One of the collective behavior in complex system is phase transition. Critical point is between two phases, order phase and disorder phase. One of feature of criticality is high correlation in system. Because of high correlation between neurons, performance of brain is very good. For better understanding of brain function we should study the behavior of neurons and therefore we have investigated dynamic of neural avalanches. in this research , we have simulated the dynamics of neurons by using nonlinear integrated and fire model. In the simulation neurons potential changes according to this model and because a neuron in the brain fires, in this study we have defined a potential that when neuron reaches to this potential level, fire and then decrease to its first potential again(rest potential). Firing of neuron is along with increase of potential of another neurons, potential that exchanges between neurons called coupling. We can calculate neuron avalanche using number of neuron fires. Study of avanches help to understand whether neurons system perform criticality or not. Another useful parameter to study this issue, is power spectrum. Some experiments show that if avalanches and power spectrum have power low behavior, it means there is high correlation between neurons and we can say it is in critical point.
