imaging protocol with a spatial resolution of 2.2 × 2.2 × 6.5 mm3. An eight-slice imaging protocol covering the entire vocal tract achieved a nominal imaging speed of 12.8 fps with the identical spatial resolution. The effectiveness of the proposed method and its practical utility was also demonstrated in a phonetic investigation.
Conclusion
High spatiotemporal resolution with full-vocal-tract spatial coverage can be achieved for dynamic speech imaging experiments with low-rank and sparsity constraints.
doi:10.1002/mrm.25302
PMCID: PMC4261062  PMID: 24912452
partial separability modeling; low-rank approximation; sparsity; spiral navigation; dynamic speech imaging
3.  Distracted and down: neural mechanisms of affective interference in subclinical depression 
Previous studies have shown that depressed individuals have difficulty directing attention away from negative distractors, a phenomenon known as affective interference. However, findings are mixed regarding the neural mechanisms and network dynamics of affective interference. The present study addressed these issues by comparing neural activation during emotion-word and color-word Stroop tasks in participants with varying levels of (primarily subclinical) depression. Depressive symptoms predicted increased activation to negative distractors in areas of dorsal anterior cingulate cortex (dACC) and posterior cingulate cortex (PCC), regions implicated in cognitive control and internally directed attention, respectively. Increased dACC activity was also observed in the group-average response to incongruent distractors, suggesting that dACC activity during affective interference is related to overtaxed cognitive control. In contrast, regions of PCC were deactivated across the group in response to incongruent distractors, suggesting that PCC activity during affective interference represents task-independent processing. A psychophysiological interaction emerged in which higher depression predicted more positively correlated activity between dACC and PCC during affective interference, i.e. greater connectivity between cognitive control and internal-attention systems. These findings suggest that, when individuals high in depression are confronted by negative material, increased attention to internal thoughts and difficulty shifting resources to the external world interfere with goal-directed behavior.
doi:10.1093/scan/nsu100
PMCID: PMC4420741  PMID: 25062838
depression; executive function; emotion; default network; connectivity
4.  Fully automated open‐source lesion mapping of T2‐FLAIR images with FSL correlates with clinical disability in MS  
Brain and Behavior  2016;e00440.
Abstract
Background
T2 Lesion Volume (T2LV) has been an important biomarker for multiple sclerosis (MS). Current methods available to quantify lesions from MR images generally require manual adjustments or multiple images with different contrasts. Further, implementations are often not easily or openly accessible.
Objective
We created a fully unsupervised, single T2 FLAIR image T2LV quantification package based on the popular open‐source imaging toolkit FSL.
Methods
By scripting various processing tools in FSL, we developed an image processing pipeline that distinguishes normal brain tissue from CSF and lesions. We validated our method by hierarchical multiple regression (HMR) with a preliminary study to see if our T2LVs correlate with clinical disability measures in MS when controlled for other variables.
Results
Pearson correlations between T2LV and Expanded Disability Status Scale (EDSS: r = 0.344, P = 0.013), Six‐Minute Walk (6MW: r = −0.513, P = 0.000), Timed 25‐Foot Walk (T25FW: r = −0.438, P = .000), and Symbol Digit Modalities Test (SDMT: r = −0.499, P = 0.000) were all significant. Partial correlations controlling for age were significant between T2LV and 6MW (r = −0.433, P = 0.002), T25FW (r = −0.392, P = 0.004), and SDMT (r = −0.450, P = 0.001). In HMR, T2LV explained significant additional variance in 6MW (R 2 change = 0.082, P = 0.020), after controlling for confounding variables such as age, white matter volume (WMV), and gray matter volume (GMV).
Conclusion
Our T2LV quantification software produces T2LVs from a single FLAIR image that correlate with physical disability in MS and is freely available as open‐source software.
doi:10.1002/brb3.440
PMCID: PMC4731385  PMID: 26855828
Atrophy; magnetic resonance imaging; multiple sclerosis; outcome measurement; T2 lesions
5.  Fully automated open‐source lesion mapping of T2‐FLAIR images with FSL correlates with clinical disability in MS  
Brain and Behavior  2016;6(3):e00440.
Abstract
Background
T2 Lesion Volume (T2LV) has been an important biomarker for multiple sclerosis (MS). Current methods available to quantify lesions from MR images generally require manual adjustments or multiple images with different contrasts. Further, implementations are often not easily or openly accessible.
