New resting-state fMRI related studies at PubMed

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Young children in different linguistic environments: A multimodal neuroimaging study of the inferior frontal gyrus.

Tue, 07/17/2018 - 14:40
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Young children in different linguistic environments: A multimodal neuroimaging study of the inferior frontal gyrus.

Brain Cogn. 2018 Jul 11;:

Authors: Thieba C, Long X, Dewey D, Lebel C

Abstract
Magnetic resonance imaging (MRI) studies show that bilingual adults display structural and functional brain alterations, especially in the inferior frontal gyrus (IFG), dependent on when they learned their second language. However, it is unclear whether these differences are due to early exposure to another language, or to lifelong adaptation. We studied 22 children aged 3-5 years growing up in a multilingual environment and 22 age- and sex-matched controls exposed to an English-only environment. Resting-state functional MRI and T1-weighted MRI were used to assess functional connectivity and structure of the IFG. Children in a multilingual environment had higher functional connectivity between the left IFG and dorsal language and attention areas compared to children from a monolingual environment. Children in a multilingual environment also displayed decreased functional connectivity to temporal, anterior cingulate, and prefrontal areas. No significant group differences in IFG structure were observed. Our results suggest a more integrated functional language network, which is more segregated from other networks, in children who grow up in a multilingual environment. These findings suggest that functional alterations to the IFG due to second language learning occur early, while structural changes may not be apparent until later.

PMID: 30007529 [PubMed - as supplied by publisher]

Functional MR Imaging: Blood Oxygen Level-Dependent and Resting State Techniques in Mild Traumatic Brain Injury.

Tue, 07/17/2018 - 14:40
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Functional MR Imaging: Blood Oxygen Level-Dependent and Resting State Techniques in Mild Traumatic Brain Injury.

Neuroimaging Clin N Am. 2018 Feb;28(1):107-115

Authors: Rosenthal S, Gray M, Fatima H, Sair HI, Whitlow CT

Abstract
This article discusses mild traumatic brain injury (mTBI)-associated effects on brain functional connectivity assessed via resting-state functional MR (fMR) imaging. Several studies have reported acute post-injury default mode network hyperconnectivity, followed by a period of decreased connectivity before later connectivity normalization in some patients. Other studies have reported mTBI associated effects on connectivity that remain evident for up to 5-years or more. Discordance in the published literature regarding the direction of network connectivity changes (eg, increased versus decreased connectivity) may reflect differences in timing of data collection post-injury, as well as the need to standardize MR imaging acquisition protocols and processing methods.

PMID: 29157847 [PubMed - indexed for MEDLINE]

Frequency and amplitude modulation of resting-state fMRI signals and their functional relevance in normal aging.

Sun, 07/15/2018 - 12:20
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Frequency and amplitude modulation of resting-state fMRI signals and their functional relevance in normal aging.

Neurobiol Aging. 2018 Jun 15;70:59-69

Authors: Yang AC, Tsai SJ, Lin CP, Peng CK, Huang NE

Abstract
The intrinsic composition and functional relevance of resting-state blood oxygen level-dependent signals are fundamental in research using functional magnetic resonance imaging (fMRI). Using the Hilbert-Huang Transform to estimate high-resolution time-frequency spectra, we investigated the instantaneous frequency and amplitude modulation of resting-state fMRI signals, as well as their functional relevance in a large normal-aging cohort (n = 420, age = 21-89 years). We evaluated the cognitive function of each participant and recorded respiratory signals during fMRI scans. The results showed that the Hilbert-Huang Transform effectively categorized resting-state fMRI power spectra into high (0.087-0.2 Hz), low (0.045-0.087 Hz), and very-low (≤0.045 Hz) frequency bands. The high-frequency power was associated with respiratory activity, and the low-frequency power was associated with cognitive function. Furthermore, within the cognition-related low-frequency band (0.045-0.087 Hz), we discovered that aging was associated with the increased frequency modulation and reduced amplitude modulation of the resting-state fMRI signal. These aging-related changes in frequency and amplitude modulation of resting-state fMRI signals were unaccounted for by the loss of gray matter volume and were consistently identified in the default mode and salience network. These findings indicate that resting-state fMRI signal modulations are dynamic during the normal aging process. In summary, our results refined the functionally related blood oxygen level-dependent frequency band in a considerably narrow band at a low-frequency range (0.045-0.087 Hz) and challenged the current method of resting-fMRI preprocessing by using low-frequency filters with a relatively wide range below 0.1 Hz.

PMID: 30007165 [PubMed - as supplied by publisher]

Spontaneous Changes in Functional Connectivity of Independent Components of fMRI Signal in Healthy Volunteers at Rest and in Subjects with Mild Depression.

