Cognitive reserve moderates the association between functional network anti-correlations and memory in MCI.
Neurobiol Aging. 2016 Dec 01;:
Authors: Franzmeier N, Buerger K, Teipel S, Stern Y, Dichgans M, Ewers M, Alzheimer's Disease Neuroimaging Initiative (ADNI)
Cognitive reserve (CR) shows protective effects on cognitive function in older adults. Here, we focused on the effects of CR at the functional network level. We assessed in patients with amnestic mild cognitive impairment (aMCI) whether higher CR moderates the association between low internetwork cross-talk on memory performance. In 2 independent aMCI samples (n = 76 and 93) and healthy controls (HC, n = 36), CR was assessed via years of education and intelligence (IQ). We focused on the anti-correlation between the dorsal attention network (DAN) and an anterior and posterior default mode network (DMN), assessed via sliding time window analysis of resting-state functional magnetic resonance imaging (fMRI). The DMN-DAN anti-correlation was numerically but not significantly lower in aMCI compared to HC. However, in aMCI, lower anterior DMN-DAN anti-correlation was associated with lower memory performance. This association was moderated by CR proxies, where the association between the internetwork anti-correlation and memory performance was alleviated at higher levels of education or IQ. In conclusion, lower DAN-DMN cross-talk is associated with lower memory in aMCI, where such effects are buffered by higher CR.
PMID: 28017480 [PubMed - as supplied by publisher]
Relationship between resting state functional magnetic resonance imaging and memory function in mesial temporal lobe epilepsy.
J Neurol Sci. 2017 Jan 15;372:117-125
Authors: Chen S, Chen L, Huang H, Lin W
OBJECT: To study memory impairment mechanisms of the medial temporal lobe epilepsy (MTLE) by analyzing the functional connectivity (FC) through resting state functional magnetic resonance imaging (rs-fMRI).
METHODS: Rs-fMRI data were acquired from 13 patients with left MTLE and 11 patients with right MTLE. Another 13 healthy volunteers were selected as controls. The altered FC pattern between the unilateral hippocampus and other regions of the brain in MTLE patients was compared to that of the normal control group. Then the correlation between the strength of FC and the clinical memory scale scores in patients with MTLE was determined.
RESULTS: The scores of the following check points of MTLE patients including point to memory, recognition of nonsense figure, associative learning, the image free recall, portrait characteristic recall and memory quotient were significantly lower than those in the normal group (all P<0.05). The scores of point to memory and recognition of nonsense figure were different between R-MTLE and L-MTLE patients. Different correlations between the strength of FC and the clinical memory scale scores were detected between R-MTLE and L-MTLE patients.
CONCLUSIONS: The memory function of patients with MTLE was impaired. Patients with L-MTLE showed lower score on pure verbal memory test and those with R-MTLE showed weaker performance on pure visual memory test. Patients with MTLE showed extensive abnormal FC between hippocampus and particular encephalic regions.
PMID: 28017196 [PubMed - in process]
Structural and resting-state MRI detects regional brain differences in young and mid-age healthy APOE-e4 carriers compared with non-APOE-e4 carriers.
NMR Biomed. 2016 May;29(5):614-24
Authors: Dowell NG, Evans SL, Tofts PS, King SL, Tabet N, Rusted JM
The presence of the e4 allele of the apolipoprotein E (APOE) gene is the best-known genetic risk factor for Alzheimer's disease. In this study, we investigated the link between functional and behavioural differences and regional brain volume and cortical thickness differences in those who carry the e4 allele (e4+) and those who only carry the e3 allele (e3/e3). We studied these genotype populations in two age groups: a young group (average age, 21 years) and a mid-age group (average age, 50 years). High-resolution T1 -weighted MRI scans were analysed with Freesurfer to measure regional white matter brain volume and cortical thickness differences between genotype groups at each age. These data were correlated with behavioural findings in the same cohort. Resting-state MRI was also conducted to identify differences in underlying brain functional connectivity. We found that there was a positive correlation between the thickness of the parahippocampal cortex in young e4+ individuals and performance on an episodic memory task. Young e4+ individuals also showed a positive correlation between white matter volume in the left anterior cingulate and performance on a covert attention task. At mid-age, e4+ individuals had structural differences relative to e3/e3 individuals in these areas: the parahippocampal cortex was thicker and white matter volume in the left anterior cingulate was greater than in e3/e3 individuals. We discuss the possibility that an over-engagement with these regions by e4+ individuals in youth may have a neurogenic effect that is observable later in life. The cuneus appears to be an important region for APOE-driven differences in the brain, with greater functional connectivity among young e3/e3 individuals and greater white matter volume in young e4+ individuals.
