Krista and Tatiana Hogan are in many ways normal 5-year old twin girls. They like to play with their puppies and watch Dora the Explorer. However, they were born conjoined at the head; their two skulls merge together toward the top. They were introduced to the world in a National Geographicdocumentary and were the subject of a New York Times article last year that detailed their everyday lives, in addition to some of their unique features.
In addition to connected skulls, the girls’ brains also have a connection that is apparently unique in the history of medicine. Called a “thalamic bridge” by their neurosurgeon Douglas Cochrane, it shows up clearly in brain images taken of the two. This connection, along with the massive amount of connected skull and other tissue, has ruled out any prospect of attempting to separate them.
Cochrane believes that this special brain bridge allows events that are perceived by one of the twins to also travel to the brain of the other. When they appeared on a recent episode of the daytime talk show, Anderson Cooper, as Krista avidly consumed some ketchup, something she loves, Tatiana, who hates ketchup, made a horrible face. When the Times’ reporter tickled Tatiana’s foot, out of Krista’s view, Krista laughed. The family accepts that this happens, since they have frequently seen one girl laughing at a television program only the other could see. (Their heads are conjoined in such a way that their faces are angled away from each other, so that their fields of view have very little overlap.)