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Neuroimaging Applications in Tourette's Syndrome.

Tue, 11/27/2018 - 19:31
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Neuroimaging Applications in Tourette's Syndrome.

Int Rev Neurobiol. 2018;143:65-108

Authors: Martino D, Ganos C, Worbe Y

Abstract
Tics are neurodevelopmental hyperkinetic symptoms typically associated with unpleasant sensory experiences called premonitory urges. Tourette syndrome (TS) is the primary chronic tic disorder for which medical surveillance is most frequently required, and is associated with a complex phenotypical spectrum encompassing different types of abnormal behaviors. Animal models of tics support their link to phasic activity changes throughout the sensorimotor loop of the cortico-basal ganglia-thalamo-cortical network. Event-related functional magnetic resonance imaging (fMRI) studies on patients with TS showed that the supplementary motor area relays preparatory signals related to tics to the primary motor area and other cortical regions relevant to action monitoring, following which cortico-basal ganglia-thalamo-cortical activation leads to the manifestation of tics. Despite their methodological heterogeneity, structural MRI studies highlighted the existence of anatomical markers of distinct sub-phenotypes of the TS spectrum. Initial evidence suggests that combining MRI structural methods and functional intrinsic connectivity assessed during resting state could even discriminate between TS patients and control groups. MR-spectroscopy and positron emission tomography studies suggest that TS may be related to a complex interplay between different neurotransmitters (particularly dopamine, GABA and glutamate), but discrepancy across studies prevents firm conclusions. Recent volumetric, cortical thickness and fMRI studies results showed an association between premonitory urges and somatosensory and insular cortical regions, involved in the processing of interoceptive and enteroceptive stimuli and motor output modulation. Finally, both structural and functional MRI studies have provided important support to the subtyping of the TS spectrum with respect to behavioral co-morbidities, in line with a "dimensional approach" to the classification of neuropsychiatric disorders, which is based on the identification of neurocognitive endophenotypes and of their anatomical substrate.

PMID: 30473198 [PubMed - in process]

Spatial and Temporal Organization of the Individual Human Cerebellum.

Tue, 11/27/2018 - 19:31
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Spatial and Temporal Organization of the Individual Human Cerebellum.

Neuron. 2018 Nov 21;100(4):977-993.e7

Authors: Marek S, Siegel JS, Gordon EM, Raut RV, Gratton C, Newbold DJ, Ortega M, Laumann TO, Adeyemo B, Miller DB, Zheng A, Lopez KC, Berg JJ, Coalson RS, Nguyen AL, Dierker D, Van AN, Hoyt CR, McDermott KB, Norris SA, Shimony JS, Snyder AZ, Nelson SM, Barch DM, Schlaggar BL, Raichle ME, Petersen SE, Greene DJ, Dosenbach NUF

Abstract
The cerebellum contains the majority of neurons in the human brain and is unique for its uniform cytoarchitecture, absence of aerobic glycolysis, and role in adaptive plasticity. Despite anatomical and physiological differences between the cerebellum and cerebral cortex, group-average functional connectivity studies have identified networks related to specific functions in both structures. Recently, precision functional mapping of individuals revealed that functional networks in the cerebral cortex exhibit measurable individual specificity. Using the highly sampled Midnight Scan Club (MSC) dataset, we found the cerebellum contains reliable, individual-specific network organization that is significantly more variable than the cerebral cortex. The frontoparietal network, thought to support adaptive control, was the only network overrepresented in the cerebellum compared to the cerebral cortex (2.3-fold). Temporally, all cerebellar resting state signals lagged behind the cerebral cortex (125-380 ms), supporting the hypothesis that the cerebellum engages in a domain-general function in the adaptive control of all cortical processes.

PMID: 30473014 [PubMed - in process]

Amplitude of Low Frequency Fluctuation (ALFF) study of the spontaneous brain activities of patients with phantom limb pain.

Sun, 11/25/2018 - 23:48
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Amplitude of Low Frequency Fluctuation (ALFF) study of the spontaneous brain activities of patients with phantom limb pain.

