Search results for "connectivity"
showing 10 items of 246 documents
Multi-band SWIFT enables quiet and artefact-free EEG-fMRI and awake fMRI studies in rat
2020
Functional magnetic resonance imaging (fMRI) studies in animal models provide invaluable information regarding normal and abnormal brain function, especially when combined with complementary stimulation and recording techniques. The echo planar imaging (EPI) pulse sequence is the most common choice for fMRI investigations, but it has several shortcomings. EPI is one of the loudest sequences and very prone to movement and susceptibility-induced artefacts, making it suboptimal for awake imaging. Additionally, the fast gradient-switching of EPI induces disrupting currents in simultaneous electrophysiological recordings. Therefore, we investigated whether the unique features of Multi-Band SWeep…
Information decomposition of multichannel EMG to map functional interactions in the distributed motor system
2019
AbstractThe central nervous system needs to coordinate multiple muscles during postural control. Functional coordination is established through the neural circuitry that interconnects different muscles. Here we used multivariate information decomposition of multichannel EMG acquired from 14 healthy participants during postural tasks to investigate the neural interactions between muscles. A set of information measures were estimated from an instantaneous linear regression model and a time-lagged VAR model fitted to the EMG envelopes of 36 muscles. We used network analysis to quantify the structure of functional interactions between muscles and compared them across experimental conditions. Co…
Pattern analyses reveal separate experience-based fear memories in the human right Amygdala
2017
Learning fear via the experience of contingencies between a conditioned stimulus (CS) and an aversive unconditioned stimulus (US) is often assumed to be fundamentally different from learning fear via instructions. An open question is whether fear-related brain areas respond differently to experienced CS–US contingencies than to merely instructed CS–US contingencies. Here, we contrasted two experimental conditions where subjects were instructed to expect the same CS–US contingencies while only one condition was characterized by prior experience with the CS–US contingency. Using multivoxel pattern analysis of fMRI data, we found CS-related neural activation patterns in the right amygdala (but…
The chronnectome of musical beat
2020
Keeping time is fundamental for our everyday existence. Various isochronous activities, such as locomotion, require us to use internal timekeeping. This phenomenon comes into play also in other human pursuits such as dance and music. When listening to music, we spontaneously perceive and predict its beat. The process of beat perception comprises both beat inference and beat maintenance, their relative importance depending on the salience of beat in the music. To study functional connectivity associated with these processes in a naturalistic situation, we used functional magnetic resonance imaging to measure brain responses of participants while they were listening to a piece of music contai…
Resonance of cortico-cortical connections of the motor system with the observation of goal directed grasping movements
2010
Goal directed movements require the activation of parietal, premotor and primary motor areas. In monkeys, neurons of these areas become active also during the observation of movements performed by others, especially for coding the goal of the action (mirror system). Using bifocal transcranial magnetic stimulation (TMS) in healthy subjects, we tested whether the observation of goal directed reach to grasp actions may lead to specific changes in the short-latency connections linking key areas of the mirror system, such as the anterior intraparietal cortex (AIP) and the ventral premotor cortex (PMv), with the primary motor cortex (M1). We found that AIP-M1 and PMv-M1 cortico-cortical interacti…
In vivo definition of parieto-motor connections involved in planning of grasping movements
2010
We combined bifocal transcranial magnetic stimulation (TMS) and diffusion tensor imaging (DTI) tractography to investigate in humans the contribution of connections originating from different parietal areas in planning of different reaching to grasp movements. TMS experiments revealed that in the left hemisphere functional connectivity between the primary motor cortex (M1) and a portion of the angular gyrus (AG) close to the caudal intraparietal sulcus was activated during early preparation of reaching and grasping movements only when the movement was made with a whole hand grasp (WHG) towards objects in contralateral space. In contrast, a different pathway, linking M1 with a part of the su…
Hyperexcitability of parietal-motor functional connections in the intact left-hemisphere of patients with neglect
2008
Hemispatial neglect is common after unilateral brain damage, particularly to perisylvian structures in the right-hemisphere (RH). In this disabling syndrome, behaviour and awareness are biased away from the contralesional side of space towards the ipsilesional side. Theoretical accounts of this in terms of hemispheric rivalry have speculated that the intact left-hemisphere (LH) may become hyper-excitable after a RH lesion, due to release of inhibition from the damaged hemisphere. We tested this directly using a novel twin-coil transcranial magnetic stimulation (TMS) approach to measure excitability within the intact LH of neglect patients. This involved applying a conditioning TMS pulse ove…
Maturation changes the excitability and effective connectivity of the frontal lobe : A developmental TMS-EEG study
2019
The combination of transcranial magnetic stimulation with simultaneous electroencephalography (TMS–EEG) offers direct neurophysiological insight into excitability and connectivity within neural circuits. However, there have been few developmental TMS–EEG studies to date, and they all have focused on primary motor cortex stimulation. In the present study, we used navigated high‐density TMS–EEG to investigate the maturation of the superior frontal cortex (dorsal premotor cortex [PMd]), which is involved in a broad range of motor and cognitive functions known to develop with age. We demonstrated that reactivity to frontal cortex TMS decreases with development. We also showed that although fron…
On the approximability of the range assignment problem on radio networks in presence of selfish agents
2005
AbstractWe consider the range assignment problem in ad-hoc wireless networks in the context of selfish agents: A network manager aims to assigning transmission ranges to the stations in order to achieve strong connectivity of the network within a minimal overall power consumption. Station is not directly controlled by the manager and may refuse to transmit with a certain transmission range because it might be costly in terms of power consumption.We investigate the existence of payment schemes which induce the stations to follow the decisions of a network manager in computing a range assignment, that is, truthful mechanisms for the range assignment problem. We provide both positive and negat…
Robust estimation of partial directed coherence by the vector optimal parameter search algorithm
2009
We propose a method for the accurate estimation of Partial Directed Coherence (PDC) from multichannel time series. The method is based on multivariate vector autoregressive (MVAR) model identification performed through the recently proposed Vector Optimal Parameter Search (VOPS) algorithm. Using Monte Carlo simulations generated by different MVAR models, the proposed VOPS algorithm is compared with the traditional Vector Least Squares (VLS) identification method. We show that the VOPS provides more accurate PDC estimates than the VLS (either overall and single-arc errors) in presence of interactions with long delays and missing terms, and for noisy multichannel time series. ©2009 IEEE.