Sun, 07/15/2018 - 12:20
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Spontaneous Changes in Functional Connectivity of Independent Components of fMRI Signal in Healthy Volunteers at Rest and in Subjects with Mild Depression.

Bull Exp Biol Med. 2018 Jul 14;:

Authors: Bezmaternykh DD, Mel'nikov ME, Petrovskii ED, Kozlova LI, Shtark MB, Savelov AA, Shubina OS, Natarova KA

Abstract
Depression is associated with changes in the pattern of interaction of cerebral networks, which can reflect both existing symptoms and compensatory processes. The study is based on analysis of resting state fMRI data from 15 patients with mild depression and 19 conventionally healthy individuals. From fMRI signal recorded at rest for 4 min, the independent components were reconstructed. The intergroup differences and dynamics of functional connectivity from the first to the second recording were analyzed. Initially, depressive patients demonstrated weaker connectivity between cerebellar declive network (CN) and left central executive network (CEN) and also sensorimotor network (SMN); left CEN and primary visual network (PVN). During the second recording, the patients demonstrated more intensive reciprocal connection of the dorsal domain of default mode network (DMN) and auditory network (AN). In healthy subjects, positive correlations of the dorsal DMN and left CEN, right CEN and CN, and negative correlation of dorsal DMN and visuospatial network weakened from the first to second record. In the depression group, the interaction of AN with PVN, the right CEN with the anterior salience network and with ventral DMN weakened. At the same time, the connectivity between SMN and CN were strengthened. The results can be interpreted as spontaneous normalization of brain activity, but no direct evidence for their relation to the improvement of depression symptoms was found.

PMID: 30006882 [PubMed - as supplied by publisher]

The affinity of antipsychotic drugs to dopamine and serotonin 5-HT2 receptors determines their effects on prefrontal-striatal functional connectivity.

Sun, 07/15/2018 - 12:20
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The affinity of antipsychotic drugs to dopamine and serotonin 5-HT2 receptors determines their effects on prefrontal-striatal functional connectivity.

Eur Neuropsychopharmacol. 2018 Jul 10;:

Authors: Tollens F, Gass N, Becker R, Schwarz AJ, Risterucci C, Künnecke B, Lebhardt P, Reinwald J, Sack M, Weber-Fahr W, Meyer-Lindenberg A, Sartorius A

Abstract
One of the major challenges of cross-species translation in psychiatry is the identification of quantifiable brain phenotypes linked to drug efficacy and/or side effects. A measure that has received increasing interest is the effect of antipsychotic drugs on resting-state functional connectivity (FC) in magnetic resonance imaging. However, quantitative comparisons of antipsychotic drug-induced alterations of FC patterns are missing. Consideration of receptor binding affinities provides a means for the effects of antipsychotic drugs on extended brain networks to be related directly to their molecular mechanism of action. Therefore, we examined the relationship between the affinities of three second-generation antipsychotics (amisulpride, risperidone and olanzapine) to dopamine and serotonin receptors and FC patterns related to the prefrontal cortex (PFC) and striatum in Sprague-Dawley rats. FC of the relevant regions was quantified by correlation coefficients and local network properties. Each drug group (32 animals per group) was subdivided into three dose groups and a vehicle control group. A linear relationship was discovered for the mid-dose of antipsychotic compounds, with stronger affinity to serotonin 5-HT2A, 5-HT2C and 5-HT1A receptors and decreased affinity to D3 receptors associated with increased prefrontal-striatal FC (p = 0.0004, r² = 0.46; p = 0.004, r² = 0.33; p = 0.002, r² = 0.37; p = 0.02, r² = 0.22, respectively). Interestingly, no correlation was observed for the low and high dose groups, and for D2 receptors. Our results indicate that drug-induced FC patterns may be linked to antipsychotic mechanism of action on the molecular level and suggest the technique's value for drug development, especially if our results are extended to a larger number of antipsychotics.

PMID: 30006253 [PubMed - as supplied by publisher]

Intrinsic overlapping modular organization of human brain functional networks revealed by a multiobjective evolutionary algorithm.

Sun, 07/15/2018 - 12:20
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Intrinsic overlapping modular organization of human brain functional networks revealed by a multiobjective evolutionary algorithm.

