I think you overestimate the amount of brain matter required to maintain personality.<p>It is possible to lose an entire brain hemisphere and retain complete functionality
(see <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Hemispherectomy" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Hemispherectomy</a>).<p>There is a huge amount of redundancy in the brain, and most brain matter is only concerned with I&#x2F;O, signal processing, and life support. It&#x27;s one of the reasons I have a lot of hope that cryonics is feasible -- massive loss of brain tissue need not mean irreversible loss of an individual.