Microglia protect the brain. They are macrophages that engulf, eat up, bad stuff or pathogens: -
"We've been able to define, for the first time, a set of genes microglia use to sense their environment, which we are calling the microglial sensome," says Joseph El Khoury, MD, of the MGH Center for Immunology and Inflammatory Diseases and Division of Infectious Diseases, senior author of the study. "Identifying these genes will allow us to specifically target them in diseases of the central nervous system by developing ways to upregulate or downregulate their expression."-
http://medicalxpress.com/news/2013-11-genes-uniquely-brain-immune-cells.html-Need I note that genes are just big biochemical molecules. Sensing is done biochemically. The word 'sensing', implying neurological activity, should not ever carry that implication.