Combined spatiotemporal ICA (stICA) for continuous and dynamic lag structure analysis of MREG data.
Neuroimage. 2017 Jan 11;:
Authors: Raatikainen V, Huotari N, Korhonen V, Rasila A, Kananen J, Raitamaa L, Keinänen T, Kantola J, Tervonen O, Kiviniemi V
This study investigated lag structure in the resting-state fMRI by applying a novel independent component (ICA) method to magnetic resonance encephalography (MREG) data. Briefly, the spatial ICA (sICA) was used for defining the frontal and back nodes of the default mode network (DMN), and the temporal ICA (tICA), which is enabled by the high temporal resolution of MREG (TR=100ms), was used to separate both neuronal and physiological components of these two spatial map regions. Subsequently, lag structure was investigated between the frontal (DMNvmpf) and posterior (DMNpcc) DMN nodes using both conventional method with all-time points and a sliding-window approach. A rigorous noise exclusion criterion was applied for tICs to remove physiological pulsations, motion and system artefacts. All the de-noised tICs were used to calculate the null-distributions both for expected lag variability over time and over subjects. Lag analysis was done for the three highest correlating denoised tICA pairs. Mean time lag of 0.6s (± 0.5 std) and mean absolute correlation of 0.69 (± 0.08) between the highest correlating tICA pairs of DMN nodes was observed throughout the whole analyzed period. In dynamic 2min window analysis, there was large variability over subjects as ranging between 1-10sec. Directionality varied between these highly correlating sources an average 28.8% of the possible number of direction changes. The null models show highly consistent correlation and lag structure between DMN nodes both in continuous and dynamic analysis. The mean time lag of a null-model over time between all denoised DMN nodes was 0.0s and, thus the probability of having either DMNpcc or DMNvmpf as a preceding component is near equal. All the lag values of highest correlating tICA pairs over subjects lie within the standard deviation range of a null-model in whole time window analysis, supporting the earlier findings that there is a consistent temporal lag structure across groups of individuals. However, in dynamic analysis, there are lag values exceeding the threshold of significance of a null-model meaning that there might be biologically meaningful variation in this measure. Taken together the variability in lag and the presence of high activity peaks during strong connectivity indicate that individual avalanches may play an important role in defining dynamic independence in resting state connectivity within networks.
PMID: 28088482 [PubMed - as supplied by publisher]
Test-Retest Reproducibility of the Intrinsic Default Mode Network: Influence of fMRI Slice-Order Acquisition and Head-Motion Correction Methods.
Brain Connect. 2017 Jan 13;:
Authors: Marchitelli R, Collignon O, Jovicich J
Head-motion is a known challenge in resting-state fMRI studies for biasing functional connectivity among distinct anatomical regions. These persist even with small motion, limiting comparisons of groups with different head-motion characteristics. This motivates an interest in the optimization of acquisition and correction strategies to minimize motion sensitivity. In this test-retest study of healthy young volunteers (N=24), we investigate the effects of slice-order acquisitions (sequential or interleaved) and head-motion correction methods (volume- or slice-based) on the test-retest reproducibility of intrinsic connectivity of the default mode network (DMN). We evaluated the reproducibility of the entire DMN and each main node using the absolute percentage error, intra class correlation coefficient (ICC) and the Jaccard coefficient. Regardless of slice-order acquisition, the slice-based motion correction method systematically estimated larger motion and returned significantly higher gray matter tSNR. Although consistently extracted across all acquisition and motion correction approaches, DMN connectivity was sensitive to these choices. However, the reproducibility of the whole DMN was stable and showed no sensitivity to the methods tested (absolute reproducibility=7%, ICC=0.47 and Jaccard=40%). Percentage errors and ICCs were consistent across single nodes but the Jaccard coefficients were not. The posterior cingulate was the most reproducible node (Jaccard=52%) whereas the anterior cingulate was the least reproducible (Jaccard=30%). Our study suggests that the slice-order and motion correction methods evaluated offer comparable sensitivity to detect DMN connectivity changes in a longitudinal study of individuals with low head-motion characteristics but that controlling for the consistency in acquisition and correction protocols is important in cross-sectional studies.
PMID: 28084793 [PubMed - as supplied by publisher]
Common and distinct brain networks underlying verbal and visual creativity.
