The Face Is An Entryway to The Self

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What happens in the brain when you seereally seea friend's smile or scowl

MICHAEL WOLOSCHINOW

The serial number of a human specimen is the face, that accidental and unrepeatable combination of features. Milan Kundera, Immortality,1988

Faces are the glue that holds us together and that gives us our identity. All of us but the visually impaired and blind are experts at recognizing people's identity, gender, age and ethnicity from looking at their faces. First impressions of attractiveness or competence take but a brief glimpse of somebody's face. Newly born infants already tend to fixate on faces. This bias also turns up in art. Paintings and movies are filled with faces staring at the viewer. Who can forget the endless close-ups of the feuding husband and wife in Ingmar Bergman's Cimmerian masterpiece Scenes from a Marriage?

Because recognizing a face is so vital to our social lives, it comes as no surprise that a lot of real estate in the cerebral cortexthe highly convoluted region that makes up the bulk of our brainis devoted to a task crucial to processing faces and their identity. We note whether someone looks our way or not. We discern emotional expressions, whether they register joy, fear or anger. Indeed, functional brain imaging has identified a set of adjacent regions, referred to as the fusiform face area (FFA), that are situated on the left and the right sides of the brain, at the bottom of the temporal lobe of the cerebral cortex. The FFA turns up its activity when subjects look at portraits or close-ups of faces or even when they just think about these images.

Two just published studies of the brain's visual networks, including the FFA, enlarge what we know about the physical basis of face perception. Both explore the unique access to the brain afforded by patients whose epileptic seizures have proved resistant to drugs. A surgical treatment finds the locations in the brain where the hypersynchronized activity that characterizes a seizure begins before spreading from its point of origin to engulf one or sometimes both hemispheres. If a single pointa focus where the seizure beginscan be found, it can be removed. After this procedure, a patient usually has significantly fewer seizuresand some remain seizure-free. To triangulate the location of the focus, neurosurgeons insert electrodes into the brain to monitor electrical activity that occurs during a seizure.

This clinical setup is the starting point for these two related but quite different studies that provide fascinating new details about whether the brain, like a camera, captures a literal rendition of a face or whether that image is synthesized in the brain by neurons in the cortex.

Prez 42 Morphs into Prez 43 To describe the first experiment, it is best to re-create what happened to the subjects. Keep your eyes steady on the red square in the top panel of the figure at the right for a fraction of a minute. Out of the corner of your eyes, you will see Bill Clinton on the left and his successor on the right. Now quickly shift your gaze to the bottom red square and note what you see. Don't hesitate. Just go for it! Most people see George W. Bush in the image on the left and his predecessor on the right. Yet when you compare the two photographs, you will realize that they are the same, a morphed image of the two presidents. Call this hybrid Clintush, the 42nd and a half president. This illusion is an instance of a general class of phenomena, called sensory adaptations, that are a hallmark of the mind. As you stare at the face, the neuronal mechanisms supporting its perception undergo a process of recalibration. The longer you stare at the same image, the more it changes. So when you look for a while at Clinton and then quickly glance at Clintush, you will perceive Bush, although this illusory perception quickly dies away, and the picture becomes ambiguous again.

How do the myriad nerve cells that make up the visual brain respond to such images? Neurons early on, say, in the eye, will respond to the chiaroscuro patterns of the photographs no matter what the brain the eye is attached to sees. That is, they register an image of the outside world. But somewhere in the upper reaches of the brain, there must be neurons that actively construct what the mind's eye sees when looking at Clintush. And depending on circumstances, that can be a picture of Bush or of Clinton.

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The Face Is An Entryway to The Self