PMID: 26929040 [PubMed - indexed for MEDLINE]
Modular structure of brain functional networks: breaking the resolution limit by Surprise.
Sci Rep. 2016 Jan 14;6:19250
Authors: Nicolini C, Bifone A
The modular organization of brain networks has been widely investigated using graph theoretical approaches. Recently, it has been demonstrated that graph partitioning methods based on the maximization of global fitness functions, like Newman's Modularity, suffer from a resolution limit, as they fail to detect modules that are smaller than a scale determined by the size of the entire network. Here we explore the effects of this limitation on the study of brain connectivity networks. We demonstrate that the resolution limit prevents detection of important details of the brain modular structure, thus hampering the ability to appreciate differences between networks and to assess the topological roles of nodes. We show that Surprise, a recently proposed fitness function based on probability theory, does not suffer from these limitations. Surprise maximization in brain co-activation and functional connectivity resting state networks reveals the presence of a rich structure of heterogeneously distributed modules, and differences in networks' partitions that are undetectable by resolution-limited methods. Moreover, Surprise leads to a more accurate identification of the network's connector hubs, the elements that integrate the brain modules into a cohesive structure.
PMID: 26763931 [PubMed - indexed for MEDLINE]
Mapping effective connectivity in the human brain with concurrent intracranial electrical stimulation and BOLD-fMRI.
J Neurosci Methods. 2016 Dec 21;:
Authors: Oya H, Howard MA, Magnotta VA, Kruger A, Griffiths TD, Lemieux L, Carmichael DW, Petkov CI, Kawasaki H, Kovach CK, Sutterer MJ, Adolphs R
BACKGROUND: Understanding brain function requires knowledge of how one brain region causally influences another. This information is difficult to obtain directly in the human brain, and is instead typically inferred from resting-state fMRI.
NEW METHOD: Here, we demonstrate the safety and scientific promise of a novel and complementary approach: concurrent electrical stimulation and fMRI (es-fMRI) at 3T in awake neurosurgical patients with implanted depth electrodes.
RESULTS: We document the results of safety testing, actual experimental setup, and stimulation parameters, that safely and reliably evoke activation in distal structures through stimulation of amygdala, cingulate, or prefrontal cortex. We compare connectivity inferred from the evoked patterns of activation with that estimated from standard resting-state fMRI in the same patients: while connectivity patterns obtained with each approach are correlated, each method produces unique results. Response patterns were stable over the course of 11min of es-fMRI runs. COMPARISON WITH EXISTING METHOD: es-fMRI in awake humans yields unique information about effective connectivity, complementing resting-state fMRI. Although our stimulations were below the level of inducing any apparent behavioral or perceptual effects, a next step would be to use es-fMRI to modulate task performances. This would reveal the acute network-level changes induced by the stimulation that mediate the behavioral and cognitive effects seen with brain stimulation.
CONCLUSIONS: es-fMRI provides a novel and safe approach for mapping effective connectivity in the human brain in a clinical setting, and will inform treatments for psychiatric and neurodegenerative disorders that use deep brain stimulation.
PMID: 28012852 [PubMed - as supplied by publisher]
Lateralization of intrinsic frontoparietal network connectivity and symptoms in schizophrenia.