Hum Brain Mapp. 2017 Jan 13;:
Authors: Zhu W, Chen Q, Xia L, Beaty RE, Yang W, Tian F, Sun J, Cao G, Zhang Q, Chen X, Qiu J
Creativity is imperative to the progression of human civilization, prosperity, and well-being. Past creative researches tends to emphasize the default mode network (DMN) or the frontoparietal network (FPN) somewhat exclusively. However, little is known about how these networks interact to contribute to creativity and whether common or distinct brain networks are responsible for visual and verbal creativity. Here, we use functional connectivity analysis of resting-state functional magnetic resonance imaging data to investigate visual and verbal creativity-related regions and networks in 282 healthy subjects. We found that functional connectivity within the bilateral superior parietal cortex of the FPN was negatively associated with visual and verbal creativity. The strength of connectivity between the DMN and FPN was positively related to both creative domains. Visual creativity was negatively correlated with functional connectivity within the precuneus of the pDMN and right middle frontal gyrus of the FPN, and verbal creativity was negatively correlated with functional connectivity within the medial prefrontal cortex of the aDMN. Critically, the FPN mediated the relationship between the aDMN and verbal creativity, and it also mediated the relationship between the pDMN and visual creativity. Taken together, decreased within-network connectivity of the FPN and DMN may allow for flexible between-network coupling in the highly creative brain. These findings provide indirect evidence for the cooperative role of the default and executive control networks in creativity, extending past research by revealing common and distinct brain systems underlying verbal and visual creative cognition. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc.
PMID: 28084656 [PubMed - as supplied by publisher]
Intra- and inter-network functional alterations in Parkinson's disease with mild cognitive impairment.
Hum Brain Mapp. 2017 Jan 13;:
Authors: Peraza LR, Nesbitt D, Lawson RA, Duncan GW, Yarnall AJ, Khoo TK, Kaiser M, Firbank MJ, O'Brien JT, Barker RA, Brooks DJ, Burn DJ, Taylor JP
Mild cognitive impairment (MCI) is prevalent in 15%-40% of Parkinson's disease (PD) patients at diagnosis. In this investigation, we study brain intra- and inter-network alterations in resting state functional magnetic resonance imaging (rs-fMRI) in recently diagnosed PD patients and characterise them as either cognitive normal (PD-NC) or with MCI (PD-MCI). Patients were divided into two groups, PD-NC (N = 62) and PD-MCI (N = 37) and for comparison, healthy controls (HC, N = 30) were also included. Intra- and inter-network connectivity were investigated from participants' rs-fMRIs in 26 resting state networks (RSNs). Intra-network differences were found between both patient groups and HCs for networks associated with motor control (motor cortex), spatial attention and visual perception. When comparing both PD-NC and PD-MCI, intra-network alterations were found in RSNs related to attention, executive function and motor control (cerebellum). The inter-network analysis revealed a hyper-synchronisation between the basal ganglia network and the motor cortex in PD-NC compared with HCs. When both patient groups were compared, intra-network alterations in RSNs related to attention, motor control, visual perception and executive function were found. We also detected disease-driven negative synchronisations and synchronisation shifts from positive to negative and vice versa in both patient groups compared with HCs. The hyper-synchronisation between basal ganglia and motor cortical RSNs in PD and its synchronisation shift from negative to positive compared with HCs, suggest a compensatory response to basal dysfunction and altered basal-cortical motor control in the resting state brain of PD patients. Hum Brain Mapp, 2016. © 2016 Wiley Periodicals, Inc.
PMID: 28084651 [PubMed - as supplied by publisher]
A Supervoxel-Based Method for Groupwise Whole Brain Parcellation with Resting-State fMRI Data.
Front Hum Neurosci. 2016;10:659
Authors: Wang J, Wang H
Node definition is a very important issue in human brain network analysis and functional connectivity studies. Typically, the atlases generated from meta-analysis, random criteria, and structural criteria are utilized as nodes in related applications. However, these atlases are not originally designed for such purposes and may not be suitable. In this study, we combined normalized cut (Ncut) and a supervoxel method called simple linear iterative clustering (SLIC) to parcellate whole brain resting-state fMRI data in order to generate appropriate brain atlases. Specifically, Ncut was employed to extract features from connectivity matrices, and then SLIC was applied on the extracted features to generate parcellations. To obtain group level parcellations, two approaches named mean SLIC and two-level SLIC were proposed. The cluster number varied in a wide range in order to generate parcellations with multiple granularities. The two SLIC approaches were compared with three state-of-the-art approaches under different evaluation metrics, which include spatial contiguity, functional homogeneity, and reproducibility. Both the group-to-group reproducibility and the group-to-subject reproducibility were evaluated in our study. The experimental results showed that the proposed approaches obtained relatively good overall clustering performances in different conditions that included different weighting functions, different sparsifying schemes, and several confounding factors. Therefore, the generated atlases are appropriate to be utilized as nodes for network analysis. The generated atlases and major source codes of this study have been made publicly available at http://www.nitrc.org/projects/slic/.
