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https://www.readbyqxmd.com/read/29338310/therapy-induced-plasticity-in-chronic-aphasia-is-associated-with-behavioral-improvement-and-time-since-stroke
#1
Priya Santhanam, E Susan Duncan, Steven L Small
Cortical reorganization after stroke is thought to underlie functional improvement. Patterns of reorganization may differ depending on the amount of time since the stroke or the degree of improvement. We investigated these issues in a study of brain connectivity changes with aphasia therapy. Twelve individuals with chronic aphasia participated in a 6-week trial of imitation-based speech therapy. We assessed improvement on a repetition test and analyzed effective connectivity during functional magnetic resonance imaging (fMRI) of a speech observation task before and after therapy...
January 16, 2018: Brain Connectivity
https://www.readbyqxmd.com/read/29337235/frequency-specific-effective-connectivity-in-subjects-with-cerebral-infarction-as-revealed-by-nirs-method
#2
Qianying Liu, Bitian Wang, Ying Liu, Zeping Lv, Wenhao Li, Zengyong Li, Yubo Fan
A connectivity-based approach can highlight the network reorganization in the chronic phases after stroke and contributes to the development of therapeutic interventions. Using dynamic Bayesian inference, this study aimed to assess the effective connectivity(EC)in various frequency bands through the near-infrared spectroscopy(NIRS) method in subjects with cerebral infarction(CI). A phase-coupling model was established based on phase information extracted using the wavelet transform of NIRS signals. Coupling strength and the main coupling direction were estimated using dynamic Bayesian inference...
January 11, 2018: Neuroscience
https://www.readbyqxmd.com/read/29324886/changes-in-network-connectivity-during-motor-imagery-and-execution
#3
Yun Kwan Kim, Eunhee Park, Ahee Lee, Chang-Hwan Im, Yun-Hee Kim
BACKGROUND: Recent studies of functional or effective connectivity in the brain have reported that motor-related brain regions were activated during motor execution and motor imagery, but the relationship between motor and cognitive areas has not yet been completely understood. The objectives of our study were to analyze the effective connectivity between motor and cognitive networks in order to define network dynamics during motor execution and motor imagery in healthy individuals. Second, we analyzed the differences in effective connectivity between correct and incorrect responses during motor execution and imagery using dynamic causal modeling (DCM) of electroencephalography (EEG) data...
2018: PloS One
https://www.readbyqxmd.com/read/29304417/spectral-and-temporal-electroencephalography-measures-reveal-distinct-neural-networks-for-the-acquisition-consolidation-and-interlimb-transfer-of-motor-skills-in-healthy-young-adults
#4
M P Veldman, N M Maurits, M A M Nijland, N E Wolters, J C Mizelle, T Hortobágyi
OBJECTIVE: Plasticity of the central nervous system likely underlies motor learning. It is however unclear, whether plasticity in cortical motor networks is motor learning stage-, activity-, or connectivity-dependent. METHODS: From electroencephalography (EEG) data, we quantified effective connectivity by the phase slope index (PSI), neuronal activity by event-related desynchronization, and sensorimotor integration by N30 during the stages of visuomotor skill acquisition, consolidation, and interlimb transfer...
December 20, 2017: Clinical Neurophysiology: Official Journal of the International Federation of Clinical Neurophysiology
https://www.readbyqxmd.com/read/29284140/effective-connectivity-during-working-memory-and-resting-states-a-dcm-study
#5
Kyesam Jung, Karl J Friston, Chongwon Pae, Hanseul Choi, Sungho Tak, Yoon Kyoung Choi, Bumhee Park, Chan-A Park, Chaejoon Cheong, Hae-Jeong Park
Although the relationship between resting-state functional connectivity and task-related activity has been addressed, the relationship between task and resting-state directed or effective connectivity - and its behavioral concomitants - remains elusive. We evaluated effective connectivity under an N-back working memory task in 24 participants using stochastic dynamic causal modelling (DCM) of 7 Tesla fMRI data. We repeated the analysis using resting-state data, from the same subjects, to model connectivity among the same brain regions engaged by the N-back task...
