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See detailContrasting the role of Ih and ICaT currents in post-inhibitory rebound mechanisms in reciprocal-inhibitory networks
Dethier, Julie ULg; Drion, Guillaume ULg; Sepulchre, Rodolphe

Poster (2014, November 16)

Models with reciprocal inhibition are ubiquitous in the literature. For instance, common rhythmic motor behaviors produced by central pattern generators (CPGs) involve half-center oscillators, which ... [more ▼]

Models with reciprocal inhibition are ubiquitous in the literature. For instance, common rhythmic motor behaviors produced by central pattern generators (CPGs) involve half-center oscillators, which consist of two inhibitory neurons that are not endogenous oscillators, but produce rhythmic outputs when reciprocally connected (Marder & Calabrese 1996). Models of thalamocortical spindle oscillations also suggest that the rhythm originates from the thalamic reticular nucleus, which consists in interacting inhibitory nonoscillatory neurons (Wang & Rinzel 1992). [less ▲]

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See detailOscillations in the basal ganglia: illustration of a cellular effect at the network level
Dethier, Julie ULg; Drion, Guillaume ULg; Franci, Alessio et al

Poster (2013, June)

Parkinson’s disease (PD) is a neuro-degenerative pathology affecting the basal ganglia (BG), a set of small subcortical nervous system nuclei. The hallmark of the disease is a dopaminergic denervation of ... [more ▼]

Parkinson’s disease (PD) is a neuro-degenerative pathology affecting the basal ganglia (BG), a set of small subcortical nervous system nuclei. The hallmark of the disease is a dopaminergic denervation of the striatum, al- tering information patterns along movement-related ganglia-mediated path- ways in the brain. Severe motor symptoms result from the pathological state: tremor at rest, bradykinesia, akinesia, and rigidity. The transition to the disease state correlates with a switch in the firing mode of the neurons in the BG, from tonic pacemaker activity to burst firing. At the network level, macro-electrode recordings reveal excessive oscillations in the beta (8- 30Hz) frequency band. The oscillations generation mechanism and their functional role remain under debate. We propose a network model where a cellular mechanism controls the dynamical state of the network. In our model, the oscillatory state impacts the neural information processing prop- erties of the network. The network model predicts that a single decrease of the dopaminergic level in the parkinsonnian condition switches the network into an abnormal oscillatory dynamical and globally insensitive state. The brief dopaminergic increase prior to voluntary movements suppresses beta oscillations to drive the network to a conductive state to sensory processing and cognition. [less ▲]

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See detailImpacts of a unicellular mechanism on network behaviors
Dethier, Julie ULg; Drion, Guillaume ULg; Franci, Alessio et al

Conference (2013, March 26)

Parkinson’s disease (PD) is a neurodegenerative disorder af- fecting the basal ganglia (BG), a set of small subcortical nervous system nuclei. The hallmark of the disease is a dopaminergic denervation of ... [more ▼]

Parkinson’s disease (PD) is a neurodegenerative disorder af- fecting the basal ganglia (BG), a set of small subcortical nervous system nuclei. The hallmark of the disease is a dopaminergic denervation of the striatum—the input stage of the BG—altering information patterns along movement- related ganglia-mediated pathways in the brain. Severe mo- tor symptoms result from the pathological state: tremor at rest, bradykinesia—the slowness and impaired scaling of voluntary movement—and akinesia—the poverty of volun- tary movements. It is still unclear how dopamine depletion causes those motor symptoms. Experimental studies have shown that abnormally synchronized oscillatory activities— rhythmic bursting activity at the unicellular level and beta frequency band (from 8 to 30Hz) oscillations at the network level—emerge in PD at multiple levels of the BG-cortical loops and correlate with motor symptoms. The mechanisms underlying these pathological beta oscillations remain elu- sive. We propose that a cellular mechanism generates burst- ing activities and beta band oscillations at the network level. [less ▲]

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See detailA Balance Equation Determines a Switch in Neuronal Excitability
Franci, Alessio ULg; Drion, Guillaume ULg; Seutin, Vincent ULg et al

in PLoS Computational Biology (2013)

We use the qualitative insight of a planar neuronal phase portrait to detect an excitability switch in arbitrary conductance-based models from a simple mathematical condition. The condition expresses a ... [more ▼]

We use the qualitative insight of a planar neuronal phase portrait to detect an excitability switch in arbitrary conductance-based models from a simple mathematical condition. The condition expresses a balance between ion channels that provide a negative feedback at resting potential (restorative channels) and those that provide a positive feedback at resting potential (regenerative channels). Geometrically, the condition imposes a transcritical bifurcation that rules the switch of excitability through the variation of a single physiological parameter. Our analysis of six di erent published conductance based models always nds the transcritical bifurcation and the associated switch in excitability, which suggests that the mathematical predictions have a physiological rel- evance and that a same regulatory mechanism is potentially involved in the excitability and signaling of many neurons. [less ▲]

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See detailA novel phase portrait for neuronal excitability
Drion, Guillaume ULg; Franci, Alessio ULg; Seutin, Vincent ULg et al

in PLoS ONE (2012), 7(8),

Fifty years ago, FitzHugh introduced a phase portrait that became famous for a twofold reason: it captured in a physiological way the qualitative behavior of Hodgkin-Huxley model and it revealed the power ... [more ▼]

Fifty years ago, FitzHugh introduced a phase portrait that became famous for a twofold reason: it captured in a physiological way the qualitative behavior of Hodgkin-Huxley model and it revealed the power of simple dynamical models to unfold complex firing patterns. To date, in spite of the enormous progresses in qualitative and quantitative neural modeling, this phase portrait has remained a core picture of neuronal excitability. Yet, a major difference between the neurophysiology of 1961 and of 2011 is the recognition of the prominent role of calcium channels in firing mechanisms. We show that including this extra current in Hodgkin-Huxley dynamics leads to a revision of FitzHugh-Nagumo phase portrait that affects in a fundamental way the reduced modeling of neural excitability. The revisited model considerably enlarges the modeling power of the original one. In particular, it captures essential electrophysiological signatures that otherwise require non-physiological alteration or considerable complexification of the classical model. As a basic illustration, the new model is shown to highlight a core dynamical mechanism by which calcium channels control the two distinct firing modes of thalamocortical neurons. [less ▲]

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See detailAn Organizing Center in a Planar Model of Neuronal Excitability
Franci, Alessio ULg; Drion, Guillaume ULg; Sepulchre, Rodolphe ULg

in SIAM Journal on Applied Dynamical Systems (2012), 11(4), 1698-1722

The paper studies the excitability properties of a generalized FitzHugh-Nagumo model. The model differs from the purely competitive FitzHugh-Nagumo model in that it accounts for the effect of cooperative ... [more ▼]

The paper studies the excitability properties of a generalized FitzHugh-Nagumo model. The model differs from the purely competitive FitzHugh-Nagumo model in that it accounts for the effect of cooperative gating variables such as activation of calcium currents. Excitability is explored by unfolding a pitchfork bifurcation that is shown to organize five different types of excitability. In addition to the three classical types of neuronal excitability, two novel types are described and distinctly associated to the presence of cooperative variables. [less ▲]

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See detailM-type channels selectively control bursting in rat dopaminergic neurons
Drion, Guillaume ULg; Bonjean, Maxime; Waroux, Olivier ULg et al

in European Journal of Neuroscience (2010), 31

Detailed reference viewed: 123 (58 ULg)