# What OT-knn does
# Why neighborhood information matters
# How the alignment works in practice
- 1Apply an optimal transport algorithm to those representations to produce probabilistic correspondences between spots across slices.
The probabilistic output allows partial matches (a spot can map with weights to multiple targets) which helps when slices differ in cell composition or resolution.
# Evaluation and datasets used The authors evaluated OT-knn on both simulated data with known ground-truth alignments and multiple real ST datasets across platforms and species:
- Human dorsolateral prefrontal cortex (DLPFC) profiled with 10x Genomics Visium.
- Mouse brain aging data with MERFISH for both within-donor and cross-donor comparisons.
- Cross-platform alignment of mouse embryo data profiled by Stereo-seq and seqFISH.
Across these tasks OT-knn delivered accurate and robust alignments, notably in scenarios with spatial deformation, donor heterogeneity, developmental variation, and cross-platform differences.
# Practical strengths and use cases OT-knn targets comparative ST analyses where aligning spatial measurements is a prerequisite. Use cases include:
- Comparing gene expression patterns across serial sections where slicing causes shifts and warping.
- Integrating datasets collected with different ST technologies to expand cross-study comparisons.
- Tracking spatial changes across development or aging when tissue composition and geometry change.
# Output and interpretation The method yields probabilistic correspondences rather than one-to-one hard matches. That representation is useful for downstream analyses that expect uncertainty (for example, transferring annotations with confidence weights, aggregating matched regions, or smoothing cross-sample comparisons).
# What to expect when applying OT-knn
# Where data and resources are available The paper lists locations for several datasets used in evaluation, including GEO accessions and public ST data repositories for Visium, MERFISH, Stereo-seq, and seqFISH resources. These datasets can be used for method reproduction and benchmarking.
# Bottom line OT-knn is a neighborhood-aware alignment method that integrates local spatial context with optimal transport to produce probabilistic cross-slice correspondences. It is designed to improve robustness when single-spot expression is noisy and when samples differ in shape, biology, or technology.