Lag threads organize the brain's intrinsic activity.
Proc Natl Acad Sci U S A. 2015 Mar 30;
Authors: Mitra A, Snyder AZ, Blazey T, Raichle ME
It has been widely reported that intrinsic brain activity, in a variety of animals including humans, is spatiotemporally structured. Specifically, propagated slow activity has been repeatedly demonstrated in animals. In human resting-state fMRI, spontaneous activity has been understood predominantly in terms of zero-lag temporal synchrony within widely distributed functional systems (resting-state networks). Here, we use resting-state fMRI from 1,376 normal, young adults to demonstrate that multiple, highly reproducible, temporal sequences of propagated activity, which we term "lag threads," are present in the brain. Moreover, this propagated activity is largely unidirectional within conventionally understood resting-state networks. Modeling experiments show that resting-state networks naturally emerge as a consequence of shared patterns of propagation. An implication of these results is that common physiologic mechanisms may underlie spontaneous activity as imaged with fMRI in humans and slowly propagated activity as studied in animals.
PMID: 25825720 [PubMed - as supplied by publisher]
Altered attention networks in benign childhood epilepsy with centrotemporal spikes (BECTS): A resting-state fMRI study.
Epilepsy Behav. 2015 Mar 27;
Authors: Xiao F, Li L, An D, Lei D, Tang Y, Yang T, Ren J, Chen S, Huang X, Gong Q, Zhou D
It is noteworthy that some children with benign childhood epilepsy with centrotemporal spikes (BECTS) show attention problems despite their favorable seizure outcome. Resting-state functional magnetic resonance imaging (fMRI) is a method widely used to detect brain network alterations in neuropsychiatric diseases. We used resting-state functional magnetic resonance imaging (fMRI) to investigate specific brain networks related to attention deficit in children with BECTS. Resting-state fMRI was performed in patients with BECTS with ADHD (n=15) and those with BECTS without ADHD (n=15) and in healthy controls (n=15). Unbiased seed-based whole-brain functional connectivity analysis was used to study the connectivity pattern of three resting-state networks, including the ventral attention network (VAN) and the dorsal attention network (DAN) and the default mode network (DMN). Patients with BECTS with ADHD displayed decreased functional connectivity in the DAN compared with other two groups, while patients with BECTS without ADHD showed increased functional connectivity in the DAN. Moreover, we found increased functional connectivity in the VAN and in the DMN in patients with BECTS with or without ADHD when comparing with controls. These results showed that the newly-diagnosed children with BECTS displayed brain activity alterations in the ventral and dorsal attention networks. The difference in the extent of impairment in the dorsal attention network of patients with BECTS with ADHD and patients with BECTS without ADHD may lead to improved understanding of the underlying neuropathophysiology and treatment of BECTS with ADHD and BECTS without ADHD.
PMID: 25825370 [PubMed - as supplied by publisher]
HIV Infection Is Associated with Attenuated Frontostriatal Intrinsic Connectivity: A Preliminary Study.
