Optimized birefringence changes during isolated nerve activation.

Single trial, birefringence signals associated with action potentials from isolated lobster nerves were optimized with high-intensity light-emitting diodes (LEDs) and glass polarizers. The narrow spectral output of the LEDs allowed us to select specific wavelengths, increasing the effectiveness of the polarizers and minimizing the stray light in the system. The LEDs produced intensity profiles equivalent to narrowband filtered 100-W halogen light, and birefringence signals were comparable or superior in size and clarity to halogen lamp recordings. The results support a direct correlation between signal size and polarizer extinction coefficient. Increasing the sensitivity of birefringence detection through the use of LED light sources could ameliorate noninvasive brain imaging techniques that employ fast optical consequences associated with action potential propagation.