FENS Forum 2010 - Amsterdam

- Posters
To be on display from 8:00 to 13:15 in the morning and from 13:30 to 18:45 in the afternoon.
Poster sessions run from 09:30 to 13:15 in the morning and from 13:30 to 17:30 in the afternoon.
A one hour time block is dedicated to discussion with the authors (authors should be in attendance at their posters as from the time indicated.)
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First author: Battaglia, Demian (poster)

Poster board B4 - Tue 06/07/2010, 11:15 - Hall 1
Session 130 - Network interactions 1
Abstract n° 130.4
Publication ref.: FENS Abstr., vol.5, 130.4, 2010

Authors Battaglia D. (1, 2), Witt A. (1, 2), Geisel T. (1, 2) & Wolf F. (1, 2)
Addresses (1) Max Planck Institute for Dynamics and Self-organization, Goettingen, Germany; (2) Bernstein Center for Computational Neuroscience, Goettingen, Germany
Title Dynamic transitions in the effective connectivity of interacting cortical areas
Text Anatomic connections between cortical local areas constrain the spatio-temporal complexity of brain rhythms. Such structural connectivity does not however coincide with effective connectivity, related to the more elusive question "Which areas cause the activity of which others?". Effective connectivity is directed and task-phase dependent. Its fast changes are incompatible with the slow variation of anatomical connections in a mature brain and might be explained as dynamical transitions in the collective organization of neural activity. We consider here small network motifs of interacting cortical areas, modeled first as mean-field rate units and then as large populations of spiking neurons. Local couplings are mainly inhibitory while longer-range couplings are purely excitatory. All the interactions are delayed. Even when the structural networks are fully symmetric, varying the strength of local inhibition and the delays of local and long-range interactions generates oscillatory patterns which spontaneously break the symmetry under permutation of the areas. Areas leading in phase over laggard areas can be unambiguously pinpointed. The natural emergence of directionality in inter-areal communication is probed by analysing the time-series obtained from simulations by means of tools such as Granger causality or Transfer Entropy. Remarkably, for stronger inter-areal couplings, chaotic states emerge which amplify the asymmetries of the polyrhythms from which they originate. In such configurations, the firing rate of laggard areas undergoes significantly stronger and more irregular amplitude fluctuations than leading areas. Asymmetric chaotic states can be described as conditions of effective entrainment in which laggard areas are driven into chaos by the more periodic firing of leader areas. Fully symmetric structural networks can thus give thus rise to multiple alternative effective networks with reduced symmetry, in which the inter-areal flow of information is anisotropic. Transitions between different effective connectivities are thus achieved via transient perturbations of the dynamics without need for costly rearrangements of the structural connections.
Theme B - Excitability, synaptic transmission, network functions
Network interactions / Oscillations and synchrony

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