J Int Neuropsychol Soc. 2015 Mar 31;:1-11
Authors: Ipser JC, Brown GG, Bischoff-Grethe A, Connolly CG, Ellis RJ, Heaton RK, Grant I, Translational Methamphetamine AIDS Research Center (TMARC) Group
HIV-associated cognitive impairments are prevalent, and are consistent with injury to both frontal cortical and subcortical regions of the brain. The current study aimed to assess the association of HIV infection with functional connections within the frontostriatal network, circuitry hypothesized to be highly vulnerable to HIV infection. Fifteen HIV-positive and 15 demographically matched control participants underwent 6 min of resting-state functional magnetic resonance imaging (RS-fMRI). Multivariate group comparisons of age-adjusted estimates of connectivity within the frontostriatal network were derived from BOLD data for dorsolateral prefrontal cortex (DLPFC), dorsal caudate and mediodorsal thalamic regions of interest. Whole-brain comparisons of group differences in frontostriatal connectivity were conducted, as were pairwise tests of connectivity associations with measures of global cognitive functioning and clinical and immunological characteristics (nadir and current CD4 count, duration of HIV infection, plasma HIV RNA). HIV - associated reductions in connectivity were observed between the DLPFC and the dorsal caudate, particularly in younger participants (<50 years, N=9). Seropositive participants also demonstrated reductions in dorsal caudate connectivity to frontal and parietal brain regions previously demonstrated to be functionally connected to the DLPFC. Cognitive impairment, but none of the assessed clinical/immunological variables, was also associated with reduced frontostriatal connectivity. In conclusion, our data indicate that HIV is associated with attenuated intrinsic frontostriatal connectivity. Intrinsic connectivity of this network may therefore serve as a marker of the deleterious effects of HIV infection on the brain, possibly via HIV-associated dopaminergic abnormalities. These findings warrant independent replication in larger studies. (JINS, 2015, 21, 1-11).
PMID: 25824201 [PubMed - as supplied by publisher]
Contralesional Thalamic Surface Atrophy and Functional Disconnection 3 Months after Ischemic Stroke.
Cerebrovasc Dis. 2015 Mar 25;39(3-4):232-241
Authors: Yassi N, Malpas CB, Campbell BC, Moffat B, Steward C, Parsons MW, Desmond PM, Donnan GA, Davis SM, Bivard A
BACKGROUND: Remote structural and functional changes have been previously described after stroke and may have an impact on clinical outcome. We aimed to use multimodal MRI to investigate contralesional subcortical structural and functional changes 3 months after anterior circulation ischemic stroke.
METHODS: Fifteen patients with acute ischemic stroke had multimodal MRI imaging (including high resolution structural T1-MPRAGE and resting state fMRI) within 1 week of onset and at 1 and 3 months. Seven healthy controls of similar age group were also imaged at a single time point. Contralesional subcortical structural volume was assessed using an automated segmentation algorithm in FMRIB's Integrated Registration and Segmentation Tool (FIRST). Functional connectivity changes were assessed using the intrinsic connectivity contrast (ICC), which was calculated using the functional connectivity toolbox for correlated and anticorrelated networks (Conn).
RESULTS: Contralesional thalamic volume in the stroke patients was significantly reduced at 3 months compared to baseline (median change -2.1%, interquartile range [IQR] -3.4-0.4, p = 0.047), with the predominant areas demonstrating atrophy geometrically appearing to be the superior and inferior surface. The difference in volume between the contralesional thalamus at baseline (mean 6.41 ml, standard deviation [SD] 0.6 ml) and the mean volume of the 2 thalami in controls (mean 7.22 ml, SD 1.1 ml) was not statistically significant. The degree of longitudinal thalamic atrophy in patients was correlated with baseline stroke severity with more severe strokes being associated with a greater degree of atrophy (Spearman's rho -0.54, p = 0.037). There was no significant difference between baseline contralesional thalamic ICC in patients and control thalamic ICC. However, in patients, there was a significant linear reduction in the mean ICC of the contralesional thalamus over the imaging time points (p = 0.041), indicating reduced connectivity to the remainder of the brain.
CONCLUSIONS: These findings highlight the importance of remote brain areas, such as the contralesional thalamus, in stroke recovery. Similar methods have the potential to be used in the prediction of stroke outcome or as imaging biomarkers of stroke recovery. © 2015 S. Karger AG, Basel.
PMID: 25823493 [PubMed - as supplied by publisher]
Regional functional connectivity predicts distinct cognitive impairments in Alzheimer's disease spectrum.