December 25, 2017: NeuroImage
https://www.readbyqxmd.com/read/29275004/handling-or-being-the-concept-an-fmri-study-on-metonymy-representations-in-coverbal-gestures
#6
Gina Joue, Linda Boven, Klaus Willmes, Vito Evola, Liliana R Demenescu, Julius Hassemer, Irene Mittelberg, Klaus Mathiak, Frank Schneider, Ute Habel
In "Two heads are better than one," "head" stands for people and focuses the message on the intelligence of people. This is an example of figurative language through metonymy, where substituting a whole entity by one of its parts focuses attention on a specific aspect of the entity. Whereas metaphors, another figurative language device, are substitutions based on similarity, metonymy involves substitutions based on associations. Both are figures of speech but are also expressed in coverbal gestures during multimodal communication...
December 21, 2017: Neuropsychologia
https://www.readbyqxmd.com/read/29249925/determining-excitatory-and-inhibitory-neuronal-activity-from-multimodal-fmri-data-using-a-generative-hemodynamic-model
#7
Martin Havlicek, Dimo Ivanov, Alard Roebroeck, Kamil Uludağ
Hemodynamic responses, in general, and the blood oxygenation level-dependent (BOLD) fMRI signal, in particular, provide an indirect measure of neuronal activity. There is strong evidence that the BOLD response correlates well with post-synaptic changes, induced by changes in the excitatory and inhibitory (E-I) balance between active neuronal populations. Typical BOLD responses exhibit transients, such as the early-overshoot and post-stimulus undershoot, that can be linked to transients in neuronal activity, but they can also result from vascular uncoupling between cerebral blood flow (CBF) and venous cerebral blood volume (venous CBV)...
2017: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/29244638/memory-contextualization-the-role-of-prefrontal-cortex-in-functional-integration-across-item-and-context-representational-regions
#8
Wei Zhang, Vanessa A van Ast, Floris Klumpers, Karin Roelofs, Erno J Hermans
Memory recall is facilitated when retrieval occurs in the original encoding context. This context dependency effect likely results from the automatic binding of central elements of an experience with contextual features (i.e., memory "contextualization") during encoding. However, despite a vast body of research investigating the neural correlates of explicit associative memory, the neural interactions during encoding that predict implicit context-dependent memory remain unknown. Twenty-six participants underwent fMRI during encoding of salient stimuli (faces), which were overlaid onto unique background images (contexts)...
December 15, 2017: Journal of Cognitive Neuroscience
https://www.readbyqxmd.com/read/29243004/altered-effective-connectivity-contributes-to-micrographia-in-patients-with-parkinson-s-disease-and-freezing-of-gait
#9
Evelien Nackaerts, Alice Nieuwboer, Sanne Broeder, Stephan Swinnen, Wim Vandenberghe, Elke Heremans
Recently, it was shown that patients with Parkinson's disease (PD) and freezing of gait (FOG) can also experience freezing episodes during handwriting and present writing problems outside these episodes. So far, the neural networks underlying increased handwriting problems in subjects with FOG are unclear. This study used dynamic causal modeling of fMRI data to investigate neural network dynamics underlying freezing-related handwriting problems and how these networks changed in response to visual cues. Twenty-seven non-freezers and ten freezers performed a pre-writing task with and without visual cues in the scanner with their right hand...
December 14, 2017: Journal of Neurology
https://www.readbyqxmd.com/read/29239622/coactivation-of-cognitive-control-networks-during-task-switching
#10
Shouhang Yin, Gedeon Deák, Antao Chen
OBJECTIVE: The ability to flexibly switch between tasks is considered an important component of cognitive control that involves frontal and parietal cortical areas. The present study was designed to characterize network dynamics across multiple brain regions during task switching. METHOD: Functional magnetic resonance images (fMRI) were captured during a standard rule-switching task to identify switching-related brain regions. Multiregional psychophysiological interaction (PPI) analysis was used to examine effective connectivity between these regions...
