Combining electrical and optical techniques to develop a novel modality for neural activation

Infrared neural stimulation (INS) provides an artifact-free, contact-free and spatially selective alternative to electrical methods of neural activation. However, INS is limited by an approximately 2:1 ratio of radiant exposures (J/cm²) inducing damage to those required for stimulation. Current laser power requirements for stimulation also provide challenges to implanting INS-based technology. While characteristics of INS are desirable in both the clinical and research arenas, these challenges must be overcome for INS to see widespread application. Here we describe a novel nerve stimulation modality combining optical and electrical techniques of neural stimulation. Radiant exposures required for stimulation are reduced by as much as 3-fold when delivered concomitantly with a sub-threshold electrical stimulus, effectively increasing the aforementioned ratio from 2:1 to 6:1. Spatial selectivity attributed to INS is maintained with hybrid stimulation. These results will directly facilitate the applications and technology associated with INS.