Neuroimage Clin. 2014;5:385-95
Authors: Ranasinghe KG, Hinkley LB, Beagle AJ, Mizuiri D, Dowling AF, Honma SM, Finucane MM, Scherling C, Miller BL, Nagarajan SS, Vossel KA
Understanding neural network dysfunction in neurodegenerative disease is imperative to effectively develop network-modulating therapies. In Alzheimer's disease (AD), cognitive decline associates with deficits in resting-state functional connectivity of diffuse brain networks. The goal of the current study was to test whether specific cognitive impairments in AD spectrum correlate with reduced functional connectivity of distinct brain regions. We recorded resting-state functional connectivity of alpha-band activity in 27 patients with AD spectrum--22 patients with probable AD (5 logopenic variant primary progressive aphasia, 7 posterior cortical atrophy, and 10 early-onset amnestic/dysexecutive AD) and 5 patients with mild cognitive impairment due to AD. We used magnetoencephalographic imaging (MEGI) to perform an unbiased search for regions where patterns of functional connectivity correlated with disease severity and cognitive performance. Functional connectivity measured the strength of coherence between a given region and the rest of the brain. Decreased neural connectivity of multiple brain regions including the right posterior perisylvian region and left middle frontal cortex correlated with a higher degree of disease severity. Deficits in executive control and episodic memory correlated with reduced functional connectivity of the left frontal cortex, whereas visuospatial impairments correlated with reduced functional connectivity of the left inferior parietal cortex. Our findings indicate that reductions in region-specific alpha-band resting-state functional connectivity are strongly correlated with, and might contribute to, specific cognitive deficits in AD spectrum. In the future, MEGI functional connectivity could be an important biomarker to map and follow defective networks in the early stages of AD.
PMID: 25180158 [PubMed - indexed for MEDLINE]
Network structure of functional hippocampal lateralization in birds.
Hippocampus. 2015 Mar 26;
Authors: Jonckers E, Güntürkün O, De Groof G, van der Linden A, Bingman VP
Functional hemispheric asymmetry is a common feature of vertebrate brain organization, yet little is known about how hemispheric dominance is implemented at the neural level. One notable example of hemispheric dominance in birds is the leading role of the left hippocampal formation in controlling navigational processes that support homing in pigeons. Relying on resting state fMRI analyses (where Functional connectivity (FC) can be determined by placing a reference 'seed' for connectivity in one hemisphere), we show that following seeding in either an anterior or posterior region of the hippocampal formation of homing pigeons and starlings, the emergent functional connectivity maps are consistently larger following seeding of the left hippocampus. Left seedings are also more likely to result in functional connectivity maps that extend to the contralateral hippocampus and outside the boundaries of the hippocampus. The data support the hypothesis that broader functional connectivity is one neural-organizational property that confers, with respect to navigation, functional dominance to the left hippocampus of birds. This article is protected by copyright. All rights reserved.
PMID: 25821141 [PubMed - as supplied by publisher]
A splitting brain: Imbalanced neural networks in schizophrenia.
Psychiatry Res. 2015 Mar 11;
Authors: Li M, Deng W, He Z, Wang Q, Huang C, Jiang L, Gong Q, Ziedonis DM, King JA, Ma X, Zhang N, Li T
Dysconnectivity between key brain systems has been hypothesized to underlie the pathophysiology of schizophrenia. The present study examined the pattern of functional dysconnectivity across whole-brain neural networks in 121 first-episode, treatment-naïve patients with schizophrenia by using resting-state functional magnetic resonance imaging (rsfMRI). Group independent component analysis (ICA) was first applied to rsfMRI data to extract 90 functional components of the brain. The functional connectivity between these ICA components was then evaluated and compared between the patient and control groups. To examine the functional roles of significantly altered between-component connections in patients, each ICA component was ascribed to one of 10 previously well-defined brain networks/areas. Relative to findings in healthy controls (n=103), 29 altered functional connections including 19 connections with increased connectivity and 10 connections with decreased connectivity in schizophrenia patients were found. Increased connectivity was mainly within the default mode network (DMN) and between the DMN and cognitive networks, whereas decreased connectivity was predominantly associated with sensory networks. Given the key roles of the DMN in internal mental processes and sensory networks in inputs from the external environment, these patterns of altered brain network connectivity could suggest imbalanced neural processing of internal and external information in schizophrenia.
