In this Radiolab podcast about Einstein’s brain is an interview with a neurologist named Sebastian Song (spelling?). He says forget about relativity we cannot even explain what a thought is. We can point to where a thought occurs in the brain but we cannot say how a thought is made there.
If a thought is a thing then something should remain and dissipate at death. But nothing “dissipates”. Only the process called thinking and life ends. The body remains without the process of thought, that is, when thinking ends we are no longer alive.