This real case explains everything:
CT scan of the brain of a 44-year-old civil servant who has lost more than 90% of his brain tissue due to hydrocephalus, but lives almost a normal life with two children, having verbal IQ 84 and performance IQ 70 (Lancet. 2007;370(9583):262). The scan picture supports the view that for conscious activities, minimal neural structures required are the upper layers of the cerebral cortex and the brainstem.
Source: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(07)61127-1/fulltext
More on the case: https://www.sciencealert.com/a-man-...hallenging-our-understanding-of-consciousness
CT scan of the brain of a 44-year-old civil servant who has lost more than 90% of his brain tissue due to hydrocephalus, but lives almost a normal life with two children, having verbal IQ 84 and performance IQ 70 (Lancet. 2007;370(9583):262). The scan picture supports the view that for conscious activities, minimal neural structures required are the upper layers of the cerebral cortex and the brainstem.
90% of his brain is gone.
Source: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(07)61127-1/fulltext
More on the case: https://www.sciencealert.com/a-man-...hallenging-our-understanding-of-consciousness