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Dietmar PLENZ"Neuronal Avalanches in the Cortex"

Abstract :


Complex systems, when poised near a critical point of a phase transition between order and disorder, exhibit scale-free, power law dynamics. Critical systems are highly adaptive and flexibly process and store information, which prompted the conjecture that the cortex might operate at criticality. This view is supported by the recent discovery of neuronal avalanches in superficial layers of cortex. The spatiotemporal, synchronized activity patterns of avalanches form a scale-free organization that spontaneously emerges in vitro as well as in vivo in the anesthetized rat and awake monkeys. Avalanches are established at the time of superficial layer differentiation, require balanced fast excitation and inhibition, and are regulated via an inverted-U profile of NMDA/dopamine-D1 interaction. Neuronal synchronization in the form of avalanches naturally incorporates driven conditions such as found in nested theta/gamma-oscillations. Neuronal avalanches also pose a general stochastic framework that for sequential activations similar to synfire chains. Importantly, a single avalanche is not an isolated network event, but rather its specific occurrence in time, its spatial spread, and overall size is part of an elementary organization of the dynamics that is described by three fundamental power laws. Overall, these results suggest that neuronal avalanches indicate a critical network dynamics at which the cortex gains universal properties found at criticality. These properties constitute a novel framework that allow for a precise quantification of cortex function such as the absolute discrimination of pathological from non-pathological synchronization, and the identification of maximal dynamic range for input-output processing.


Selected publications

Spontaneous cortical activity in awake monkeys composed of neuronal avalanches.Petermann T, Thiagarajan TC, Lebedev MA, Nicolelis MA, Chialvo DR, Plenz D. Proc Natl Acad Sci U S A. 2009 Aug 26. [Epub ahead of print]   

Efficient network reconstruction from dynamical cascades identifies small-world topology of neuronal avalanches.Pajevic S, Plenz D.PLoS Comput Biol. 2009 Jan;5(1):e1000271. Epub 2009 Jan 30.
    
Neuronal avalanches organize as nested theta- and beta/gamma-oscillations during development of cortical layer 2/3.Gireesh ED, Plenz D. Proc Natl Acad Sci U S A. 2008 May 27;105(21):7576-81. Epub 2008 May 22.