Psychiatry Res. 2016 Dec 16;260:23-28
Authors: Son S, Miyata J, Mori Y, Isobe M, Urayama SI, Aso T, Fukuyama H, Murai T, Takahashi H
It has been frequently reported that schizophrenia patients have reduced functional lateralization in the areas related to language processing. Furthermore, there is evidence supporting that schizophrenia patients have disrupted functional connectivity in the bilateral frontoparietal networks (FPNs), of which the left is strongly associated with a cognition-language paradigm, using resting-state functional magnetic resonance imaging (rsfMRI). To examine the laterality of resting-state functional connectivity in schizophrenia, we investigated the bilateral FPNs. We investigated 41 schizophrenia and 35 healthy participants using independent component analysis for rsfMRI. We extracted mean connectivity values of both left and right FPNs and calculated their laterality index by (left - right)/(left + right). Subsequently, we investigated group differences of these values and the correlation between these values and symptoms. In schizophrenia, mean connectivity values of both left and right FPNs were significantly lower than in healthy controls, whereas their laterality indices were not significantly different. However, correlation analyses revealed that the laterality index was negatively correlated with positive symptoms, and that mean connectivity of left FPN was negatively correlated with depressive symptoms in schizophrenia. Our results suggest that language-related networks and their laterality might be one of the neural correlates of schizophrenia symptoms.
PMID: 28012423 [PubMed - as supplied by publisher]
State-dependent modulation of functional connectivity in early blind individuals.
Neuroimage. 2016 Dec 20;:
Authors: Pelland M, Orban P, Dansereau C, Lepore F, Bellec P, Collignon O
Resting-state functional connectivity (RSFC) studies have provided strong evidences that visual deprivation influences the brain's functional architecture. In particular, reduced RSFC coupling between occipital (visual) and temporal (auditory) regions has been reliably observed in early blind individuals (EB) at rest. In contrast, task-dependent activation studies have repeatedly demonstrated enhanced co-activation and connectivity of occipital and temporal regions during auditory processing in EB. To investigate this apparent discrepancy, the functional coupling between temporal and occipital networks at rest was directly compared to that of an auditory task in both EB and sighted controls (SC). Functional brain clusters shared across groups and cognitive states (rest and auditory task) were defined. In EBs, we observed higher occipito-temporal correlations in activity during the task than at rest. The reverse pattern was observed in SC. We also observed higher temporal variability of occipito-temporal RSFC in EB suggesting that occipital regions in this population may play a role of multiple demand system. Our study reveals how the connectivity profile of sighted and early blind people is differentially influenced by their cognitive state, bridging the gap between previous task-dependent and RSFC studies. Our results also highlight how inferring group-differences in functional brain architecture solely based on resting-state acquisition has to be considered with caution.
PMID: 28011254 [PubMed - as supplied by publisher]
Mental rotation task specifically modulates functional connectivity strength of intrinsic brain activity in low frequency domains: A maximum uncertainty linear discriminant analysis.
Behav Brain Res. 2016 Dec 20;320:233-243
Authors: Gao M, Zhang D, Wang Z, Liang B, Cai Y, Gao Z, Li J, Chang S, Jiao B, Huang R, Liu M
Neuroimaging studies have highlighted that intrinsic brain activity is modified to implement task demands. However, the relation between mental rotation and intrinsic brain activity remains unclear. To answer this question, we collected functional MRI (fMRI) data from 30 healthy participants in two mental rotation task periods (1st-task state, 2nd-task state) and two rest periods before (pre-task resting state) and after the task (post-task resting state) respectively. By combining the spatial independent component analysis (ICA) and voxel-wise functional connectivity strength (FCS), we identified FCS maps of 10 brain resting state networks (RSNs) within six different bands (i.e., 0-0.05, 0.05-0.1, 0.1-0.15, 0.15-0.2, 0.2-0.25, and 0.01-0.08Hz) corresponding to the four states for each subject. The maximum uncertainty linear discriminant analysis (MLDA) method showed that the FCS within the low frequency bandwidth of 0.05-0.1Hz could effectively classify the mental rotation task state from pre-/post-task resting states but failed to discriminate the pre- and post-task resting states. Discriminative FCSs were observed in the cognitive executive-control network (central executive and attention) and the imagery-based internal mental manipulation network (default mode, primary sensorimotor, and primary visual). Imagery manipulation is a stable mental element of mental rotation, and the involvement of executive control is dependent on the degree of task familiarity. Together, the present study provides evidence that mental rotation task specifically modifies intrinsic brain activity to complement cognitive demands, which provides further insight into the neural basis of mental rotation manipulation.
