Hemispherectomies reveal the surprising degree to which each hemisphere of the brain can be independent, as well as the ability of the brain to rewire itself when necessary. Split-brain patients reveal the nature of the mind as separate processes acting in concert.
Cognite researchers believed that, if given sufficient time and careful training, new modules could be folded seamlessly into transhuman minds. A human brain could be augmented with a third hemisphere, a sub-sentient AI, adding new modes of thought to the transhuman mental arsenal.
Physically, the third hemisphere is a cyberbrain peripheral, designed to connect through the simulated corpus collosum. Mentally, the AI is designed to mesh with a human mind and seek synchronicity, but simultaneously provide access to modes of thought difficult for the natural brain. Typically the AI is designed to provide talent at Bayesian analyses, game theory analyses, formal logic, and various higher-level mathematics.
With proper psychosurgical adjustments and training, the brain and new hemisphere will grow into each other, becoming so smoothly intertwined as to become indistinguishable, forming one mind just as the two hemispheres of a natural brain form one mind. At first, the brain will have no way to interpret the signals of the new hemisphere. Plasticity, training and psychosurgery, however, given time, allow the brain to begin to understand and incorporate the new source of information. After a decade of use, the union is total.
A third hemisphere is cyberware [Expensive]
It grants the anamolous mind and math wiz traits, as well as the equivalent of the savant calculation and pattern recognition sleights.