Planery Talk: " Rhythms pattern activity and collective oscillations in neural structures: exploring the role of the different frequency bands"

FERNANDO MONTANI

Workshop; Ordinal methods: Concepts, applications, new developments and challenges; 2022

The multiple sensations experienced by our body are accompanied by exchanges of information in the form of electrical signals within the brain. These electrical signals can be waves, like the way radio waves are used to broadcast music from the transmitter to the receptors. In the brain, different areas can function as transmitters or receivers of signals depending on the situation. Neural oscillations, or brain waves, are rhythmic or repetitive patterns of neural activity in the cortex. The interaction between neurons can result in oscillations with a frequency different from the firing frequency of individual neurons that depends on the possible rules of synaptic strength between neurons. These neuronal oscillations are a fundamental mechanism that allows synchronization of neuronal activity within and between brain regions that facilitates precise temporal coordination of the neural processes underlying cognition, memory, perception, and behavior.Synchronization in neural networks has attracted a lot of attention in recent years, focusing on the type of transitions of different oscillations’ patterns in the network. Whether the transition could appear as a continuous or a burst it could depend on the structure of the network, as well as synaptic plasticity rules. We consider the effect of synaptic interaction as well as structural connectivity on the synchronization transition in network models, of regularly spiking neurons, with different neuronal rhythms. Synaptic strength depresses low activation and enhances high activation of postsynaptic neurons. Importantly, triplet spike dependent plasticity (STDP) has been shown to describe plasticity experiments that the classical STDP rule, based on spiking pairs, has failed to capture. We consider a triplet model of STDP that depends on the interactions of three synchronized spikes with a network of excitatory and inhibitory neurons that emulate the activity of the cortex. We study the dynamic evolution of the triplet model with STDP synchronization, contrasting it to a classical pairwise model. Then the electrical recordings in patients with refractory epilepsy is investigated to discern the underlying oscillatory mechanisms during the epileptic process. For this, neuronal activity is studied for basal (far from the seizure) and preictal (immediately before the seizure) periods through recordings of intracerebral electrodes implanted in patients to achieve a greater resolution of the local field potential. We explore how the different STDP models can reproduce the observed dynamics. The intrinsic dynamics of the two types of records is discerned by using a time windows analysis and studying the amplitude and phase couplings for each signal. The causality of these records is quantified through information theory tools and a symbolic method of analysis that accounts for the ordinal structure of the time series, showing an enhancing of information of brain oscillations in the range of high frequencies.