Eur Rev Med Pharmacol Sci. 2018 Nov;22(21):7164-7171

Authors: Du JG, Xiao H, Zuo YX

Abstract
OBJECTIVE: Our objective was to use Amplitude of Low-Frequency Fluctuation (ALFF) method to investigate the changes in spontaneous brain activity in HM patients and their relationships with clinical features.
PATIENTS AND METHODS: This study was set out to observe, using Functional magnetic resonance imaging (fMRI), the changes in spontaneous brain activity in patients with phantom limb pain (PLP). Eleven amputees with PLP closely matched in age, sex, and education in a right side lower limb were scanned using fMRI to measure the amplitude of low-frequency fluctuation (ALFF) and functional connectivity (FC) in the resting state of the brain (GPLP) before use of prosthetic. They were then scanned again after recovering from PLP (GPLPr) after use of artificial limbs. Eleven healthy volunteers (GC) were also scanned.
RESULTS: When compared to GC, GPLP exhibited decreased ALFF in the left inferior parietal lobule, and GPLPr exhibited decreased ALFF in the left precuneus. When compared to GPLP, GC showed positive FC in the part regions of the limbic system structure. When compared to GC, the positive FC in GPLPr was significantly decreased in the midbrain. Finally, when compared to GPLPr, GPLP showed significantly decreased positive FC in the right precuneus and inferior parietal lobe. The central nervous system shows functional changes in the resting state of the brain in patients with PLP, which may indicate the presence of neurobiological changes. The recovery time of the changes may be longer than the pain symptoms of patients.
CONCLUSIONS: The technique of fMRI of the resting network of the brain in patients with PLP may be able to be used to monitor clinical therapeutic effects.

PMID: 30468457 [PubMed - in process]

Shifts in the functional topography of frontal cortex-striatum connectivity in alcohol use disorder.

Sun, 11/25/2018 - 23:48
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Shifts in the functional topography of frontal cortex-striatum connectivity in alcohol use disorder.

Addict Biol. 2018 Nov 23;:

Authors: Gerchen MF, Rentsch A, Kirsch M, Kiefer F, Kirsch P

Abstract
Frontostriatal circuits are centrally involved in the selection of behavioral programs and play a prominent role in alcohol use disorder (AUD) as well as other mental disorders. However, how frontal regions change their striatal connectivity to implement adaptive cognitive control is still not fully understood. Here, we developed an approach for functional magnetic resonance imaging (fMRI) connectivity analysis in which we change the focus from connectivity to individual voxels towards spatial information about the location of strongest functional connectivity. In resting state data of n = 66 participants with AUD and n = 40 healthy controls (HC) we used the approach to estimate frontostriatal connectivity gradients consistent with nonhuman primate tract-tracing studies, characterized for each frontal voxel the striatal peak connectivity location on this gradient (PeaCoG), and tested for group differences and associations with clinical variables. We identified a cluster in the right orbitofrontal cortex (rOFC) with a peak connectivity shift towards ventral striatal regions in AUD. Reduced variability of rOFC striatal peak connectivity in the AUD group suggests a "clamping" to the ventral striatum as the underlying effect. Within the AUD group striatal peak connectivity in the superior frontal gyrus was associated with self-efficacy to abstain from alcohol, in the medial frontal and dorsolateral prefrontal cortex with alcohol dependency, and in the right inferior frontal gyrus with the urge to consume alcohol. Our results demonstrate that the functional topography of frontostriatal circuits exhibits interindividual variability, which provides insight into frontostriatal network adaptations in AUD and potentially other mental disorders.

PMID: 30468293 [PubMed - as supplied by publisher]

fMRI data processing in MRTOOL: to what extent does anatomical registration affect the reliability of functional results?

Sun, 11/25/2018 - 23:48
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fMRI data processing in MRTOOL: to what extent does anatomical registration affect the reliability of functional results?

Brain Imaging Behav. 2018 Nov 22;:

Authors: Ganzetti M, Taberna GA, Mantini D

Abstract
Spatial registration is an essential step in the analysis of fMRI data because it enables between-subject analyses of brain activity, measured either during task performance or in the resting state. In this study, we investigated how anatomical registration with MRTOOL affects the reliability of task-related fMRI activity. We used as a benchmark the results from two other spatial registration methods implemented in SPM12: the Unified Segmentation algorithm and the DARTEL toolbox. Structural alignment accuracy and the impact on functional activation maps were assessed with high-resolution T1-weighted images and a set of task-related functional volumes acquired in 10 healthy volunteers. Our findings confirmed that anatomical registration is a crucial step in fMRI data processing, contributing significantly to the total inter-subject variance of the activation maps. MRTOOL and DARTEL provided greater registration accuracy than Unified Segmentation. Although DARTEL had superior gray matter and white matter tissue alignment than MRTOOL, there were no significant differences between DARTEL and MRTOOL in test-retest reliability. Likewise, we found only limited differences in BOLD activation morphology between MRTOOL and DARTEL. The test-retest reliability of task-related responses was comparable between MRTOOL and DARTEL, and both proved superior to Unified Segmentation. We conclude that MRTOOL, which is suitable for single-subject processing of structural and functional MR images, is a valid alternative to other SPM12-based approaches that are intended for group analysis. MRTOOL now includes a normalization module for fMRI data and is freely available to the scientific community.

PMID: 30467743 [PubMed - as supplied by publisher]

Correspondence Between Resting-State and Episodic Memory-Task Related Networks in Elderly Subjects.

Sun, 11/25/2018 - 23:48
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Correspondence Between Resting-State and Episodic Memory-Task Related Networks in Elderly Subjects.

