Integrated Calendar

Neuronal networks can generate complex patterns of activity that depend on membrane properties of individual neurons as well as on functional synapses. To decipher the impact of synaptic properties and connectivity on neuronal network behavior, we studied using a combination of electrophysiological recordings and the synaptic depression-facilitation model, the responses of neuronal ensembles from small (between 5-30 cells in a restricted sphere) and large (acute hippocampal slice) networks to single electrical stimulation.
Interestingly, in both cases, a single stimulus generated a synchronous long-lasting bursting activity. We characterized this activity in neuronal populations using electrophysiological recordings and we also extract the network time constant parameters using the mean-field model based on synaptic facilitation/depression. While the initial spikes triggered a reverberating network activity that lasted 2-5 seconds for small networks, it lasted only up to 300 milliseconds in slices, a phenomena that was also present in our simulations. We found here that the reverberation time has a bell shaped relation with the synaptic density. In addition, before reaching its maximum, this reverberation time increased sub-linearly with the network connectivity parameter.
We conclude that synaptic properties and the network connectivity shape the mean burst duration, which persists across various network scales. This synchronization is an inherent property of sufficiently connected neural networks based on synaptic depression and facilitation.

Abstract: We will consider different examples of flows on the beta-plane in a rotating tank . These flows include eddies, zonal jets and Rossby waves and are relevant to meso- and large-scale dynamics of the Earth's oceans and atmosphere. The flows are generated by a barotropic or baroclinic forcing either spatially localized or distributed over the domain. Laboratory (optical) altimetry is used to measure the surface elevation and to obtain the velocity fields of the flow, not unlike satellite altimetry used by oceanographers. The beta-plume mechanism will be discussed as a concept which unifies all these different flows.