Neuroimage. 2018 Jul 10;:

Authors: Lin Y, Ma J, Gu Y, Yang S, Wai Li LM, Dai Z

Abstract
A wealth of research on resting-state functional MRI (R-fMRI) data has revealed modularity as a fundamental characteristic of the human brain functional network. The modular structure has recently been suggested to be overlapping, meaning that a brain region may engage in multiple modules. However, not only the overlapping modular structure remains inconclusive, the topological features and functional roles of overlapping regions are also poorly understood. To address these issues, the present work utilized the maximal-clique based multiobjective evolutionary algorithm to explore the overlapping modular structure of the R-fMRI data obtained from 57 young healthy adults. Without prior knowledge, brain regions were optimally grouped into eight modules with wide overlap. Based on the topological features captured by graph theory analyses, overlapping regions were classified into an integrated club and a dominant minority club through clustering. Functional flexibility analysis found that overlapping regions in both clubs were significantly more flexible than non-overlapping ones. Lesion simulations revealed that targeted attack at overlapping regions were more damaging than random failure or even targeted attack at hub regions. In particular, overlapping regions in the dominant minority club were more flexible and more crucial for information communication than the others were. Together, our findings demonstrated the highly organized overlapping modular architecture and revealed the importance as well as complexity of overlapping regions from both topological and functional aspects, which provides important implications for their roles in executing multiple tasks and maintaining information communication.

PMID: 30005918 [PubMed - as supplied by publisher]

Multimodal cortical and hippocampal prediction of episodic-memory plasticity in young and older adults.

Sat, 07/14/2018 - 11:20

Multimodal cortical and hippocampal prediction of episodic-memory plasticity in young and older adults.

Hum Brain Mapp. 2018 Jul 13;:

Authors: Bråthen ACS, de Lange AG, Rohani DA, Sneve MH, Fjell AM, Walhovd KB

Abstract
Episodic memory can be trained in both early and late adulthood, but there is considerable variation in cognitive improvement across individuals. Which brain characteristics make some individuals benefit more than others? We used a multimodal approach to investigate whether volumetric magnetic resonance imaging (MRI) and resting-state functional MRI characteristics of the cortex and hippocampus, brain regions involved in episodic-memory function, were predictive of cognitive improvement after memory training. We hypothesized that these brain characteristics would differentially predict memory improvement in young and older adults, given the vulnerability of cortical regions as well as the hippocampus to healthy aging. Following structural and resting-state activity magnetic resonance scans, 50 young and 76 older participants completed 10 weeks of strategic episodic-memory training. Both age groups improved their memory performance, but the young adults more so than the older. Vertex-wise analyses of cortical volume showed no significant relation to memory benefit. When analyzing the two age groups separately, hippocampal volume was predictive of memory improvement in the group of older participants only. In this age group, the lower resting-state activity of the hippocampus was also predictive of memory improvement. Both volumetric and resting-state characteristics of the hippocampus explained unique variance of the improvement in the older participants suggesting that a multimodal imaging approach is valuable for the understanding of mechanisms underlying memory plasticity in aging.

PMID: 30004603 [PubMed - as supplied by publisher]

Altered nuclei-specific thalamic functional connectivity patterns in multiple sclerosis and their associations with fatigue and cognition.

Sat, 07/14/2018 - 11:20

Altered nuclei-specific thalamic functional connectivity patterns in multiple sclerosis and their associations with fatigue and cognition.

Mult Scler. 2018 Jul 01;:1352458518788218

Authors: Lin F, Zivadinov R, Hagemeier J, Weinstock-Guttman B, Vaughn C, Gandhi S, Jakimovski D, Hulst HE, Benedict RH, Bergsland N, Fuchs T, Dwyer MG

Abstract
BACKGROUND: The thalamus, affected early in multiple sclerosis (MS), is a heterogeneous composition of functionally distinct nuclei and is associated with fatigue, cognition, and other outcomes. However, most previous functional imaging studies considered the thalamus only as a whole.
OBJECTIVE: To investigate MS-related abnormalities in nuclei-specific thalamic functional connectivity (FC) and their associations with fatigue and cognitive outcomes.
METHODS: Resting-state functional magnetic resonance imaging (fMRI) was analyzed in 64 MS patients and 26 healthy controls (HC). Whole-brain FC maps for four thalamic subregions seeds were computed for each subject. FC maps were compared between groups, and group by FC interaction effects were assessed for fatigue and cognitive measures.
RESULTS: MS patients had decreased FC between the left medial thalamic nuclei and left angular gyrus and reduced FC between the left posterior thalamic nuclei and left supramarginal gyrus, as well as decreased right medial thalamic nuclei connectivity with bilateral caudate/thalamus and left cerebellar areas ( p < 0.05 corrected). MS patients had increased FC between the left anterior thalamic nuclei and anterior cingulate cortex bilaterally. There were significant relationships between connectivity alterations and fatigue and cognitive measures between groups ( p < 0.05 corrected).
CONCLUSION: FC alteration is nuclei-specific and is differentially associated with fatigue and cognition.