Front Aging Neurosci. 2018;10:362

Authors: Simon-Vermot L, Taylor ANW, Araque Caballero MÀ, Franzmeier N, Buerger K, Catak C, Janowitz D, Kambeitz-Ilankovic LM, Ertl-Wagner B, Duering M, Ewers M

Abstract
Resting-state fMRI studies demonstrated temporally synchronous fluctuations in brain activity among ensembles of brain regions, suggesting the existence of intrinsic functional networks. A spatial match between some of the resting-state networks and regional brain activation during cognitive tasks has been noted, suggesting that resting-state networks support particular cognitive abilities. However, the spatial match and predictive value of any resting-state network and regional brain activation during episodic memory is only poorly understood. In order to address this research gap, we obtained fMRI acquired both during rest and a face-name association task in 38 healthy elderly subjects. In separate independent component analyses, networks of correlated brain activity during rest or the episodic memory task were identified. For the independent components identified for task-based fMRI, the design matrix of successful encoding or retrieval trials was regressed against the time course of each of the component to identify significantly activated networks. Spatial regression was used to assess the match of resting-state networks against those related to successful memory encoding or retrieval. We found that resting-state networks covering the medial temporal, middle temporal, and frontal areas showed increased activity during successful encoding. Resting-state networks located within posterior brain regions showed increased activity during successful recognition. However, the level of resting-state network connectivity was not predictive of the task-related activity in these networks. These results suggest that a circumscribed number of functional networks detectable during rest become engaged during successful episodic memory. However, higher intrinsic connectivity at rest may not translate into higher network expression during episodic memory.

PMID: 30467476 [PubMed]

Comparison of Resting-State Brain Activation Detected by BOLD, Blood Volume and Blood Flow.

Sun, 11/25/2018 - 23:48
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Comparison of Resting-State Brain Activation Detected by BOLD, Blood Volume and Blood Flow.

Front Hum Neurosci. 2018;12:443

Authors: Zhang K, Huang D, Shah NJ

Abstract
Resting-state brain activity has been widely investigated using blood oxygenation level dependent (BOLD) contrast techniques. However, BOLD signal changes reflect a combination of the effects of cerebral blood flow (CBF), cerebral blood volume (CBV), as well as the cerebral metabolic rate of oxygen (CMRO2). In this study, resting-state brain activation was detected and compared using the following techniques: (a) BOLD, using a gradient-echo echo planar imaging (GE-EPI) sequence; (b) CBV-weighted signal, acquired using gradient and spin echo (GRASE) based vascular space occupancy (VASO); and (c) CBF, using pseudo-continuous arterial spin labeling (pCASL). Reliable brain networks were detected using VASO and ASL, including sensorimotor, auditory, primary visual, higher visual, default mode, salience and left/right executive control networks. Differences between the resting-state activation detected with ASL, VASO and BOLD could potentially be due to the different temporal signal-to-noise ratio (tSNR) and the short post-labeling delay (PLD) in ASL, along with differences in the spin-echo readout of VASO. It is also possible that the dynamics of spontaneous fluctuations in BOLD, CBV and CBF could differ due to biological reasons, according to their location within the brain.

PMID: 30467468 [PubMed]

Cesarean Delivery Impacts Infant Brain Development.

Sun, 11/25/2018 - 23:48
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Cesarean Delivery Impacts Infant Brain Development.

AJNR Am J Neuroradiol. 2018 Nov 22;:

Authors: Deoni SC, Adams SH, Li X, Badger TM, Pivik RT, Glasier CM, Ramakrishnaiah RH, Rowell AC, Ou X

Abstract
BACKGROUND AND PURPOSE: The cesarean delivery rate has increased globally in the past few decades. Neurodevelopmental outcomes associated with cesarean delivery are still unclear. This study investigated whether cesarean delivery has any effect on the brain development of offspring.
MATERIALS AND METHODS: A total of 306 healthy children were studied retrospectively. We included 3 cohorts: 2-week-old neonates (cohort 1, n = 32/11 for vaginal delivery/cesarean delivery) and 8-year-old children (cohort 2, n = 37/23 for vaginal delivery/cesarean delivery) studied at Arkansas Children's Hospital, and a longitudinal cohort of 3-month to 5-year-old children (cohort 3, n = 164/39 for vaginal delivery/cesarean delivery) studied independently at Brown University. Diffusion tensor imaging, myelin water fraction imaging, voxel-based morphometry, and/or resting-state fMRI data were analyzed to evaluate white matter integrity, myelination, gray matter volume, and/or functional connectivity, respectively.
RESULTS: While not all MR imaging techniques were shared across the institutions/cohorts, post hoc analyses showed similar results of potential effects of cesarean delivery. The cesarean delivery group in cohort 1 showed significantly lower white matter development in widespread brain regions and significantly lower functional connectivity in the brain default mode network, controlled for a number of potential confounders. No group differences were found in cohort 2 in white matter integrity or gray matter volume. Cohort 3 had significantly different trajectories of white matter myelination between groups, with those born by cesarean delivery having reduced myelin in infancy but normalizing with age.
CONCLUSIONS: Cesarean delivery may influence infant brain development. The impact may be transient because similar effects were not observed in older children. Further prospective and longitudinal studies may be needed to confirm these novel findings.