Objective
We created a fully unsupervised, single T2 FLAIR image T2LV quantification package based on the popular open‐source imaging toolkit FSL.
Methods
By scripting various processing tools in FSL, we developed an image processing pipeline that distinguishes normal brain tissue from CSF and lesions. We validated our method by hierarchical multiple regression (HMR) with a preliminary study to see if our T2LVs correlate with clinical disability measures in MS when controlled for other variables.
Results
Pearson correlations between T2LV and Expanded Disability Status Scale (EDSS: r = 0.344, P = 0.013), Six‐Minute Walk (6MW: r = −0.513, P = 0.000), Timed 25‐Foot Walk (T25FW: r = −0.438, P = .000), and Symbol Digit Modalities Test (SDMT: r = −0.499, P = 0.000) were all significant. Partial correlations controlling for age were significant between T2LV and 6MW (r = −0.433, P = 0.002), T25FW (r = −0.392, P = 0.004), and SDMT (r = −0.450, P = 0.001). In HMR, T2LV explained significant additional variance in 6MW (R 2 change = 0.082, P = 0.020), after controlling for confounding variables such as age, white matter volume (WMV), and gray matter volume (GMV).
Conclusion
Our T2LV quantification software produces T2LVs from a single FLAIR image that correlate with physical disability in MS and is freely available as open‐source software.
doi:10.1002/brb3.440
PMCID: PMC4731385  PMID: 26855828
Atrophy; magnetic resonance imaging; multiple sclerosis; outcome measurement; T2 lesions
6.  Comparing Aging and Fitness Effects on Brain Anatomy 
Recent studies suggest that cardiorespiratory fitness (CRF) mitigates the brain’s atrophy typically associated with aging, via a variety of beneficial mechanisms. One could argue that if CRF is generally counteracting the negative effects of aging, the same regions that display the greatest age-related volumetric loss should also show the largest beneficial effects of fitness. To test this hypothesis we examined structural MRI data from 54 healthy older adults (ages 55–87), to determine the overlap, across brain regions, of the profiles of age and fitness effects. Results showed that lower fitness and older age are associated with atrophy in several brain regions, replicating past studies. However, when the profiles of age and fitness effects were compared using a number of statistical approaches, the effects were not entirely overlapping. Interestingly, some of the regions that were most influenced by age were among those not influenced by fitness. Presumably, the age-related atrophy occurring in these regions is due to factors that are more impervious to the beneficial effects of fitness. Possible mechanisms supporting regional heterogeneity may include differential involvement in motor function, the presence of adult neurogenesis, and differential sensitivity to cerebrovascular, neurotrophic and metabolic factors.
doi:10.3389/fnhum.2016.00286
PMCID: PMC4923123  PMID: 27445740
aging; cardiorespiratory fitness; exercise; brain anatomy; FreeSurfer
7.  A Brain Network Instantiating Approach and Avoidance Motivation 
Psychophysiology  2012;49(9):1200-1214.
Research indicates that dorsolateral prefrontal cortex (DLPFC) is important for pursuing goals, and areas of DLPFC are differentially involved in approach and avoidance motivation. Given the complexity of the processes involved in goal pursuit, DLPFC is likely part of a network that includes orbitofrontal cortex (OFC), cingulate, amygdala, and basal ganglia. This hypothesis was tested with regard to one component of goal pursuit, the maintenance of goals in the face of distraction. Examination of connectivity with motivation-related areas of DLPFC supported the network hypothesis. Differential patterns of connectivity suggest a distinct role for DLPFC areas, with one involved in selecting approach goals, one in selecting avoidance goals, and one in selecting goal pursuit strategies. Finally, differences in trait motivation moderated connectivity between DLPFC and OFC, suggesting that this connectivity is important for instantiating motivation.
doi:10.1111/j.1469-8986.2012.01443.x
PMCID: PMC4559331  PMID: 22845892
8.  Investigating Age-Related Changes in Fine Motor Control Across Different Effectors and the Impact of White Matter Integrity 
NeuroImage  2014;96:81-87.