PMID: 28011171 [PubMed - as supplied by publisher]
Functional brain networks in treatment-resistant schizophrenia.
Schizophr Res. 2016 Dec 20;:
Authors: Ganella EP, Bartholomeusz CF, Seguin C, Whittle S, Bousman C, Phassouliotis C, Everall I, Pantelis C, Zalesky A
INTRODUCTION: Up to 20% of individuals with schizophrenia show minimal or no response to medication and are considered to have 'treatment-resistant' schizophrenia (TRS). Unlike early and established schizophrenia, few studies have investigated resting-state functional connectivity (rs-FC) in TRS. Here, we test for disruptions in FC and altered efficiency of functional brain networks in a well-characterized cohort of TRS patients.
METHODS: Resting-state functional magnetic resonance imaging was used to investigate functional brain networks in 42 TRS participants prescribed clozapine (30 males, mean age=41.3(10)) and 42 healthy controls (24 males, mean age=38.4(10)). Graph analysis was used to characterize between-group differences in local and global efficiency of functional brain network organization as well as the strength of FC.
RESULTS: Global brain FC was reduced in TRS patients (p=0.0001). Relative to controls, 3.4% of all functional connections showed reduced strength in TRS (p<0.001), predominantly involving fronto-temporal, fronto-occipital and temporo-occipital connections. Global efficiency was reduced in TRS (p=0.0015), whereas local efficiency was increased (p=0.0042).
CONCLUSIONS: TRS is associated with widespread reductions in rs-FC and altered network topology. Increased local functional network efficiency coupled with decreased global efficiency suggests that hub-to-hub connections are preferentially affected in TRS. These findings further our understanding of the neurobiological impairments in TRS.
PMID: 28011131 [PubMed - as supplied by publisher]
Abnormal brain functional connectivity leads to impaired mood and cognition in hyperthyroidism: a resting-state functional MRI study.
Oncotarget. 2016 Dec 21;:
Authors: Li L, Zhi M, Hou Z, Zhang Y, Yue Y, Yuan Y
Patients with hyperthyroidism frequently have neuropsychiatric complaints such as lack of concentration, poor memory, depression, anxiety, nervousness, and irritability, suggesting brain dysfunction. However, the underlying process of these symptoms remains unclear. Using resting-state functional magnetic resonance imaging (rs-fMRI), we depicted the altered graph theoretical metric degree centrality (DC) and seed-based resting-state functional connectivity (FC) in 33 hyperthyroid patients relative to 33 healthy controls. The peak points of significantly altered DC between the two groups were defined as the seed regions to calculate FC to the whole brain. Then, partial correlation analyses were performed between abnormal DC, FC and neuropsychological performances, as well as some clinical indexes. The decreased intrinsic functional connectivity in the posterior lobe of cerebellum (PLC) and medial frontal gyrus (MeFG), as well as the abnormal seed-based FC anchored in default mode network (DMN), attention network, visual network and cognitive network in this study, possibly constitutes the latent mechanism for emotional and cognitive changes in hyperthyroidism, including anxiety and impaired processing speed.
PMID: 28009983 [PubMed - as supplied by publisher]
Altered Long- and Short-Range Functional Connectivity in Patients with Betel Quid Dependence: A Resting-State Functional MRI Study.
Cell Physiol Biochem. 2016 Dec 23;40(6):1626-1636
Authors: Liu T, Li J, Zhang Z, Xu Q, Lu G, Huang S, Pan M, Chen F
OBJECTIVE: Addiction is a chronic relapsing brain disease. Brain structural abnormalities may constitute an abnormal neural network that underlies the risk of drug dependence. We hypothesized that individuals with Betel Quid Dependence (BQD) have functional connectivity alterations that can be described by long- and short-range functional connectivity density(FCD) maps.