PMID: 30004291 [PubMed - as supplied by publisher]

Test-retest variability of resting-state networks in healthy aging and prodromal Alzheimer's disease.

Sat, 07/14/2018 - 11:20
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Test-retest variability of resting-state networks in healthy aging and prodromal Alzheimer's disease.

Neuroimage Clin. 2018;19:948-962

Authors: Conwell K, von Reutern B, Richter N, Kukolja J, Fink GR, Onur OA

Abstract
In recent years, changes in resting-state networks (RSN), identified by functional magnetic resonance imaging (fMRI), have gained increasing attention as potential biomarkers and trackers of neurological disorders such as Alzheimer's disease (AD). Intersession reliability of RSN is fundamental to this approach. In this study, we investigated the test-retest reliability of three memory related RSN (i.e., the default mode, salience, and executive control network) in 15 young, 15 healthy seniors (HS), and 15 subjects affected by mild cognitive impairment (MCI) with positive biomarkers suggestive of incipient AD (6 females each). FMRI was conducted on three separate occasions. Independent Component Analysis decomposed the resting-state data into RSNs. Comparisons of variation in functional connectivity between groups were made applying different thresholds in an explorative approach. Intersession test-retest reliability was evaluated by intraclass correlation coefficient (ICC) comparisons. To assess the effect of gray matter volume loss, motion, cerebrospinal fluid based biomarkers and the time gap between sessions on intersession variation, the former four were correlated separately with the latter. Data showed that i) young subjects ICCs (relative to HS/MCI-subjects) had higher intersession reliability, ii) stringent statistical thresholds need to be applied to prevent false-positives, iii) both HS and MCI-subjects (relative to young) showed significantly more clusters of intersession variation in all three RSN, iv) while intersession variation was highly correlated with head motion, it was also correlated with biomarkers (especially phospho-tau), the time gap between sessions and local GMV. Results indicate that time gaps between sessions should be kept constant and that head motion must be taken into account when using RSN to assess aging and neurodegeneration. In patients with prodromal AD, re-test reliability may be increased by accouting for overall disease burden by including biomarkers of neuronal injury (especially phospho-tau) in statistical analyses. Local atrophy however, does not seem to play a major role in regards to reliability, but should be used as covariate depending on the research question.

PMID: 30003032 [PubMed - in process]

Abnormal dynamic functional connectivity between speech and auditory areas in schizophrenia patients with auditory hallucinations.

Sat, 07/14/2018 - 11:20
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Abnormal dynamic functional connectivity between speech and auditory areas in schizophrenia patients with auditory hallucinations.

Neuroimage Clin. 2018;19:918-924

Authors: Zhang W, Li S, Wang X, Gong Y, Yao L, Xiao Y, Liu J, Keedy SK, Gong Q, Sweeney JA, Lui S

Abstract
Purpose: Auditory hallucinations (AH), typically hearing voices, are a core symptom in schizophrenia. They may result from deficits in dynamic functional connectivity (FC) between cortical regions supporting speech production and language perception that interfere with the ability to recognize self-generated speech as not coming from external sources. We tested this hypothesis by investigating dynamic connectivity between the frontal cortex region related to language production and the temporal cortex region related to auditory processing.
Methods: Resting-state fMRI scans were acquired from 18 schizophrenia patients with AH (AH+), 17 schizophrenia patients without AH (AH-) and 22 healthy controls. A multiband sequence with TR = 427 ms was adopted to provide relatively high temporal resolution data for characterizing dynamic FC. Analysis focused on connectivity between speech production and language comprehension areas, eloquent language cortex in the left hemisphere. Two frequency bands of brain oscillatory activity were evaluated (0.01-0.027 Hz, 0.027-0.08 Hz) in which differential alterations that have been previously linked to schizophrenia. Conventional static FC maps of these seeds were also calculated.
Results: Dynamic connectivity analysis indicated that AH+ patients showed not only less temporal variability but transient lower strength in connectivity between speech and auditory areas than healthy controls, while AH- patients not. These findings were restricted to 0.027-0.08 Hz activity. In static connectivity analysis, no significant differences were observed in connectivity between speech production and language comprehension areas in either frequency band.
Conclusions: Reduced temporal variability and connectivity strength between key regions of eloquent language cortex may represent a mechanism for AH in schizophrenia.

PMID: 30003029 [PubMed - in process]

Pharmacological fMRI: Effects of subanesthetic ketamine on resting-state functional connectivity in the default mode network, salience network, dorsal attention network and executive control network.

Sat, 07/14/2018 - 11:20
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Pharmacological fMRI: Effects of subanesthetic ketamine on resting-state functional connectivity in the default mode network, salience network, dorsal attention network and executive control network.