Changes in fine motor control that eventually compromise dexterity accompany advanced age; however there is evidence that age-related decline in motor control may not be uniform across effectors. Particularly, the role of central mechanisms in effector-specific decline has not been examined but is relevant for placing age-related motor declines into the growing literature of age-related changes in brain function. We examined sub-maximal force control across three different effectors (fingers, lips, and tongue) in 18 young and 14 older adults. In parallel with the force variability measures we examined changes in white matter structural integrity in effector-specific pathways in the brain with diffusion tensor imaging (DTI). Motor pathways for each effector were identified by using an fMRI localizer task followed by tractography to identify the fiber tracts propagating to the midbrain. Increases in force control variability were found with age in all three effectors but the effectors showed different degrees of age-related variability. Motor control changes were accompanied by a decline in white matter structural integrity with age shown by measures of fractional anisotropy and radial diffusivity. The DTI metrics appear to mediate some of the age-related declines in motor control. Our findings indicate that the structural integrity of descending motor systems may play a significant role in age-related increases in motor performance variability, but that differential age-related declines in oral and manual effectors are not likely due to structural integrity of descending motor pathways in the brain.
doi:10.1016/j.neuroimage.2014.03.045
PMCID: PMC4043873  PMID: 24657352
Aging; Diffusion Tensor Imaging; Motor Variability; Fiber Tracking
9.  Using MRI for Assessing Velopharyngeal Structures and Function 
Objective
Direct visualization of the velopharynx and, in particular, the levator muscle is particularly important in the assessment of velopharyngeal function and normal speech production. The purpose of this study is to demonstrate the development of a static and dynamic magnetic resonance imaging protocol for evaluation of velopharyngeal structures and function.
Methods
A high-resolution, T2-weighted turbo-spin-echo three-dimensional anatomical scan (sampling perfection with application optimized contrasts using different flip angle evolution) was used to acquire a large field of view covering the velopharyngeal anatomy. Dynamic speech assessment was obtained using a fast-gradient echo, fast low-angle shot, multi-shot spiral technique to acquire 15.8 frames per second (fps) of the sagittal and oblique coronal image planes.
Results
Using a three-dimensional data set, as opposed to two-dimensional data, the full contour of the levator muscle can be appreciated. Dynamic images were obtained at 15.8 fps in the sagittal and oblique coronal planes, enabling visualization of the movements of the velum, posterior pharyngeal wall, lateral pharyngeal walls, and levator muscle during speech.
Conclusions
A three-dimensional magnetic resonance imaging sequence, such as that used in the present study, may provide better analyses and more precise measurements. A dynamic fast low-angle shot sequence allows for visualization of the levator muscle and the velum during speech at a high image rate. This protocol could have a significant impact in improving the process of visualizing pathology and promoting clinical treatment plans for individuals born with cleft lip and palate.
doi:10.1597/12-083
PMCID: PMC4496581  PMID: 23566261
cleft palate; dynamic MRI during speech; MRI
10.  Morphology of the Levator Veli Palatini Muscle Using Magnetic Resonance Imaging 
Background
No studies have reported the circumference and diameter of the levator veli palatini muscle at multiple points along its length and from both views (frontal and lateral). The purpose of this study was to provide quantitative data regarding the levator muscle morphology along the length of the muscle using magnetic resonance imaging and advanced three-dimensional computer technology.
Methods
Ten Caucasian male subjects participated in the study. Subjects were scanned using a Siemens 3 T Trio. Levator muscle measures were obtained using a two-dimensional image plane. A three-dimensional model was used to measure the circumference and muscle diameter (in two directions) at six points along the length of the levator muscle.
Results
Levator muscle length ranged from 41.67 mm to 52.85 mm across all subjects. Mean extravelar muscle length was 30.55 mm (SD, 2.8 mm) and 30.01 mm (SD, 2.9 mm) for right and left muscles. The mean circumference at the origin was 18.90 mm (SD, 2.6 mm). At the second point, the muscle circumference mean increased slightly (mean, 22.40 mm; SD, 4.9 mm). The means for the remainder of the measures (points 3, 4, 5, and 6) were consistent, showing little to no change.
Conclusion
Circumference and diameter values were similar to those reported in previous literature. The muscle did diverge at the point where the muscle bundle entered the velum, as it has been previously described. Instead, the muscle diverges near the midline insertion becoming sparser (smaller superior-to-inferior diameter).
doi:10.1597/11-125
PMCID: PMC4496582  PMID: 22023112
levator veli palatini muscle; magnetic resonance imaging; muscle morphology
11.  Sexual Dimorphism of the Levator Veli Palatini Muscle: An Imaging Study 
Objective
Magnetic resonance imaging studies of the levator veli palatini muscle have used small numbers of subjects and have not consistently controlled for sex, race, or age. The purpose of this study was to conduct a structural assessment using a large homogeneous sample to examine the sex differences in the levator muscle morphology.
