# Longitudinal Drift **Domain:** Neural Interfaces / Measurement Stability **Doc Type:** Technical Constraint Node **Maturity:** Active Research **Primary Source:** [[articles/The Art is Long|The Art is Long: Vespucci of Immortality]] **Related:** [[wiki/Biocompatibility|Biocompatibility]], [[wiki/Neural Data Provenance|Neural Data Provenance]], [[wiki/BCI Metadata|BCI Metadata]], [[wiki/Continuity Telemetry|Continuity Telemetry]] --- ## Definition **Longitudinal drift** is change over time in the relationship between a neural system, its sensors, and the models interpreting their signals. Sources include electrode movement, tissue response, neural plasticity, device aging, changing impedance, and decoder adaptation. ## Continuity Context Without calibration history and provenance, drift can make measurements from different times appear commensurable when their biological or instrumental meaning has changed. A continuity record must preserve not just decoded output but the changing measurement relationship that produced it.