Cryosphere Podcast Aschwin de Wolf & Andy McKenzie - Fixation vs. Vitrification
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Nov 15, 2025 
Aschwin de Wolf, a leader in brain preservation research, and Andy McKenzie, a specialist in chemical preservation, dive into the fixation versus vitrification debate in cryonics. They unpack the significance of preserving the brain's connectome and ultrastructure while discussing viability versus structural preservation. The duo examines how different preservation methods can impact revival outcomes and explore ideal protocols versus real-world practices. They even tackle intriguing questions on the future of memory extraction and the viability of fixed brains.
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Two Fundamental Preservation Strategies
- Vitrification arrests metabolism by freezing with cryoprotectants to avoid ice formation.
- Chemical fixation uses aldehydes to crosslink molecules and preserve structure without keeping tissue viable.
Preserve The Biomolecule-Annotated Connectome
- The key preservation goal is the biomolecule-annotated connectome because it likely encodes long-term memory and identity.
- Preserving ultrastructure at EM resolution is what gives confidence future revival or emulation can reconstruct memories.
Fixation Excels In EM-Based Tests
- Aldehyde-stabilized methods already match electron-microscopy prep and thus performed well in connectome challenges.
- That success partly reflects fixation being the standard EM preparation technique.