Methods
Thirty white adult subjects (15 men and 15 women) were imaged using a 3 Tesla MRI system. A high-resolution SPACE (sampling perfection with application-optimized contrasts using different flip-angle evolution) sequence was used to acquire images of the velopharyngeal anatomy. Levator muscle measurements were obtained.
Results
Men displayed significantly greater levator extravelar segment length (P = .003), levator intravelar segment muscle length (P < .001), greater distance between levator insertion points (P < .001), and greater angles of origin (P= .008) compared with women. There was no statistically significant variation between men and women in the distance between points of origin at the base of the skull.
Conclusions
This study provides normative data to improve understanding of levator dysmorphology such as that in cleft palate muscle anatomy. Results of the study demonstrate significant differences between white men and women across several levator muscle measures. Variations in the relative size of the cranium or height of the individual were not proportionate to the variations observed in the levator muscle.
doi:10.1597/12-128
PMCID: PMC4496583  PMID: 23782419
imaging study; levator veli palatini muscle; MRI
12.  Objectively Measured Physical Activity Is Associated with Brain Volumetric Measurements in Multiple Sclerosis 
Behavioural Neurology  2015;2015:482536.
Background. Little is known about physical activity and its association with volumes of whole brain gray matter and white matter and deep gray matter structures in persons with multiple sclerosis (MS). Purpose. This study examined the association between levels of physical activity and brain volumetric measures from magnetic resonance imaging (MRI) in MS. Method. 39 persons with MS wore an accelerometer for a 7-day period and underwent a brain MRI. Normalized GM volume (NGMV), normalized WM volume (NWMV), and deep GM structures were calculated from 3D T1-weighted structural brain images. We conducted partial correlations (pr) controlling for demographic and clinical variables. Results. Moderate-to-vigorous physical activity (MVPA) was significantly associated with NGMV (pr = 0.370, p < 0.05), NWMV (pr = 0.433, p < 0.01), hippocampus (pr = 0.499, p < 0.01), thalamus (pr = 0.380, p < 0.05), caudate (pr = 0.539, p < 0.01), putamen (pr = 0.369, p < 0.05), and pallidum (pr = 0.498, p < 0.01) volumes, when controlling for sex, age, clinical course of MS, and Expanded Disability Status Scale score. There were no associations between sedentary and light physical activity with MRI outcomes. Conclusion. Our results provide the first evidence that MVPA is associated with volumes of whole brain GM and WM and deep GM structures that are involved in motor and cognitive functions in MS.
doi:10.1155/2015/482536
PMCID: PMC4471328  PMID: 26146460
13.  TRANSDIAGNOSTIC DIMENSIONS OF ANXIETY AND DEPRESSION MODERATE MOTIVATION-RELATED BRAIN NETWORKS DURING GOAL MAINTENANCE 
Depression and anxiety  2014;31(10):805-813.
Background
Advancing research on the etiology, prevention, and treatment of psychopathology requires the field to move beyond modular conceptualizations of neural dysfunction toward understanding disturbance in key brain networks. Although some studies of anxiety and depression have begun doing so, they typically suffer from several drawbacks, including: (1) a categorical approach ignoring transdiagnostic processes, (2) failure to account for substantial anxiety and depression comorbidity, (3) examination of networks at rest, which overlooks disruption manifesting only when networks are challenged. Accordingly, the present study examined relationships between transdiagnostic dimensions of anxiety/depression and patterns of functional connectivity while goal maintenance was challenged.
Methods
Participants (n = 179, unselected community members and undergraduates selected to be high/low on anxiety/depression) performed a task in which goal maintenance was challenged (color-word Stroop) while fMRI data were collected. Analyses examined moderation by anxiety/depression of condition-dependent coupling between regions of dorsolateral prefrontal cortex (dlPFC) previously associated with approach and avoidance motivation and amygdala/orbitofrontal cortex (OFC).
Results
Anxious arousal was positively associated with amygdala↔right dlPFC coupling. Depression was positively associated with OFC↔right dlPFC coupling and negatively associated with OFC↔left dlPFC coupling.