PMID: 25819347 [PubMed - as supplied by publisher]
Brain Network Disturbance Related to Posttraumatic Stress and Traumatic Brain Injury in Veterans.
Biol Psychiatry. 2015 Feb 18;
Authors: Spielberg JM, McGlinchey RE, Milberg WP, Salat DH
BACKGROUND: Understanding the neural causes and consequences of posttraumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI) is a high research priority, given the high rates of associated disability and suicide. Despite remarkable progress in elucidating the brain mechanisms of PTSD and mTBI, a comprehensive understanding of these conditions at the level of brain networks has yet to be achieved. The present study sought to identify functional brain networks and topological properties (measures of network organization and function) related to current PTSD severity and mTBI.
METHODS: Graph theoretic tools were used to analyze resting-state functional magnetic resonance imaging data from 208 veterans of Operation Enduring Freedom, Operation Iraqi Freedom, and Operation New Dawn, all of whom had experienced a traumatic event qualifying for PTSD criterion A. Analyses identified brain networks and topological network properties linked to current PTSD symptom severity, mTBI, and the interaction between PTSD and mTBI.
RESULTS: Two brain networks were identified in which weaker connectivity was linked to higher PTSD re-experiencing symptoms, one of which was present only in veterans with comorbid mTBI. Re-experiencing was also linked to worse functional segregation (necessary for specialized processing) and diminished influence of key regions on the network, including the hippocampus.
CONCLUSIONS: Findings of this study demonstrate that PTSD re-experiencing symptoms are linked to weakened connectivity in a network involved in providing contextual information. A similar relationship was found in a separate network typically engaged in the gating of working memory, but only in veterans with mTBI.
PMID: 25818631 [PubMed - as supplied by publisher]
Decreased resting-state connections within the visuospatial attention-related network in advanced aging.
Neurosci Lett. 2015 Mar 26;
Authors: Li Y, Li C, Wu Q, Xu Z, Kurata T, Ohno S, Kanazawa S, Abe K, Wu J
Advanced aging is accompanied by a decline in visuospatial attention. Previous neuroimaging and electrophysiological studies have demonstrated dysfunction in specific brain areas related to visuospatial attention. However, it is still unclear how the functional connectivity between brain regions causes the decline of visuospatial attention. Here, we combined task and rest functional magnetic resonance imaging (fMRI) to investigate the age-dependent alterations of resting-state functional connectivity within the task-related network. Twenty-three young subjects and nineteen elderly subjects participated in this study, and a modified Posner paradigm was used to define the region of interest (ROI). Our results showed that a marked reduction in the number of connections occurred with age, but this effect was not uniform throughout the brain: while there was a significant loss of communication in the anterior portion of the brain and between the anterior and posterior cerebral cortices, communication in the posterior portion of the brain was preserved. Moreover, the older adults exhibited weakened resting-state functional connectivity between the supplementary motor area and left anterior insular cortex. These findings suggest that, the disrupted functional connectivity of the brain network for visuospatial attention that occurs during normal aging may underlie the decline in cognitive performance.
PMID: 25817360 [PubMed - as supplied by publisher]
Detecting Static and Dynamic Differences between Eyes-Closed and Eyes-Open Resting States Using ASL and BOLD fMRI.
