The concept of the human brain not working at the full capacity is a little outdated. The fMRI studies show that the brain uses everything it has. Evolutionary speaking, your body won't feed cells that it doesn't use and the immune system will reabsorb them. The brain is the second consumer of glucose in the body (after the heart), so having a brain and not using it is very wasteful and unacceptable in evolutionary biology.
So the co-morbidity between different neurological disorders and high IQ doesn't stem from how we use the brain, but from the structural differences in the neural network.
For example... In the last ten years, using tools like fMRI, it is been established that the higher IQ individuals follow a different curve when it comes to cortical thickening and thinning. It looks like the higher the IQ, the longer the brain spends first over-connecting, reaching the peak much later in the childhood - around 13-14, instead of 7-8. After that it thins out almost or even faster than in typical children.
Now if it look at disorders such as autism, ADHD and schizophrenia, the research also points to a differentiated process of cortical thickening and thinning. In ASD individuals, the brain is often much larger than in normal children, showing signs of overconnectivity and lack of normal neural pruning - immune system function that targets neural connections that are unused, unneeded etc. As the brain prunes itself, the understanding becomes more streamlined, the speech becomes less garbled, the attention span gets longer etc... In the absence of it - sensory overload, speech delays and inability to understand and execute instructions well, typical in ASD. ADHD also shows a delay in cortical thinning when the children reach the peak, but at a later age, basically following a similar trajectory as the high IQ individuals. Some research into schizophrenia shows that the hallmark symptom - hallucinations - may come from unpruned connections, where the brain can self-generate stimuli that doesn't exist or use older memories as the new input.
So the same presentation - overconnected brain - can either result in out-of-box thinking, creativity and ability to see what others can't or in difficulty understanding human language and sensory overstimulation. Or both.
It looks like the bigger the brain capacity/connectivity, the easier it is for the brain to fall into a less typical developmental trajectory, with various symptoms and abnormalities - hence a high correlation between learning disabilities and high IQ.
Last edited by Chicagomom; 05/09/16 02:33 PM.
