Influence of ROI selection on resting state functional connectivity: an individualized approach for resting state fMRI analysis.
Front Neurosci. 2015;9:280
Authors: Sohn WS, Yoo K, Lee YB, Seo SW, Na DL, Jeong Y
The differences in how our brain is connected are often thought to reflect the differences in our individual personalities and cognitive abilities. Individual differences in brain connectivity has long been recognized in the neuroscience community however it has yet to manifest itself in the methodology of resting state analysis. This is evident as previous studies use the same region of interest (ROIs) for all subjects. In this paper we demonstrate that the use of ROIs which are standardized across individuals leads to inaccurate calculations of functional connectivity. We also show that this problem can be addressed by taking an individualized approach by using subject-specific ROIs. Finally we show that ROI selection can affect the way we interpret our data by showing different changes in functional connectivity with aging.
PMID: 26321904 [PubMed]
3D interactive tractography-informed resting-state fMRI connectivity.
Front Neurosci. 2015;9:275
Authors: Chamberland M, Bernier M, Fortin D, Whittingstall K, Descoteaux M
In the past decade, the fusion between diffusion magnetic resonance imaging (dMRI) and functional magnetic resonance imaging (fMRI) has opened the way for exploring structure-function relationships in vivo. As it stands, the common approach usually consists of analysing fMRI and dMRI datasets separately or using one to inform the other, such as using fMRI activation sites to reconstruct dMRI streamlines that interconnect them. Moreover, given the large inter-individual variability of the healthy human brain, it is possible that valuable information is lost when a fixed set of dMRI/fMRI analysis parameters such as threshold values are assumed constant across subjects. By allowing one to modify such parameters while viewing the results in real-time, one can begin to fully explore the sensitivity of structure-function relations and how they differ across brain areas and individuals. This is especially important when interpreting how structure-function relationships are altered in patients with neurological disorders, such as the presence of a tumor. In this study, we present and validate a novel approach to achieve this: First, we present an interactive method to generate and visualize tractography-driven resting-state functional connectivity, which reduces the bias introduced by seed size, shape and position. Next, we demonstrate that structural and functional reconstruction parameters explain a significant portion of intra- and inter-subject variability. Finally, we demonstrate how our proposed approach can be used in a neurosurgical planning context. We believe this approach will promote the exploration of structure-function relationships in a subject-specific aspect and will open new opportunities for connectomics.
PMID: 26321901 [PubMed]
Bipolar disorder: Functional neuroimaging markers in relatives.
Neurosci Biobehav Rev. 2015 Aug 28;
Authors: Piguet C, Fodoulian L, Aubry JM, Vuilleumier P, Houenou J
Neural models of anatomical and functional alterations have been proposed for bipolar disorders (BD). However, studies in affected patients do not allow disentangling alterations linked to the liability to BD from those associated with the evolution, medication and comorbidities of BD. Explorations in high risk subjects allow the study of these risk markers. We reported and summarized all functional magnetic resonance imaging (fMRI) studies focusing on first-degree relatives of BD patients. We found 29 studies reporting neural correlates of working memory (WM), emotional processing, executive functions and resting state in relatives of BD patients, compared to healthy subjects. Overall, the same regions that have been involved in patients, such as the inferior frontal gyrus and limbic areas, seem to be functionally altered in high-risk subjects. We conclude that the same brain regions already implicated in the pathophysiology of the disease such as the amygdala are also associated with the risk of BD. However longitudinal studies are required to understand their implication in the transition to BD.
PMID: 26321590 [PubMed - as supplied by publisher]
Resting-state functional connectivity abnormalities correlate with psychometric hepatic encephalopathy score in cirrhosis.
Eur J Radiol. 2015 Aug 18;
Authors: Chen HJ, Jiang LF, Sun T, Liu J, Chen QF, Shi HB
BACKGROUND & AIMS: Neurocognitive impairment is a common complication of cirrhosis and regarded as the important characteristic for early stage of hepatic encephalopathy (HE). This study aimed to investigate the changes in brain network centrality of functional connectivity among cirrhotic patients and uncover the mechanisms about early HE.