PLoS One. 2015;10(3):e0121757
Authors: Zou Q, Yuan BK, Gu H, Liu D, Wang DJ, Gao JH, Yang Y, Zang YF
Resting-state fMRI studies have increasingly focused on multi-contrast techniques, such as BOLD and ASL imaging. However, these techniques may reveal different aspects of brain activity (e.g., static vs. dynamic), and little is known about the similarity or disparity of these techniques in detecting resting-state brain activity. It is therefore important to assess the static and dynamic characteristics of these fMRI techniques to guide future applications. Here we acquired fMRI data while subjects were in eyes-closed (EC) and eyes-open (EO) states, using both ASL and BOLD techniques, at two research centers (NIDA and HNU). Static brain activity was calculated as voxel-wise mean cerebral blood flow (CBF) using ASL, i.e., CBF-mean, while dynamic activity was measured by the amplitude of low frequency fluctuations (ALFF) of BOLD, i.e., BOLD-ALFF, at both NIDA and HNU, and CBF, i.e., CBF-ALFF, at NIDA. We showed that mean CBF was lower under EC than EO in the primary visual cortex, while BOLD-ALFF was higher under EC in the primary somatosensory cortices extending to the primary auditory cortices and lower in the lateral occipital area. Interestingly, mean CBF and BOLD-ALFF results overlapped at the visual cortex to a very small degree. Importantly, these findings were largely replicated by the HNU dataset. State differences found by CBF-ALFF were located in the primary auditory cortices, which were generally a subset of BOLD-ALFF and showed no spatial overlap with CBF-mean. In conclusion, static brain activity measured by mean CBF and dynamic brain activity measured by BOLD- and CBF-ALFF may reflect different aspects of resting-state brain activity and a combination of ASL and BOLD may provide complementary information on the biophysical and physiological processes of the brain.
PMID: 25816237 [PubMed - in process]
Altered hemodynamic activity in conduct disorder: a resting-state FMRI investigation.
PLoS One. 2015;10(3):e0122750
Authors: Zhou J, Yao N, Fairchild G, Zhang Y, Wang X
BACKGROUND: Youth with conduct disorder (CD) not only inflict serious physical and psychological harm on others, but are also at greatly increased risk of sustaining injuries, developing depression or substance abuse, and engaging in criminal behaviors. The underlying neurobiological basis of CD remains unclear.
OBJECTIVE: The present study investigated whether participants with CD have altered hemodynamic activity under resting-state conditions.
METHODS: Eighteen medication-naïve boys with CD and 18 age- and sex- matched typically developing (TD) controls underwent functional magnetic resonance imaging (MRI) scans in the resting state. The amplitude of low-frequency fluctuations (ALFF) was measured and compared between the CD and TD groups.
RESULTS: Compared with the TD participants, the CD participants showed lower ALFF in the bilateral amygdala/parahippocampus, right lingual gyrus, left cuneus and right insula. Higher ALFF was observed in the right fusiform gyrus and right thalamus in the CD participants compared to the TD group.
CONCLUSIONS: Youth with CD displayed widespread functional abnormalities in emotion-related and visual cortical regions in the resting state. These results suggest that deficits in the intrinsic activity of resting state networks may contribute to the etiology of CD.
PMID: 25816069 [PubMed - in process]
Use of resting-state functional MRI to study brain development and injury in neonates.
Semin Perinatol. 2015 Mar;39(2):130-140
Authors: Smyser CD, Neil JJ
Advances in methodology have led to expanded application of resting-state functional MRI (rs-fMRI) to the study of term and prematurely born infants during the first years of life, providing fresh insight into the earliest forms of functional cerebral development. In this review, we detail our evolving understanding of the use of rs-fMRI for studying neonates. We initially focus on the biological processes of cortical development related to resting-state network development. We then review technical issues principally affecting neonatal investigations, including the effects of subject motion during acquisition and image distortions related to magnetic susceptibility effects. We next summarize the literature in which rs-fMRI is used to study normal brain development during the early postnatal period, the effects of prematurity, and the effects of cerebral injury. Finally, we review potential future directions for the field, such as the use of complementary imaging modalities and advanced analysis techniques.
PMID: 25813667 [PubMed - as supplied by publisher]
The presupplementary area within the language network: a resting state functional magnetic resonance imaging functional connectivity analysis.