Conclusions
Findings advance the field toward an integrative model of the neural instantiation of anxiety/depression by identifying specific, distinct dysfunctions associated with anxiety and depression in networks important for maintaining approach and avoidance goals. Specifically, findings shed light on potential neural mechanisms involved in attentional biases in anxiety and valuation biases in depression and underscore the importance of examining transdiagnostic dimensions of anxiety/depression while networks are challenged.
doi:10.1002/da.22271
PMCID: PMC4418555  PMID: 24753242
amygdale; anxiety; depression; dorsolateral prefrontal cortex; orbitofrontal cortex, network; transdiagnostic
14.  3D Multislab, Multishot Acquisition for Fast, Whole-Brain MR Elastography with High SNR Efficiency 
Purpose
To develop an acquisition scheme for generating magnetic resonance elastography (MRE) displacement data with whole-brain coverage, high spatial resolution, and adequate signal-to-noise ratio (SNR) in a short scan time.
Theory and Methods
A 3D multislab, multishot acquisition for whole-brain MRE with 2.0 mm isotropic spatial resolution is proposed. The multislab approach allowed for the use of short repetition time to achieve very high SNR efficiency. High SNR efficiency allowed for a reduced acquisition time of only six minutes while the minimum SNR needed for inversion was maintained.
Results
The mechanical property maps estimated from whole-brain displacement data with nonlinear inversion (NLI) demonstrated excellent agreement with neuroanatomical features, including the cerebellum and brainstem. A comparison with an equivalent 2D acquisition illustrated the improvement in SNR efficiency of the 3D multislab acquisition. The flexibility afforded by the high SNR efficiency allowed for higher resolution with a 1.6 mm isotropic voxel size, which generated higher estimates of brainstem stiffness compared with the 2.0 mm isotropic acquisition.
Conclusions
The acquisition presented allows for the capture of whole-brain MRE displacement data in a short scan time, and may be used to generate local mechanical property estimates of neuroanatomical features throughout the brain.
doi:10.1002/mrm.25065
PMCID: PMC4061282  PMID: 24347237
15.  Depression and Anxious Apprehension Distinguish Frontocingulate Cortical Activity during Top-Down Attentional Control 
Journal of abnormal psychology  2011;120(2):272-285.
A network consisting of left dorsal lateral prefrontal cortex (LDLPFC) and dorsal anterior cingulate cortex (dACC) has been implicated in top-down attentional control. Few studies have systematically investigated how this network is altered in psychopathology, despite evidence that depression and anxiety are associated with attentional control impairments. fMRI and dense-array ERP data were collected in separate sessions from 100 participants during a color-word Stroop task. fMRI results guided ERP source modeling to characterize the time course of activity in LDLPFC (300-440 ms) and dACC (520-680 ms). At low levels of depression, LDLPFC activity was indirectly related to Stroop interference and only via dACC activity. In contrast, at high levels of depression, dACC did not play an intervening role, and increased LDLPFC activity was directly related to decreased Stroop interference. Specific to high levels of anxious apprehension, higher dACC activity was related to more Stroop interference. Results indicate that depression and anxious apprehension modulate temporally and functionally distinct aspects of the frontocingulate network involved in top-down attention control.
doi:10.1037/a0023204
PMCID: PMC4406398  PMID: 21553941
depression; anxious apprehension; dACC; LDLPFC; attention; color-word Stroop
16.  Co-occurring Anxiety Influences Patterns of Brain Activity in Depression 
Brain activation associated with anhedonic depression and co-occurring anxious arousal and anxious apprehension was measured by fMRI during performance of an emotion-word Stroop task. Consistent with EEG findings, depression was associated with rightward frontal lateralization in dorsolateral prefrontal cortex (DLPFC), but only when anxious arousal was elevated and anxious apprehension was low. Activity in right inferior frontal gyrus (IFG) was also reduced for depression under the same conditions. In contrast, depression was associated with more activity in anterior cingulate cortex (dACC and rACC) and bilateral amygdala. Results imply that depression, particularly when accompanied by anxious arousal, may result in a failure to implement top-down processing by appropriate brain regions (left DLPFC, right IFG) due to increased activation in regions associated with responding to emotionally salient information (right DLPFC, amygdala).
doi:10.3758/CABN.10.1.141
PMCID: PMC4403735  PMID: 20233962
17.  Education mitigates age-related decline in N-Acetylaspartate levels 
Brain and Behavior  2015;5(3):e00311.
