TWO heads are better than one 鈥� particularly if you鈥檙e studying the brain activity underlying social interaction. The problem is that imaging technologies such as MRI have only been able to handle one brain at a time 鈥� until now. at Princeton University has developed the world鈥檚 first . The innovation allows the simultaneous imaging of the brain activity of two people lying in the same scanner.
Usually, a lone person lies inside a scanner鈥檚 narrow tunnel, cocooned by powerful magnets and radio-frequency coils which detect how hydrogen atoms in the body respond to magnetic fields, or how the flow of oxygenated blood changes as a result of brain activity. Although it is possible to squeeze two adults into most MRI machines 鈥� Willibrord Weijmar Schultz at the University of Groningen in the Netherlands famously scanned the bodies of couples as they copulated inside an MRI 鈥� attempting to scan both their brains at once would produce too fuzzy an image.
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So Lee designed a pair of coils that fits into a scanner, providing two distinct loops in which to place each participant鈥檚 head (see picture). He also fitted a window between the coils so participants can see one another. 鈥淭his opens up a new area of MRI,鈥� says , head of neuro-radiology at George Washington University Medical Center in Washington DC. 鈥淚 haven鈥檛 seen anything like this.鈥�
To test the scanner, Lee asked couples to lie facing one another and blink in unison. Brain activity in the fusiform gyrus 鈥� involved in facial recognition 鈥� was tightly correlated. Lee also asked couples to repeatedly embrace and release one another, and observed similarly synchronised brain activity. He announced his results in November 2010 at the Society for Neuroscience conference in San Diego, California.
鈥淚n close proximity, people tend to mimic each other in all kinds of ways, especially through non-verbal signals,鈥� says at the University of California, Los Angeles. 鈥淣ow we can examine brain activity of an intimate pair copying each other in real time. That hasn鈥檛 been done before.鈥�
at the University of Virginia in Charlottesville is also eager to test the device: 鈥淧eople distribute neural processing across multiple brains when solving problems,鈥� he says. 鈥淵ou essentially contract out part of a given problem to someone else鈥檚 mind. Lee鈥檚 work would give us the opportunity to see two brains reacting to a problem simultaneously.鈥�
at Stanford University in California says it remains unclear just how advantageous scanning people in the same machine will be compared with scanning people in different machines who are linked by video. He points out that if people move around too much inside a scanner, they disrupt the signal, so interactions may be limited to small gestures.
But Coan stresses the potency of even minor actions: 鈥淐ouples could hold each other or rub each other鈥檚 back,鈥� he says, 鈥渁nd simply having another human face inches from their own is a very powerful stimulus. With a little creativity, the sky鈥檚 the limit for figuring out how brains respond to each other.鈥�
