Via the Physics arXiv blog.
The first question is why biological systems should be nearly critical. What benets does operation at this special point in parameters pace provide for these systems? For birds, we have seen that criticality confers high susceptibility to external perturbations, and this enhanced reactivity endows them with a better defense mechanim against predators. Similarly, in the auditory system, being close to a bifurcation point allows for arbitrarily high gains and accurate frequency selectivity in response weak sounds.
In neural populations, the naive idea underlying the theory of branching processes makes criticality seem almost inevitable, a middle point between death and epilepsy. However, the function of neural networks is not only to be reactive, but also to carry and process complex information in a collective manner through its patterns of activity. The observation and analysis of metastable states, both in retinal acitivity analyzed within the maximum entropy framework  and in the activity of cortical slices analyzed with the theory of branching processes , suggest that criticality may be coupled to the explosion of these states, allowing for a wider set of coding options.