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      Scaling of a Large-Scale Simulation of Synchronous Slow-Wave and Asynchronous Awake-Like Activity of a Cortical Model With Long-Range Interconnections

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          Cortical synapse organization supports a range of dynamic states on multiple spatial and temporal scales, from synchronous slow wave activity (SWA), characteristic of deep sleep or anesthesia, to fluctuating, asynchronous activity during wakefulness (AW). Such dynamic diversity poses a challenge for producing efficient large-scale simulations that embody realistic metaphors of short- and long-range synaptic connectivity. In fact, during SWA and AW different spatial extents of the cortical tissue are active in a given timespan and at different firing rates, which implies a wide variety of loads of local computation and communication. A balanced evaluation of simulation performance and robustness should therefore include tests of a variety of cortical dynamic states. Here, we demonstrate performance scaling of our proprietary Distributed and Plastic Spiking Neural Networks (DPSNN) simulation engine in both SWA and AW for bidimensional grids of neural populations, which reflects the modular organization of the cortex. We explored networks up to 192 × 192 modules, each composed of 1,250 integrate-and-fire neurons with spike-frequency adaptation, and exponentially decaying inter-modular synaptic connectivity with varying spatial decay constant. For the largest networks the total number of synapses was over 70 billion. The execution platform included up to 64 dual-socket nodes, each socket mounting 8 Intel Xeon Haswell processor cores @ 2.40 GHz clock rate. Network initialization time, memory usage, and execution time showed good scaling performances from 1 to 1,024 processes, implemented using the standard Message Passing Interface (MPI) protocol. We achieved simulation speeds of between 2.3 × 10 9 and 4.1 × 10 9 synaptic events per second for both cortical states in the explored range of inter-modular interconnections.

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          Most cited references 40

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          NEST (NEural Simulation Tool)

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            Spontaneous events outline the realm of possible sensory responses in neocortical populations.

            Neocortical assemblies produce complex activity patterns both in response to sensory stimuli and spontaneously without sensory input. To investigate the structure of these patterns, we recorded from populations of 40-100 neurons in auditory and somatosensory cortices of anesthetized and awake rats using silicon microelectrodes. Population spike time patterns were broadly conserved across multiple sensory stimuli and spontaneous events. Although individual neurons showed timing variations between stimuli, these were not sufficient to disturb a generally conserved sequential organization observed at the population level, lasting for approximately 100 ms with spiking reliability decaying progressively after event onset. Preserved constraints were also seen in population firing rate vectors, with vectors evoked by individual stimuli occupying subspaces of a larger but still constrained space outlined by the set of spontaneous events. These results suggest that population spike patterns are drawn from a limited "vocabulary," sampled widely by spontaneous events but more narrowly by sensory responses.
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              Fast global oscillations in networks of integrate-and-fire neurons with low firing rates.

              We study analytically the dynamics of a network of sparsely connected inhibitory integrate-and-fire neurons in a regime where individual neurons emit spikes irregularly and at a low rate. In the limit when the number of neurons --> infinity, the network exhibits a sharp transition between a stationary and an oscillatory global activity regime where neurons are weakly synchronized. The activity becomes oscillatory when the inhibitory feedback is strong enough. The period of the global oscillation is found to be mainly controlled by synaptic times but depends also on the characteristics of the external input. In large but finite networks, the analysis shows that global oscillations of finite coherence time generically exist both above and below the critical inhibition threshold. Their characteristics are determined as functions of systems parameters in these two different regions. The results are found to be in good agreement with numerical simulations.

                Author and article information

                Front Syst Neurosci
                Front Syst Neurosci
                Front. Syst. Neurosci.
                Frontiers in Systems Neuroscience
                Frontiers Media S.A.
                23 July 2019
                : 13
                1INFN, Sezione di Roma , Rome, Italy
                2PhD Program in Behavioural Neuroscience, “Sapienza” University , Rome, Italy
                3National Center for Radiation Protection and Computational Physics, Istituto Superiore di Sanità , Rome, Italy
                4Systems Neuroscience, IDIBAPS , Barcelona, Spain
                5Department of Life and Medical Sciences, ICREA , Barcelona, Spain
                Author notes

                Edited by: Preston E. Garraghty, Indiana University Bloomington, United States

                Reviewed by: Sacha Jennifer van Albada, Julich Research Centre, Germany; Sergio E. Lew, University of Buenos Aires, Argentina

                *Correspondence: Elena Pastorelli elena.pastorelli@ 123456roma1.infn.it
                Copyright © 2019 Pastorelli, Capone, Simula, Sanchez-Vives, Del Giudice, Mattia and Paolucci.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                Page count
                Figures: 9, Tables: 3, Equations: 4, References: 50, Pages: 16, Words: 11031
                Funded by: Istituto Superiore di Sanità 10.13039/501100004008
                Funded by: Institució Catalana de Recerca i Estudis Avançats 10.13039/501100003741
                Funded by: Instituto Nazionale di Fisica Nucleare 10.13039/501100004007
                Original Research


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