New resting-state fMRI related studies at PubMed

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Estimated hemodynamic response function parameters obtained from resting state BOLD fMRI signals in subjects with autism spectrum disorder and matched healthy subjects.

Wed, 09/19/2018 - 10:40
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Estimated hemodynamic response function parameters obtained from resting state BOLD fMRI signals in subjects with autism spectrum disorder and matched healthy subjects.

Data Brief. 2018 Aug;19:1305-1309

Authors: Yan W, Rangaprakash D, Deshpande G

Abstract
In Functional magnetic resonance imaging (fMRI), the blood oxygen level dependent (BOLD) signal is modeled as a convolution of the hemodynamic response function (HRF) and the unmeasured latent neural signal. Although most cortical and subcortical brain regions share the canonical shape of the HRF, the temporal structure of HRFs are variable across brain regions and subjects. This variability is induced by both neural and non-neural factors. The variability between subjects can be examined by three parameters that characterize the HRF: response height (RH), time-to-peak (TTP) and full-width at half-max (FWHM). This data provides three HRF parameters at every voxel, obtained from Autism Spectrum Disorder (ASD) patients (N = 531), and matched healthy controls (N = 571). Since ongoing studies suggest that non-standard populations have important differences in their HRFs when compared with healthy control, this data set is valuable in studying variability of HRF in ASD group and inferring the underlying pathology that also affects the HRF. It also has implications for fMRI analyses like resting-sate connectivity analysis.

PMID: 30225289 [PubMed]

Personality Profiles Are Associated with Functional Brain Networks Related to Cognition and Emotion.

Wed, 09/19/2018 - 10:40
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Personality Profiles Are Associated with Functional Brain Networks Related to Cognition and Emotion.

Sci Rep. 2018 Sep 17;8(1):13874

Authors: Mulders P, Llera A, Tendolkar I, van Eijndhoven P, Beckmann C

Abstract
Personality factors as defined by the "five-factor model" are some of the most investigated characteristics that underlie various types of complex behavior. These are, however, often investigated as isolated traits that are conceptually independent, yet empirically are typically strongly related to each other. We apply Independent Component Analysis to these personality factors as measured by the NEO-FFI in 471 healthy subjects from the Human Connectome Project to investigate independent personality profiles that incorporate all five original factors. Subsequently we examine how these profiles are related to patterns of resting-state brain activity in specific networks-of-interest related to cognition and emotion. We find that a personality profile of contrasting openness and agreeableness is associated with engagement of a subcortical-medial prefrontal network and the dorsolateral prefrontal cortex. Likewise, a profile of contrasting extraversion and conscientiousness is associated with activity in the precuneus. This study shows a novel approach to investigating personality and how it is related to patterns of activity in the resting brain.

PMID: 30224828 [PubMed - in process]

Process-Specific Alliances (PSAs) in Cognitive Neuroscience.

Wed, 09/19/2018 - 10:40
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Process-Specific Alliances (PSAs) in Cognitive Neuroscience.

Trends Cogn Sci. 2018 Sep 14;:

Authors: Cabeza R, Stanley ML, Moscovitch M

Abstract
Most cognitive neuroscience theories have focused on the functions of individual brain regions, but cognitive abilities depend also on functional interactions among multiple regions. Many recent studies on these interactions have examined large-scale, resting-state networks, but these networks are difficult to link to theories about specific cognitive processes. Cognitive theories are easier to link to the mini-networks we call process specific alliances (PSAs). A PSA is a small team of brain regions that rapidly assemble to mediate a cognitive process in response to task demands but quickly disassemble when the process is no longer needed. We compare PSAs to resting-state networks and to other connectivity-based, task-related networks, and we characterize the advantages and disadvantages of each type of network.

PMID: 30224232 [PubMed - as supplied by publisher]

Prefrontal glutamate levels predict altered amygdala-prefrontal connectivity in traumatized youths.

Wed, 09/19/2018 - 10:40
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Prefrontal glutamate levels predict altered amygdala-prefrontal connectivity in traumatized youths.

