prePostTree. The pre-stimulation and post-stimulation merge trees: The hierarchy of sample-merges to construct a template from ten well-clustered samples before (left) and after (right) stimulation. The leaves denote original samples and are marked with numerical labels. The internal nodes indicate sub-templates with the final template at the root. The cost of forming a sub-template (the merge cost of two children) is also shown at each non-leaf node.