METHODS: Twenty-four cirrhotic patients without overt HE and 21 healthy controls were enrolled and underwent resting-state fMRI and Psychometric Hepatic Encephalopathy Score (PHES) tests. Whole-brain functional network was constructed by measuring the temporal correlations of every pairs of brain gray matter voxels; and then voxel-wise degree centrality (DC), an index reflecting importance of a node in functional integration, was calculated and compared between two groups. A seed-based resting-state functional connectivity (RSFC) analysis was further performed to investigate abnormal functional connectivity pattern of those regions with changed DC.
RESULTS: Compared with controls, the cirrhotic patients had worse performances in all neurocognitive tests and lower PHES score. Meanwhile, patients showed decreased DC in bilateral medial prefrontal gyrus and anterior cingulate cortex, left middle frontal gyrus, and bilateral thalamus; while increased DC in right middle occipital gyrus and parahippocampal gyrus/inferior temporal gyrus. The seed-based RSFC analyses revealed that the relevant functional networks, such as default-mode and attention networks, visual network, and thalamo-cortical circuits, were disturbed in cirrhotic patients. The DC changes were correlated with PHES score in patient group.
CONCLUSIONS: Our findings further confirm brain network disorganization in cirrhotic patients with neurocognitive impairments and may provide a new perspective for understanding HE-related mechanisms.
PMID: 26321490 [PubMed - as supplied by publisher]
Thalamocortical connectivity is enhanced following functional hemispherotomy for intractable lateralized epilepsy.
Epilepsy Behav. 2015 Aug 24;51:281-285
Authors: Ibrahim GM, Morgan BR, Smith ML, Kerr E, Donner E, Go CY, Doesburg S, Taylor M, Widjaja E, Rutka JT, Snead OC
Although developmental outcomes may improve following functional hemispherotomy for lateralized, catastrophic childhood epilepsy, the neuronal processes mediating these improvements are unknown. We report the case of a 14-year-old child with neurocognitive impairment who underwent functional hemispherotomy with longitudinal resting-state fMRI. Compared with preoperative fMRI, we report significantly more robust thalamo-default mode network connectivity on postoperative neuroimaging. Furthermore, we show decreased connectivity to nodes within the disconnected hemisphere, providing direct evidence that functional interactions are dependent upon structural connectivity. Since the vascular supply to these nodes remains intact, although they are disconnected from the remainder of the brain, these findings also confirm that blood-oxygen level dependent oscillations are driven primarily by neuronal activity. The current study highlights the importance of thalamocortical interactions in the understanding of neural oscillations and cognitive function, and their impairment in childhood epilepsy.
PMID: 26318790 [PubMed - as supplied by publisher]
Functional Organization of the Action Observation Network in Autism: A Graph Theory Approach.
PLoS One. 2015;10(8):e0137020
Authors: Alaerts K, Geerlings F, Herremans L, Swinnen SP, Verhoeven J, Sunaert S, Wenderoth N
BACKGROUND: The ability to recognize, understand and interpret other's actions and emotions has been linked to the mirror system or action-observation-network (AON). Although variations in these abilities are prevalent in the neuro-typical population, persons diagnosed with autism spectrum disorders (ASD) have deficits in the social domain and exhibit alterations in this neural network.
METHOD: Here, we examined functional network properties of the AON using graph theory measures and region-to-region functional connectivity analyses of resting-state fMRI-data from adolescents and young adults with ASD and typical controls (TC).
RESULTS: Overall, our graph theory analyses provided convergent evidence that the network integrity of the AON is altered in ASD, and that reductions in network efficiency relate to reductions in overall network density (i.e., decreased overall connection strength). Compared to TC, individuals with ASD showed significant reductions in network efficiency and increased shortest path lengths and centrality. Importantly, when adjusting for overall differences in network density between ASD and TC groups, participants with ASD continued to display reductions in network integrity, suggesting that also network-level organizational properties of the AON are altered in ASD.
CONCLUSION: While differences in empirical connectivity contributed to reductions in network integrity, graph theoretical analyses provided indications that also changes in the high-level network organization reduced integrity of the AON.
PMID: 26317222 [PubMed - in process]
Baseline Striatal Functional Connectivity as a Predictor of Response to Antipsychotic Drug Treatment.
