I have pledged my brain and spinal cord to multiple sclerosis research with the UK MS Tissue Bank. They also need people without MS to donate their central nervous systems so that they can make comparisons.
The rest of me can be cremated. Not that I will care by then!
In related news I have just watched the first episode of the documentary series on Terry Pratchett and his early onset Altzheimer's (Posterial Cortical Atrophy or PCA in his case). It was both funny (because he always is) and depressing because his symptoms echo some of mine with the MS. My vision and cognitive issued overlap the symptoms of PCA / Altzheimer's a lot. Sobering.