METHODS: We tested this hypothesis using functional magnetic resonance imaging (fMRI) data from subjects of the Han ethnic group in Hainan, China. Here, we examined BQD individuals (n = 33) and age-, sex-, and education-matched healthy controls (HCs) (n = 32) in a rs-fMRI study to observe FCD alterations associated with the severity of BQD.
RESULTS: Compared with HCs, long-range FCD was decreased in the right anterior cingulate cortex (ACC) and increased in the left cerebellum posterior lobe (CPL) and bilateral inferior parietal lobule (IPL) in the BQD group. Short-range FCD was reduced in the right ACC and left dorsolateral prefrontal cortex (dlPFC), and increased in the left CPL. The short-range FCD alteration in the right ACC displayed a negative correlation with the Betel Quid Dependence Scale (BQDS) (r=-0.432, P=0.012), and the long-range FCD alteration of left IPL showed a positive correlation with the duration of BQD(r=0.519, P=0.002) in BQD individuals.
CONCLUSIONS: fMRI revealed differences in long- and short- range FCD in BQD individuals, and these alterations might be due to BQ chewing, BQ dependency, or risk factors for developing BQD.
PMID: 28006783 [PubMed - as supplied by publisher]
Metrics of brain network architecture capture the impact of disease in children with epilepsy.
Neuroimage Clin. 2017;13:201-208
Authors: Paldino MJ, Zhang W, Chu ZD, Golriz F
BACKGROUND AND OBJECTIVE: Epilepsy is associated with alterations in the structural framework of the cerebral network. The aim of this study was to measure the potential of global metrics of network architecture derived from resting state functional MRI to capture the impact of epilepsy on the developing brain.
METHODS: Pediatric patients were retrospectively identified with: 1. Focal epilepsy; 2. Brain MRI at 3 Tesla, including resting state functional MRI; 3. Full scale IQ measured by a pediatric neuropsychologist. The cerebral cortex was parcellated into approximately 700 gray matter network nodes. The strength of a connection between two nodes was defined as the correlation between their resting BOLD signal time series. The following global network metrics were then calculated: clustering coefficient, transitivity, modularity, path length, and global efficiency. Epilepsy duration was used as an index for the cumulative impact of epilepsy on the brain.
RESULTS: 45 patients met criteria (age: 4-19 years). After accounting for age of epilepsy onset, epilepsy duration was inversely related to IQ (p: 0.01). Epilepsy duration predicted by a machine learning algorithm on the basis of the five global network metrics was highly correlated with actual epilepsy duration (r: 0.95; p: 0.0001). Specifically, modularity and to a lesser extent path length and global efficiency were independently associated with epilepsy duration.
CONCLUSIONS: We observed that a machine learning algorithm accurately predicted epilepsy duration based on global metrics of network architecture derived from resting state fMRI. These findings suggest that network metrics have the potential to form the basis for statistical models that translate quantitative imaging data into patient-level markers of cognitive deterioration.
PMID: 28003958 [PubMed - in process]
Intrinsic functional architecture of the macaque dorsal and ventral lateral frontal cortex.
J Neurophysiol. 2016 Dec 21;:jn.00486.2016
Authors: Goulas A, Stiers P, Hutchison RM, Everling S, Petrides M, Margulies DS
Investigations of the cellular and connectional organization of the lateral frontal cortex (LFC) of the macaque monkey provide indispensable knowledge for generating hypotheses about the human LFC. However, despite numerous investigations, there are still debates on the organization of this brain region. In vivo neuroimaging techniques such as resting-state fMRI can be used to define the functional circuitry of brain areas producing results largely consistent with gold-standard invasive tract-tracing techniques and offering the opportunity for cross-species comparison within the same modality. Our results using resting-state fMRI from macaque monkeys to uncover the intrinsic functional architecture of the LFC corroborate previous findings and inform current debates. Specifically, we show that i) the region in the midline and anterior to the superior arcuate sulcus is divided in two areas separated by the posterior supraprincipal dimple; ii) the cytoarchitectonically defined area 6DC/F2 contains two connectional divisions; and, iii) a distinct area occupies the cortex around the spur of the arcuate, updating what was previously proposed to be the border between dorsal and ventral motor/premotor areas. Within the ventral LFC specifically, the derived parcellation clearly suggests the presence of distinct areas i) with a somatomotor/orofacial connectional signature (putative area 44), ii) with an occulomotor connectional signature (putative frontal eye fields), and iii) premotor areas possibly hosting laryngeal and arm representations. Our results illustrate in detail the intrinsic functional architecture of the macaque LFC, thus providing valuable evidence for debates on its organization.