PMID: 28082885 [PubMed - in process]
Sevoflurane Alters Spatiotemporal Functional Connectivity Motifs That Link Resting-State Networks during Wakefulness.
Front Neural Circuits. 2016;10:107
Authors: Kafashan M, Ching S, Palanca BJ
Background: The spatiotemporal patterns of correlated neural activity during the transition from wakefulness to general anesthesia have not been fully characterized. Correlation analysis of blood-oxygen-level dependent (BOLD) functional magnetic resonance imaging (fMRI) allows segmentation of the brain into resting-state networks (RSNs), with functional connectivity referring to the covarying activity that suggests shared functional specialization. We quantified the persistence of these correlations following the induction of general anesthesia in healthy volunteers and assessed for a dynamic nature over time. Methods: We analyzed human fMRI data acquired at 0 and 1.2% vol sevoflurane. The covariance in the correlated activity among different brain regions was calculated over time using bounded Kalman filtering. These time series were then clustered into eight orthogonal motifs using a K-means algorithm, where the structure of correlated activity throughout the brain at any time is the weighted sum of all motifs. Results: Across time scales and under anesthesia, the reorganization of interactions between RSNs is related to the strength of dynamic connections between member pairs. The covariance of correlated activity between RSNs persists compared to that linking individual member pairs of different RSNs. Conclusions: Accounting for the spatiotemporal structure of correlated BOLD signals, anesthetic-induced loss of consciousness is mainly associated with the disruption of motifs with intermediate strength within and between members of different RSNs. In contrast, motifs with higher strength of connections, predominantly with regions-pairs from within-RSN interactions, are conserved among states of wakefulness and sevoflurane general anesthesia.
PMID: 28082871 [PubMed - in process]
Evaluating the Influence of Spatial Resampling for Motion Correction in Resting-State Functional MRI.
Front Neurosci. 2016;10:591
Authors: Yuan L, He H, Zhang H, Zhong J
Head motion is one of major concerns in current resting-state functional MRI studies. Image realignment including motion estimation and spatial resampling is often applied to achieve rigid-body motion correction. While the accurate estimation of motion parameters has been addressed in most studies, spatial resampling could also produce spurious variance, and lead to unexpected errors on the amplitude of BOLD signal. In this study, two simulation experiments were designed to characterize these variance related with spatial resampling. The fluctuation amplitude of spurious variance was first investigated using a set of simulated images with estimated motion parameters from a real dataset, and regions more likely to be affected by spatial resampling were found around the peripheral regions of the cortex. The other simulation was designed with three typical types of motion parameters to represent different extents of motion. It was found that areas with significant correlation between spurious variance and head motion scattered all over the brain and varied greatly from one motion type to another. In the last part of this study, four popular motion regression approaches were applied respectively and their performance in reducing spurious variance was compared. Among them, Friston 24 and Voxel-specific 12 model (Friston et al., 1996), were found to have the best outcomes. By separating related effects during fMRI analysis, this study provides a better understanding of the characteristics of spatial resampling and the interpretation of motion-BOLD relationship.
PMID: 28082860 [PubMed - in process]
The relationship between BOLD fMRI response and the underlying white matter as measured by fractional anisotropy (FA): a systematic review.
Neuroimage. 2017 Jan 07;:
Authors: Warbrick T, Rosenberg J, Shah NJ
Despite the relationship between brain structure and function being of fundamental interest in cognitive neuroscience, the relationship between the brain's white matter, measured using fractional anisotropy (FA), and the functional magnetic resonance imaging (fMRI) blood oxygen level dependent (BOLD) response is poorly understood. A systematic review of literature investigating the association between FA and fMRI BOLD response was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The PubMed and Web of Knowledge databases were searched up until 22.04.2016 using a predetermined set of search criteria. The search identified 363 papers, 28 of which met the specified inclusion criteria. Positive relationships were mainly observed in studies investigating the primary sensory and motor systems and in resting state data. Both positive and negative relationships were seen in studies using cognitive tasks. This systematic review suggests that there is a relationship between FA and the fMRI BOLD response and that the relationship is task and region dependent. Behavioural and/or clinical variables were shown to be essential in interpreting the relationships between imaging measures. The results highlight the heterogeneity in the methods used across papers in terms of fMRI task, population investigated and data analysis techniques. Further investigation and replication of current findings are required before definitive conclusions can be drawn.