PMID: 30467219 [PubMed - as supplied by publisher]

Arithmetic learning modifies the functional connectivity of the fronto-parietal network.

Wed, 11/21/2018 - 15:19
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Arithmetic learning modifies the functional connectivity of the fronto-parietal network.

Cortex. 2018 Jul 31;111:51-62

Authors: Zhao H, Li X, Karolis V, Feng Y, Niu H, Butterworth B

Abstract
How Resting-State Functional Connectivity (RSFC) is modified by learning is an important but rarely asked question. Here we used functional near-infrared spectroscopy (fNIRS) to measure changes in RSFC after learning novel subtraction and multiplication facts by forty-one young adult volunteers. We also measured changes in regional hemoglobin concentration. Fronto-parietal RSFC was modified by arithmetic learning and the fronto-parietal RSFC configuration before learning predicted the effectiveness of arithmetic learning. We also found a significant learning effect indicated by a monotonic decrease in reaction time and an increase in accuracy. Regional task-dependent oxy-hemoglobin concentration differentiated subtraction from multiplication learning supporting previous fMRI findings. These results suggest the sensitivity and importance of fronto-parietal connectivity to arithmetic learning.

PMID: 30453223 [PubMed - as supplied by publisher]

Resting-state functional connectivity after concussion is associated with clinical recovery.

Wed, 11/21/2018 - 15:19
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Resting-state functional connectivity after concussion is associated with clinical recovery.

Hum Brain Mapp. 2018 Nov 19;:

Authors: Kaushal M, España LY, Nencka AS, Wang Y, Nelson LD, McCrea MA, Meier TB

Abstract
There has been a recent call for longitudinal imaging studies to better characterize the time course of physiological recovery following sport-related concussion (SRC) and its relationship with clinical recovery. To address this, we evaluated changes to resting-state functional connectivity (rs-FC) of the whole-brain network following SRC and explored associations between rs-FC and measures of clinical outcome. High school and collegiate football athletes were enrolled during preseason. Athletes that suffered SRC (N = 62) were assessed across the acute (within 48 hr) and sub-acute (days 8, 15, and 45) phases. Matched football athletes without concussion served as controls (N = 60) and participated in similar visits. Multi-band resting-state fMRI was used to assess whole-brain rs-FC at each visit using network-based statistic and average nodal strength from regions of interest defined using a common whole-brain parcellation. Concussed athletes had elevated symptoms, psychological distress, and oculomotor, balance, and memory deficits at 48 hr postconcussion relative to controls, with diminished yet significant elevations in symptoms and psychological distress at 8 days. Both rs-FC analyses showed that concussed athletes had a global increase in connectivity at 8 days postconcussion relative to controls, with no differences at the 48-hr, 15-day, or 45-day visits. Further analysis revealed the group effect at the 8-day visit was driven by the large minority of concussed athletes still symptomatic at their visit; asymptomatic concussed athletes did not differ from controls. Findings from this large-scale, prospective study suggest whole-brain rs-FC alterations following SRC are delayed in onset but associated with the presence of self-reported symptoms.

PMID: 30451340 [PubMed - as supplied by publisher]

Evaluating cerebrovascular reactivity during the early symptomatic phase of sport concussion.

Wed, 11/21/2018 - 15:19
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Evaluating cerebrovascular reactivity during the early symptomatic phase of sport concussion.

J Neurotrauma. 2018 Nov 18;:

Authors: Churchill N, Hutchison M, Graham S, Schweizer TA

Abstract
Cerebrovascular reactivity (CVR) indexes the ability of blood vessels to respond to vasoactive stimuli and may be a sensitive biomarker of concussion. However, alterations in whole-brain CVR remain poorly understood during the early symptomatic phase of injury. In this study, CVR was assessed using blood-oxygenation level dependent functional magnetic resonance imaging (BOLD fMRI) combined with a respiratory challenge paradigm; resting cerebral blood flow (CBF) was also evaluated using arterial spin labelling (ASL). Imaging data were collected for 77 university-level athletes, including 56 athletic uninjured controls and 21 concussed athletes scanned in the early symptomatic phase of injury (<7 days post-injury). The normal response to respiratory challenge was assessed in the athletic control group, in which a robust whole-brain response was seen. The concussed athletes were then compared to a matched subset of controls. Concussion was associated with greater reductions in BOLD activity during the early phase of the respiratory task, localized primarily in frontal and prefrontal areas, whereas no significant effects on resting global CBF were observed. In addition, greater symptom severity was associated with greater reductions in BOLD response, with effects seen throughout the brain. The study establishes fMRI with respiratory challenge as a robust method for assessing acute concussion-related alterations in CVR. Moreover, it highlights the importance of examining neurovascular response to physiological stressors after a concussion.

