Abstract
Many complex systems, such as the brain, display large-scale coordinated interactions that create ordered patterns. Classically, such patterns have been studied using the framework of criticality, i.e., at a transition point between two qualitatively distinct patterns. This kind of system is generally characterized by a scale-invariant organization, in space and time, optimally described by a power-law distribution whose slope is quantified by an exponent α. The dynamics of these systems is characterized by alternating periods of activations, called avalanches, with quiescent periods. To maximize its efficiency, the system must find a trade-off between its stability and ease of propagation of activation, which is achieved by a branching process. It is quantified by a branching parameter σ defined as the average ratio between the number of activations in consecutive time bins. The brain is itself a complex system and its activity can be described as a series of neuronal avalanches. It is known that critical aspects of brain dynamics are modeled with a branching parameter σ = , and the neuronal avalanches distribution fits well with a power law distribution exponent α = -3/2. The aim of our work was to study a self-organized criticality system in which there was a change in neuronal circuits due to genetic causes. To this end, we have compared the characteristics of neuronal avalanches in a group of 10 patients affected by Rett syndrome, during an open-eye resting-state condition estimated using magnetoencephalography, with respect to 10 healthy subjects. The analysis was performed both in broadband and in the five canonical frequency bands. We found, for both groups, a branching parameter close to 1. In this critical condition, Rett patients show a lower distribution parameter α in the delta and broadband. These results suggest that the large-scale coordination of activity occurs to a lesser extent in RTT patients.
Highlights
Rett syndrome (RTT) is a severe neurodevelopmental disorder, characterized by clinically normal development for the first 12–18 months of life, when an overall arrest and regression of the psychomotor development begins
To demonstrate the robustness of the estimation of the branching parameter, we estimated the variance around sigma both when we split our dataset into two segments (Table 2) and when we divided it into three segments (Table 3)
The study originated from recent evidence showing that the dynamics of resting-state brain activity, measured using MEG, produces scale-invariant neuronal avalanches, suggesting that the critical state is a physiological condition that is optimal to the brain functioning
Summary
Rett syndrome (RTT) is a severe neurodevelopmental disorder, characterized by clinically normal development for the first 12–18 months of life, when an overall arrest and regression of the psychomotor development begins. The dysfunction of MeCP2 provokes multiple effects, such as impaired neuronal maturation, altered GABAergic signaling, and, more importantly, a local imbalance between neuronal excitation and inhibition at the circuit level (Pohodich and Zoghbi, 2015). All these molecular and circuital evidence are scarcely linked to the clinically evident deficits in higher cognitive functions. Effective coordination of largescale activity is considered necessary for the emergence of highlevel cognitive abilities All these features make RTT a potential model for studying how an alteration of the normal development process interferes with the activity of brain networks
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
