Infrared Neural Stimulation of Thalamocortical Brain Slices

Infrared neural stimulation (INS) has been well characterized in the peripheral nervous system, and has been shown to enable stimulation with high spatial precision and without causing the typical electrical stimulation artifact on the recording electrode. The next step in the development of INS is to demonstrate feasibility to stimulate neurons located in the central nervous system (CNS). Thalamocortical brain slices were used to establish feasibility of INS in the CNS and to optimize laser parameters. Infrared light was used to evoke action potentials in the brain slice with no electrical stimulation artifact. This response was blocked by the application of tetrodotoxin demonstrating neurological origin of the recorded signal. Threshold radiant exposure decreased as the absorption coefficient of the wavelength of light increased. Higher repetition rates lead to a decrease in threshold radiant exposure, and threshold radiant exposure was found to decrease as the spot size diameter increased. Additionally, neuronal responses to INS were intracellularly recorded demonstrating artifact free electrical recordings. The results from this paper lay the foundation for future in vivo studies to develop INS for CNS stimulation.