Psychol Med. 2018 Sep 18;:1-9

Authors: Ousdal OT, Milde AM, Craven AR, Ersland L, Endestad T, Melinder A, Huys QJ, Hugdahl K

Abstract
BACKGROUND: Neurobiological models of stress and stress-related mental illness, including post-traumatic stress disorder, converge on the amygdala and the prefrontal cortex (PFC). While a surge of research has reported altered structural and functional connectivity between amygdala and the medial PFC following severe stress, few have addressed the underlying neurochemistry.
METHODS: We combined resting-state functional magnetic resonance imaging measures of amygdala connectivity with in vivo MR-spectroscopy (1H-MRS) measurements of glutamate in 26 survivors from the 2011 Norwegian terror attack and 34 control subjects.
RESULTS: Traumatized youths showed altered amygdala-anterior midcingulate cortex (aMCC) and amygdala-ventromedial prefrontal cortex (vmPFC) connectivity. Moreover, the trauma survivors exhibited reduced levels of glutamate in the vmPFC which fits with the previous findings of reduced levels of Glx (glutamate + glutamine) in the aMCC (Ousdal et al., 2017) and together suggest long-term impact of a traumatic experience on glutamatergic pathways. Importantly, local glutamatergic metabolite levels predicted the individual amygdala-aMCC and amygdala-vmPFC functional connectivity, and also mediated the observed group difference in amygdala-aMCC connectivity.
CONCLUSIONS: Our findings suggest that traumatic stress may influence amygdala-prefrontal neuronal connectivity through an effect on prefrontal glutamate and its compounds. Understanding the neurochemical underpinning of altered amygdala connectivity after trauma may ultimately lead to the discovery of new pharmacological agents which can prevent or treat stress-related mental illness.

PMID: 30223909 [PubMed - as supplied by publisher]

Validation of impedance cardiography in pulmonary arterial hypertension.

Wed, 09/19/2018 - 10:40
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Validation of impedance cardiography in pulmonary arterial hypertension.

Clin Physiol Funct Imaging. 2018 Mar;38(2):254-260

Authors: Panagiotou M, Vogiatzis I, Jayasekera G, Louvaris Z, Mackenzie A, Mcglinchey N, Baker JS, Church AC, Peacock AJ, Johnson MK

Abstract
BACKGROUND: Non-invasive methods of measuring cardiac output are highly desirable in pulmonary arterial hypertension (PAH). We therefore sought to validate impedance cardiography (ICG) against thermodilution (TD) and cardiac magnetic resonance (CMR) in the measurement of cardiac output in patients under investigation for PAH.
METHODS: A prospective, cross-sectional study was performed to compare single-point measurements of cardiac output obtained by impedance cardiography (COICG ) technology (PhysioFlow® ) with (i) contemporaneous TD measurements (COTD ) at rest and steady-state exercise during right heart catheterization and (ii) CMR measurements (COCMR ) at rest obtained within 72 h.
RESULTS: Paired COICG and COTD measurements were obtained in 25 subjects at rest and 16 subjects at exercise. COCMR measurements were obtained in 16 subjects at rest. There was unsatisfactory correlation and agreement between COICG and COTD at rest (r = 0·42, P = 0·035; bias: 1·21 l min-1 , 95% CI: -2·33 to 4·75 l min-1 ) and exercise (r = .65, P = .007; bias: 1·41 l min-1 ; 95% CI: -3·99 to 6·81 l min-1 ) and in the change in COICG and COTD from rest to exercise (r = 0·53, P = 0·033; bias: 0·76 l min-1 , 95% CI: -3·74 to 5·26 l min-1 ). There was also a lack of correlation and unsatisfactory agreement between resting COICG and COCMR (r = 0·38, P = 0·1; bias: 1·40 l min-1 , 95% CI: -2·48 to 5·28 l min-1 ). In contrast, there was close correlation and agreement between resting COTD and COCMR (r = 0·87, P<0·001; bias: -0·16 l min-1 , 95% CI: -1·97 to 1·65).
CONCLUSIONS: In a representative population of patients under investigation for PAH, ICG showed insufficient qualitative and quantitative value in the measurement of resting and exercise cardiac output when compared with TD and CMR.

PMID: 28168802 [PubMed - indexed for MEDLINE]

Nuisance effects and the limitations of nuisance regression in dynamic functional connectivity fMRI.

Tue, 09/18/2018 - 16:00
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Nuisance effects and the limitations of nuisance regression in dynamic functional connectivity fMRI.