Neuroimage Clin. 2018;19:745-757

Authors: Mueller F, Musso F, London M, de Boer P, Zacharias N, Winterer G

Abstract
Background: Subanesthetic dosages of the NMDAR antagonist, S-Ketamine, can cause changes in behavior in healthy subjects, which are similar to the state acute psychosis and are relevant in translational schizophrenia research. Functional magnetic resonance imaging (fMRI) can be used for non-hypothesis-driven analysis of brain connectivity. The correlation between clinical behavioral scores and neuroimaging can help to characterize ketamine effects on healthy brains in resting state.
Method: seventeen healthy, male subjects (mean: 27.42 years, SD: 4.42) were administered an infusion with S-Ketamine (initial bolus 1 mg/kg and continuous infusion of 0.015625 mg/kg/min with dosage reduction -10%/10 min) or saline in a randomized, double-blind, cross-over study. During infusion, resting state connectivity was measured and analyzed with a seed-to-voxel fMRI analysis approach. The seed regions were located in the posterior cingulate cortex, intraparietal sulcus, dorsolateral prefrontal cortex and fronto-insular cortex. Receiver operating characteristics (ROC) were calculated to assess the accuracy of the ketamine-induced functional connectivity changes. Bivariate Pearson correlation was used for correlation testing of functional connectivity changes with changes of clinical scores (PANSS, 5D-ASC).
Results: In the executive network (ECN), ketamine significantly increases the functional connectivity with parts of the anterior cingulum and superior frontal gyrus, but no significant correlations with clinical symptoms were found. Decreased connectivity between the salience network (SN) and the calcarine fissure was found, which is significantly correlated with negative symptoms (PANSS) (R2 > 0.4).
Conclusion: Decreased ketamine-induced functional connectivity in the salience network may qualify as accurate and highly predictive biomarkers for ketamine induced negative symptoms.

PMID: 30003027 [PubMed - in process]

Altered Intrinsic Coupling between Functional Connectivity Density and Amplitude of Low-Frequency Fluctuation in Mild Cognitive Impairment with Depressive Symptoms.

Sat, 07/14/2018 - 11:20
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Altered Intrinsic Coupling between Functional Connectivity Density and Amplitude of Low-Frequency Fluctuation in Mild Cognitive Impairment with Depressive Symptoms.

Neural Plast. 2018;2018:1672708

Authors: Liu X, Chen J, Shen B, Wang G, Li J, Hou H, Chen X, Guo Z, Mao C

Abstract
Neuroimaging studies have demonstrated that major depressive disorder increases the risk of dementia in older individuals with mild cognitive impairment. We used resting-state functional magnetic resonance imaging to explore the intrinsic coupling patterns between the amplitude and synchronisation of low-frequency brain fluctuations using the amplitude of low-frequency fluctuations (ALFF) and the functional connectivity density (FCD) in 16 patients who had mild cognitive impairment with depressive symptoms (D-MCI) (mean age: 69.6 ± 6.2 years) and 18 patients with nondepressed mild cognitive impairment (nD-MCI) (mean age: 72.1 ± 9.7 years). Coupling was quantified as the correlations between the ALFF values and their associated FCDs. The results showed that the ALFF values in the D-MCI group were higher in the left medial prefrontal cortex (mPFC) and lower in the right precentral gyrus (preCG), and the FCD values were higher in the left medial temporal gyrus (MTG) than those in the nD-MCI group. Further, correlation analyses demonstrated that, in the D-MCI group, the mPFC was negatively correlated with the MTG. These findings may relate to the characteristics of mood disorders in patients with MCI, and they offer further insight into the neuropathophysiology of MCI with depressive symptoms.

PMID: 30002672 [PubMed - in process]

Increasing isoflurane dose reduces homotopic correlation and functional segregation of brain networks in mice as revealed by resting-state fMRI.

Sat, 07/14/2018 - 11:20
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Increasing isoflurane dose reduces homotopic correlation and functional segregation of brain networks in mice as revealed by resting-state fMRI.