Background
Greater educational attainment is associated with better neurocognitive health in older adults and is thought to reflect a measure of cognitive reserve. In vivo neuroimaging tools have begun to identify the brain systems and networks potentially responsible for reserve.
Methods
We examined the relationship between education, a commonly used proxy for cognitive reserve, and N-acetylaspartate (NAA) in neurologically healthy older adults (N = 135; mean age = 66 years). Using single voxel MR spectroscopy, we predicted that higher levels of education would moderate an age-related decline in NAA in the frontal cortex.
Results
After controlling for the variance associated with cardiorespiratory fitness, sex, annual income, and creatine levels, there were no significant main effects of education (B = 0.016, P = 0.787) or age (B = −0.058, P = 0.204) on NAA levels. However, consistent with our predictions, there was a significant education X age interaction such that more years of education offset an age-related decline in NAA (B = 0.025, P = 0.031). When examining working memory via the backwards digit span task, longer span length was associated with greater education (P < 0.01) and showed a trend with greater NAA concentrations (P < 0.06); however, there was no age X education interaction on digit span performance nor a significant moderated mediation effect between age, education, and NAA on digit span performance.
Conclusions
Taken together, these results suggest that higher levels of education may attenuate an age-related reduction in neuronal viability in the frontal cortex.
doi:10.1002/brb3.311
PMCID: PMC4356844  PMID: 25798329
Aging; brain reserve; cognitive reserve; education; fitness
18.  Cardiorespiratory fitness and its association with thalamic, hippocampal, and basal ganglia volumes in multiple sclerosis 
NeuroImage : Clinical  2015;7:661-666.
Background
There is little known about cardiorespiratory fitness and its association with volumes of the thalamus, hippocampus, and basal ganglia in multiple sclerosis (MS). Such inquiry is important for identifying a possible behavioral approach (e.g., aerobic exercise training) that might change volumes of deep gray matter (DGM) structures associated with cognitive and motor functions in MS.
Purpose
This study examined the association between cardiorespiratory fitness and volumes of the thalamus, hippocampus, and basal ganglia in MS.
Method
We enrolled 35 persons with MS who underwent a maximal exercise test for measuring cardiorespiratory fitness as peak oxygen consumption (VO2peak) and brain MRI. Volumes of the thalamus, hippocampus, caudate, putamen, and pallidum were calculated from 3D T1-weighted structural brain images. We examined associations using partial (pr) correlations controlling for demographic and clinical variables.
Results
VO2peak was significantly associated with composite scaled volumes of the caudate(pr = .47, p < .01), putamen (pr = .44, p < .05), pallidum (pr = .40, p < .05), and hippocampus (pr = .42, p < .05), but not thalamus (pr = .31, p = .09), when controlling for sex, age, disability, and duration of MS.
Conclusion
Our results provide novel evidence that cardiorespiratory fitness is associated with volumes of DGM structures that are involved in motor and cognitive functions in MS.
Highlights
•We examine the association between cardiorespiratory fitness and deep gray matter structures in multiple sclerosis.•Cardiorespiratory fitness was positively associated with volumes of basal ganglia nuclei in multiple sclerosis.•Researchers should examine aerobic exercise training for improving brain health in multiple sclerosis.
doi:10.1016/j.nicl.2015.02.017
PMCID: PMC4375633  PMID: 25844320
Brain; Multiple sclerosis; Exercise; MRI; Physical activity
19.  Education mitigates age‐related decline in N‐Acetylaspartate levels 
Brain and Behavior  2015;e00311.
Abstract
Background
Greater educational attainment is associated with better neurocognitive health in older adults and is thought to reflect a measure of cognitive reserve. In vivo neuroimaging tools have begun to identify the brain systems and networks potentially responsible for reserve.
Methods
We examined the relationship between education, a commonly used proxy for cognitive reserve, and N‐acetylaspartate (NAA) in neurologically healthy older adults (N = 135; mean age = 66 years). Using single voxel MR spectroscopy, we predicted that higher levels of education would moderate an age‐related decline in NAA in the frontal cortex.
