These twins share a brain, access each other's feelings, see through each other's eyes

Editor's note: This article was originally published on August 3, 2022. It has since been updated.

Krista and Tatiana Hogan are inseparable twins, both literally and metaphorically. Joined at the head, the twins' brains are connected by a thalamic bridge, granting them unique abilities. They can access each other's feelings and even see through each other's eyes.

Craniopagus twins joined at the head are a rare occurrence at just one in 2.5 million. Most craniopagus twins do not survive beyond 24 hours. Krista and Tatiana Hogan were given a survival chance of 20%. The Hogan twins were born on October 25, 2006, in Vancouver, Canada. Sixteen medics were needed to deliver them safely, reported CBC.

The pair was featured as part of a documentary titled "Inseparable," which highlighted neurological capabilities that have since astounded researchers. They can read each other's thoughts without having to mouth the words. The twins say it's like, “Talking in our heads.”  

"They can sit there and not say anything to each other, and all of a sudden, one of them will pop up and grab something to eat for the other one. Like, there's no words being spoken between the two of them at all, and they know exactly what the other one wants," their mother, Felicia Simms told 60 Minutes Australia in 2012. "You can tickle one, and the other one laughs. You pinch one, the other one will cry with her like she's feeling it," she added.

A CT scan revealed that they could not be separated without the risk of serious injury or death. Neurosurgeon Dr. Douglas Cochrane, who has followed the girls' progress since they were born, is aware of the dangers their separation holds. Cochrane noted only one recorded case of this type of joining, involving two Iranian sisters. They chose to have surgery as they neared adulthood but didn't make it, reported MamaMia.

Krista and Tatiana Hogan are healthy, but they are diabetic and have epilepsy. They require regular blood tests, daily insulin injections and pills. Their parents and family are determined to help them live happy, independent lives. They have three  siblings―sisters Rosa and Shaylee and a brother Christopher. They attend school, even though they started a little later than the others. The structure of their brains is unique given their thalamus relays sensory and motor signals to either person and regulates their consciousness as well.

The pair can even control each other's limbs. They can also access each other's senses, such as touch and taste. They even proved that they can see out of each other's eyes. While Tatiana can see out of both of Krista's eyes, Krista can only see out of one of Tatiana's. Similarly, they don't have full access to each other's limbs. They can fully control their own limbs. Tatiana controls three arms and a leg, while Krista controls three legs and an arm.

They also have completely different personalities. While Tatiana is outgoing and talkative, Krista is quieter and loves to tell jokes. They like to go around on a bicycle, specially built for the duo. They are also learning to swim as part of their physical therapy. While many have spoken to their mother about a separation, Felicia Simms says people aren't even aware of the risks when they make such comments. "There's nobody in the world that's connected the same way that they are," their mother said in 2017. "I could have never imagined that they could do anything they can do now."