PMID: 28003408 [PubMed - as supplied by publisher]
Resting-state fMRI data reflects default network activity rather than null data: A defense of commonly employed methods to correct for multiple comparisons.
Cogn Neurosci. 2016 Dec 22;:
Authors: Slotnick SD
Analysis of functional magnetic resonance imaging (fMRI) data typically involves over one hundred thousand independent statistical tests; therefore, it is necessary to correct for multiple comparisons to control familywise error. Eklund, Nichols, and Knutsson (2016, Proceedings of the National Academy of Sciences of the United States of America, 113, 7900-7905) used resting-state fMRI data to evaluate commonly employed methods to correct for multiple comparison and reported unacceptable rates of familywise error. Eklund et al.'s analysis was based on the assumption that resting-state fMRI data reflects null data; however, their "null data" actually reflected default network activity that inflated familywise error. As such, Eklund et al.'s results provide no basis to question the validity of the tens of thousands of published fMRI studies that have corrected for multiple comparisons or the commonly employed methods to correct for multiple comparisons.
PMID: 28002981 [PubMed - as supplied by publisher]
Trait-Related Cortical-Subcortical Dissociation in Bipolar Disorder: Analysis of Network Degree Centrality.
J Clin Psychiatry. 2016 Dec 20;:
Authors: Zhou Q, Womer FY, Kong L, Wu F, Jiang X, Zhou Y, Wang D, Bai C, Chang M, Fan G, Xu K, He Y, Tang Y, Wang F
BACKGROUND: Bipolar disorder is a systemic brain disorder. Accumulated evidence suggested that cortical-subcortical imbalance could be a trait-related pathogenic factor of bipolar disorder. Degree centrality, a robust index of focal connectivity in which the number of direct connections from one node to all nodes is counted, has not previously been studied in bipolar disorder as a whole.
METHODS: Resting state functional magnetic resonance imaging was performed on 52 patients with DSM-IV bipolar I disorder and 70 healthy controls recruited between September 2009 and July 2014. Degree centrality was calculated within cerebral gray matter for each subject and compared between patients with bipolar disorder and healthy controls. Hub distributions of both groups were explored. Effects of medication exposure and mood state on degree centrality, as well as cortical-subcortical degree centrality correlations, were explored.
RESULTS: Compared to healthy controls, patients with bipolar disorder exhibited significant decrease in degree centrality in cortical regions, including the middle temporal pole, inferior temporal gyrus, and ventral prefrontal cortex, but showed significant increase in degree centrality mainly in subcortical regions, including caudate, thalamus, parahippocampal gyrus, hippocampi, anterior cingulate, insula, and amygdala, and a small portion of cortical regions, such as superior and middle frontal gyrus (P < .05, corrected). Spatial distributions of the 2 groups were very similar. No significant effects of medication exposure or mood state on degree centrality were found. Patients with bipolar disorder also showed significant decrease in cortical-subcortical degree centrality correlation (P = .003).
CONCLUSIONS: These findings further contribute to the mounting evidence of cortical-subcortical dissociation in bipolar disorder pathophysiology. In addition, this study supports the continued development and implementation of graph-based techniques to enhance our understanding of the underlying neural mechanisms in mental disorders such as bipolar disorder, which are increasingly viewed as systemic brain disorders rather than disorders arising from disruption within a single structure or a limited number of structures. Due to the heterogeneity of our sample, as well as the small sample size of each medication and mood state subgroups, further investigation is needed to support our findings.