PMID: 30451069 [PubMed - as supplied by publisher]

Abnormal Global Brain Functional Connectivity in Primary Insomnia Patients: A Resting-State Functional MRI Study.

Wed, 11/21/2018 - 15:19
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Abnormal Global Brain Functional Connectivity in Primary Insomnia Patients: A Resting-State Functional MRI Study.

Front Neurol. 2018;9:856

Authors: Yan CQ, Wang X, Huo JW, Zhou P, Li JL, Wang ZY, Zhang J, Fu QN, Wang XR, Liu CZ, Liu QQ

Abstract
Background: Resting-state functional magnetic resonance imaging (fMRI) studies have uncovered the disruptions of functional brain networks in primary insomnia (PI) patients. However, the etiology and pathogenesis underlying this disorder remains ambiguous, and the insomnia related symptoms are influenced by a complex network organization in the brain. The purpose of this study was to explore the abnormal intrinsic functional hubs in PI patients using a voxel-wise degree centrality (DC) analysis and seed-based functional connectivity (FC) approach. Methods: A total of 26 PI patients and 28 healthy controls were enrolled, and they underwent resting-state fMRI. Degree centrality was measured across the whole brain, and group differences in DC were compared. The peak points, which significantly altered DC between the two groups, were defined as the seed regions and were further used to calculate FC of the whole brain. Later, correlation analyses were performed between the changes in brain function and clinical features. Results: Primary insomnia patients showed DC values lower than healthy controls in the left inferior frontal gyrus (IFG) and middle temporal gyrus (MTG) and showed a higher DC value in the right precuneus. The seed-based analyses demonstrated decreased FC between the left MTG and the left posterior cingulate cortex (PCC), and decreased FC was observed between the right precuneus and the right lateral occipital cortex. Reduced DC in the left IFG and decreased FC in the left PCC were positively correlated with the Pittsburgh sleep quality index and the insomnia severity index. Conclusions: This study revealed that PI patients exhibited abnormal intrinsic functional hubs in the left IFG, MTG, and the right precuneus, as well as abnormal seed-based FC in these hubs. These results contribute to better understanding of how brain function influences the symptoms of PI.

PMID: 30450072 [PubMed]

Altered Brain Fraction Amplitude of Low Frequency Fluctuation at Resting State in Patients With Early Left and Right Bell's Palsy: Do They Have Differences?

Wed, 11/21/2018 - 15:19
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Altered Brain Fraction Amplitude of Low Frequency Fluctuation at Resting State in Patients With Early Left and Right Bell's Palsy: Do They Have Differences?

Front Neurosci. 2018;12:797

Authors: Han X, Li H, Wang X, Zhu Y, Song T, Du L, Sun S, Guo R, Liu J, Shi S, Fu C, Gao W, Zhang L, Ma G

Abstract
Purpose: Bell's palsy refers to acute idiopathic unilateral facial nerve palsy. It is a common disorder of the main motor pathway to the facial muscles. This study aimed to investigate the abnormal fraction amplitude of low frequency fluctuation (fALFF) of the brain in patients with early left and right Bell's palsy. Materials and Methods: Sixty-seven patients (left 33, right 34) and 37 age- and sex-matched healthy controls underwent resting-state functional magnetic resonance imaging (R-fMRI) examination. The fALFF values were measured from all subjects and were compared among the left palsy, right palsy, and control groups. Then, correlations between the Toronto Facial Grading System (TFGS) scores of the patients and the fALFF values of abnormal brain regions were analyzed. Results: Significant group differences in fALFF values among the three groups were observed mainly in the cerebral cortical, subcortical, and deep gray matter regions. Compared with the right Bell's palsy group, the left Bell's palsy group showed significantly decreased fALFF values in the left temporal pole of the superior temporal gyrus (TPOsup), right supramarginal, left and right middle cingulate cortex (MCC), left superior frontal gyrus (SFG), and left precentral gyrus (PreCG), and increased fALFF values were observed in the right SFG and PreCG. Furthermore, altered fALFF values correlated positively with the TFGS scores in the left superior TPO, bilateral MCC, and right PreCG, and correlated negatively with the TFGS scores in the right SFG of the left Bell's palsy group. Altered fALFF values correlated positively with the TFGS scores in the bilateral MCC and right PreCG and correlated negatively with the TFGS scores in the left superior TPO and SFG of the right Bell's palsy group. Conclusion: Regulatory mechanisms seem to differ between patients with left and right early Bell's palsy. The severity of the disease is associated with these functional alterations.

