Talk by Dr. Jonas Ranft (CSN Virtual Seminar)

We hereby announce the next talk in 'CSN Virtual Seminar' series

Synchronization, stochasticity, and phase waves in neuronal networks with spatially-structured connectivity

Speaker: Dr. Jonas Ranft, Ecole Normale Supérieure & CNRS, Paris

Abstract
Oscillations in the beta/low gamma range (10–45 Hz) are observed in diverse neural structures. An intriguing example are beta oscillations in motor cortex during movement preparation in instructed-delay reaching tasks, which in primates have been shown to organize in different types of travelling waves. In the first part of this talk, I will present an effective rate model description of sparsely synchronized oscillations in excitatory-inhibitory (E-I) networks of spiking neurons, that have been supposed to underly such brain rhythms. This description allows us to investigate quantitatively the dynamical regimes of oscillatory E-I modules coupled by long-range excitation in the presence of fluctuations due to finite population sizes. I will show that on the one hand, these fluctuations tend to promote synchronization between different modules, while on the other hand, independent fluctuations on different modules tend to disrupt synchronization. From the rate-model equations we can derive analytical expressions for the correlation between modules that allow to quantitatively capture our simulations. More generally, stochastic dephasing of neighboring modules produces transient phase gradients and the transient appearance of phase waves. In the second part of the talk, I will then present how an extended, two-dimensional version of our model where we additionally consider synaptic kinetics, conduction delays, and input fluctuations can be calibrated to quantitatively reproduce statistics of LFP recordings in monkeys during an instructed-delay reaching task. Using this simple model of motor cortex, we show that the interplay of fluctuating inputs and spatially-structure connectivity can account for the observed statistics of different wave patterns in the experimental data. We find that global input fluctuations are correlated with the appearance of specific patterns, and that anisotropies in recurrent and/or input connections can lead to preferred directions for traveling waves. Different from previously proposed mechanistic explanations, the model suggests that traveling waves in motor cortex are the reflection of the dephasing by external inputs, putatively of thalamic origin, of an oscillatory activity that would otherwise be spatially synchronized by recurrent connectivity.

You can dial in using the following zoom room information:
https://zoom.us/j/99314955130?pwd=YXkvaW1wY2s2OHJsMFRWVDNtcERiUT09
Meeting ID: 993 1495 5130
Passcode: 4pM2Z8

Please, note that the event is going to be in hybrid format.