PMID: 28002659 [PubMed - as supplied by publisher]
The Resting-State Functional Connectivity of the Default Mode Networks in Patients With Obstructive Sleep Apnea-Hypopnea Syndrome.
CNS Neurol Disord Drug Targets. 2016 Dec 19;
Authors: Chen T, Yang M, Liu B, Liu YT, Zhang HX, Liu CC, Zhu Y, Huang ZC, Yuan TF
Obstructive sleep apnea-hypopnea syndrome (OSAHS) is normally linked to cognitive and functional dysfunctions. In this study, we explored the resting-state functional connectivity (rsFC) in the default mode network (DMN) to show the mechanism of neurophysiology in patients with OSAHS. Resting-state structural and functional Magnetic Resonance Imaging data were obtained from sixteen male moderate-to- severe patients with untreated OSAHS and 15 male matched healthy control subjects. The rsFC in the DMN was analyzed between OSAHS and healthy controls by the CONN software. Compared with the controls, the rsFC showed a significant decrease in the the medial prefrontal cortex, anterior cingulate and posterior cingulate, and showed an increase in the left inferior parietal lobule in OSAHS patients. The results indicated that the OSAHS patients presented alternatives of rsFC in the DMN compared with the controls.
PMID: 28000557 [PubMed - as supplied by publisher]
Disturbed Interhemispheric Functional Connectivity Rather than Structural Connectivity in Irritable Bowel Syndrome.
Front Mol Neurosci. 2016;9:141
Authors: Qi R, Liu C, Weng Y, Xu Q, Chen L, Wang F, Zhang LJ, Lu GM
Neuroimaging studies have demonstrated that irritable bowel syndrome (IBS)-a relapsing functional bowel disorder-presents with disrupted brain connections. However, little is known about the alterations of interhemispheric functional connectivity and underlying structural connectivity in IBS. This study combined resting-state functional magnetic resonance imaging (rs-fMRI) and diffusion tensor imaging (DTI) to investigate changes in interhemispheric coordination in IBS patients. Resting-state functional and structural magnetic resonance images were acquired from 65 IBS patients and 67 healthy controls (HCs; matched for age, sex and educational level). Interhemispheric voxel-mirrored homotopic connectivity (VMHC) was calculated and compared between groups. Homotopic regions showing abnormal VMHC in patients were targeted as regions of interest (ROIs) for analysis of DTI tractography. The fractional anisotropy (FA), fiber number and fiber length were compared between groups. Statistical analysis was also performed by including anxiety and depression as covariates to evaluate their effect. A Pearson correlation analysis between abnormal interhemispheric connectivity and clinical indices of IBS patients was performed. Compared to HCs, IBS patients had higher interhemispheric functional connectivity between bilateral thalami, cuneus, posterior cingulate cortices (PCC), lingual gyri and inferior occipital/cerebellum lobes, as well as lower interhemispheric functional connectivity between bilateral ventral anterior cingulate cortices (vACC) and inferior parietal lobules (IPL). The inclusion of anxiety and depression as covariates abolished VMHC difference in vACC. Microstructural features of white matter tracts connecting functionally abnormal regions did not reveal any differences between the groups. VMHC values in vACC negatively correlated with the quality of life (QOL) scores of patients. In conclusion, this study provides preliminary evidence of the disrupted functional coordination rather than anatomic coordination between interhemispheric regions within the cortex-thalamus circuit in IBS patients, which could partly account for the enhanced visceral information processing and impaired endogenous pain or emotion inhibition associated with IBS.
PMID: 27999530 [PubMed]
Cardiopulmonary exercise testing in the MRI environment.