PMID: 28082105 [PubMed - as supplied by publisher]
Regional Homogeneity Changes in Nicotine Addicts by Resting-State fMRI.
PLoS One. 2017;12(1):e0170143
Authors: Chen H, Mo S
OBJECTIVE: To reveal the brain functional changes of nicotine addicts compared with those of non-smokers and explore the objective biomarker for nicotine dependence evaluation.
METHODS: A total of 14 smokers and 11 non-smoking controls were recruited for this study. Resting-state functional magnetic resonance imaging and regional homogeneity (ReHo) were applied in the neural activity analysis. Two-sample t-test was performed to examine the voxel-wise difference between the smokers and the controls. Correlation analysis between the ReHo values and the Fagerstrom Test for Nicotine Dependence (FTND) scores were performed to explore the biomarkers for the clinical characteristics of smokers.
RESULTS: The ReHo values from the right superior frontal gyrus of the Brodmann's area (BA) 9 to the right middle frontal gyrus and the ReHo value from the left and right precuneus (BA 23) to the left and right middle cingulum gyrus were lower in the smokers than in the non-smokers. The ReHo value in the precuneus (BA 23) was significantly and positively correlated with the FTND score of smokers.
CONCLUSION: The ReHo values in the right superior frontal gyrus and left precuneus can be used to separate the smokers from the non-smokers. In particular, the left precuneus is a potential neuroimaging biomarker for nicotine addicts.
PMID: 28081226 [PubMed - in process]
Maintenance and Representation of Mind Wandering during Resting-State fMRI.
Sci Rep. 2017 Jan 12;7:40722
Authors: Chou YH, Sundman M, Whitson HE, Gaur P, Chu ML, Weingarten CP, Madden DJ, Wang L, Kirste I, Joliot M, Diaz MT, Li YJ, Song AW, Chen NK
Major advances in resting-state functional magnetic resonance imaging (fMRI) techniques in the last two decades have provided a tool to better understand the functional organization of the brain both in health and illness. Despite such developments, characterizing regulation and cerebral representation of mind wandering, which occurs unavoidably during resting-state fMRI scans and may induce variability of the acquired data, remains a work in progress. Here, we demonstrate that a decrease or decoupling in functional connectivity involving the caudate nucleus, insula, medial prefrontal cortex and other domain-specific regions was associated with more sustained mind wandering in particular thought domains during resting-state fMRI. Importantly, our findings suggest that temporal and between-subject variations in functional connectivity of above-mentioned regions might be linked with the continuity of mind wandering. Our study not only provides a preliminary framework for characterizing the maintenance and cerebral representation of different types of mind wandering, but also highlights the importance of taking mind wandering into consideration when studying brain organization with resting-state fMRI in the future.
PMID: 28079189 [PubMed - in process]
Abnormalities of regional brain function in Parkinson's disease: a meta-analysis of resting state functional magnetic resonance imaging studies.
Sci Rep. 2017 Jan 12;7:40469
Authors: Pan P, Zhang Y, Liu Y, Zhang H, Guan D, Xu Y
There is convincing evidence that abnormalities of regional brain function exist in Parkinson's disease (PD). However, many resting-state functional magnetic resonance imaging (rs-fMRI) studies using amplitude of low-frequency fluctuations (ALFF) have reported inconsistent results about regional spontaneous neuronal activity in PD. Therefore, we conducted a comprehensive meta-analysis using the Seed-based d Mapping and several complementary analyses. We searched PubMed, Embase, and Web of Science databases for eligible whole-brain rs-fMRI studies that measured ALFF differences between patients with PD and healthy controls published from January 1st, 2000 until June 24, 2016. Eleven studies reporting 14 comparisons, comparing 421 patients and 381 healthy controls, were included. The most consistent and replicable findings in patients with PD compared with healthy controls were identified, including the decreased ALFFs in the bilateral supplementary motor areas, left putamen, left premotor cortex, and left inferior parietal gyrus, and increased ALFFs in the right inferior parietal gyrus. The altered ALFFs in these brain regions are related to motor deficits and compensation in PD, which contribute to understanding its neurobiological underpinnings and could serve as specific regions of interest for further studies.
PMID: 28079169 [PubMed - in process]
Co-Variation of Peripheral Levels of miR-1202 and Brain Activity and Connectivity During Antidepressant Treatment.