Brain Connect. 2014 Aug;4(6):440-53
Authors: Ter Minassian A, Ricalens E, Nguyen The Tich S, Dinomais M, Aubé C, Beydon L
The presupplementary motor area (pre-SMA) is involved in volitional selection. Despite the lateralization of the language network and different functions for both pre-SMA, few studies have reported the lateralization of pre-SMA activity and very little is known about the possible lateralization of pre-SMA connectivity. Via functional connectivity analysis, we sought to understand how the language network may be connected to other intrinsic connectivity networks (ICNs) through the pre-SMA. We performed a spatial independent component analysis of resting state functional magnetic resonance imaging in 30 volunteers to identify the language network. Subsequently, we applied seed-to-voxel functional connectivity analyses centered on peaks detected in the pre-SMA. Three signal peaks were detected in the pre-SMA. The left rostral pre-SMA intrinsic connectivity network (LR ICN) was left lateralized in contrast to bilateral ICNs associated to right pre-SMA peaks. The LR ICN was anticorrelated with the dorsal attention network and the right caudal pre-SMA ICN (RC ICN) anticorrelated with the default mode network. These two ICNs overlapped minimally. In contrast, the right rostral ICN overlapped the LR ICN. Both right ICNs overlapped in the ventral attention network (vATT). The bilateral connectivity of the right rostral pre-SMA may allow right hemispheric recruitment to process semantic ambiguities. Overlap between the right pre-SMA ICNs in vATT may contribute to internal thought to external environment reorientation. Distinct ICNs connected to areas involved in lexico-syntactic selection and phonology converge in the pre-SMA, which may constitute the resolution space of competing condition-action associations for speech production.
PMID: 24939724 [PubMed - indexed for MEDLINE]
Save the global: global signal connectivity as a tool for studying clinical populations with functional magnetic resonance imaging.
Brain Connect. 2014 Aug;4(6):395-403
Authors: Hahamy A, Calhoun V, Pearlson G, Harel M, Stern N, Attar F, Malach R, Salomon R
The global signal is commonly removed from resting-state data, as it was presumed to reflect physiological noise. However, removal of the global signal is now under debate, as this signal may reflect important neuronal components, and its removal may introduce artifacts into the data. Here, we show that the functional connectivity (FC) of the global signal is of functional relevance, as it differentiates between schizophrenia patients and healthy controls during rest. We also demonstrate that other reported findings related to various clinical populations may actually reflect alternations in global signal FC. The evidence of the clinical relevance of the global signal propose its usage as a research tool, and extend previously reported perils of global signal removal in resting-state data of clinical populations.
PMID: 24923194 [PubMed - indexed for MEDLINE]
Early evaluation of nerve regeneration after nerve injury and repair using functional connectivity MRI.
Neurorehabil Neural Repair. 2014 Sep;28(7):707-15
Authors: Li R, Hettinger PC, Liu X, Machol J, Yan JG, Matloub HS, Hyde JS
Resting state functional connectivity magnetic resonance imaging studies in rat brain show brain reorganization caused by nerve injury and repair. In this study, distinguishable differences were found in healthy, nerve transection without repair (R-) and nerve transection with repair (R+) groups in the subacute stage (2 weeks after initial injury). Only forepaw on the healthy side was used to determine seed voxel regions in this study. Disturbance of neuronal network in the primary sensory region of cortex occurs within two hours after initial injury, and the network pattern was restored in R+ group in subacute stage, while the disturbed pattern remained in R- group. These are the central findings of the study. This technique provides a novel way of detecting and monitoring the effectiveness of peripheral nerve injury treatment in the early stage and potentially offers a tool for clinicians to avoid poor clinical outcomes.
PMID: 24515926 [PubMed - indexed for MEDLINE]
Combined cognitive-psychological-physical intervention induces reorganization of intrinsic functional brain architecture in older adults.