PMID: 30450029 [PubMed]

Disturbed effective connectivity patterns in an intrinsic triple network model are associated with posttraumatic stress disorder.

Tue, 11/20/2018 - 18:18
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Disturbed effective connectivity patterns in an intrinsic triple network model are associated with posttraumatic stress disorder.

Neurol Sci. 2018 Nov 17;:

Authors: Weng Y, Qi R, Zhang L, Luo Y, Ke J, Xu Q, Zhong Y, Li J, Chen F, Cao Z, Lu G

Abstract
BACKGROUND: Disturbance of the triple network model was recently proposed to be associated with the occurrence of posttraumatic stress disorder (PTSD) symptoms. Based on resting-state dynamic causal modeling (rs-DCM) analysis, we investigated the neurobiological model at a neuronal level along with potential neuroimaging biomarkers for identifying individuals with PTSD.
METHODS: We recruited survivors of a devastating typhoon including 27 PTSD patients, 33 trauma-exposed controls (TECs), and 30 healthy controls without trauma exposure. All subjects underwent resting-state functional magnetic resonance imaging. Independent components analysis was used to identify triple networks. Detailed effective connectivity patterns were estimated by rs-DCM analysis. Spearman correlation analysis was performed on aberrant DCM parameters with clinical assessment results relevant to PTSD diagnosis. We also carried out step-wise binary logistic regression and receiver operating characteristic curve (ROC) analysis to confirm the capacity of altered effective connectivity parameters to distinguish PTSD patients.
RESULTS: Within the executive control network, enhanced positive connectivity from the left posterior parietal cortex to the left dorsolateral prefrontal cortex was correlated with intrusion symptoms and showed good performance (area under the receiver operating characteristic curve = 0.879) in detecting PTSD patients. In the salience network, we observed a decreased causal flow from the right amygdala to the right insula and a lower transit value for the right amygdala in PTSD patients relative to TECs.
CONCLUSION: Altered effective connectivity patterns in the triple network may reflect the occurrence of PTSD symptoms, providing a potential biomarker for detecting patients. Our findings shed new insight into the neural pathophysiology of PTSD.

PMID: 30448966 [PubMed - as supplied by publisher]

Imaging functional motor connectivity in hemiparetic children with perinatal stroke.

Sun, 11/18/2018 - 21:16
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Imaging functional motor connectivity in hemiparetic children with perinatal stroke.

Hum Brain Mapp. 2018 Nov 17;:

Authors: Saunders J, Carlson HL, Cortese F, Goodyear BG, Kirton A

Abstract
Perinatal stroke causes lifelong disability, particularly hemiparetic cerebral palsy. Arterial ischemic strokes (AIS) are large, cortical, and subcortical injuries acquired near birth due to acute occlusion of the middle cerebral artery. Periventricular venous infarctions (PVI) are smaller, subcortical strokes acquired prior to 34 weeks gestation involving injury to the periventricular white matter. Both stroke types can damage motor pathways, thus, we investigated resulting alterations in functional motor networks and probed function. We measured blood oxygen level dependent (BOLD) fluctuations at rest in 38 participants [10 arterial patients (age = 14.7 ± 4.1 years), 10 venous patients (age = 13.5 ± 3.7 years), and 18 typically developing controls (TDCs) (age = 15.3 ± 5.1 years)] and explored strength and laterality of functional connectivity in the motor network. Inclusion criteria included MRI-confirmed, unilateral perinatal stroke, symptomatic hemiparetic cerebral palsy, and 6-19 years old at time of imaging. Seed-based functional connectivity analyses measured temporal correlations in BOLD response over the whole brain using primary motor cortices as seeds. Laterality indices based on mean z-scores in lesioned and nonlesioned hemispheres explored laterality. In AIS patients, significant differences in both strength and laterality of motor network connections were observed compared with TDCs. In PVI patients, motor networks largely resembled those of healthy controls, albeit slightly weaker and asymmetric, despite subcortical damage and hemiparesis. Functional connectivity strengths were not related to motor outcome scores for either stroke group. This study serves as a foundation to better understand how resting-state fMRI can assess motor functional connectivity and potentially be applied to explore mechanisms of interventional therapies after perinatal stroke.

PMID: 30447082 [PubMed - as supplied by publisher]

Frequency-specific noninvasive modulation of memory retrieval and its relationship with hippocampal network connectivity.

Sun, 11/18/2018 - 21:16
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Frequency-specific noninvasive modulation of memory retrieval and its relationship with hippocampal network connectivity.

Hippocampus. 2018 Nov 17;:

Authors: Hermiller MS, VanHaerents S, Raij T, Voss JL

Abstract
Episodic memory is thought to rely on interactions of the hippocampus with other regions of the distributed hippocampal-cortical network (HCN) via interregional activity synchrony in the theta frequency band. We sought to causally test this hypothesis using network-targeted transcranial magnetic stimulation. Healthy humans participants completed four experimental sessions, each involving a different stimulation pattern delivered to the same individualized parietal cortex location of the HCN for all sessions. There were three active stimulation conditions, including continuous theta-burst stimulation, intermittent theta-burst stimulation, and beta-frequency (20-Hz) repetitive stimulation, and one sham condition. Resting-state fMRI and episodic memory testing were used to assess the impact of stimulation on hippocampal fMRI connectivity related to retrieval success. We hypothesized that theta-burst stimulation conditions would most strongly influence hippocampal-HCN fMRI connectivity and retrieval, given the hypothesized relevance of theta-band activity for HCN memory function. Continuous theta-burst stimulation improved item retrieval success relative to sham and relative to beta-frequency stimulation, whereas intermittent theta-burst stimulation led to numerical but nonsignificant item retrieval improvement. Mean hippocampal fMRI connectivity did not vary for any stimulation conditions, whereas individual differences in retrieval improvements due to continuous theta-burst stimulation were associated with corresponding increases in fMRI connectivity between the hippocampus and other HCN locations. No such memory-related connectivity effects were identified for the other stimulation conditions, indicating that only continuous theta-burst stimulation affected memory-related hippocampal-HCN connectivity. Furthermore, these effects were specific to the targeted HCN, with no significant memory-related fMRI connectivity effects for two distinct control brain networks. These findings support a causal role for fMRI connectivity of the hippocampus with the HCN in episodic memory retrieval and indicate that contributions of this network to retrieval are particularly sensitive to continuous theta-burst noninvasive stimulation. This article is protected by copyright. All rights reserved.

PMID: 30447076 [PubMed - as supplied by publisher]

Non-invasive evaluation of cerebral perfusion in patients with transient ischemic attack: an fMRI study.

Sun, 11/18/2018 - 21:16
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Non-invasive evaluation of cerebral perfusion in patients with transient ischemic attack: an fMRI study.

J Neurol. 2018 Nov 16;:

Authors: Lv Y, Wei W, Song Y, Han Y, Zhou C, Zhou D, Zhang F, Xue Q, Liu J, Zhao L, Zhang C, Li L, Zang YF, Han X

Abstract
Detection of hypoperfused tissue due to the ischemia is considered to be important in understanding the cerebral perfusion status and may be helpful in guiding therapeutic decisions for patients with transient ischemic attack (TIA). We hypothesized that the combination of two non-invasive fMRI techniques: resting-state BOLD-fMRI time-shift analysis (TSA) approach and 3D ASL, could detect the cerebral hemodynamic status in TIA patients noninvasively. From April 2015 to June 2016, 51 TIA patients were recruited in this study. We calculated the time delay between the resting-state BOLD signal at each voxel and the whole-brain signal using TSA approach and compared the results to CBF map derived from ASL. Out of the 51 patients, 24 patients with normal arrival time and CBF were in Stage 0; 14 patients who showed delayed arrival time and normal CBF which indicated elevated CBV were in Stage I; the other 13 patients who had both delayed arrival time and decreased CBF were in Stage II, the group average spatial overlap, i.e., Dice coefficient, of the two measurements was 0.55. Four patients in Stage 0 (17.4%), three patients in Stage I (23.1%) and five patients in Stage II (45.5%) suffered ischemic stroke or TIA symptoms in 1 year after MRI scan. The patients in Stage II was at highest risk of subsequent events when compared to other two stages. The combination of resting-state BOLD-fMRI and ASL hold the potential to noninvasively identify the hemodynamic status in TIA patients and help predict the risk of subsequent events.

PMID: 30446964 [PubMed - as supplied by publisher]

Early functional connectivity deficits and progressive microstructural alterations in the TgF344-AD rat model of Alzheimer's Disease: A longitudinal MRI study.

Sun, 11/18/2018 - 21:16
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Early functional connectivity deficits and progressive microstructural alterations in the TgF344-AD rat model of Alzheimer's Disease: A longitudinal MRI study.

Neurobiol Dis. 2018 Nov 13;:

Authors: Anckaerts C, Blockx I, Summer P, Michael J, Hamaide J, Kreutzer C, Boutind H, Couillard-Després S, Verhoye M, Van der Linden A

Abstract
The development and characterization of new improved animal models is pivotal in Alzheimer's Disease (AD) research, since valid models enable the identification of early pathological processes, which are often not accessible in patients, as well as subsequent target discovery and evaluation. The TgF344-AD rat model of AD, bearing mutant human amyloid precursor protein (APPswe) and Presenilin 1 (PSEN1ΔE9) genes, has been described to manifest the full spectrum of AD pathology similar to human AD, i.e. progressive cerebral amyloidosis, tauopathy, neuronal loss and age-dependent cognitive decline. Here, AD-related pathology in female TgF344-AD rats was examined longitudinally between 6 and 18 months by means of complementary translational MRI techniques: resting state functional MRI (rsfMRI) to evaluate functional connectivity (FC) and diffusion tensor imaging (DTI) to assess the microstructural integrity. Additionally, an evaluation of macroscopic changes (3D anatomical MRI) and an image-guided validation of ex vivo pathology were performed. We identified slightly decreased FC at 6 months followed by severe and widespread hypoconnectivity at 10 months of age as the earliest detectable pathological MRI hallmark. This initial effect was followed by age-dependent progressive microstructural deficits in parallel with age-dependent ex vivo AD pathology, without signs of macroscopic alterations such as hippocampal atrophy. This longitudinal MRI study in the TgF344-AD rat model of AD revealed early rsfMRI and DTI abnormalities as seen in human AD patients. The characterization of AD pathology in this rat model using non-invasive MRI techniques further highlights the translational value of this model, as well as its use for potential treatment evaluation.

PMID: 30445024 [PubMed - as supplied by publisher]

Regularized Spatial Filtering Method (R-SFM) for detection of Attention Deficit Hyperactivity Disorder (ADHD) from resting-state functional Magnetic Resonance Imaging (rs-fMRI).

Sun, 11/18/2018 - 21:16
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Regularized Spatial Filtering Method (R-SFM) for detection of Attention Deficit Hyperactivity Disorder (ADHD) from resting-state functional Magnetic Resonance Imaging (rs-fMRI).

Conf Proc IEEE Eng Med Biol Soc. 2018 Jul;2018:5541-5544

Authors: Aradhya AMS, Subbaraju V, Sundaram S, Sundararajan N

Abstract
Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental problem in children. Resting state functional magnetic resonance imaging (rs-fMRI) provides an important tool in understanding the aberrant functional mechanisms in ADHD patients and assist in clinical diagnosis. Recently, spatio-temporal decomposition via spatial filtering (Fukunaga-Koontz transform, ICA) have gained attention in the analysis of fMRI time-series data. Their ability to decompose the blood oxygen level dependent (BOLD) rs-fMRI time series data into discriminative spatial and temporal components have resulted in better classification accuracy and the ability to isolate the important brain circuits responsible for the observed differences in brain activity. However, they are prone to errors in the estimation of covariance matrices due to the significant presence of atypical samples in the ADHD dataset. In this paper, we present a regularization framework to obtain a robust estimation of the covariance matrices such that the effect of atypical samples is reduced. The resulting approach called as regularized spatial filtering method (R-SFM) further uses Mahalanobis whitening to lower the effect of two-way correlations while preserving the spatial arrangement of the data in the feature extraction process. R-SFM was evaluated on the benchmark ADHD200 dataset and not only obtained a 6% improvement in classification accuracy, but also a 66.66% decrease in standard deviation over the previously developed SFM approach. Also R-SFM produces higher specificity which results in lower misclassification of ADHD, thereby reducing the risk of misdiagnosis. These results clearly show that R- SFM provides an accurate and reliable tool for detection of ADHD from BOLD rs-fMRI time series data.

PMID: 30441592 [PubMed - in process]

Craniectomy Effects on Resting State Functional Connectivity and Cognitive Performance in Immature Rats.

Sun, 11/18/2018 - 21:16
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Craniectomy Effects on Resting State Functional Connectivity and Cognitive Performance in Immature Rats.

Conf Proc IEEE Eng Med Biol Soc. 2018 Jul;2018:5414-5417

Authors: Sargolzaei S, Cai Y, Walker MJ, Hovda DA, Harris NG, Giza CC

Abstract
Experimental models have been proven to be valuable tools to understand downstream cellular mechanisms of Traumatic Brain Injury (TBI). The models allow for reduction of confounding variables and tighter control of varying parameters. It has been recently reported that craniectomy induces pro-inflammatory responses, which therefore needs to be properly addressed given the fact that craniectomy is often considered a control procedure for experimental TBI models. The current study aims to determine whether a craniectomy induces alterations in Resting State Network (RSN) in a developmental rodent model. Functional Magnetic Resonance Imaging (fMRI) data-driven RSN show clusters of peak differences (left caudate putamen, somatosensory cortex, amygdala and piriform cortex) between craniectomy and control group, four days post-craniectomy. In addition, the Novel Object Recognition (NOR) task revealed impaired working memory in the craniectomy group. This evidence supports craniectomy-induced neurological changes which need to be carefully addressed, considering the frequent use of craniectomy as a control procedure for experimental models of TBI.

PMID: 30441561 [PubMed - in process]