Am J Psychiatry. 2015 Aug 28;:appiajp201514121571
Authors: Sarpal DK, Argyelan M, Robinson DG, Szeszko PR, Karlsgodt KH, John M, Weissman N, Gallego JA, Kane JM, Lencz T, Malhotra AK
OBJECTIVE: Clinical response to antipsychotic drug treatment is highly variable, yet prognostic biomarkers are lacking. The authors recently demonstrated that successful antipsychotic drug treatment alters resting-state functional connectivity of the striatum. The goal of the present study was to test whether intrinsic striatal connectivity patterns provide prognostic information and can serve as a potential biomarker of treatment response to antipsychotic drugs.
METHOD: The authors used resting-state functional MRI (fMRI) to develop a prognostic index in a discovery cohort of 41 first-episode schizophrenia patients, then tested this index in an independent cohort of 40 newly hospitalized chronic patients with acute psychosis. In the discovery cohort, patients underwent resting-state fMRI scanning at the initiation of randomized controlled treatment with a second-generation antipsychotic. Whole-brain functional connectivity maps were generated for each subject from striatal seed regions. A stringent measure of clinical response was calculated that required sustained improvement over two consecutive study visits. Clinical response was entered into a survival analysis, and Cox regression was applied to the functional connectivity data. A striatal connectivity index was created, comprising functional connections of the striatum that predicted treatment response. This striatal connectivity index was tested on a generalizability cohort of patients with psychotic disorders who were hospitalized for an acute psychotic episode.
RESULTS: A total of 91 regions functionally connected with the striatum provided significant prognostic information. Connectivity in these regions was used to create a baseline striatal connectivity index that predicted response to antipsychotic treatment with high sensitivity and specificity in both the discovery and generalizability cohorts.
CONCLUSIONS: These results provide evidence that individual differences in striatal functional connectivity predict response to antipsychotic drug treatment in acutely psychotic patients. With further development, this has the potential to serve as a prognostic biomarker with clinical utility and to reduce the overall burden associated with psychotic illnesses.
PMID: 26315980 [PubMed - as supplied by publisher]
Aging Effects on Whole-Brain Functional Connectivity in Adults Free of Cognitive and Psychiatric Disorders.
Cereb Cortex. 2015 Aug 26;
Authors: Ferreira LK, Regina AC, Kovacevic N, Martin MD, Santos PP, Carneiro CG, Kerr DS, Amaro E, McIntosh AR, Busatto GF
Aging is associated with decreased resting-state functional connectivity (RSFC) within the default mode network (DMN), but most functional imaging studies have restricted the analysis to specific brain regions or networks, a strategy not appropriate to describe system-wide changes. Moreover, few investigations have employed operational psychiatric interviewing procedures to select participants; this is an important limitation since mental disorders are prevalent and underdiagnosed and can be associated with RSFC abnormalities. In this study, resting-state fMRI was acquired from 59 adults free of cognitive and psychiatric disorders according to standardized criteria and based on extensive neuropsychological and clinical assessments. We tested for associations between age and whole-brain RSFC using Partial Least Squares, a multivariate technique. We found that normal aging is not only characterized by decreased RSFC within the DMN but also by ubiquitous increases in internetwork positive correlations and focal internetwork losses of anticorrelations (involving mainly connections between the DMN and the attentional networks). Our results reinforce the notion that the aging brain undergoes a dedifferentiation processes with loss of functional diversity. These findings advance the characterization of healthy aging effects on RSFC and highlight the importance of adopting a broad, system-wide perspective to analyze brain connectivity.
PMID: 26315689 [PubMed - as supplied by publisher]
Disruption of cortical integration during midazolam-induced light sedation.
Hum Brain Mapp. 2015 Aug 28;
Authors: Liang P, Zhang H, Xu Y, Jia W, Zang Y, Li K
This work examines the effect of midazolam-induced light sedation on intrinsic functional connectivity of human brain, using a randomized, double-blind, placebo-controlled, cross-over, within-subject design. Fourteen healthy young subjects were enrolled and midazolam (0.03 mg/kg of the participant's body mass, to a maximum of 2.5 mg) or saline were administrated with an interval of one week. Resting-state fMRI was conducted before and after administration for each subject. We focus on two types of networks: sensory related lower-level functional networks and higher-order functions related ones. Independent component analysis (ICA) was used to identify these resting-state functional networks. We hypothesize that the sensory (visual, auditory, and sensorimotor) related networks will be intact under midazolam-induced light sedation while the higher-order (default mode, executive control, salience networks, etc.) networks will be functionally disconnected. It was found that the functional integrity of the lower-level networks was maintained, while that of the higher-level networks was significantly disrupted by light sedation. The within-network connectivity of the two types of networks was differently affected in terms of direction and extent. These findings provide direct evidence that higher-order cognitive functions including memory, attention, executive function, and language were impaired prior to lower-level sensory responses during sedation. Our result also lends support to the information integration model of consciousness. Hum Brain Mapp, 2015. © 2015 Wiley Periodicals, Inc.