Neuroimage. 2018 Sep 14;:

Authors: Nalci A, Rao BD, Liu TT

Abstract
In resting-state fMRI, dynamic functional connectivity (DFC) measures are used to characterize temporal changes in the brain's intrinsic functional connectivity. A widely used approach for DFC estimation is the computation of the sliding window correlation between blood oxygenation level dependent (BOLD) signals from different brain regions. Although the source of temporal fluctuations in DFC estimates remains largely unknown, there is growing evidence that they may reflect dynamic shifts between functional brain networks. At the same time, recent findings suggest that DFC estimates might be prone to the influence of nuisance factors such as the physiological modulation of the BOLD signal. Therefore, nuisance regression is used in many DFC studies to regress out the effects of nuisance terms prior to the computation of DFC estimates. In this work we examined the relationship between seed-specific sliding window correlation-based DFC estimates and nuisance factors. We found that DFC estimates were significantly correlated with temporal fluctuations in the magnitude (norm) of various nuisance regressors. Strong correlations between the DFC estimates and nuisance regressor norms were found even when the underlying correlations between the nuisance and fMRI time courses were relatively small. We then show that nuisance regression does not necessarily eliminate the relationship between DFC estimates and nuisance norms, with significant correlations observed between the DFC estimates and nuisance norms even after nuisance regression. We present theoretical bounds on the difference between DFC estimates obtained before and after nuisance regression and relate these bounds to limitations in the efficacy of nuisance regression with regards to DFC estimates.

PMID: 30223062 [PubMed - as supplied by publisher]

Normative pathways in the functional connectome.

Tue, 09/18/2018 - 16:00
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Normative pathways in the functional connectome.

Neuroimage. 2018 Sep 14;:

Authors: Leming M, Su L, Chattopadhyay S, Suckling J

Abstract
Functional connectivity is frequently derived from fMRI data to reduce a complex image of the brain to a graph, or "functional connectome". Often shortest-path algorithms are used to characterize and compare functional connectomes. Previous work on the identification and measurement of semi-metric (shortest circuitous) pathways in the functional connectome has discovered cross-sectional differences in major depressive disorder (MDD), autism spectrum disorder (ASD), and Alzheimer's disease. However, while measurements of shortest path length have been analyzed in functional connectomes, less work has been done to investigate the composition of the pathways themselves, or whether the edges composing pathways differ between individuals. Developments in this area would help us understand how pathways might be organized in mental disorders, and if a consistent pattern can be found. Furthermore, studies in structural brain connectivity and other real-world graphs suggest that shortest pathways may not be as important in functional connectivity studies as previously assumed. In light of this, we present a novel measurement of the consistency of pathways across functional connectomes, and an algorithm for improvement by selecting the most frequently occurring "normative pathways" from the k shortest paths, instead of just the shortest path. We also look at this algorithm's effect on various graph measurements, using randomized matrix simulations to support the efficacy of this method and demonstrate our algorithm on the resting-state fMRI (rs-fMRI) of a group of 34 adolescent control participants. Additionally, a comparison of normative pathways is made with a group of 82 age-matched participants, diagnosed with MDD, and in doing so we find the normative pathways that are most disrupted. Our results, which are carried out with estimates of connectivity derived from correlation, partial correlation, and normalized mutual information connectomes, suggest disruption to the default mode, affective, and ventral attention networks. Normative pathways, especially with partial correlation, make greater use of critical anatomical pathways through the striatum, cingulum, and the cerebellum. In summary, MDD is characterized by a disruption of normative pathways of the ventral attention network, increases in alternative pathways in the frontoparietal network in MDD, and a mixture of both in the default mode network. Additionally, within- and between-groups findings depend on the estimate of connectivity.

PMID: 30223061 [PubMed - as supplied by publisher]

Hard to wake up? The cerebral correlates of sleep inertia assessed using combined behavioral, EEG and fMRI measures.

Tue, 09/18/2018 - 16:00
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Hard to wake up? The cerebral correlates of sleep inertia assessed using combined behavioral, EEG and fMRI measures.

Neuroimage. 2018 Sep 14;:

Authors: Vallat R, Meunier D, Nicolas A, Ruby P

Abstract
The first minutes following awakening from sleep are typically marked by reduced vigilance, increased sleepiness and impaired performance, a state referred to as sleep inertia. Although the behavioral aspects of sleep inertia are well documented, its cerebral correlates remain poorly understood. The present study aimed at filling this gap by measuring in 34 participants the changes in behavioral performance (descending subtraction task, DST), EEG spectral power, and resting-state fMRI functional connectivity across three time points: before an early-afternoon 45-min nap, 5 min after awakening from the nap and 25 min after awakening. Our results showed impaired performance at the DST at awakening and an intrusion of sleep-specific features (spectral power and functional connectivity) into wakefulness brain activity, the intensity of which was dependent on the prior sleep duration and depth for the functional connectivity (14 participants awakened from N2 sleep, 20 from N3 sleep). Awakening in N3 (deep) sleep induced the most robust changes and was characterized by a global loss of brain functional segregation between task-positive (dorsal attention, salience, sensorimotor) and task-negative (default mode) networks. Significant correlations were observed notably between the EEG delta power and the functional connectivity between the default and dorsal attention networks, as well as between the percentage of mistake at the DST and the default network functional connectivity. These results highlight (1) significant correlations between EEG and fMRI functional connectivity measures, (2) significant correlations between the behavioral aspect of sleep inertia and measures of the cerebral functioning at awakening (both EEG and fMRI), and (3) the important difference in the cerebral underpinnings of sleep inertia at awakening from N2 and N3 sleep.

PMID: 30223060 [PubMed - as supplied by publisher]

Functional reorganisation and recovery following cortical lesions: A preliminary study in macaque monkeys.

Sun, 09/16/2018 - 11:40

Functional reorganisation and recovery following cortical lesions: A preliminary study in macaque monkeys.

Neuropsychologia. 2018 Sep 12;119:382-391

Authors: Ainsworth M, Browncross H, Mitchell DJ, Mitchell AS, Passingham RE, Buckley MJ, Duncan J, Bell AH

Abstract
Damage following traumatic brain injury or stroke can often extend beyond the boundaries of the initial insult and can lead to maladaptive cortical reorganisation. On the other hand, beneficial cortical reorganisation leading to recovery of function can also occur. We used resting state FMRI to investigate how cortical networks in the macaque brain change across time in response to lesions to the prefrontal cortex, and how this reorganisation correlated with changes in behavioural performance in cognitive tasks. After prelesion testing and scanning, two monkeys received a lesion to regions surrounding the left principal sulcus followed by periodic testing and scanning. Later, the animals received another lesion to the opposite hemisphere and additional testing and scanning. Following the first lesion, we observed both a behavioural impairment and decrease in functional connectivity, predominantly in frontal-frontal networks. Approximately 8 weeks later, performance and connectivity patterns both improved. Following the second lesion, we observed a further behavioural deficit and decrease in connectivity that showed little recovery. We discuss how different mechanisms including alternate behavioural strategies and reorganisation of specific prefrontal networks may have led to improvements in behaviour. Further work will be needed to confirm these mechanisms.

PMID: 30218841 [PubMed - as supplied by publisher]

Relationship between extraversion personality and gray matter volume and functional connectivity density in healthy young adults: an fMRI study.

Sat, 09/15/2018 - 11:40

Relationship between extraversion personality and gray matter volume and functional connectivity density in healthy young adults: an fMRI study.

Psychiatry Res Neuroimaging. 2018 Sep 01;281:19-23

Authors: Zou L, Su L, Qi R, Zheng S, Wang L

Abstract
Extraversion and neuroticism are two main dimensions of Eysenck's personality. We assessed the relationship between extraversion and neuroticism with brain structure and function by voxel-based morphometry (VBM) and functional connectivity density (FCD). The resting state functional magnetic resonance image and high resolution structural T1 weighted images of 100 young healthy subjects were used in analysis. Our results showed that extraversion was negatively correlated with gray matter volume (GMV) of the bilateral putamen, and it was negatively correlated with FCD in the precuneus. No associations between neuroticism and brain structure and function changes. Overall, our results suggested that several brain regions involved in shaping of extraversion traits among young individuals, which may provide a neurobiological basis of extraversion.

PMID: 30216860 [PubMed - as supplied by publisher]

Functional and structural connectome properties in the 5XFAD transgenic mouse model of Alzheimer's disease.

Sat, 09/15/2018 - 11:40
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Functional and structural connectome properties in the 5XFAD transgenic mouse model of Alzheimer's disease.

