Flap its wing in the Brazilian rainforest, trigger a hurricane in the Gulf of Mexico...

This is the classic example of how small perturbations in a complex system poised near chaos can have dramatic effects throughout the entire system. The brain is certainly a complex system, although still minimally understood, so discovering physical evidence of the theoretical characteristcs of complex systems is quite exciting.

Researchers from the Howard Hughes Medical Institute lead by Yang Dan of the University of California, Berkeley have presented evidence of a complex system in an anesthetized rat brain. They tried to stimilate a single cortical brain cell and then monitor the change in global neuronal activity elsewhere in the brain.

And global change there was. Each neuron can have thousands of interconnections, so the structural network is amazingly complicated. However, the system can be resting in a state that if the network activity just crosses a certain threshold, then the entire system can undergo what might be compared to a phase transition. And the hurricane can begin to form in the brain.