Optical Characterization of Pulsed Infrared Light Evoked Cortical Brain Activity

Abstract

Infrared neural stimulation (INS) uses pulsed infrared light to directly stimulate neural tissue with high spatiotemporal precision and is well documented for peripheral nerve applications; however, prior to this dissertation, INS had not been demonstrated for the central nervous system. This dissertation presents the first successful application of INS in the central nervous system and increases our understanding the effects of pulsed infrared light irradiation on cellular dynamics in the brain. Pulsed infrared light is shown to evoke both excitatory and inhibitory neural activity, and evokes robust optical intrinsic signals indicating multiple cellular mechanisms are activated by INS. Optical imaging of calcium signals evoked by INS identified astrocyte sensitivity to pulsed infrared light confirming that both neurons and astrocytes are stimulated. Application of INS in non-human primate visual cortex demonstrated that pulsed infrared light evokes excitatory neural activity and modulates visually evoked signals, identifying the potential of INS to encode functionally relevant signals into cortex. Overall, these results establish INS as neurostimulation modality for use in the brain, and this dissertation provides the necessary foundation to further develop INS for use in the central nervous system in both research and clinical applications.