Neuropsychopharmacology. 2017 Jan 12;:
Authors: Lopez JP, Pereira F, Richard-Devantoy S, Berlim M, Chachamovich E, Fiori LM, Niola P, Turecki G, Jollant F
MicroRNAs are short non-coding molecules that play a major role in regulating gene expression. Peripheral levels of miR-1202 have been shown to predict and mediate antidepressant response. However, it is not clear to what extent these peripheral measures reflect central neural changes in vivo. We approached this problem with the combined use of peripheral miR-1202 measures and neuroimaging. At baseline and after 8 weeks of Desvenlafaxine (50-100 mg die), twenty patients were scanned with 3T Magnetic Resonance Imaging, first at rest then during the Go/NoGo task, a classical test of response inhibition. Blood samples were collected at both time points. During resting state, lower baseline miR-1202 levels were predictive of increased connectivity from T0 to T8 between the posterior cingulate and the prefrontal, parietal and occipital cortices. Changes in miR-1202 levels following Desvenlafaxine treatment were negatively correlated with changes in activity in right precuneus within the default-mode network, and in connectivity between the posterior cingulate and the temporal and prefrontal cortices, and the precuneus. During the Go/NoGo task, baseline miR-1202 levels and changes in these levels were correlated with activity changes in different regions, including bilateral prefrontal, insular, cingulate, and temporal cortices, and left putamen and claustrum. Finally, secondary analyses in a subset of patients showed a trend for a significant correlation between miR-1202 levels and glutamate levels measured by spectroscopy. Changes in peripheral miR-1202 levels were therefore associated with changes in brain activity and connectivity in a network of brain regions associated with depression and antidepressant response. These effects may be mediated by the glutamatergic system.Neuropsychopharmacology accepted article preview online, 12 January 2017. doi:10.1038/npp.2017.9.
PMID: 28079059 [PubMed - as supplied by publisher]
Formation of Long-Term Locomotor Memories Is Associated with Functional Connectivity Changes in the Cerebellar-Thalamic-Cortical Network.
J Neurosci. 2017 Jan 11;37(2):349-361
Authors: Mawase F, Bar-Haim S, Shmuelof L
Although motor adaptation is typically rapid, accumulating evidence shows that it is also associated with long-lasting behavioral and neuronal changes. Two processes were suggested to explain the formation of long-term motor memories: recall, reflecting a retrieval of previous motor actions, and faster relearning, reflecting an increased sensitivity to errors. Although these manifestations of motor memories were initially demonstrated in the context of adaptation experiments in reaching, indications of long-term motor memories were also demonstrated recently in other kinds of adaptation such as in locomotor adaptation. Little is known about the neural processes that underlie these distinct aspects of memory. We hypothesize that recall and faster relearning reflect different learning processes that operate at the same time and depend on different neuronal networks. Seventeen subjects performed a multisession locomotor adaptation experiment in the laboratory, together with resting-state and localizer fMRI scans, after the baseline and the locomotor adaptation sessions. We report a modulation of the cerebellar-thalamic-cortical and cerebellar-basal ganglia networks after locomotor adaptation. Interestingly, whereas thalamic-cortical baseline connectivity was correlated with recall, cerebellar-thalamic baseline connectivity was correlated with faster relearning. Our results suggest that separate neuronal networks underlie error sensitivity and retrieval components. Individual differences in baseline resting-state connectivity can predict idiosyncratic combination of these components.
SIGNIFICANCE STATEMENT: The ability to shape our motor behavior rapidly in everyday activity, such as when walking on sand, suggests the existence of long-term motor memories. It was suggested recently that this ability is achieved by the retrieval of previous motor actions and by enhanced relearning capacity. Little is known about the neural mechanisms that underlie these memory processes. We studied the modularity in long-term motor memories in the context of locomotor adaptation using resting-state fMRI. We show that retrieval and relearning effects are associated with separate locomotor control networks and that intersubject variability in learning and in the generation of motor memories could be predicted from baseline resting-state connectivity in locomotor-related networks.
PMID: 28077714 [PubMed - in process]
Altered fractional amplitude of low frequency fluctuation associated with cognitive dysfunction in first-episode drug-naïve major depressive disorder patients.
BMC Psychiatry. 2017 Jan 11;17(1):11
Authors: Huang M, Lu S, Yu L, Li L, Zhang P, Hu J, Zhou W, Hu S, Wei N, Huang J, Weng J, Xu Y
BACKGROUND: Previous studies have demonstrated that abnormities of both resting-state brain activity and cognitive dysfunction are frequently observed in patients with major depressive disorder (MDD). However, the underlying relationship between these two aspects is less investigated. In this context, the aim of the present study was to investigate the association between cognitive dysfunction and altered resting-state brain function in first-episode drug-naïve MDD patients.