December 14, 2017: Neuropsychology
https://www.readbyqxmd.com/read/29238300/supervised-estimation-of-granger-based-causality-between-time-series
#11
Danilo Benozzo, Emanuele Olivetti, Paolo Avesani
Brain effective connectivity aims to detect causal interactions between distinct brain units and it is typically studied through the analysis of direct measurements of the neural activity, e.g., magneto/electroencephalography (M/EEG) signals. The literature on methods for causal inference is vast. It includes model-based methods in which a generative model of the data is assumed and model-free methods that directly infer causality from the probability distribution of the underlying stochastic process. Here, we firstly focus on the model-based methods developed from the Granger criterion of causality, which assumes the autoregressive model of the data...
2017: Frontiers in Neuroinformatics
https://www.readbyqxmd.com/read/29238085/communication-dynamics-in-complex-brain-networks
#12
REVIEW
Andrea Avena-Koenigsberger, Bratislav Misic, Olaf Sporns
Neuronal signalling and communication underpin virtually all aspects of brain activity and function. Network science approaches to modelling and analysing the dynamics of communication on networks have proved useful for simulating functional brain connectivity and predicting emergent network states. This Review surveys important aspects of communication dynamics in brain networks. We begin by sketching a conceptual framework that views communication dynamics as a necessary link between the empirical domains of structural and functional connectivity...
December 14, 2017: Nature Reviews. Neuroscience
https://www.readbyqxmd.com/read/29236724/the-role-of-cortical-oscillations-in-a-spiking-neural-network-model-of-the-basal-ganglia
#13
Zafeirios Fountas, Murray Shanahan
Although brain oscillations involving the basal ganglia (BG) have been the target of extensive research, the main focus lies disproportionally on oscillations generated within the BG circuit rather than other sources, such as cortical areas. We remedy this here by investigating the influence of various cortical frequency bands on the intrinsic effective connectivity of the BG, as well as the role of the latter in regulating cortical behaviour. To do this, we construct a detailed neural model of the complete BG circuit based on fine-tuned spiking neurons, with both electrical and chemical synapses as well as short-term plasticity between structures...
2017: PloS One
https://www.readbyqxmd.com/read/29223740/statistical-models-for-brain-signals-with-properties-that-evolve-across-trials
#14
REVIEW
Hernando Ombao, Mark Fiecas, Chee-Ming Ting, Yin Fen Low
Most neuroscience cognitive experiments involve repeated presentations of various stimuli across several minutes or a few hours. It has been observed that brain responses, even to the same stimulus, evolve over the course of the experiment. These changes in brain activation and connectivity are believed to be associated with learning and/or habituation. In this paper, we present two general approaches to modeling dynamic brain connectivity using electroencephalograms (EEGs) recorded across replicated trials in an experiment...
December 6, 2017: NeuroImage
https://www.readbyqxmd.com/read/29222818/task-related-effective-connectivity-reveals-that-the-cortical-rich-club-gates-cortex-wide-communication
#15
Mario Senden, Niels Reuter, Martijn P van den Heuvel, Rainer Goebel, Gustavo Deco, Matthieu Gilson
Higher cognition may require the globally coordinated integration of specialized brain regions into functional networks. A collection of structural cortical hubs-referred to as the rich club-has been hypothesized to support task-specific functional integration. In the present paper, we use a whole-cortex model to estimate directed interactions between 68 cortical regions from functional magnetic resonance imaging activity for four different tasks (reflecting different cognitive domains) and resting state. We analyze the state-dependent input and output effective connectivity (EC) of the structural rich club and relate these to whole-cortex dynamics and network reconfigurations...
