Tatiana and Krista Hogan, age 4, are joined at the head — medical term craniopagus — a 1 in 2,500,000 event only a few survive. But they have something that makes them even more distinct, even in the annals of medical literature; brain images show an attenuated line stretching between their two brains, what Dr. Douglas Cochrane of British Columbia Children’s Hospital called a thalamic bridge, because he believes it links the thalamus of one girl to the thalamus of her sister.
The thalamus is a kind of switchboard, a two-lobed organ that filters most sensory input and has long been thought to be essential in the neural loops that create consciousness.
Since the thalamus functions as a relay station, doctors believe it is entirely possible that the sensory input that one girl receives could somehow cross that bridge into the brain of the other. One girl drinks, another girl feels it. Joined at the head, they share a neural bridge, but may also share their mind.
Could Conjoined Twins Share a Mind? - Susan Dominus, New York Times Magazine