Sci Rep. 2018 Jul 12;8(1):10591

Authors: Bukhari Q, Schroeter A, Rudin M

Abstract
Effects of anesthetics on brain functional networks are not fully understood. In this work, we investigated functional brain networks derived from resting-state fMRI data obtained under different doses of isoflurane in mice using stationary and dynamic functional connectivity (dFC) analysis. Stationary network analysis using FSL Nets revealed a modular structure of functional networks, which could be segregated into a lateral cortical, an associative cortical network, elements of the prefrontal network, a subcortical network, and a thalamic network. Increasing isoflurane dose led to a loss of functional connectivity between the bilateral cortical regions. In addition, dFC analysis revealed a dominance of dynamic functional states (dFS) exhibiting modular structure in mice anesthetized with a low dose of isoflurane, while at high isoflurane levels dFS showing widespread unstructured correlation displayed highest weights. This indicates that spatial segregation across brain functional networks is lost with increasing dose of the anesthetic drug used. To what extent this indicates a state of deep anesthesia remains to be shown. Combining the results of stationary and dynamic FC analysis indicates that increasing isoflurane levels leads to loss of modular network organization, which includes loss of the strong bilateral interactions between homotopic brain areas.

PMID: 30002419 [PubMed - in process]

Resting-state fMRI study on drug-naive patients of essential tremor with and without head tremor.

Sat, 07/14/2018 - 11:20
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Resting-state fMRI study on drug-naive patients of essential tremor with and without head tremor.

Sci Rep. 2018 Jul 12;8(1):10580

Authors: Wang L, Lei D, Suo X, Li N, Lu Z, Li J, Peng J, Gong Q, Peng R

Abstract
This study used resting-state functional MRI (r-fMRI) to evaluate intrinsic brain activity in drug-naive patients with essential tremor (ET) with and without head tremor. We enrolled 20 patients with ET with hand and head tremor (h-ET), 27 patients with ET without head tremor (a-ET), and 27 healthy controls (HCs). All participants underwent r-fMRI scans on a 3-T MR system. The amplitude of low-frequency fluctuation (ALFF) of blood oxygen level-dependent signals was used to characterize regional cerebral function. We identified increased ALFF value in the bilateral posterior lobe of cerebellum in the h-ET patients relative to a-ET and HCs and demonstrated that h-ET is related to abnormalities in the cerebello-cortical areas, while the a-ET is related to abnormalities in the thalamo-cortical areas. In addition, we observed the ALFF abnormality in the cerebellum (left cerebellum VIII and right cerebellum VI) correlated with the tremor score in h-ET patients and abnormal ALFF in the left precentral gyrus correlated with the age at onset and disease duration in h-ET patients. These findings may be helpful for facilitating further understanding of the potential mechanisms underlying different subtypes of ET.

PMID: 30002390 [PubMed - in process]

Preoperative Mapping of the Supplementary Motor Area in Patients with Brain Tumor Using Resting-State fMRI with Seed-Based Analysis.

Sat, 07/14/2018 - 11:20
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Preoperative Mapping of the Supplementary Motor Area in Patients with Brain Tumor Using Resting-State fMRI with Seed-Based Analysis.

AJNR Am J Neuroradiol. 2018 Jul 12;:

Authors: Wongsripuemtet J, Tyan AE, Carass A, Agarwal S, Gujar SK, Pillai JJ, Sair HI

Abstract
BACKGROUND AND PURPOSE: The supplementary motor area can be a critical region in the preoperative planning of patients undergoing brain tumor resection because it plays a role in both language and motor function. While primary motor regions have been successfully identified using resting-state fMRI, there is variability in the literature regarding the identification of the supplementary motor area for preoperative planning. The purpose of our study was to compare resting-state fMRI to task-based fMRI for localization of the supplementary motor area in a large cohort of patients with brain tumors presenting for preoperative brain mapping.
MATERIALS AND METHODS: Sixty-six patients with brain tumors were evaluated with resting-state fMRI using seed-based analysis of hand and orofacial motor regions. Rates of supplementary motor area localization were compared with those in healthy controls and with localization results by task-based fMRI.
RESULTS: Localization of the supplementary motor area using hand motor seed regions was more effective than seeding using orofacial motor regions for both patients with brain tumor (95.5% versus 34.8%, P < .001) and controls (95.2% versus 45.2%, P < .001). Bilateral hand motor seeding was superior to unilateral hand motor seeding in patients with brain tumor for either side (95.5% versus 75.8%/75.8% for right/left, P < .001). No difference was found in the ability to identify the supplementary motor area between patients with brain tumors and controls.
CONCLUSIONS: In addition to task-based fMRI, seed-based analysis of resting-state fMRI represents an equally effective method for supplementary motor area localization in patients with brain tumors, with the best results obtained with bilateral hand motor region seeding.

PMID: 30002054 [PubMed - as supplied by publisher]

Hippocampal dysfunction is associated with memory impairment in multiple sclerosis: A volumetric and functional connectivity study.

Sat, 07/14/2018 - 11:20
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Hippocampal dysfunction is associated with memory impairment in multiple sclerosis: A volumetric and functional connectivity study.

