Picturing the Brain

You may well have already heard about neuro images, a new blog from Neurophilosophy's Mo. As the name suggests, it's all about pictures of the brain. All of them are very pretty. Some are also pretty gruesome.

But images are, of course, more than decoration. There are dozens of ways of picturing the brain, each illuminating different aspects of neural function. Neuropathologists diagnose diseases by examining tissue under the microscope; using various stains you can visualize normal and abnormal cell types -

FDG-PET scans reveal metabolic activity in different areas, which can be used to diagnose tumors amongst much else -

Egaz Moniz, better known as the inventor of "psychosurgery", pioneered cerebral angiography, a technique for visualizing the blood vessels of the brain using x-rays (this is the view from below) -

And so on. However, for all too many cognitive neuroscientists - e.g. fMRI researchers - the only kind of brain images that matter are MRI scans, traditionally black-and-white with "activity" depicted on top in colour -

fMRI is a powerful technique. But there is much more to the brain than that. Even a casual glance down a microscope reveals that brain tissue is composed of a rich variety of cells, the most numerous of which, glia, do not transmit neural signals - they are not "brain cells" at all. And there are many different types of brain cells, which inhabit distinct layers of the cerebral cortex - the cortex has at least six layers in most places, and different things happen in each one.

The brain, in other words, is a living organ, not a grey canvas across which activity patterns occasionally flash. Of course, no-one denies this, but all too many neuroscientists forget it because in their day-to-day work all they see of the brain is what an MRI scan reveals. This is especially true for those scientists who came to fMRI from a psychology background, many of whom have never studied neurobiology.

Maybe researchers should have to spend a week with a scalpel cutting up an actual brain before they get allowed to use fMRI - this might help to guard against the kind of simplistic "Region X does Y" thinking that plagues the field.