Consecutive hippocampal change had lower covariance within hemispheres than across hemispheres in 176 selected DLBS 1.3.0 adults

We tested consecutive hippocampal volume changes in 176 selected adults from DLBS, OpenNeuro ds004856 version 1.3.0. We used annual rates from natural log volume ratios. Within hemisphere covariance was lower than across hemisphere covariance. The contrast was -3.534 in units of (log percentage points per year) squared. A whole-person bootstrap with 20000 samples gave a primary 95% interval of [-6.516, -1.441]. All planned checks kept a negative contrast. We proved a scan error formula and two covariance bounds under stated assumptions. A check chosen after the primary result allowed separate visit error variances. At within-visit error correlation zero, its upper contrast interval crossed zero. The data do not identify a biological cause. The package contains exact source files, retrieval code, a reusable covariance tool, proofs, participant decisions, bootstrap arrays, figures, and reproduction commands. An independent source audit passed. A new source download and full numeric repeat matched all 11 result files byte for byte.

hippocampus · longitudinal MRI · hemispheric asymmetry · covariance · measurement error · OpenNeuro