Netw Neurosci. 2018;2(2):241-258

Authors: Kesler SR, Acton P, Rao V, Ray WJ

Abstract
Neurodegeneration in Alzheimer's disease (AD) is associated with amyloid-beta peptide accumulation into insoluble amyloid plaques. The five-familial AD (5XFAD) transgenic mouse model exhibits accelerated amyloid-beta deposition, neuronal dysfunction, and cognitive impairment. We aimed to determine whether connectome properties of these mice parallel those observed in patients with AD. We obtained diffusion tensor imaging and resting-state functional magnetic resonance imaging data for four transgenic and four nontransgenic male mice. We constructed both structural and functional connectomes and measured their topological properties by applying graph theoretical analysis. We compared connectome properties between groups using both binarized and weighted networks. Transgenic mice showed higher characteristic path length in weighted structural connectomes and functional connectomes at minimum density. Normalized clustering and modularity were lower in transgenic mice across the upper densities of the structural connectome. Transgenic mice also showed lower small-worldness index in higher structural connectome densities and in weighted structural networks. Hyper-correlation of structural and functional connectivity was observed in transgenic mice compared with nontransgenic controls. These preliminary findings suggest that 5XFAD mouse connectomes may provide useful models for investigating the molecular mechanisms of AD pathogenesis and testing the effectiveness of potential treatments.

PMID: 30215035 [PubMed]

Heritability of the human connectome: A connectotyping study.

Sat, 09/15/2018 - 11:40
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Heritability of the human connectome: A connectotyping study.

Netw Neurosci. 2018;2(2):175-199

Authors: Miranda-Dominguez O, Feczko E, Grayson DS, Walum H, Nigg JT, Fair DA

Abstract
Recent progress in resting-state neuroimaging demonstrates that the brain exhibits highly individualized patterns of functional connectivity-a "connectotype." How these individualized patterns may be constrained by environment and genetics is unknown. Here we ask whether the connectotype is familial and heritable. Using a novel approach to estimate familiality via a machine-learning framework, we analyzed resting-state fMRI scans from two well-characterized samples of child and adult siblings. First we show that individual connectotypes were reliably identified even several years after the initial scanning timepoint. Familial relationships between participants, such as siblings versus those who are unrelated, were also accurately characterized. The connectotype demonstrated substantial heritability driven by high-order systems including the fronto-parietal, dorsal attention, ventral attention, cingulo-opercular, and default systems. This work suggests that shared genetics and environment contribute toward producing complex, individualized patterns of distributed brain activity, rather than constraining local aspects of function. These insights offer new strategies for characterizing individual aberrations in brain function and evaluating heritability of brain networks.

PMID: 30215032 [PubMed]

Amygdala functional connectivity in female patients with major depressive disorder with and without suicidal ideation.

Sat, 09/15/2018 - 11:40
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Amygdala functional connectivity in female patients with major depressive disorder with and without suicidal ideation.

Ann Gen Psychiatry. 2018;17:37

Authors: Wei S, Chang M, Zhang R, Jiang X, Wang F, Tang Y

Abstract
Background: Major depressive disorder (MDD) is a known major risk factor for suicide and is one of the most common mental disorders. Meanwhile, gender differences in suicidal behavior have long been recognized including the finding that women have higher rates of suicidal ideation and/or suicidal behavior than men. The mechanism underlying suicide ideation in female patients with MDD remains poorly understood. The aim of the present study was to examine possible suicidal behavior-related neural circuitry in female MDD.
Methods: In this study, 15 female participants with the first-episode MDD with suicidal ideation and 24 participants with the first-episode MDD without suicidal ideation as well as 39 female participants in a healthy control (HC) group, ranging in age from 18 to 50 years, underwent resting-state functional magnetic resonance imaging. The whole-brain amygdala resting-state functional connectivity (rsFC) was compared among these three groups.
Results: Compared with female participants with the first-episode MDD without suicidal ideation and those in the HC group, female participants with the first-episode MDD with suicidal ideation showed a significant difference in rsFC between the amygdala and precuneus/cuneus (p < 0.05, corrected). No significant difference in amygdala-precuneus/cuneus rsFC was observed between female patients with the first-episode MDD without suicidal ideation and the HC group (p < 0.05, corrected).
Conclusions: Our findings suggest that suicidal ideation in female patients with the first-episode MDD may be related to an abnormality in amygdala neural circuitry. The abnormality in amygdala-precuneus/cuneus functional connectivity might present the trait feature for suicide in women with the first-episode MDD. The precuneus/cuneus may be an important region related to suicide and require future study.

PMID: 30214465 [PubMed]

Sex Differences in Spontaneous Brain Activity in Adolescents With Conduct Disorder.

Sat, 09/15/2018 - 11:40
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Sex Differences in Spontaneous Brain Activity in Adolescents With Conduct Disorder.