Mult Scler. 2017 Dec;23(14):1854-1863

Authors: González Torre JA, Cruz-Gómez ÁJ, Belenguer A, Sanchis-Segura C, Ávila C, Forn C

Abstract
BACKGROUND: Previous studies have suggested a relationship between neuroanatomical and neurofunctional hippocampal alterations and episodic memory impairments in multiple sclerosis (MS) patients.
OBJECTIVE: We examined hippocampus volume and functional connectivity (FC) changes in MS patients with different episodic memory capabilities.
METHODS: Hippocampal subfield volume and FC changes were compared in two subgroups of MS patients with and without episodic memory impairment (multiple sclerosis impaired (MSi) and multiple sclerosis preserved (MSp), respectively) and healthy controls (HC). A discriminant function (DF) analysis was used to identify which of these neuroanatomical and neurofunctional parameters were the most relevant components of the mnemonic profiles of HC, MSp, and MSi.
RESULTS: MSi showed reduced volume in several hippocampal subfields compared to MSp and HC. Ordinal gradation (MSi > MSp > HC) was also observed for FC between the posterior hippocampus and several cortical areas. DF-based analyses revealed that reduced right fimbria volume and enhanced FC at the right posterior hippocampus were the main neural signatures of the episodic memory impairments observed in the MSi group.
CONCLUSION: Before any sign of episodic memory alterations (MSp), FC increased on several pathways that connect the hippocampus with cortical areas. These changes further increased when the several hippocampal volumes reduced and memory deficits appeared (MSi).

PMID: 28086035 [PubMed - indexed for MEDLINE]

Typhoon-Related Post-Traumatic Stress Disorder and Trauma Might Lead to Functional Integration Abnormalities in Intra- and Inter-Resting State Networks: a Resting-State Fmri Independent Component Analysis.

Fri, 07/13/2018 - 16:20
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Typhoon-Related Post-Traumatic Stress Disorder and Trauma Might Lead to Functional Integration Abnormalities in Intra- and Inter-Resting State Networks: a Resting-State Fmri Independent Component Analysis.

Cell Physiol Biochem. 2018 Jul 12;48(1):99-110

Authors: Ke J, Zhang L, Qi R, Xu Q, Zhong Y, Liu T, Li J, Lu G, Chen F

Abstract
BACKGROUND/AIMS: Functional connectivity studies based on region of interest approach suggest altered functional connectivity of the default mode network (DMN), executive control network (ECN), and salience network (SN). The aim of this study is to determine whether intranetwork and internetwork brain connectivity are altered in both post-traumatic stress disorder (PTSD) patients and traumatized subjects without PTSD using a data-driven approach.
METHODS: Resting-state functional MRI data were acquired for 27 patients with typhoon-related PTSD, 33 trauma-exposed controls (TEC), and 30 healthy controls (HC). Functional connectivity within the DMN, ECN, and SN as well as functional and effective connectivity between these resting-state networks were examined with independent component analysis (ICA), and then compared between groups by conducting analysis of variance.
RESULTS: Within the DMN, the TEC group showed decreased and increased functional connectivity in the superior frontal gyrus compared with the PTSD group and the HC group, respectively. The TEC group showed increased angular functional connectivity within the DMN and decreased functional connectivity in the superior temporal gyrus/posterior insula within the SN relative to the HC group. Compared with the TEC group, the PTSD group showed increased functional connectivity in the middle frontal gyrus and supplementary motor area within the ECN as well as in the inferior frontal gyrus/anterior insula within the SN. The PTSD group showed decreased functional connectivity in the supplementary motor area within the SN relative to both control groups. Moreover, the PTSD showed increased excitatory influence from the ECN to DMN compared with both control groups, while the TEC group showed increased inhibitory influence from the DMN to ECN compared with the HC group. Intranetwork functional connectivity within the DMN and SN is altered in traumatized subjects irrespective of PTSD diagnosis. PTSD patients also showed altered intranetwork functional connectivity within the ECN.
CONCLUSIONS: Distinct changes of effective connectivity between the DMN and ECN in the PTSD group and TEC group may reflect different compensatory mechanisms for rebalance of resting-state networks in the two groups.

PMID: 30001548 [PubMed - as supplied by publisher]

Topological analyses of functional connectomics: A crucial role of global signal removal, brain parcellation, and null models.

Fri, 07/13/2018 - 16:20
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Topological analyses of functional connectomics: A crucial role of global signal removal, brain parcellation, and null models.

