title: Exploring the spectrum of dynamical regimes and timescales in spontaneous cortical activity.
abstract: Rhythms at slow (<1 Hz) frequency of alternating Up and Down states occur during slow-wave sleep states, under deep anaesthesia and in cortical slices of mammals maintained in vitro. Such spontaneous oscillations result from the interplay between network reverberations nonlinearly sustained by a strong synaptic coupling and a fatigue mechanism inhibiting the neurons firing in an activity-dependent manner. Varying pharmacologically the excitability level of brain slices we exploit the network dynamics underlying slow rhythms, uncovering an intrinsic anticorrelation between Up and Down state durations. Besides, a non-monotonic change of Down state duration is also observed, which shrinks the distribution of the accessible frequencies of the slow rhythms. Attractor dynamics with activity-dependent self-inhibition predicts a similar trend even when the system excitability is reduced, because of a stability loss of Up and Down states. Hence, such cortical rhythms tend to display a maximal size of the distribution of Up/Down frequencies, envisaging the location of the system dynamics on a critical boundary of the parameter space. This would be an optimal solution for the system in order to display a wide spectrum of dynamical regimes and timescales.
authors.affiliation: Istituto Superiore di Sanità, viale Regina Elena 299, 00161 Rome, Italy ; Istituto Superiore di Sanità, viale Regina Elena 299, 00133 Rome, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Mattia
authors.forename: Maria V
authors.initials: MV
authors.lastname: Sanchez-Vives
keywords: Bifurcation analysis; Cortical rhythms; IF neuron networks; Mean-field theory; Relaxation oscillators; Slow oscillations; Up and Down states