Front Psychol. 2018;9:1598

Authors: Cao W, Sun X, Dong D, Yao S, Huang B

Abstract
Purpose: Sex differences in conduct disorder (CD) pathophysiology have yet to be resolved. In this study, we applied the amplitude of low-frequency fluctuations (ALFF) and fractional ALFF (fALFF) to compare spontaneous brain activity in male versus female adolescents diagnosed with CD in light of the gender paradox hypothesis. Materials and Methods: Resting-state functional magnetic resonance imaging (rs-fMRI) examinations were conducted with 51 CD patients (35 males) and 53 age-matched healthy controls (HCs; 35 males). Pearson analysis was conducted to detect relationship between ALFF/fALFF values in gender-differentiated regions and clinical characteristics. Results: We observed that male CD patients showed significant increased ALFF in the bilateral superior temporal gyrus (STG)/insula, and significant decreased ALFF in the left anterior cingulate cortex (ACC), left middle frontal gyrus (BA8 andBA11), left middle temporal gyrus and left inferior/middle temporal gyrus relative to female CD patients. The fALFF in male CD patients was significantly increased in the right STG/insula, decreased in the right superior frontal gyrus, left middle frontal gyrus, right inferior frontal gyrus, and right postcentral gyrus relative to female CD patients. Considering the sex-by-diagnosis interactions in CD patients, the male CD patients had significantly higher fALFF in the left putamen, lower fALFF in the right postcentral gyrus relative to the female CD patients. Conclusion: The brain regions whose activity index values differed in relation to sex should be further explored in CD pathophysiology studies, particularly with respect to sex differences in clinical symptoms, emotional features, cognitive features, and prevalence rates in CD. The present findings are consistent with the gender paradox hypothesis.

PMID: 30214422 [PubMed]

Anatomical Templates of the Midbrain Ventral Tegmental Area and Substantia Nigra for Asian Populations.

Fri, 09/14/2018 - 15:40
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Anatomical Templates of the Midbrain Ventral Tegmental Area and Substantia Nigra for Asian Populations.

Front Psychiatry. 2018;9:383

Authors: Nakamura Y, Okada N, Kunimatsu A, Kasai K, Koike S

Abstract
Increasing evidence shows that the midbrain dopaminergic system is involved in various functions. However, details of the role of the midbrain dopaminergic system in these functions are still to be determined in humans. Considering that the ventral tegmental area (VTA) and substantia nigra (SN) in the midbrain are the primary dopamine producers, creating reliable anatomical templates of the VTA and SN through neuroimaging studies would be useful for achieving a detailed understanding of this dopaminergic system. Although VTA and SN anatomical templates have been created, no specific templates exist for the Asian population. Thus, we conducted anatomical and resting-state functional magnetic resonance imaging (rs-fMRI) studies to create VTA and SN templates for the Asian population. First, a neuromelanin-sensitive MRI technique was used to visualize the VTA and SN, and then individual hand-drawn VTA and SN regions of interests (ROIs) were traced on a small sample of neuromelanin-sensitive MRIs (dataset 1). Second, individual hand-drawn VTA and SN ROIs were normalized to create normalized VTA and SN templates for the Asian population. Third, a seed-based functional connectivity analysis was performed on rs-fMRI data using hand-drawn ROIs to calculate neural networks of VTA and SN in dataset 1. Fourth, a seed-based functional connectivity analysis was performed using VTA and SN seeds that were created based on normalized templates from dataset 1. Subsequently, a seed-based functional connectivity analysis was performed using VTA and SN seeds in another, larger sample (dataset 2) to assess whether neural networks of VTA or SN seeds from dataset 1 would be replicated in dataset 2. The Asian VTA template was smaller and located in a more posterior and inferior part of the midbrain compared to the published VTA template, while the Asian SN template, relative to the published SN template, did not differ in size but was located in the more inferior part of the midbrain. The neural networks of the VTA and SN seeds in dataset 1 were replicated in dataset 2. Altogether, our normalized template of the VTA and SN could be used for measuring fMRI activities related to the VTA and SN in the Asian population.

PMID: 30210369 [PubMed]

Associations of brain entropy (BEN) to cerebral blood flow and fractional amplitude of low-frequency fluctuations in the resting brain.

Fri, 09/14/2018 - 15:40
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Associations of brain entropy (BEN) to cerebral blood flow and fractional amplitude of low-frequency fluctuations in the resting brain.