Results
After controlling for the variance associated with cardiorespiratory fitness, sex, annual income, and creatine levels, there were no significant main effects of education (B = 0.016, P = 0.787) or age (B = −0.058, P = 0.204) on NAA levels. However, consistent with our predictions, there was a significant education X age interaction such that more years of education offset an age‐related decline in NAA (B = 0.025, P = 0.031). When examining working memory via the backwards digit span task, longer span length was associated with greater education (P < 0.01) and showed a trend with greater NAA concentrations (P < 0.06); however, there was no age X education interaction on digit span performance nor a significant moderated mediation effect between age, education, and NAA on digit span performance.
Conclusions
Taken together, these results suggest that higher levels of education may attenuate an age‐related reduction in neuronal viability in the frontal cortex.
doi:10.1002/brb3.311
PMCID: PMC4356844  PMID: 25798329
Aging; brain reserve; cognitive reserve; education; fitness
20.  Neurovascular coupling in normal aging: A combined optical, ERP and fMRI study 
NeuroImage  2013;85(0 1):10.1016/j.neuroimage.2013.04.113.
Brain aging is characterized by changes in both hemodynamic and neuronal responses, which may be influenced by the cardiorespiratory fitness of the individual. To investigate the relationship between neuronal and hemodynamic changes, we studied the brain activity elicited by visual stimulation (checkerboard reversals at different frequencies) in younger adults and in older adults varying in physical fitness. Four functional brain measures were used to compare neuronal and hemodynamic responses obtained from BA17: two reflecting neuronal activity (the event-related optical signal, EROS, and the C1 response of the ERP), and two reflecting functional hemodynamic changes (functional magnetic resonance imaging, fMRI, and near-infrared spectroscopy, NIRS). The results indicated that both younger and older adults exhibited a quadratic relationship between neuronal and hemodynamic effects, with reduced increases of the hemodynamic response at high levels of neuronal activity. Although older adults showed reduced activation, similar neurovascular coupling functions were observed in the two age groups when fMRI and deoxy-hemoglobin measures were used. However, the coupling between oxy-and deoxy-hemoglobin changes decreased with age and increased with increasing fitness. These data indicate that departures from linearity in neurovascular coupling may be present when using hemodynamic measures to study neuronal function.
doi:10.1016/j.neuroimage.2013.04.113
PMCID: PMC3791333  PMID: 23664952
Neurovascular coupling; aging; fitness; Event-related optical signal (EROS); Near-infrared spectroscopy (NIRS); Functional magnetic resonance imaging (fMRI); Event-related brain potentials (ERPs)
21.  The influence of aerobic fitness on cerebral white matter integrity and cognitive function in older adults: Results of a one-year exercise intervention 
Human brain mapping  2012;34(11):2972-2985.
Cerebral white matter degeneration occurs with increasing age and is associated with declining cognitive function. Research has shown that cardiorespiratory fitness and exercise are effective as protective, even restorative, agents against cognitive and neurobiological impairments in older adults. In this study, we investigated whether the beneficial impact of aerobic fitness would extend to white matter integrity in the context of a one-year exercise intervention. Further, we examined the pattern of diffusivity changes to better understand the underlying biological mechanisms. Finally, we assessed whether training-induced changes in white matter integrity would be associated with improvements in cognitive performance independent of aerobic fitness gains. Results showed that aerobic fitness training did not affect group-level change in white matter integrity, executive function, or short-term memory, but that greater aerobic fitness derived from the walking program was associated with greater change in white matter integrity in the frontal and temporal lobes, and greater improvement in short-term memory. Increases in white matter integrity, however, were not associated with short-term memory improvement, independent of fitness improvements. Therefore, while not all findings are consistent with previous research, we provide novel evidence for correlated change in training-induced aerobic fitness, white matter integrity, and cognition among healthy older adults.
doi:10.1002/hbm.22119
PMCID: PMC4096122  PMID: 22674729
Diffusion tensor imaging; Anisotropy; Cerebrum; Cognition; Physical fitness; Aging
22.  Investigation and validation of intersite fMRI studies using the same imaging hardware 
Purpose
To provide a between site comparison of functional MRI (fMRI) signal reproducibility in two laboratories equipped with identical imaging hardware and software. Many studies have looked at within subject reliability and more recent efforts have begun to calibrate responses across sites, magnetic field strengths, and software. By comparing identical imaging hardware and software, we provide a benchmark for future multi-site comparisons.
Materials and Methods
We evaluated system compatibility based on noise and stability properties of phantom scans and contrast estimates from repeated runs of a blocked motor and visual task on the same four subjects at both sites.