METHODS: Twenty-five drug-naïve MDD patients and twenty-six age-, sex-, and education-matched normal controls were recruited in this study. Cognitive function was evaluated by using a series of validated test procedures. The resting-state functional magnetic resonance imaging data were obtained on a Philips 3.0 Tesla scanner and analysed using the fractional amplitude of low frequency fluctuation (fALFF) method. Correlations of fALFF values with cognitive dysfunction were further analysed.
RESULTS: Compared with healthy controls, MDD patients showed significantly fewer completed categories in the Wisconsin Card Sorting Test (WCST) and decreased scores in the first and second subtests of the Continuous Performance Test (CPT). However, the two groups did not differ in their performance on the Stroop Colour Word Test and Trail-making Test. MDD patients exhibited significantly decreased fALFF values in the left superior frontal gyrus (SFG), left middle frontal gyrus, and left inferior frontal gyrus, as well as increased fALFF values in the left inferior temporal gyrus (ITG), bilateral parahippocampal gyrus, and the right caudate. Finally, the correlation analyses revealed that fALFF values in the left SFG and left ITG were associated with the number of WSCT completed categories and scores on the second subtest of the CPT in MDD, respectively.
CONCLUSIONS: The present findings suggest that there is little evidence of an association between regional abnormalities in resting-state brain function and cognitive deficits in MDD.
PMID: 28077120 [PubMed - in process]
Disrupted global metastability and static and dynamic brain connectivity across individuals in the Alzheimer's disease continuum.
Sci Rep. 2017 Jan 11;7:40268
Authors: Córdova-Palomera A, Kaufmann T, Persson K, Alnæs D, Doan NT, Moberget T, Lund MJ, Barca ML, Engvig A, Brækhus A, Engedal K, Andreassen OA, Selbæk G, Westlye LT
As findings on the neuropathological and behavioral components of Alzheimer's disease (AD) continue to accrue, converging evidence suggests that macroscale brain functional disruptions may mediate their association. Recent developments on theoretical neuroscience indicate that instantaneous patterns of brain connectivity and metastability may be a key mechanism in neural communication underlying cognitive performance. However, the potential significance of these patterns across the AD spectrum remains virtually unexplored. We assessed the clinical sensitivity of static and dynamic functional brain disruptions across the AD spectrum using resting-state fMRI in a sample consisting of AD patients (n = 80) and subjects with either mild (n = 44) or subjective (n = 26) cognitive impairment (MCI, SCI). Spatial maps constituting the nodes in the functional brain network and their associated time-series were estimated using spatial group independent component analysis and dual regression, and whole-brain oscillatory activity was analyzed both globally (metastability) and locally (static and dynamic connectivity). Instantaneous phase metrics showed functional coupling alterations in AD compared to MCI and SCI, both static (putamen, dorsal and default-mode) and dynamic (temporal, frontal-superior and default-mode), along with decreased global metastability. The results suggest that brains of AD patients display altered oscillatory patterns, in agreement with theoretical premises on cognitive dynamics.
PMID: 28074926 [PubMed - in process]
Confirmation of resting-state BOLD fluctuations in the human brainstem and spinal cord after identification and removal of physiological noise.
Magn Reson Med. 2017 Jan 11;:
Authors: Harita S, Stroman PW
PURPOSE: Resting-state functional MRI (rs-fMRI) has been used to investigate networks within the cortex, but its use in the brainstem (BS) and spinal cord (SC) has been limited. This region presents challenges for fMRI, partly because of sources of physiological noise. This study aims to quantify noise contributions to rs-fMRI, and to obtain evidence of resting-state blood oxygenation level-dependent (BOLD) fluctuations.
METHODS: Resting-state-fMRI data were obtained from the BS/SC in 16 participants, at 3 Tesla, with T2 -weighted single-shot fast spin-echo imaging. The peripheral pulse, respiration, and expired CO2 were recorded continuously. Physiological noise was modeled from these recordings, movement parameters, and white matter regions. Model fits were then subtracted from the data. BOLD contributions were then investigated through connectivity.
RESULTS: Bulk motion was the largest contributor to the signal variance (19% of the total), followed by cardiac-related motion (14%), nonspecific signal variations detected in white matter (10%), respiratory-related motion (2.6%), and end-tidal CO2 variations (0.7%). After noise was removed, significant left-right connectivity was detected in the SC dorsal horns and ventral horns.
