LDLMM or Large Deformation Diffeomorphic Metric Mapping is like playing with clay. Have you ever made a cartoon or an animal by first taking a blob of clay and then shaping it the way you want? It's a lot like that.
Scientists use LDLMM to look at pictures of brains and see how they're different from each other. They start with a picture of a brain, like taking a blob of clay, and use computer programs to stretch and pull it in different ways. This helps them to see what parts of the brain are different between people.
But unlike clay, the scientists use special rules for stretching and pulling the brain images. They use fancy math to understand how the pictures change when they're pulled and stretched. This way, they can compare different brains and tell how similar or different they are.
This helps doctors and scientists understand what happens in different brain diseases, and how to treat them.