The human brain must mantain a balance of excitation of inhibition, of order and disorder. This is necessary for activity to neither explode (as in an epileptic seizure) nor die out. If, on average, one neuron elicits activity on more than one neuron, then this will lead to a chain reaction leading to a huge burst of activity, and the converse if less than one neuron is excited.

Together with Dr. Dante Chialvo (CONICET, Argentina) we study the dynamical properties of the brain at the critical point between the disorder and ordered phase, where this scenario is possible. We have found many tell-tale signs of criticality in fMRI recordings, such as a demonstration of scale-free avalanches (distributed with the same power-law exponent as their electrophysiological counterparts!). We also showed how a simple model at the critical point of a second order phase transition can reproduce many characteristic features of resting state fMRI recordings.

Hemodynamic avalanches spreading throughout the cortex.

Hemodynamic avalanches spreading throughout the cortex.

Journal references:

Tagliazucchi, E., Balenzuela, P., Fraiman, D., Chialvo, D. R. (2012). Criticality in large-scale brain fMRI dynamics unveiled by a novel point process analysis. Frontiers in Physiology.

Haimovici, A., Tagliazucchi, E., Balenzuela, P., Chialvo, D. R. (2013). Brain Organization into Resting State Networks Emerges at Criticality on a Model of the Human Connectome. Physical Review Letters.