Patients without heavy burdens of beta-amyloid plaques throughout their brains may still be vulnerable to Alzheimer’s disease and related pathologies, especially when localized deposits interfere with critical brain networks, researchers said here.  For most such patients, the traditional explanation has been that they have some other non-amyloid disease process to account for their neuropathology. But some researchers have wondered whether relatively low levels of beta-amyloid could still be toxic in some way.  The advent of PET imaging for beta-amyloid plaques, using tracers such as Pittsburgh Compound B (PiB), has made it possible to identify and study such individuals while still alive.  {read more here}