CONCLUSIONS: Resting-state BOLD fluctuations are demonstrated in the SC, as are the dominant noise contributions. These findings are an essential step toward establishing rs-fMRI in the BS/SC. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
PMID: 28074492 [PubMed - as supplied by publisher]
Dopamine controls Parkinson's tremor by inhibiting the cerebellar thalamus.
Brain. 2017 Jan 09;:
Authors: Dirkx MF, den Ouden HE, Aarts E, Timmer MH, Bloem BR, Toni I, Helmich RC
Parkinson's resting tremor is related to altered cerebral activity in the basal ganglia and the cerebello-thalamo-cortical circuit. Although Parkinson's disease is characterized by dopamine depletion in the basal ganglia, the dopaminergic basis of resting tremor remains unclear: dopaminergic medication reduces tremor in some patients, but many patients have a dopamine-resistant tremor. Using pharmacological functional magnetic resonance imaging, we test how a dopaminergic intervention influences the cerebral circuit involved in Parkinson's tremor. From a sample of 40 patients with Parkinson's disease, we selected 15 patients with a clearly tremor-dominant phenotype. We compared tremor-related activity and effective connectivity (using combined electromyography-functional magnetic resonance imaging) on two occasions: ON and OFF dopaminergic medication. Building on a recently developed cerebral model of Parkinson's tremor, we tested the effect of dopamine on cerebral activity associated with the onset of tremor episodes (in the basal ganglia) and with tremor amplitude (in the cerebello-thalamo-cortical circuit). Dopaminergic medication reduced clinical resting tremor scores (mean 28%, range -12 to 68%). Furthermore, dopaminergic medication reduced tremor onset-related activity in the globus pallidus and tremor amplitude-related activity in the thalamic ventral intermediate nucleus. Network analyses using dynamic causal modelling showed that dopamine directly increased self-inhibition of the ventral intermediate nucleus, rather than indirectly influencing the cerebello-thalamo-cortical circuit through the basal ganglia. Crucially, the magnitude of thalamic self-inhibition predicted the clinical dopamine response of tremor. Dopamine reduces resting tremor by potentiating inhibitory mechanisms in a cerebellar nucleus of the thalamus (ventral intermediate nucleus). This suggests that altered dopaminergic projections to the cerebello-thalamo-cortical circuit have a role in Parkinson's tremor.
PMID: 28073788 [PubMed - as supplied by publisher]
Role of testosterone and Y chromosome genes for the masculinization of the human brain.
Hum Brain Mapp. 2017 Jan 10;:
Authors: Savic I, Frisen L, Manzouri A, Nordenstrom A, Lindén Hirschberg A
Women with complete androgen insensitivity syndrome (CAIS) have a male (46,XY) karyotype but no functional androgen receptors. Their condition, therefore, offers a unique model for studying testosterone effects on cerebral sex dimorphism. We present MRI data from 16 women with CAIS and 32 male (46,XY) and 32 female (46,XX) controls.
METHODS: FreeSurfer software was employed to measure cortical thickness and subcortical structural volumes. Axonal connections, indexed by fractional anisotropy, (FA) were measured with diffusion tensor imaging, and functional connectivity with resting state fMRI.
RESULTS: Compared to men, CAIS women displayed a "female" pattern by having thicker parietal and occipital cortices, lower FA values in the right corticospinal, superior and inferior longitudinal tracts, and corpus callosum. Their functional connectivity from the amygdala to the medial prefrontal cortex, was stronger and amygdala-connections to the motor cortex weaker than in control men. CAIS and control women also showed stronger posterior cingulate and precuneus connections in the default mode network. Thickness of the motor cortex, the caudate volume, and the FA in the callosal body followed, however, a "male" pattern.
CONCLUSION: Altogether, these data suggest that testosterone modulates the microstructure of somatosensory and visual cortices and their axonal connections to the frontal cortex. Testosterone also influenced functional connections from the amygdala, whereas the motor cortex could, in agreement with our previous reports, be moderated by processes linked to X-chromosome gene dosage. These data raise the question about other genetic factors masculinizing the human brain than the SRY gene and testosterone. Hum Brain Mapp, 2016. © 2016 Wiley Periodicals, Inc.
PMID: 28070912 [PubMed - as supplied by publisher]
Cerebellar tDCS modulates neural circuits during semantic prediction: A combined tDCS-fMRI study.