Neural Plast. 2015;2015:713104
Authors: Zheng Z, Zhu X, Yin S, Wang B, Niu Y, Huang X, Li R, Li J
Mounting evidence suggests that enriched mental, physical, and socially stimulating activities are beneficial for counteracting age-related decreases in brain function and cognition in older adults. Here, we used functional magnetic resonance imaging (fMRI) to demonstrate the functional plasticity of brain activity in response to a combined cognitive-psychological-physical intervention and investigated the contribution of the intervention-related brain changes to individual performance in healthy older adults. The intervention was composed of a 6-week program of combined activities including cognitive training, Tai Chi exercise, and group counseling. The results showed improved cognitive performance and reorganized regional homogeneity of spontaneous fluctuations in the blood oxygen level-dependent (BOLD) signals in the superior and middle temporal gyri, and the posterior lobe of the cerebellum, in the participants who attended the intervention. Intriguingly, the intervention-induced changes in the coherence of local spontaneous activity correlated with the improvements in individual cognitive performance. Taken together with our previous findings of enhanced resting-state functional connectivity between the medial prefrontal cortex and medial temporal lobe regions following a combined intervention program in older adults, we conclude that the functional plasticity of the aging brain is a rather complex process, and an effective cognitive-psychological-physical intervention is helpful for maintaining a healthy brain and comprehensive cognition during old age.
PMID: 25810927 [PubMed - in process]
Effects of rTMS of Pre-Supplementary Motor Area on Fronto Basal Ganglia Network Activity during Stop-Signal Task.
J Neurosci. 2015 Mar 25;35(12):4813-23
Authors: Watanabe T, Hanajima R, Shirota Y, Tsutsumi R, Shimizu T, Hayashi T, Terao Y, Ugawa Y, Katsura M, Kunimatsu A, Ohtomo K, Hirose S, Miyashita Y, Konishi S
Stop-signal task (SST) has been a key paradigm for probing human brain mechanisms underlying response inhibition, and the inhibition observed in SST is now considered to largely depend on a fronto basal ganglia network consisting mainly of right inferior frontal cortex, pre-supplementary motor area (pre-SMA), and basal ganglia, including subthalamic nucleus, striatum (STR), and globus pallidus pars interna (GPi). However, causal relationships between these frontal regions and basal ganglia are not fully understood in humans. Here, we partly examined these causal links by measuring human fMRI activity during SST before and after excitatory/inhibitory repetitive transcranial magnetic stimulation (rTMS) of pre-SMA. We first confirmed that the behavioral performance of SST was improved by excitatory rTMS and impaired by inhibitory rTMS. Afterward, we found that these behavioral changes were well predicted by rTMS-induced modulation of brain activity in pre-SMA, STR, and GPi during SST. Moreover, by examining the effects of the rTMS on resting-state functional connectivity between these three regions, we showed that the magnetic stimulation of pre-SMA significantly affected intrinsic connectivity between pre-SMA and STR, and between STR and GPi. Furthermore, the magnitudes of changes in resting-state connectivity were also correlated with the behavioral changes seen in SST. These results suggest a causal relationship between pre-SMA and GPi via STR during response inhibition, and add direct evidence that the fronto basal ganglia network for response inhibition consists of multiple top-down regulation pathways in humans.
PMID: 25810512 [PubMed - in process]
Age-Related Changes in Intrinsic Function of the Superior Temporal Sulcus in Autism Spectrum Disorders.
Soc Cogn Affect Neurosci. 2015 Mar 25;
Authors: Alaerts K, Nayar K, Kelly C, Raithel J, Milham MP, Di Martino A
Currently, the developmental trajectories of neural circuits implicated in autism spectrum disorders (ASD) are largely unknown. Here, we specifically focused on age-related changes in the functional circuitry of the posterior superior temporal sulcus (pSTS), a key hub underlying social-cognitive processes known to be impaired in ASD. Using a cross-sectional approach, we analyzed resting-state fMRI data collected from children, adolescents, and adults available through the Autism Brain Imaging Data Exchange repository (n=106 with ASD and n=109 typical controls [TC], ages 7-30 years). The observed age-related changes of pSTS intrinsic functional connectivity (iFC) suggest that no single developmental pattern characterizes ASD. Instead, pSTS circuitry displayed a complex developmental picture, with some functional circuits showing patterns consistent with atypical development in ASD relative to TC (pSTS-iFC with fusiform gyrus and angular gyrus) and others showing delayed maturation (pSTS-iFC with regions of the action perception network). Distinct developmental trajectories in different functional circuits in ASD likely reflect differential age-related changes in the socio-cognitive processes they underlie. Increasing insight on these mechanisms is a critical step in the development of age-specific interventions in ASD.