Brain Imaging Behav. 2018 Sep 12;:

Authors: Song D, Chang D, Zhang J, Ge Q, Zang YF, Wang Z

Abstract
Entropy is a fundamental trait of human brain. Using fMRI-based brain entropy (BEN) mapping, interesting findings have been increasingly revealed in normal brain and neuropsychiatric disorders. As BEN is still relatively new, an often-raised question is how much new information can this measure tell about the brain compared to other more established brain activity measures. The study aimed to address that question by examining the relationship between BEN and cerebral blood flow (CBF) and the fractional amplitude of low-frequency fluctuations (fALFF), two widely used resting state brain state measures. fMRI data acquired from a large cohort of normal subjects were used to calculate the three metrics; inter-modality associations were assessed at each voxel through the Pearson correlation analysis. A moderate to high positive BEN-CBF and BEN-fALFF correlations were found in orbito-frontal cortex (OFC) and posterior inferior temporal cortex (ITC); Strong negative BEN-fALFF correlations were found in visual cortex (VC), anterior ITC, striatum, motor network, precuneus, and lateral parietal cortex. Positive CBF-fALFF correlations were found in medial OFC (MOFC), medial prefrontal cortex (MPFC), left angular gyrus, and left precuneus. Significant gender effects were observed for all three metrics and their correlations. Our data clearly demonstrated that BEN provides unique information that cannot be revealed by CBF and fALFF.

PMID: 30209786 [PubMed - as supplied by publisher]

Aberrant default mode network in amnestic mild cognitive impairment: a meta-analysis of independent component analysis studies.

Fri, 09/14/2018 - 15:40
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Aberrant default mode network in amnestic mild cognitive impairment: a meta-analysis of independent component analysis studies.

Neurol Sci. 2018 May;39(5):919-931

Authors: Wang C, Pan Y, Liu Y, Xu K, Hao L, Huang F, Ke J, Sheng L, Ma H, Guo W

Abstract
Independent component analysis (ICA) is one of the most popular and valid methods to investigate the default mode network (DMN), an intrinsic network which attracts particular attention in amnestic mild cognitive impairment (aMCI). However, previous studies present inconsistent results regarding the topographical organization of the DMN in aMCI. Therefore, we conducted a quantitative, voxel-wise meta-analysis of resting-state ICA studies using Seed-based d Mapping to establish the most consistent pattern of DMN functional connectivity alterations in aMCI. Twenty studies, comprising 23 independent datasets involving 535 patients and 586 healthy controls, met the inclusion criteria. Patients with aMCI exhibited reliably lower DMN functional connectivity than the healthy controls in the bilateral precuneus/posterior cingulate cortices and medial temporal lobes, which are implicated in episodic memory deficits. Moreover, an exploratory meta-regression analysis revealed that greater severity of global cognitive impairment in the patient groups was associated with stronger functional connectivity in the bilateral medial frontal cortices (including the anterior cingulate cortices), left angular gyrus, and right temporal pole extending to the middle temporal gyrus, likely reflecting a compensatory mechanism for maintaining cognitive efficiency. This meta-analysis identifies a consistent pattern of aberrant DMN functional connectivity in aMCI, which facilitates understanding of the neurobiological substrates of this disease.

PMID: 29511960 [PubMed - indexed for MEDLINE]

Decreased BOLD fluctuations in lateral temporal cortices of premature born adults.

Thu, 09/13/2018 - 14:40
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Decreased BOLD fluctuations in lateral temporal cortices of premature born adults.

Hum Brain Mapp. 2018 Sep 12;:

Authors: Shang J, Bäuml JG, Koutsouleris N, Daamen M, Baumann N, Zimmer C, Bartmann P, Boecker H, Wolke D, Sorg C

Abstract
Lasting volume reductions in subcortical and temporal-insular cortices after premature birth suggest altered ongoing activity in these areas. We hypothesized altered fluctuations in ongoing neural excitability and activity, as measured by slowly fluctuating blood oxygenation of resting-state functional MRI (rs-fMRI), in premature born adults, with altered fluctuations being linked with underlying brain volume reductions. To investigate this hypothesis, 94 very preterm/very low birth weight (VP/VLBW) and 92 full-term born young adults underwent structural and rs-fMRI data acquisition with voxel-based morphometry and amplitude of low-frequency fluctuations (ALFF) as main outcome measure. In VP/VLBW adults, ALFF was reduced in lateral temporal cortices, and this reduction was positively associated with lower birth weight. Regions of reduced ALFF overlapped with reduced brain volume. On the one hand, ALFF reduction remained after controlling for volume loss, supporting the functional nature of ALFF reductions. On the other hand, ALFF decreases were positively associated with underlying brain volume loss, indicating a relation between structural and functional changes. Furthermore, within the VP/VLBW group, reduced ALFF was associated with reduced IQ, indicating the behavioral relevance of ALFF decreases in temporal cortices. These results demonstrate long-term impact of premature birth on ongoing BOLD fluctuations in lateral temporal cortices, which are linked with brain volume reductions. Data suggest permanently reduced fluctuations in ongoing neural excitability and activity in structurally altered lateral temporal cortices after premature birth.