PMID: 26314702 [PubMed - as supplied by publisher]
Eye-tracking in amyotrophic lateral sclerosis: A longitudinal study of saccadic and cognitive tasks.
Amyotroph Lateral Scler Frontotemporal Degener. 2015 Aug 27;:1-11
Authors: Proudfoot M, Menke RA, Sharma R, Berna CM, Hicks SL, Kennard C, Talbot K, Turner MR
A relative preservation of eye movements is notable in ALS, but saccadic functions have not been studied longitudinally. ALS overlaps with FTD, typically involving executive dysfunction, and eye-tracking offers additional potential for the assessment of extramotor pathology where writing and speaking are both impaired. Eye-tracking measures (including anti-saccade, trail-making and visual search tasks) were assessed at six-monthly intervals for up to two years in a group of ALS (n = 61) and primary lateral sclerosis (n = 7) patients, compared to healthy age-matched controls (n = 39) assessed on a single occasion. Task performance was explored speculatively in relation to resting-state functional MRI (R-FMRI) network connectivity. Results showed that ALS patients were impaired on executive and visual search tasks despite normal basic saccadic function, and impairments in the PLS patients were unexpectedly often more severe. No significant progression was detected longitudinally in either group. No changes in R-FMRI network connectivity were identified in relation to patient performance. In conclusion, eye-tracking offers an objective means to assess extramotor cerebral involvement in ALS. The relative resistance of pure oculomotor function is confirmed, and higher-level executive impairments do not follow the same rate of decline as physical disability. PLS patients may have more cortical dysfunction than has been previously appreciated.
PMID: 26312652 [PubMed - as supplied by publisher]
Changes in functional connectivity of pain modulatory systems in women with primary dysmenorrhea.
Pain. 2015 Aug 22;
Authors: Wei SY, Chao HT, Tu CH, Li WC, Low I, Chuang CY, Chen LF, Hsieh JC
Menstrual pain is the most prevalent gynecological complaint, and is usually without organic cause (termed as primary dysmenorrhea, PDM). The high comorbidity in the later life of PDM with many functional pain disorders (associated with central dysfunction of pain inhibition, e.g., fibromyalgia) suggests possible maladaptive functionality of pain modulatory systems already occurred in young PDM women, making them vulnerable to functional pain disorders. Periaqueductal gray matter (PAG) functions as a critical hub in the neuraxis of pain modulatory systems; therefore, we investigated the functional connectivity of PAG in PDM. Forty-six PDM subjects and 49 controls received resting-state fMRI during menstruation and peri-ovulatory phases. The PAG of PDM subjects exhibited adaptive/reactive hyper-connectivity with the sensorimotor cortex during painful-menstruation, whereas it exhibited maladaptive hypo-connectivity with the dorsolateral prefrontal cortex and default mode network (involving the ventromedial prefrontal cortex, posterior cingulate cortex or posterior parietal cortex) during menstruation or peri-ovulatory phase. We propose that the maladaptive descending pain modulatory systems in PDM may underpin the central susceptibility to subsequent development of various functional disorders later in life. This hypothesis is corroborated by the growing body of evidence that hypo-connectivity between PAG and default mode network is a co-terminal to many functional pain disorders.
PMID: 26307856 [PubMed - as supplied by publisher]
Epigenetic variation in the serotonin transporter gene predicts resting state functional connectivity strength within the salience-network.
