Giovanni Messuti — University of Salerno - INFN Napoli, Gruppo coll. SA #
Tuning the Brain to Criticality: Neuronal Avalanches and Cyclic Alternating Patterns during Sleep #
(Silvia Scarpetta, Niccolò Morisi, Carlotta Mutti, Nicoletta Azzi, Irene Trippi, Rosario Ciliento, Ilenia Apicella, Vincenzo Palmieri, Giovanni Messuti, Marianna Angiolelli, Fabrizio Lombardi, Liborio Parrino, Anna Elisabetta Vaudano) The human brain consists of billions of neurons, interacting in highly nonlinear ways. Neuronal avalanches are bursts of neuronal activity that propagate through the brain network in a cascading manner. Historically, collective emergent behavior has been observed both in vivo and in vitro in cortical networks, at rest. Recently, it has been shown that neuronal avalanches during sleep exhibit power-law distributions in size and duration, signature of scale invariance. There has been speculation about correlations between sleep and its role in tuning the brain to criticality, as deviations from power-law behavior have been observed in subjects under sleep deprivation. In this study, we record EEG of 10 healthy subjects during sleep. We confirm the scale invariant behavior of the avalanches’ sizes and duration during sleep, demonstrating also its robustness to the threshold defining the occurrence of an avalanche. We find the critical exponents and the scaling relations connecting their critical exponents in agreement with the one predicted in Mean Field Direct Percolation universality class. The investigation on the sleep structure revealed important correlations of avalanches occurrences with the Cyclic Alternating Pattern (CAP), a specific pattern in EEGs typically observed during the deeper phases of NREM sleep. This finding suggests the presence of a functional link between avalanche occurrence and occurrence of CAP phase A during NREM sleep. The large fluctuations involved in the CAP activation phase are a fingerprint of vicinity to criticality.  As a result, CAP cycles are a genuine hallmark of tuning to criticality during sleep.