How scanning the brains of the dead improves the lives of the living
For thousands of years, direct studies of the human brain required the dead. The main method of study was dissection, which needed, rather inconveniently for the owner, physical access to their brain. Despite occasional unfortunate cases where the living brain was exposed on the battlefield or the surgeon’s table, corpses and preserved brains were the source of most of our knowledge. When brain scanning technologies were invented in the 20th century they allowed the structure and function of the brain to be shown in living humans for the first time. This was as important for neuroscientists as the invention of the telescope and the cadaver slowly faded into the background of brain research. But recently, scrutiny of the post-mortem brain has seen something of a revival, a resurrection you might say, as modern researchers have become increasingly interested in applying their new scanning technologies to the brains of the deceased.
Forensic pathologists have the job of working out the cause and manner of death to present as legal evidence and have been partly responsible for this curious full circle. One of their main jobs is the autopsy, where the pathologist examines the body, inside and out, to assess its condition at the point of death.
Although the traditional autopsy has many advantages, not least the microscopic examination of body tissue, there are drawbacks. One is that within some religions cutting up the dead body is seen as an infringement of human dignity and may delay burial beyond the customary period. The other is that an autopsy is a one-shot deal. If someone disagrees with the way it has been carried out or its interpretation, it is usually too late to do anything except re-examine photos or, on the rare occasions when they may have been kept, tissue samples.
As a result, there has been increasing interest in using medical technologies such as CT and MRI scans to create 3D images of dead bodies, which can be stored and referred back to, something known as a “virtopsy”. Forensically, these images can also be compared with the object suspected of causing the injury. The shape of a suspected murder weapon, let’s say a tyre iron, or the projected path of a bullet, can be digitally compared with the injury on the 3D scan to see how well it matches.
Physician Manuela Baglivo and her team at the Institute of Forensic Medicine in Zurich recently reviewed scientific studies on post-mortem imaging and described how the pervasiveness of fatal head injuries has led to a surge in studies involving brain scanning corpses over the past decade. They also note an increasing interest from other areas of medicine where post-mortem brain scanning is helping to understand the lethal effects of brain injury, such as strokes and internal bleeds, as a way of ultimately helping to save lives.
A growing number of studies are also looking at more subtle effects by comparing the size and shape of brain structures at death in people who were diagnosed with conditions such as schizophrenia or Alzheimer’s disease. It is still possible to use traditional techniques for completing these studies, such as a camera and a scalpel, or even more advanced approaches such as mechanically cutting the brain into micro-thin slices and digitally photographing each section, but using a standard brain scanner is quick, cheap and gives scientists the option of using the same software developed for analysing living scans.
But some of the most interesting neuroscience studies on the dead are not aimed at understanding mortality but are focused on tuning technologies for the living. One of the most popular brain imaging technologies, called functional magnetic resonance imaging or fMRI, involves detecting tiny differences in radio signals emitted from brain tissues and blood as their hydrogen molecules are manipulated by large magnetic fields.
Numerous difficulties can get in the way of reliably reading these signals and much of the analysis of fMRI data is focused on adjusting for possible errors. It’s not always clear, however, from where these inaccuracies arise and sometimes the effects of things such as body movement or breathing can be mistaken for changes in brain activity.
Dead people do little moving and even less breathing and so have been used as more placid stand-ins for living humans when tracking down difficulties. One of the first studies of its kind compared living humans, cadavers and synthetic dummies and found that a previously mysterious signal thought to arise from the brain was actually an issue with the scanner technology as it turned up regardless of what was tested. Another study tested out movement correction software by scanning the still brains of the deceased to ensure a baseline reading before artificially inducing and correcting controlled movements into the signal.
More recently, neuroscientist Andrea Antal and colleagues relied on the recently departed to test whether a type of commercially popular electrical brain stimulation was causing false positive readings during fMRI experiments. They found that if they applied the stimulation to their dead subjects they seemed to show brain activity where there was none, providing an important caution for those researching the technique on the living.
Perhaps it is not surprising that as we become an ageing population, the failed brain has become a growth area for scientific research. But contrary to our ideas of corpses as being part of an outdated science, the deceased have also begun to play a surprisingly active part in perfecting new technology.
[Image via AFP]