Hum Brain Mapp. 2015 Aug 25;
Authors: Muehlhan M, Kirschbaum C, Wittchen HU, Alexander N
Genetic variation in the serotonin transporter gene (SLC6A4) has been associated with psychopathology and aberrant brain functioning in a plethora of clinical and imaging studies. In contrast, the neurobiological correlates of epigenetic signatures in SLC6A4, such as DNA methylation profiles, have only recently been explored in human brain imaging research. The present study is the first to apply a resting state functional magnetic resonance imaging approach to identify changes in brain networks related to SLC6A4 promoter methylation (N = 74 healthy individuals). The amygdalae were defined as seed regions given that resting state functional connectivity in this brain area is under serotonergic control and relates to a broad range of psychiatric phenotypes. We further used bisulfite pyrosequencing to analyze quantitative methylation at 83 CpG sites within a promoter-associated CpG island of SLC6A4 from blood-derived DNA samples. The major finding of this study indicates a positive relation of SLC6A4 promoter methylation and amygdaloid resting state functional coupling with key nodes of the salience network (SN) including the anterior insulae and the dorsal anterior cingulate cortices. Increased intra-network connectivity in the SN is thought to facilitate the detection and subsequent processing of potentially negative stimuli and reflects a core feature of psychopathology. As such, epigenetic changes within the SLC6A4 gene predict connectivity patterns in clinically and behaviorally relevant brain networks which may in turn convey increased disease susceptibility. Hum Brain Mapp, 2015. © 2015 Wiley Periodicals, Inc.
PMID: 26303978 [PubMed - as supplied by publisher]
Effects of Fronto-Temporal Transcranial Direct Current Stimulation on Auditory Verbal Hallucinations and Resting-State Functional Connectivity of the Left Temporo-Parietal Junction in Patients With Schizophrenia.
Schizophr Bull. 2015 Aug 24;
Authors: Mondino M, Jardri R, Suaud-Chagny MF, Saoud M, Poulet E, Brunelin J
Auditory verbal hallucinations (AVH) in patients with schizophrenia are associated with abnormal hyperactivity in the left temporo-parietal junction (TPJ) and abnormal connectivity between frontal and temporal areas. Recent findings suggest that fronto-temporal transcranial Direct Current stimulation (tDCS) with the cathode placed over the left TPJ and the anode over the left prefrontal cortex can alleviate treatment-resistant AVH in patients with schizophrenia. However, brain correlates of the AVH reduction are unclear. Here, we investigated the effect of tDCS on the resting-state functional connectivity (rs-FC) of the left TPJ. Twenty-three patients with schizophrenia and treatment-resistant AVH were randomly allocated to receive 10 sessions of active (2 mA, 20min) or sham tDCS (2 sessions/d for 5 d). We compared the rs-FC of the left TPJ between patients before and after they received active or sham tDCS. Relative to sham tDCS, active tDCS significantly reduced AVH as well as the negative symptoms. Active tDCS also reduced rs-FC of the left TPJ with the left anterior insula and the right inferior frontal gyrus and increased rs-FC of the left TPJ with the left angular gyrus, the left dorsolateral prefrontal cortex and the precuneus. The reduction of AVH severity was correlated with the reduction of the rs-FC between the left TPJ and the left anterior insula. These findings suggest that the reduction of AVH induced by tDCS is associated with a modulation of the rs-FC within an AVH-related brain network, including brain areas involved in inner speech production and monitoring.
PMID: 26303936 [PubMed - as supplied by publisher]
Learning to live without the cerebellum.
Neuroreport. 2015 Sep 30;26(14):809-813
Authors: Arrigoni F, Romaniello R, Nordio A, Gagliardi C, Borgatti R
The near-total absence of the cerebellum is a rare congenital condition with a wide phenotypic heterogeneity ranging from a severe to mild impairment of motor, cognitive, and behavioral functions. In this study, the case of a 48-year-old right-handed man with a near-total absence of the cerebellum was examined with the aim of understanding the long-term reorganization of a brain developed without a cerebellum. Clinical, neuropsychological evaluation and a neuroimaging study on a 3-T scanner were carried out. Both conventional structural diffusion tensor imaging (DTI) and functional (resting-state fMRI) data were acquired. A severe neuropsychomotor delay in infancy and adolescence involving motor skills, cognitive, and affective competencies was observed, which improved over the years. Conventional MRI findings confirmed the complete absence of the cerebellum. Analysis of DTI and resting-state fMRI data showed an impairment of the executive-control network, involving areas strongly connected with the cerebellum through the frontopontine fibers. The neuroimaging findings excluded the involvement of the extracerebellar structure. In conclusion, our data support the vascular genesis hypothesis for this rare pathology, consistent with an acquired embryonic cerebellar insult. This case also shows that it is possible to learn to live without the cerebellum over time.
