Synchrony, metastability, dynamic integration, and competition in the spontaneous functional connectivity of the human brain

Available online 3 June 2019.The human brain is functionally organized into large-scale neural networks that are dynamically interconnected. Multiple short-lived states of resting-state functional connectivity (rsFC) identified transiently synchronized networks and cross-network integration. However, little is known about the way brain couplings covary as rsFC states wax and wane. In this magnetoencephalography study, we explore the synchronization structure among the spontaneous interactions of well-known resting-state networks (RSNs). To do so, we extracted modes of dynamic coupling that reflect rsFC synchrony and analyzed their spatio-temporal features. These modes identified transient, sporadic rsFC changes characterized by the widespread integration of RSNs across the brain, most prominently in the β band. This is in line with the metastable rsFC state model of resting-state dynamics, wherein our modes fit as state transition processes. Furthermore, the default-mode network (DMN) stood out as being structured into competitive cross-network couplings with widespread DMN-RSN interactions, especially among the β-band modes. These results substantiate the theory that the DMN is a core network enabling dynamic global brain integration in the β band.This work was supported by the Action de Recherche Concert ee (ARC Consolidation 2015–2019, “Characterization of the electrophysiological bases, the temporal dynamics and the functional relevance of resting state network” attributed to X.D.T.) and by the research convention “Les Voies du Savoir” (Fonds Erasme, Brussels, Belgium). M.B. benefited from the program Attract of Innoviris (grant 2015-BB2B-10), the Spanish Ministry of Economy and Competitiveness (grant PSI2016-77175-P), and theMarie Skłodowska-Curie Action of the European Commission (grant 743562). M.V.G. and G.N.were supported by the Fonds Erasme. N.C. benefited from a research grant from the ARC Consolidation (2014–2017, “Characterization of the electrophysiological bases, the temporal dynamics and the functional relevance of resting state network” attributed to X.D.T.) and from the Fonds Erasme (research convention “Les Voies du Savoir”). X.D.T. is Post-doctorate Clinical Master Specialist at the Fonds de la Recherche Scientifique (F.R.S.-FNRS, Brussels, Belgium). The MEG project at the CUB – H^opital Erasme is financially supported by the Fonds Erasme (research convention “Les Voies du Savoir”)

The Use of a Robot to Insert an Electrode Array of Cochlear Implants in the Cochlea: A Feasibility Study and Preliminary Results.

peer reviewed[en] INTRODUCTION: Cochlear implants (CIs) are commonly used for the rehabilitation of profound bilateral hearing loss. However, patients with substantial residual acoustic hearing are potential CI candidates. Because of both improvements in technology and advancements in surgical techniques, it may be possible to preserve hearing to some extent. For more than a decade, it has been suggested that robots are used to perform middle ear surgery. We evaluated the use of the RobOtol® otologic robot specifically to insert CI electrodes into the inner ear. METHODS: CI surgery with the conventional approach was performed under general anesthesia. The MED-El Flex 24-electrode array was inserted using RobOtol®. Video recordings were used to calculate the speed of insertion. The positions of the electrodes were evaluated using a cone beam CT. All subjects underwent pure-tone audiometry tests before and after surgery, and the pure-tone average (PTA) was calculated from 250 to 4,000 Hz. RESULTS: The robot inserted implants in 5 patients, and complete insertion of the electrode array was achieved. The speed of insertion of the electrode array was 0.88 ± 0.12 mm/s. The mean loss of the PTA for 5 frequencies (250, 500, 1,000, 2,000, and 4,000 Hz) was 13.60 ± 7.70 dB. Only 1 patient showed a loss of the PTA by >20 dB. For these 5 patients, the cone beam CT findings showed that all the electrode arrays were in the tympanic ramp and had a grade of 0. The results were compared with those obtained from a cohort of 17 patients who underwent manual implantation of a MED-El Flex 24-electrode array. CONCLUSION: To minimize disturbance to the cochlea while atraumatic electrode arrays are inserted, electrodes can be inserted at a constant, slow speed in the inner ear with the assistance of the RobOtol® robot in a normal clinical surgical setting

Resting state fast brain dynamics predict interindividual variability in motor performance

Motor learning features rapid enhancement during practice then offline post-practice gains with the reorganization of related brain networks. We hypothesised that fast transient, sub-second variations in magnetoencephalographic (MEG) network activity during the resting-state (RS) reflect early learning-related plasticity mechanisms and/or interindividual motor variability in performance. MEG RS activity was recorded before and 20 min after motor learning. Hidden Markov modelling (HMM) of MEG power envelope signals highlighted 8 recurrent topographical states. For two states, motor performance levels were associated with HMM temporal parameters both in pre- and post-learning resting-state sessions. However, no association emerged with offline changes in performance. These results suggest a trait-like relationship between spontaneous transient neural dynamics at rest and interindividual variations in motor abilities. On the other hand, transient RS dynamics seem not to be state-dependent, i.e. modulated by learning experience and reflect neural plasticity, at least on the short timescale.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Motor learning- and consolidation-related resting state fast and slow brain dynamics across wake and sleep