December 8, 2017: Human Brain Mapping
https://www.readbyqxmd.com/read/29205291/interactive-effects-of-seizure-frequency-and-lateralization-on-intratemporal-effective-connectivity-in-temporal-lobe-epilepsy
#16
Chang-Hyun Park, Yun Seo Choi, Hyeon Jin Kim, Hwa-Kyung Chung, A-Reum Jung, Jeong Hyun Yoo, Hyang Woon Lee
OBJECTIVE: Patients with temporal lobe epilepsy (TLE) show brain connectivity changes in association with cognitive impairment. Seizure frequency and lateralization are 2 important clinical factors that characterize epileptic seizures. In this study, we sought to examine an interactive effect of the 2 seizure factors on intratemporal effective connectivity based on resting-state functional magnetic resonance imaging (rsfMRI) in patients with TLE. METHODS: For rsfMRI data acquired from 48 TLE patients and 45 healthy controls, we applied stochastic dynamical causal modeling to infer effective connectivity between 3 medial temporal lobe (MTL) regions, including the hippocampus (Hipp), parahippocampal gyrus (PHG), and amygdala (Amyg), ipsilateral to the seizure focus...
December 4, 2017: Epilepsia
https://www.readbyqxmd.com/read/29204807/analysis-of-fmri-data-using-noise-diffusion-network-models-a-new-covariance-coding-perspective
#17
Matthieu Gilson
Since the middle of the 1990s, studies of resting-state fMRI/BOLD data have explored the correlation patterns of activity across the whole brain, which is referred to as functional connectivity (FC). Among the many methods that have been developed to interpret FC, a recently proposed model-based approach describes the propagation of fluctuating BOLD activity within the recurrently connected brain network by inferring the effective connectivity (EC). In this model, EC quantifies the strengths of directional interactions between brain regions, viewed from the proxy of BOLD activity...
December 4, 2017: Biological Cybernetics
https://www.readbyqxmd.com/read/29188123/dynamics-of-the-human-brain-network-revealed-by-time-frequency-effective-connectivity-in-fnirs
#18
Grégoire Vergotte, Kjerstin Torre, Venkata Chaitanya Chirumamilla, Abdul Rauf Anwar, Sergiu Groppa, Stéphane Perrey, Muthuraman Muthuraman
Functional near infrared spectroscopy (fNIRS) is a promising neuroimaging method for investigating networks of cortical regions over time. We propose a directed effective connectivity method (TPDC) allowing the capture of both time and frequency evolution of the brain's networks using fNIRS data acquired from healthy subjects performing a continuous finger-tapping task. Using this method we show the directed connectivity patterns among cortical motor regions involved in the task and their significant variations in the strength of information flow exchanges...
November 1, 2017: Biomedical Optics Express
https://www.readbyqxmd.com/read/29184201/elucidating-the-underlying-components-of-food-valuation-in-the-human-orbitofrontal-cortex
#19
Shinsuke Suzuki, Logan Cross, John P O'Doherty
The valuation of food is a fundamental component of our decision-making. Yet little is known about how value signals for food and other rewards are constructed by the brain. Using a food-based decision task in human participants, we found that subjective values can be predicted from beliefs about constituent nutritive attributes of food: protein, fat, carbohydrates and vitamin content. Multivariate analyses of functional MRI data demonstrated that, while food value is represented in patterns of neural activity in both medial and lateral parts of the orbitofrontal cortex (OFC), only the lateral OFC represents the elemental nutritive attributes...
December 2017: Nature Neuroscience
https://www.readbyqxmd.com/read/29167639/disrupted-thalamus-white-matter-anatomy-and-posterior-default-mode-network-effective-connectivity-in-amnestic-mild-cognitive-impairment
#20
Thomas Alderson, Elizabeth Kehoe, Liam Maguire, Dervla Farrell, Brian Lawlor, Rose A Kenny, Declan Lyons, Arun L W Bokde, Damien Coyle
Alzheimer's disease (AD) and its prodromal state amnestic mild cognitive impairment (aMCI) are characterized by widespread abnormalities in inter-areal white matter fiber pathways and parallel disruption of default mode network (DMN) resting state functional and effective connectivity. In healthy subjects, DMN and task positive network interaction are modulated by the thalamus suggesting that abnormal task-based DMN deactivation in aMCI may be a consequence of impaired thalamo-cortical white matter circuitry...
2017: Frontiers in Aging Neuroscience
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