In a recent issue of Nature Neuroscience (a big scientific journal/magazine) scientists from Stanford University (California) and Brown University (Rhode Island) are showing off their latest discovery: the fusiform face area of the brain contains tons of smaller subunits that are used both for recognizing familiar faces and for telling the difference between other objects.
...Huh? So we know they're talking about the brain, but what does the rest of it mean? To understand, let's take a step back and look at the big picture:
Many functions of the human brain are as of yet unknown. This is not, of course, because of a lack of interest, but more likely because of the tremendous complexity of the way in which the human mind works. One of the many questions about the brain that scientists have been trying to answer is: how do you recognize the faces of people you know?
Early information on this subject came from studying patients that had had strokes (a "brain attack" that resulted in the death of some neurons or brain cells) or other head injuries. Studies by various neurologists and neuroscientists showed that damage to the brain in the occipital lobes (the back of the brain) could lead to a loss of depth perception or of the ability to see texture and colour. Other patients with injuries to the right posterior hemisphere (the back of the right side of the brain) developed what is called prosopagnosia (now there's a million dollar word, eh!), or the inability to recognize the faces of people they knew well, even though the rest of their brains were working normally.
Wouldn't it be odd if you knew you were talking to your closest friend or to your family but you couldn't tell it was them by looking at their face!
These discoveries lead to greater scientific curiosity with respect to facial recognition. However, for many years it was nearly impossible to study some of the more intricate ways that the brain functions because we couldn't see what was going on inside of the head. Since the 1970's computed tomography (CT scans) has been used to take snapshots of the brain. Later on, magnetic resonance imaging (MRI scans) techniques were developed in order to take a more detailed snapshot of the brain. These two techniques generate fantastic images of the anatomy of the brain but help a lot less with respect to seeing what the brain is actually doing.
Traditional CT and MRI scans are useful for seeing how the brain looks, not what the brain does.
The advent of a more specialized MRI, called functional MRI, that is able to look at the way the brain responds to different stimuli has made research into the what the brain is doing (instead of just what it looks like) much easier. Over the last 10 years scientists have used functional MRI to look at how we recognize familiar faces and how we tell them apart from other everyday objects. Another technique includes electrodes put directly into the brain (subdural electrodes) by neurosurgeons; these electrodes measure brain activity in patients with seizures and have also helped to study what the brain does. Implanted electrodes helped identify a specific region of the brain called the fusiform gyrus that generated loads of activity when patients saw familiar faces. Functional MRI then showed that the fusiform face area within the fusiform gyrus is more active when viewing photographs of faces instead of other inanimate objects.
Areas of high activity indicate regions of the brain that are likely involved in specific functions.
Today, more high-tech equipment, including functional MRI machines, and advanced computer software have enable neuroscientists to develop high-resolution functional MRI analyses to make lots of cool discoveries about what the brain is doing.
With all this in mind, let's get back to that publication from Nature Neuroscience that was mentioned at the beginning of this article.
The research group that published this manuscript has been using the high resolution imaging techniques that were described above, to better understand the fusiform face area. They found that this region of the brain can be divided into smaller functional units that have different roles. These subunits are all closely packed together within the fusiform face area and show different amounts of activity depending on whether a person sees a face or an object. So, where we thought there was one specific area of the brain for seeing faces only, these scientists have shown that there is a tightly knit group of different brain subunits all packed together. They seem to work independently depending on whether we are seeing a face or another object, but they may also work together to tell us that our brother is not the same person as our best friend or that our teacher is not the same as the tree we see when we're daydreaming out the window. Pretty interesting stuff, eh!
High resolution functional MRI images were used to show that the fusiform face area is involved both with facial recognition and distinguishing between objects.
This development is really exciting because it shows that with a closer look, using higher resolution pictures, we are making more and more discoveries about the way the brain works. As we learn more about what the brain is doing, doctors and scientists may then be able to use this information to treat patients with neurological diseases.
Bradley W, Daroff R, Fenichel G, Marsden C (editors). Neurology in Clinical Practice. 3rd ed. 2000, Buttermorth-Heinemann: USA.
Grill-Spector K, Sayres R, Ress D. 2006. High-resolution imaging reveals highly selective nonface clusters in the fusiform face area. Nature Neuroscience 9(9):1177-85 2006.
Kanwisher N, McDermott J, Chun M. 1997 The fusiform face area: a module in human extrastriate cortex specialized for face perception. Journal of Neuroscience 17:4302-4311.
Dr. Gofton completed her MSc in Pharmacology and then completed her medical schooling at Dalhousie University (Halifax, NS). Currently, she is living in London, ON, where she is doing her residency in Neurology.