Figure 2. Force probe actuates vertically to apply controlled force profiles along the animal’s midline.

A) Cross-section schematic of experiment showing contact between animal and the glass bead attached to the force probe, which is positioned near the lateral midline and moves vertically to indent freely moving animals. B) Top view schematic of the touch assay that targets the ALM or PLM neurons along the midline. C) Image processing pipeline for detecting the target on the animal. Details of process steps are described in the Methods section.