Scientists preserve brains or body parts for various reasons. Sometimes the person had an illness that bears further study with more advanced tools than an age supplies; other times the brain in question powered an extraordinary intellect. The brains we'll be talking about belong more to the former, and scientists have found that studying canned gray matter can provide a history of human mental health.
George Sandusky, a pathologist at the Indiana University School of Medicine, found out that he had an untapped genetic gold mine in a collection at the Indiana Medical History Museum in Indianapolis: preserved human brains, many very old, including some dating as far back as the 1890s. A lot of the jarred brains shared a common trait, too, as they came from the autopsies of people who had a record of mental illness.
So, why would Sandusky want to coax out history's genetic mysteries from some canned head jelly? Well, besides the fact that autopsies aren't as widespread as they used to be (what with a smorgasbord of funeral options these days, from being launched into space or liquified), institutions that still do maintain brain banks for the purposes of study "guard them carefully," according to Popular Science. That, and we just didn't really have a good way to study old remains that have been preserved in celloidin solution, which coats a sample in a hard and rubbery film.
Sandusky and his team stumbled upon a good way (albeit a not-yet-peer-reviewed way) after they had already given up, actually, foiled so by the stubborn celloidin. The brain chunks were put in freezers for keeping, submerged in liquid nitrogen and maintained at -180 degrees Celsius. When the team returned to take another whack at it, they found the celloidin had beaded up and DNA data could be extracted from the samples..
Because of the brains available, the researchers are right now looking at how the data plugs into mental illness. A good majority of the brain bits in Sandusky's care are labeled "dementia praecox," which is an old timey way of saying schizophrenia — something that, while thought to be linked to specific genes, still eludes science in exact, clear terms. Terms which Sandusky's study could help define.