The Brain's Bat Signal

Mo Costandi writes on cleanup in the brain.
Microglia are the brain's resident security guards, surveilling the organ for damage and then crawling to the injury site to engulf dead neurons. Exactly how they detect problems was unclear, but researchers now show that they respond to an SOS signal from dying cells that is relayed throughout the brain. The finding may have implications for the treatment of Alzheimer's and other neurodegenerative diseases. 
Rest of article here with cool video;
http://news.sciencemag.org/sciencenow/2012/05/the-brains-bat-signal.html?ref=hp
His blog here with more on injured neurons;
 http://www.guardian.co.uk/science/neurophilosophy/2012/may/26/1