Motor skills dynamically evolve during practice and after training. Using magnetoencephalography, we investigated the neural dynamics underpinning motor learning and its consolidation in relation to sleep during resting-state periods after the end of learning (boost window, within 30 min) and at delayed time scales (silent 4 h and next day 24 h windows) with intermediate daytime sleep or wakefulness. Resting-state neural dynamics were investigated at fast (sub-second) and slower (supra-second) timescales using Hidden Markov modelling (HMM) and functional connectivity (FC), respectively, and their relationship to motor performance. HMM results show that fast dynamic activities in a Temporal/Sensorimotor state network predict individual motor performance, suggesting a trait-like association between rapidly recurrent neural patterns and motor behaviour. Short, post-training task re-exposure modulated neural network characteristics during the boost but not the silent window. Re-exposure-related induction effects were observed on the next day, to a lesser extent than during the boost window. Daytime naps did not modulate memory consolidation at the behavioural and neural levels. These results emphasise the critical role of the transient boost window in motor learning and memory consolidation and provide further insights into the relationship between the multiscale neural dynamics of brain networks, motor learning, and consolidation.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Microstates and power envelope hidden Markov modeling probe bursting brain activity at different timescales.

State modeling of whole-brain electroencephalography (EEG) or magnetoencephalography (MEG) allows to investigate transient, recurring neurodynamical events. Two widely-used techniques are the microstate analysis of EEG signals and hidden Markov modeling (HMM) of MEG power envelopes. Both reportedly lead to similar state lifetimes on the 100 ms timescale, suggesting a common neural basis. To investigate whether microstates and power envelope HMM states describe the same neural dynamics, we used simultaneous MEG/EEG recordings at rest and compared the spatial signature and temporal activation dynamics of microstates and power envelope HMM states obtained separately from EEG and MEG. Results showed that microstates and power envelope HMM states differ both spatially and temporally. Microstates reflect sharp events of neural synchronization, whereas power envelope HMM states disclose network-level activity with 100-200 ms lifetimes. Further, MEG microstates do not correspond to the canonical EEG microstates but are better interpreted as split HMM states. On the other hand, both MEG and EEG HMM states involve the (de)activation of similar functional networks. Microstate analysis and power envelope HMM thus appear sensitive to neural events occurring over different spatial and temporal scales. As such, they represent complementary approaches to explore the fast, sub-second scale bursting electrophysiological dynamics in spontaneous human brain activity.info:eu-repo/semantics/publishe

Modulation des performances en mémoire de travail par le polymorphisme du gène COMT chez des enfants TDA/H

info:eu-repo/semantics/nonPublishe

Ethmoid schwannoma: about the management of a rare tumor of sinonasal cavities manifested by an orbital complication

editorial reviewedIntroduction: To report a rare sinonasal tumor initially manifesting by orbital cellulitis with impaired oculomotricity, and to and to take stock of the management methods proposed in the literature. Case presentation: Case report of a 72 year old patient presenting in ophthalmology emergency department with acute orbital cellulitis. Computed tomography revealed an ethmoidal mass associated with frontoethmoidal muco-pyocele. It was fully endoscopically removed and pathological diagnosis of ethmoid schwannoma has been made. Magnetic resonance imaging after 4 months showed no sign of recurrence. Discussion: The patient presented with an acute orbital cellulitis with acute loss of visual acuity and impaired oculomotricity within 24 hours associated with fever and local pain. There were no symptoms before this event. Tomodensitometry showed a large heterogeneous tumor arising from the anterior ethmoid sinus and extending to the frontoethmoidal recess and the orbital cavity with lamination of lamina papyracea. The tumor was removed by endonasal radical excision. The final pathological analysis revealed benign schwannoma. There was no sign of recurrence nor late complication during the 10 months follow up. Schwannomas of the nasal cavities are rare tumours but must be mentioned among the differential diagnoses of endonasal and endosinusal masses with sometimes orbital complications. Depending on the location and extension, endoscopic resection is a valid strategy

Comparing MEG and high-density EEG for intrinsic functional connectivity mapping

info:eu-repo/semantics/publishe

Identification précoce de l’encéphalopathie associée au sepsis: quels liens avec le devenir cognitif à court terme ?

info:eu-repo/semantics/nonPublishe

Ethmoid Schwannoma: about the management of a rare tumor of sinonasal cavities manifested by an orbital complication

editorial reviewedIntroduction: To report a rare sinonasal tumor initially manifesting by orbital cellulitis with impaired oculomotricity, and to and to take stock of the management methods proposed in the literature. Case presentation: Case report of a 72 year old patient presenting in ophthalmology emergency department with acute orbital cellulitis. Computed tomography revealed an ethmoidal mass associated with frontoethmoidal muco-pyocele. It was fully endoscopically removed and pathological diagnosis of ethmoid schwannoma has been made. Magnetic resonance imaging after 4 months showed no sign of recurrence. Discussion: The patient presented with an acute orbital cellulitis with acute loss of visual acuity and impaired oculomotricity within 24 hours associated with fever and local pain. There were no symptoms before this event. Tomodensitometry showed a large heterogeneous tumor arising from the anterior ethmoid sinus and extending to the frontoethmoidal recess and the orbital cavity with lamination of lamina papyracea. The tumor was removed by endonasal radical excision. The final pathological analysis revealed benign schwannoma. There was no sign of recurrence nor late complication during the 10 months follow up. Schwannomas of the nasal cavities are rare tumours but must be mentioned among the differential diagnoses of endonasal and endosinusal masses with sometimes orbital complications. Depending on the location and extension, endoscopic resection is a valid strategy