Hum Brain Mapp. 2018 Jul 12;:

Authors: Chen X, Liao X, Dai Z, Lin Q, Wang Z, Li K, He Y

Abstract
Recently, functional connectome studies based on resting-state functional magnetic resonance imaging (R-fMRI) and graph theory have greatly advanced our understanding of the topological principles of healthy and diseased brains. However, how different strategies for R-fMRI data preprocessing and for connectome analyses jointly affect topological characterization and contrastive research of brain networks remains to be elucidated. Here, we used two R-fMRI data sets, a healthy young adult data set and an Alzheimer's disease (AD) patient data set, and up to 42 analysis strategies to comprehensively investigate the joint influence of three key factors (global signal regression, regional parcellation schemes, and null network models) on the topological analysis and contrastive research of whole-brain functional networks. At the global level, we first found that these three factors affected not only the quantitative values but also the individual variability profile in small-world related metrics and modularity, wherein global signal regression exhibited the predominant influence. Moreover, strategies without global signal regression and with topological randomization null model enhanced the sensitivity of the detection of differences between AD and control groups in small-worldness and modularity. At the nodal level, strategies of global signal regression dominantly influenced the spatial distribution of both hubs and between-group differences in terms of nodal degree centrality. Together, we highlight the remarkable joint influence of global signal regression, regional parcellation schemes and null network models on functional connectome analyses in both health and diseases, which may provide guidance for the choice of analysis strategies in future functional network studies.

PMID: 29999567 [PubMed - as supplied by publisher]

Brain hyperconnectivity >10 years after cisplatin based chemotherapy for testicular cancer.

Fri, 07/13/2018 - 16:20
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Brain hyperconnectivity >10 years after cisplatin based chemotherapy for testicular cancer.

Brain Connect. 2018 Jul 12;:

Authors: Stouten-Kemperman MM, de Ruiter MB, Boogerd W, Kerst JM, Kirschbaum C, Reneman L, Schagen SB

Abstract
Chemotherapy for testicular cancer (TC) has been associated with neurotoxic effects shortly post treatment. Late effects of chemotherapy on brain function in this patient group are still unknown. Here we investigated differences between patients with and without chemotherapy in functional brain networks at rest and during an affective processing fMRI task on average >14 years post-treatment. In addition we report on changes in cognitive functioning during survivorship by comparing current and previous performance on a neuropschological test battery on average 11 years earlier (3 years posttreatment). Twenty-eight chemotherapy (43.1±7.5yrs) and 23 surgery-only (48.2±9.5yrs) TC survivors were examined using neurocognitive tests and 3T-fMRI >10 years after treatment end. Brain functional networks were identified using dual regression independent component analysis. Task fMRI was analyzed using a block design. Standardized domain change scores were calculated for each individual to assess cognitive change. TC patients in the chemotherapy group showed functional hyperconnectivity at rest in the precuneus network, sensory and motor function network, executive control network and the ventral stream network when compared to surgery-only patients. Further, hypoactivation was found when performing the affective processing task. Cognitive data revealed that both groups showed comparable patterns of change from 3 to 14 yrs after initial treatment. This study provides novel insights on the possible underlying neurobiological mechanisms of late neurotoxic effects of cisplatin-based chemotherapy. Current findings reveal that functional hyperconnectivity is widespread, possibly to compensate for the pathophysiological disturbances. This concurs with our previous findings of structural hyperconnectivity in white matter. Longitudinal multimodal imaging studies are warranted to further investigate the association between long-term structural and functional network connectivity data, as well as its relation with cognitive changes.

PMID: 29999422 [PubMed - as supplied by publisher]

The human brain traverses a common activation-pattern state space across task and rest.

Fri, 07/13/2018 - 16:20
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The human brain traverses a common activation-pattern state space across task and rest.

Brain Connect. 2018 Jul 12;:

Authors: Chen RH, Ito T, Kulkarni KR, Cole MW

Abstract
Much of our lives are spent in unconstrained rest states, yet cognitive brain processes are primarily investigated using task-constrained states. It may be possible to utilize the insights gained from experimental control of task processes as reference points for investigating unconstrained rest. To facilitate comparison of rest and task functional MRI data we focused on activation amplitude patterns, commonly used for task but not rest analyses. During rest, we identified spontaneous changes in temporally extended whole-brain activation-pattern states. This revealed a hierarchical organization of rest states. The top consisted of two competing states consistent with previously identified "task-positive" and "task-negative" activation patterns. These states were composed of more specific states that repeated over time and across individuals. Contrasting with the view that rest consists of only task-negative states, task-positive states occurred 40% of the time while individuals "rested," suggesting task-focused activity may occur during rest. Together our results suggest brain activation dynamics form a general hierarchy across task and rest, with a small number of dominant general states reflecting basic functional modes and a variety of specific states potentially reflecting a wide variety of cognitive processes.

PMID: 29999413 [PubMed - as supplied by publisher]

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