PMID: 26302158 [PubMed - as supplied by publisher]
Considerations for resting state functional MRI and functional connectivity studies in rodents.
Front Neurosci. 2015;9:269
Authors: Pan WJ, Billings JC, Grooms JK, Shakil S, Keilholz SD
Resting state functional MRI (rs-fMRI) and functional connectivity mapping have become widely used tools in the human neuroimaging community and their use is rapidly spreading into the realm of rodent research as well. One of the many attractive features of rs-fMRI is that it is readily translatable from humans to animals and back again. Changes in functional connectivity observed in human studies can be followed by more invasive animal experiments to determine the neurophysiological basis for the alterations, while exploratory work in animal models can identify possible biomarkers for further investigation in human studies. These types of interwoven human and animal experiments have a potentially large impact on neuroscience and clinical practice. However, impediments exist to the optimal application of rs-fMRI in small animals, some similar to those encountered in humans and some quite different. In this review we identify the most prominent of these barriers, discuss differences between rs-fMRI in rodents and in humans, highlight best practices for animal studies, and review selected applications of rs-fMRI in rodents. Our goal is to facilitate the integration of human and animal work to the benefit of both fields.
PMID: 26300718 [PubMed]
The Relevance of Fractional Amplitude of Low-Frequency Fluctuation to Interference Effect.
Behav Brain Res. 2015 Aug 20;
Authors: Deng Y, Wang Y, Ding X, Tang YY
Growing evidence has indicated a potential connection between resting-state functional magnetic resonance imaging (RS-fMRI) signal and cognitive performance. However, the relationship between intrinsic neural activity and behavioral interference effect on cognitive control has been poorly understood. In the present study, seventy-eight healthy subjects underwent RS-fMRI and performed Multi-Source Interference Task (MSIT). The fractional amplitude of low-frequency fluctuation (fALFF) was measured as an indicator of intrinsic brain activity. The difference in reaction times between interference and control conditions in MSIT was evaluated as interference effect. Then we examined the associations between fALFF and interference effect using partial correlation analysis controlling for age, gender and mean framewise displacement. The results demonstrated that fALFF values in orbital prefrontal cortex (OPFC) and right inferior frontal cortex (IFC) were negatively correlated with the interference effect in MSIT. The findings manifest that OPFC and right IFC may influence the processing efficiency of cognitive conflict and play a crucial role in cognitive control.
PMID: 26300450 [PubMed - as supplied by publisher]
Auditory-limbic interactions in chronic tinnitus: challenges for neuroimaging research.
Hear Res. 2015 Aug 20;
Authors: Leaver AM, Seydell-Greenwald A, Rauschecker JP
Tinnitus is a widespread auditory disorder affecting approximately 10-15% of the population, often with debilitating consequences. Although tinnitus commonly begins with damage to the auditory system due to loud-noise exposure, aging, or other etiologies, the exact neurophysiological basis of chronic tinnitus remains unknown. Many researchers point to a central auditory origin of tinnitus; however, a growing body of evidence also implicates other brain regions, including the limbic system. Correspondingly, we and others have proposed models of tinnitus in which the limbic and auditory systems both play critical roles and interact with one another. Specifically, we argue that damage to the auditory system generates an initial tinnitus signal, consistent with previous research. In our model, this "transient" tinnitus is suppressed when a limbic frontostriatal network, comprised of ventromedial prefrontal cortex and ventral striatum, successfully modulates thalamocortical transmission in the auditory system. Thus, in chronic tinnitus, limbic-system damage and resulting inefficiency of auditory-limbic interactions prevents proper compensation of the tinnitus signal. Neuroimaging studies utilizing connectivity methods like resting-state fMRI and diffusion MRI continue to uncover tinnitus-related anomalies throughout auditory, limbic, and other brain systems. However, directly assessing interactions between these brain regions and networks has proved to be more challenging. Here, we review existing empirical support for models of tinnitus stressing a critical role for involvement of "non-auditory" structures in tinnitus pathophysiology, and discuss the possible impact of newly refined connectivity techniques from neuroimaging on tinnitus research.