PMID: 30208256 [PubMed - as supplied by publisher]

Linking genes, circuits, and behavior: network connectivity as a novel endophenotype of externalizing.

Thu, 09/13/2018 - 14:40
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Linking genes, circuits, and behavior: network connectivity as a novel endophenotype of externalizing.

Psychol Med. 2018 Sep 12;:1-9

Authors: Sadeh N, Spielberg JM, Logue MW, Hayes JP, Wolf EJ, McGlinchey RE, Milberg WP, Schichman SA, Stone A, Miller MW

Abstract
BACKGROUND: Externalizing disorders are known to be partly heritable, but the biological pathways linking genetic risk to the manifestation of these costly behaviors remain under investigation. This study sought to identify neural phenotypes associated with genomic vulnerability for externalizing disorders.
METHODS: One-hundred fifty-five White, non-Hispanic veterans were genotyped using a genome-wide array and underwent resting-state functional magnetic resonance imaging. Genetic susceptibility was assessed using an independently developed polygenic score (PS) for externalizing, and functional neural networks were identified using graph theory based network analysis. Tasks of inhibitory control and psychiatric diagnosis (alcohol/substance use disorders) were used to measure externalizing phenotypes.
RESULTS: A polygenic externalizing disorder score (PS) predicted connectivity in a brain circuit (10 nodes, nine links) centered on left amygdala that included several cortical [bilateral inferior frontal gyrus (IFG) pars triangularis, left rostral anterior cingulate cortex (rACC)] and subcortical (bilateral amygdala, hippocampus, and striatum) regions. Directional analyses revealed that bilateral amygdala influenced left prefrontal cortex (IFG) in participants scoring higher on the externalizing PS, whereas the opposite direction of influence was observed for those scoring lower on the PS. Polygenic variation was also associated with higher Participation Coefficient for bilateral amygdala and left rACC, suggesting that genes related to externalizing modulated the extent to which these nodes functioned as communication hubs.
CONCLUSIONS: Findings suggest that externalizing polygenic risk is associated with disrupted connectivity in a neural network implicated in emotion regulation, impulse control, and reinforcement learning. Results provide evidence that this network represents a genetically associated neurobiological vulnerability for externalizing disorders.

PMID: 30207258 [PubMed - as supplied by publisher]

Brain structural basis of individual variability in dream recall frequency.

Thu, 09/13/2018 - 14:40
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Brain structural basis of individual variability in dream recall frequency.

Brain Imaging Behav. 2018 Sep 11;:

Authors: Zhou S, Xu J, Su Z, Li Y, Shao Y, Sun H, Zhu H, Zou Q, Gao JH

Abstract
Recent neuroimaging studies have indicated that inter-individual variability in dream recall frequency (DRF) is associated with both resting-state regional cerebral blood flow and task-induced brain activations. However, the brain structure underpinning this inter-individual variability in DRF remains unclear. The aim of the current study is to investigate the relationship between brain structural characteristics and DRF. We collected both T1-weighted and diffusion tensor magnetic resonance imaging data from 43 healthy volunteers. DRF was obtained from a two-week sleep diary with a subjective report of dream recall upon waking every morning. General linear model analysis was used to evaluate the relationship between brain structural characteristics (cortical volume and white matter integrity) and DRF. Not only the cortical volume of the medial portion of the right fusiform gyrus and parahippocampal gyrus but also the fractional anisotropy of white matter fibers connected to these regions were significantly negatively correlated with DRF, and these relationships were not modulated by a regular sleep. These findings provide direct evidence that brain structural characteristics are associated with inter-individual variability in DRF and may help us to better understand the structural mechanisms in the brain underlying dream recall.

PMID: 30206818 [PubMed - as supplied by publisher]

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