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Katie is a 16 year old girl diagnosed with Rasmussen's Syndrome. Rasmussen's Syndrome causes frequent seizures, and the only way to "cure" it is to surgically remove the affected cortical tissue. At age 8, Katie underwent a partial lobectomy to try and eliminate the seizures. Unfortunately, the surgery was only successful for a few years. At age 13, Katie started having seizures again. This time, Katie's parents opted for a complete left hemispherectomy. Incredibly, after surgery Katie had no motor-speech or language comprehension deficits. The only deficits present were executive function, mild right motoric movements, and right neglect. Cognitive testing improved after surgery, too. What is your reasoning behind this?
Katie's right hemisphere started taking over for her damaged left hemisphere well before the surgery.