Summary

Proceedings of the 2012 International Symposium on Nonlinear Theory and its Applications

2012

Session Number:C1L-B

Session:

Number:563

Modulating excitability in the cortical network: impact on emergent activity and traveling waves

M.V. Sanchez-Vives,  Maurizio Mattia,  

pp.563-565

Publication Date:

Online ISSN:2188-5079

DOI:10.15248/proc.1.563

PDF download (1005KB)

Recurrent connections within the neurons of the cerebral cortex network result in the spontaneous temporal organization of activity into different rhythms [1]. Slow (around or below 1 Hz) rhythms also propagate across the network [2] This is the case even in isolated pieces of the cortical network, or in vitro maintained cortical slices, where both slow [3] and fast oscillations [4] are also spontaneously generated and where slow waves propagate at an average speed of 10 mm/s [3]. Interestingly, cortical slices lack any inputs from other brain areas, thus representing what the synaptic reverberation within the isolated cortical network can autonomously generate. In order for this rhythmic patterns to occur, it is important that there is enough excitability in the network such that spontaneous firing takes place. Given that such excitability exists, network reverberations nonlinearly sustained by a strong synaptic coupling and an activity-dependent fatigue mechanism result into rhythmic oscillations. Not only a certain level of excitability is necessary for the rhythmic activity to occur, but the level of network excitability is then an important factor to sculpt the emergent activity structure. Here we will discuss the impact of different experimental strategies that result in a change of the excitability of the cortical network: changes in the inhibitory/excitatory balance [5, 6], in temperature [7] or different levels of anaesthesia. Furthermore, different cortical areas exhibit different excitability levels [8]. We find that changes in excitability lead to an intrinsic anticorrelation between the periods of activity (Up states) and silence (Down states) of each wave cycle. It also affects changes in the distribution of the accessible frequencies of the rhythms. Our experimental observations are compared against a model of attractor dynamics with activity-dependent self-inhibition [5]. We find that the system dynamics is set on a boundary of the parameter space, such that it can display a wide spectrum of dynamical regimes and timescales.

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