The virus that causes shingles is just one of a number of pathogens that may be linked to brain conditions. Here are some of the other bugs scientists have under the microscope.

Nitric oxide (NO) is a gaseous signalling molecule that is involved in the regulation of the cardiovascular, immune and nervous systems ... GMP–protein kinase G system. If it is produced ...

Chronic pain can result from nervous-system overload that creates physical symptoms in response to repressed emotions, therapist Nicole Sachs says.