Results
ANOVA and ROI analysis confirmed that site did not play a significant role in explaining variance in our large fMRI data set. Effect size analysis shows that between-subject differences account for nearly ten times more variance than site effects.
Conclusion
We show that quantitative comparisons of contrast estimates derived from cognitive experiments can reliably be compared across two sites. This allows us to establish an effective platform for comparing group differences between two sites using fMRI when group effects are potentially confounded with site, as in the study of neurocultural differences between countries or multi-center clinical trials.
doi:10.1002/jmri.21419
PMCID: PMC2785504  PMID: 18581342
functional MRI; reproducibility; intersite comparisons; effect size; cultural neuroscience
23.  Local mechanical properties of white matter structures in the human brain 
NeuroImage  2013;79:145-152.
The noninvasive measurement of the mechanical properties of brain tissue using magnetic resonance elastography (MRE) has emerged as a promising method for investigating neurological disorders. To date, brain MRE investigations have been limited to reporting global mechanical properties, though quantification of the stiffness of specific structures in the white matter architecture may be valuable in assessing the localized effects of disease. This paper reports the mechanical properties of the corpus callosum and corona radiata measured in healthy volunteers using MRE and atlas-based segmentation. Both structures were found to be significantly stiffer than overall white matter, with the corpus callosum exhibiting greater stiffness and less viscous damping than the corona radiata. Reliability of both local and global measures was assessed through repeated experiments, and the coefficient of variation for each measure was less than 10%. Mechanical properties within the corpus callosum and corona radiata demonstrated correlations with measures from diffusion tensor imaging pertaining to axonal microstructure.
doi:10.1016/j.neuroimage.2013.04.089
PMCID: PMC3676712  PMID: 23644001
elastography; brain; white matter; corpus callosum; microstructure
24.  An In Vivo Three-Dimensional Magnetic Resonance Imaging-Based Averaged Brain Collection of the Neonatal Piglet (Sus scrofa) 
PLoS ONE  2014;9(9):e107650.
Due to the fact that morphology and perinatal growth of the piglet brain is similar to humans, use of the piglet as a translational animal model for neurodevelopmental studies is increasing. Magnetic resonance imaging (MRI) can be a powerful tool to study neurodevelopment in piglets, but many of the MRI resources have been produced for adult humans. Here, we present an average in vivo MRI-based atlas specific for the 4-week-old piglet. In addition, we have developed probabilistic tissue classification maps. These tools can be used with brain mapping software packages (e.g. SPM and FSL) to aid in voxel-based morphometry and image analysis techniques. The atlas enables efficient study of neurodevelopment in a highly tractable translational animal with brain growth and development similar to humans.
doi:10.1371/journal.pone.0107650
PMCID: PMC4177841  PMID: 25254955
25.  Magnetic Resonance Elastography of the Brain using Multi-Shot Spiral Readouts with Self-Navigated Motion Correction 
MRE has been introduced in clinical practice as a possible surrogate for mechanical palpation, but its application to study the human brain in vivo has been limited by low spatial resolution and the complexity of the inverse problem associated with biomechanical property estimation. Here, we report significant improvements in brain MRE data acquisition by reporting images with high spatial resolution and signal-to-noise ratio as quantified by octahedral shear strain metrics. Specifically, we have developed a sequence for brain MRE based on multi-shot, variable-density spiral imaging and three-dimensional displacement acquisition, and implemented a correction scheme for any resulting phase errors. A Rayleigh damped model of brain tissue mechanics was adopted to represent the parenchyma, and was integrated via a finite element-based iterative inversion algorithm. A multi-resolution phantom study demonstrates the need for obtaining high-resolution MRE data when estimating focal mechanical properties. Measurements on three healthy volunteers demonstrate satisfactory resolution of grey and white matter, and mechanical heterogeneities correspond well with white matter histoarchitecture. Together, these advances enable MRE scans that result in high-fidelity, spatially-resolved estimates of in vivo brain tissue mechanical properties, improving upon lower resolution MRE brain studies which only report volume averaged stiffness values.
doi:10.1002/mrm.24473
PMCID: PMC3529970  PMID: 23001771
magnetic resonance elastography; brain; high-resolution; multi-shot; spiral; phase error; Rayleigh damping

Results 1-25 (50)