J Neurosci. 2017 Jan 09;:
Authors: D'Mello AM, Turkeltaub PE, Stoodley CJ
It has been proposed that the cerebellum acquires internal models of mental processes that enable prediction, allowing for the optimization of behavior. In language, semantic prediction speeds speech production and comprehension. Right cerebellar lobules VI and VII (including Crus I/II) are engaged during a variety of language processes and are functionally connected with cerebral cortical language networks. Further, right posterolateral cerebellar neuromodulation modifies behavior during predictive language processing. These data are consistent with a role for the cerebellum in semantic processing and semantic prediction. We combined transcranial direct current stimulation (tDCS) and functional magnetic resonance imaging (fMRI) to assess the behavioral and neural consequences of cerebellar tDCS during a sentence completion task. Task-based and resting-state fMRI data were acquired in healthy human adults (n=32; μ=23.1 years) both before and after 20min of 1.5 mA anodal (n=18) or sham (n=14) tDCS applied to the right posterolateral cerebellum. In the sentence completion task, the first four words of the sentence modulated the predictability of the final target word. In some sentences, the preceding context strongly predicted the target word, while other sentences were non-predictive. Completion of predictive sentences increased activation in right Crus I/II of the cerebellum. Relative to sham tDCS, anodal tDCS increased activation in right Crus I/II during semantic prediction and enhanced resting-state functional connectivity between hubs of the reading/language networks. These results are consistent with a role for the right posterolateral cerebellum beyond motor aspects of language, and suggest that cerebellar internal models of linguistic stimuli support semantic prediction.
SIGNIFICANCE STATEMENT: Cerebellar involvement in language tasks and language networks is now well-established, yet the specific cerebellar contribution to language processing remains unclear. It is thought that the cerebellum acquires internal models of mental processes that enable prediction, allowing for the optimization of behavior. Here we combined neuroimaging and neuromodulation to provide evidence that the cerebellum is specifically involved in semantic prediction during sentence processing. We found that activation within right Crus I/II was enhanced when semantic predictions were made, and show that modulation of this region with transcranial direct current stimulation alters both activation patterns and functional connectivity within whole-brain language networks. For the first time, these data show that cerebellar neuromodulation impacts activation patterns specifically during predictive language processing.
PMID: 28069925 [PubMed - as supplied by publisher]
Dopamine modulates the functional organization of the orbitofrontal cortex.
J Neurosci. 2017 Jan 09;:
Authors: Kahnt T, Tobler PN
Neuromodulators such as dopamine can alter the intrinsic firing properties of neurons, and may thereby change the configuration of larger functional circuits. The primate orbitofrontal cortex (OFC) receives dopaminergic input from midbrain nuclei, but the role of dopamine in the OFC is still unclear. Here we tested the idea that dopaminergic activity changes the pattern of connectivity between the OFC and the rest of the brain, and thereby reconfigures functional networks in the OFC. To this end, we combined double-blind, placebo-controlled pharmacology (D2 receptor [D2R] antagonist amisulpride) in humans with resting-state functional magnetic resonance imaging (fMRI) and clustering methods. In the placebo group, we replicated previously observed parcellations of the OFC into two and six subregions based on connectivity patterns with the rest of the brain. Most importantly, while the 2-fold clustering did not differ significantly between groups, blocking D2R receptors significantly changed the composition of the 6-fold parcellation, suggesting a dopamine-dependent reconfiguration of functional OFC subregions. Moreover, multivariate decoding analyses revealed that amisulpride changed the whole-brain connectivity patterns of individual OFC-subregions. In particular, D2R blockade shifted the balance of OFC connectivity from associative areas in the temporal and parietal lobe toward functional connectivity with the frontal cortex. In summary, our results suggest that dopamine alters the composition of functional OFC circuits, possibly indicating a broader role for neuromodulators in the dynamic reconfiguration of functional brain networks.
SIGNIFICANCE STATEMENT: A key role of any neuromodulator may be the reconfiguration of functional brain circuits. Here we test this idea with regard to dopamine and the organization of functional networks in the OFC. We show that blockade of dopamine D2-receptors has profound effects on the functional connectivity patterns of the OFC, yielding in altered connectivity-based subdivisions of this region. Our results suggest that dopamine changes the connectional configuration of the OFC, possibly leading to transitions between different operating modes that favor either sensory input or recurrent processing in the prefrontal cortex. More generally, our findings support a broader role for neuromodulators in the dynamic reconfiguration of functional brain networks and may have clinical implications for understanding the actions of antipsychotics.
PMID: 28069917 [PubMed - as supplied by publisher]