Physiol Meas. 2016 Apr;37(4):N11-25
Authors: Lafountain RA, da Silveira JS, Varghese J, Mihai G, Scandling D, Craft J, Swain CB, Franco V, Raman SV, Devor ST, Simonetti OP
Maximal oxygen consumption ([Formula: see text]max) measured by cardiopulmonary exercise testing (CPX) is the gold standard for assessment of cardiorespiratory fitness. Likewise, cardiovascular magnetic resonance (CMR) is the gold standard for quantification of cardiac function. The combination of CPX and CMR may offer unique insights into cardiopulmonary pathophysiology; however, the MRI-compatible equipment needed to combine these tests has not been available to date. We sought to determine whether CPX testing in the MRI environment, using equipment modified for MRI yields results equivalent to those obtained in standard exercise physiology (EP) lab. Ten recreationally trained subjects completed [Formula: see text]max tests in different locations; an EP laboratory and an MRI laboratory, using site specific equipment. CMR cine images of the heart were acquired before and immediately after maximal exercise to measure cardiac function. Subjects in all tests met criteria indicating that peak exercise was achieved. Despite equipment modifications for the MRI environment, [Formula: see text]max was nearly identical between tests run in the different labs (95% lower confidence limit (LCL) = 0.8182). The mean difference in [Formula: see text]max was less than 3.40 ml (kg/min)(-1), within the variability expected for tests performed on different days, in different locations, using different metabolic carts. MRI performed at rest and following peak exercise stress indicated cardiac output increased from 5.1 ± 1.0 l min(-1) to 16.4 ± 5.6 l min(-1), LVEF increased from 65.2 ± 3.3% to 78.4 ± 4.8%, while RVEF increased from 52.8 ± 5.3% to 63.4 ± 5.3%. Regression analysis revealed a significant positive correlation between [Formula: see text]max and stroke volume (R = 0.788, P = 0.006), while the correlation with cardiac output did not reach statistical significance (R = 0.505, P = 0.137). [Formula: see text]max CPX testing can be effectively performed in the MRI environment, enabling direct combination of physiological data with advanced post-exercise imaging in the same test session.
PMID: 26987361 [PubMed - indexed for MEDLINE]
Multi-echo fMRI replication sample of autobiographical memory, prospection and theory of mind reasoning tasks.
Sci Data. 2016 Dec 20;3:160116
Authors: DuPre E, Luh WM, Spreng RN
The default network is involved in self-generated thought, a class of cognition that includes autobiographical memory, prospection, and reasoning about the mental states of others. We collected a replication sample of Spreng and Grady (J Cogn. Neurosci. 22, 1112-1123, 2010), confirming that the default network differentially supports each of these forms of self-generated thought. Here we describe this dataset of multi-echo fMRI data in 31 young adults during autobiographical remembering, imagining, and mentalizing; we also provide an additional resting-state scan for each subject. In this new sample, the findings from the original report are successfully replicated using the same analysis. Physiological measures were additionally collected and allow for interrogation of the impact of multi-echo independent components preprocessing both in task and rest. Future work on this dataset may provide insight into evoked brain response for cued self-generated thought, International Affective Picture System viewing, resting state dynamics, preprocessing procedures, and more. The dataset is accompanied by experimental code for independent behavioral data collection.
PMID: 27996964 [PubMed - in process]
A Review of the Functional and Anatomical Default Mode Network in Schizophrenia.
Neurosci Bull. 2016 Dec 19;
Authors: Hu ML, Zong XF, Mann JJ, Zheng JJ, Liao YH, Li ZC, He Y, Chen XG, Tang JS
Schizophrenia is a severe mental disorder characterized by impaired perception, delusions, thought disorder, abnormal emotion regulation, altered motor function, and impaired drive. The default mode network (DMN), since it was first proposed in 2001, has become a central research theme in neuropsychiatric disorders, including schizophrenia. In this review, first we define the DMN and describe its functional activity, functional and anatomical connectivity, heritability, and inverse correlation with the task positive network. Second, we review empirical studies of the anatomical and functional DMN, and anti-correlation between DMN and the task positive network in schizophrenia. Finally, we review preliminary evidence about the relationship between antipsychotic medications and regulation of the DMN, review the role of DMN as a treatment biomarker for this disease, and consider the DMN effects of individualized therapies for schizophrenia.
PMID: 27995564 [PubMed - as supplied by publisher]