FIGURE 3.

Optical detection of AP propagation in a crayfish leg nerve. (A) Depth profile showing the glass-saline interface and multiple surfaces within the nerve. Labels L₁ and L₂ indicate two locations inside the crayfish nerve. (B) Optical path length changes due to transient displacement during AP propagation at locations L₁ and L₂ and corresponding compound AP recorded differentially with respect to ground by a pair of platinum electrodes that are placed before and after the optical read-out area. Transient increase in optical signal represents a displacement toward the reference glass surface. Stimulus (1 mA, 50 μs) is presented at 2 ms and caused a localized artifact in the electrical measurement. Fifty responses are averaged in each trace.