Loss of neuronal network resilience precedes seizures and determines the ictogenic nature of interictal synaptic perturbations

The mechanisms of seizure emergence, and the role of brief interictal epileptiform discharges (IEDs) in seizure generation are two of the most important unresolved issues in modern epilepsy research. Our study shows that the transition to seizure is not a sudden phenomenon,but a slow process characterized by the progressive loss of neuronal network resilience. From a dynamical perspective, the slow transition is governed by the principles of critical slowing, a robust natural phenomenon observable in systems characterized by transitions between dynamical regimes. In epilepsy, this process is modulated by the synchronous synaptic input from IEDs. IEDs are external perturbations that produce phasic changes in the slow transition process and exert opposing effects on the dynamics of a seizure-generating network, causing either anti-seizure or pro-seizure effects. We show that the multifaceted nature of IEDs is defined by the dynamical state of the network at the moment of the discharge occurrence

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Modelling human choices: MADeM and decision‑making

Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)

Exploitation of contempory technologies in selected compositions by Tristan Murail

At first, the compositional process of Tristan Murail's Désintégrations and the compositional process of his Allégories are partially reconstructed. Consequently, an abstract model, which applies to both of these compositional processes, is defined. It is demonstrated, that not only the comparison of the theory of timbre with this abstract model, but also the concept "spectrum of sound" itself leads to the question, what is the relation between an auditory percept of a part of Désintégrations or Allégories and an auditory percept of the sound, whose spectrum served as starting point for this part. Further, it is also demonstrated, that this abstract model leads to the question, what is the relation between an auditory percept of a chord, whose constituent pitches are derived from an aggregate of frequencies, and an auditory percept of a sound, whose partials have frequencies that have been taken from the same aggregate. Finally, the designs of two experiments, whose purpose is to answer these two questions, are outlined and the possibility of implementation of these two experiments examined

Off key or off beat?

We explored whether the ordering of pitches according to their fit to a tonal context established by so-called probe-tone studies would generalize to isochronous rhythms presented in an analogous context. In an experiment modelled on the probe-tone studies we asked participants to choose which of two isochronous rhythms presented in a simultaneously sounding poly-rhythmical context they like better. We found a strong correlation between preference orderings of rhythms and pitches. This suggests that that the phenomenon of tonality relies on a generic mechanism and gives validity to recent studies explaining tonality and meter in terms of the same family of models