PMID: 26299843 [PubMed - as supplied by publisher]
Functional connectivity MRI tracks memory networks after maze learning in rodents.
Neuroimage. 2015 Aug 20;
Authors: Nasrallah FA, To XV, Chen DY, Routtenberg A, Chuang KH
Learning and memory employs a series of cognitive processes which require the coordination of multiple areas across the brain. However in vivo imaging of cognitive function has been challenging in rodents. Since these processes involve synchronous firing among different brain loci we explored functional connectivity imaging with resting-state fMRI. After 5-day training on a hidden platform watermaze task, notable signal correlations were seen between the hippocampal CA3 and other structures, including thalamus, septum and cingulate cortex, compared to swim control or naïve animals. The connectivity sustained 7 days after training and was reorganized towards the cortex, consistent with views of memory trace distribution leading to memory consolidation. These data demonstrates that, after a cognitive task, altered functional connectivity can be detected in the subsequently sedated rodent using in vivo imaging. This approach paves the way to understand dynamics of area-dependent distribution processes in animal models of cognition.
PMID: 26299794 [PubMed - as supplied by publisher]
Nodal centrality of functional network in the differentiation of schizophrenia.
Schizophr Res. 2015 Aug 20;
Authors: Cheng H, Newman S, Goñi J, Kent JS, Howell J, Bolbecker A, Puce A, O'Donnell BF, Hetrick WP
A disturbance in the integration of information during mental processing has been implicated in schizophrenia, possibly due to faulty communication within and between brain regions. Graph theoretic measures allow quantification of functional brain networks. Functional networks are derived from correlations between time courses of brain regions. Group differences between SZ and control groups have been reported for functional network properties, but the potential of such measures to classify individual cases has been little explored. We tested whether the network measure of betweenness centrality could classify persons with schizophrenia and normal controls. Functional networks were constructed for 19 schizophrenic patients and 29 non-psychiatric controls based on resting state functional MRI scans. The betweenness centrality of each node, or fraction of shortest-paths that pass through it, was calculated in order to characterize the centrality of the different regions. The nodes with high betweenness centrality agreed well with hub nodes reported in previous studies of structural and functional networks. Using a linear support vector machine algorithm, the schizophrenia group was differentiated from non-psychiatric controls using the ten nodes with the highest betweenness centrality. The classification accuracy was around 80%, and stable against connectivity thresholding. Better performance was achieved when using the ranks as feature space as opposed to the actual values of betweenness centrality. Overall, our findings suggest that changes in functional hubs are associated with schizophrenia, reflecting a variation of the underlying functional network and neuronal communications. In addition, a specific network property, betweenness centrality, can classify persons with SZ with a high level of accuracy.
PMID: 26299706 [PubMed - as supplied by publisher]
Intrinsic brain indices of verbal working memory capacity in children and adolescents.
Dev Cogn Neurosci. 2015 Aug 4;
Authors: Yang Z, Jutagir DR, Koyama MS, Craddock RC, Yan CG, Shehzad Z, Castellanos FX, Di Martino A, Milham MP
Working memory (WM) is central to the acquisition of knowledge and skills throughout childhood and adolescence. While numerous behavioral and task-based functional magnetic resonance imaging (fMRI) studies have examined WM development, few have used resting-state fMRI (R-fMRI). Here, we present a systematic R-fMRI examination of age-related differences in the neural indices of verbal WM performance in a cross-sectional pediatric sample (ages: 7-17; n=68), using data-driven approaches. Verbal WM capacity was measured with the digit span task, a commonly used educational and clinical assessment. We found distinct neural indices of digit span forward (DSF) and backward (DSB) performance, reflecting their unique neuropsychological demands. Regardless of age, DSB performance was related to intrinsic properties of brain areas previously implicated in attention and cognitive control, while DSF performance was related to areas less commonly implicated in verbal WM storage (precuneus, lateral visual areas). From a developmental perspective, DSF exhibited more robust age-related differences in brain-behavior relationships than DSB, and implicated a broader range of networks (ventral attention, default, somatomotor, limbic networks) - including a number of regions not commonly associated with verbal WM (angular gyrus, subcallosum). These results highlight the importance of examining the neurodevelopment of verbal WM and of considering regions beyond the "usual suspects".
PMID: 26299314 [PubMed - as supplied by publisher]