Short answer- all of it. It's a common myth that only 10 or 20% of the brain is used. From an evolutionary standpoint, having an organ which only used 20% of it's capacity would be incredibly...
All of it, though not all at once. (If every neuron in your brain was firing uncontrollably all at once, you'd have an epileptic seizure.) The "10%" figure you'll occasionally see is an old wives'...
swami is great yogis and have always in "samadhi" state. so any time he can accept knowledge from aatama or say it god. he goes far beyond brain; so he is king of knowledge. thousands of brain come...