PMID: 25809403 [PubMed - as supplied by publisher]
Experimentally induced thyrotoxicosis leads to increased connectivity in temporal lobe structures: A resting state fMRI study.
Psychoneuroendocrinology. 2015 Mar 12;56:100-109
Authors: Göttlich M, Heldmann M, Göbel A, Dirk AL, Brabant G, Münte TF
Adult onset hyperthyroidism may impact on different cognitive domains, including attention and concentration, memory, perceptual function, language and executive function. Previous PET studies implicated changed functionality of limbic regions, the temporal and frontal lobes in hyperthyroidism, whereas it is unknown whether cognitive effects of hyperthyroidism may be due to changed brain connectivity. This study aimed to investigate the effect of experimentally induced short-term hyperthyroidism thyrotoxicosis on resting-state functional connectivity using functional magnetic resonance imaging. Twenty-nine healthy male right-handed subjects were examined twice, once prior and once after 8 weeks of oral administration of 250μg levothyroxine per day. Resting-state fMRI was subjected to graph-theory based analysis methods to investigate whole-brain intrinsic functional connectivity. Despite a lack of subjective changes noticed by the subjects significant thyrotoxicosis was confirmed in all subjects. This induced a significant increase in resting-state functional connectivity specifically in the rostral temporal lobes (0.05 FDR corrected at the cluster level), which is caused by an increased connectivity to the cognitive control network. The increased connectivity between temporal poles and the cognitive control network shown here under experimental conditions supports an important function of thyroid hormones in the regulation of paralimbic structures.
PMID: 25808701 [PubMed - as supplied by publisher]
Investigation of Multiple Frequency Ranges using Discrete Wavelet Decomposition of Resting State Functional Connectivity in Mild Traumatic Brain Injury Patients.
Brain Connect. 2015 Mar 26;
Authors: Sours C, Chen H, Roys S, Zhuo J, Varshney A, Gullapalli RP
The aim of this study was to investigate if discrete wavelet decomposition provides additional insight into resting state processes through the analysis of functional connectivity within specific frequency ranges within the default mode network (DMN) that may be affected by mild traumatic brain injury (mTBI). Participants included 32 mTBI patients [15 with post concussive syndrome (PCS+) and 17 without (PCS-)]. mTBI patients received rs-fMRI (resting state functional magnetic resonance imaging) at acute (within 10 days of injury) and chronic (6 months post injury) time points and were compared to 31 controls (HC). The wavelet decomposition divides the time series into multiple frequency ranges based on 4 scaling factors (SF1: 0.125-0.250 Hz, SF2: 0.060-0.125 Hz, SF3: 0.030-0.060 Hz, SF4: 0.015-0.030 Hz). Within each SF, wavelet connectivity matrices for nodes of the DMN were created for each group (HC, PCS+, PCS-), and bivariate measures of strength and diversity were calculated. The results demonstrate reduced strength of connectivity in PCS+ patients compared to PCS- patients within SF1 during both the acute and chronic stages of injury, as well as recovery of connectivity within SF1 across the two time points. Furthermore, the PCS- group demonstrated greater network strength compared to controls at both time points suggesting a potential compensatory or protective mechanism in these patients. These findings stress the importance of investigating resting state connectivity within multiple frequency ranges: however, many of our findings are within SF1, which may overlap with frequencies associated with cardiac and respiratory activity.
PMID: 25808612 [PubMed - as supplied by publisher]