Development of Wireless Sensing and Optical Stimulation Module for Optogenetic Animal Study

Abstract

Optical stimulation of target neurons, known as optogenetics, is an effective method to selectively control the genetically- modified neurons using different wavelength of light. The optical stimulation can provide spatial specificity for target cells and eliminate electrical artifacts. In this study, we develop a wireless sensing and optical stimulation module which can wirelessly control the parameters of optical stimulation for exciting dopaminergic neurons and provide fast-scan cyclic voltammetry (FSCV) for detecting the phasic dopamine (DA) release in the dorsal striatum of rat. The optical stimulator system can be remotely controlled using LabVIEW computer interface for delivering blue light (473nm) in the brain via optical fiber to evoke DA releasing. FSCV provides higher time resolution for measuring transient dopamine changes and causes less tissue damage using carbon fiber microelectrodes (7μm) as electrode for brain insertion. The measured local field potential (LFP) and dopamine signals are unidirectionally transmitted from a commercially available wireless module to the host unit. Our study first validated that the carbon fiber microelectrode coated with Nafion has increased the electrode sensitivity and improved the selectivity of DA detections. We also found that the responsive currents are increased linearly in proportion to DA concentrations (0.01-0.647μm) with a correlation coefficient of 0.999. In an in vivo test, the wireless system delivered the blue light for exciting LFP which is transmitted to the host via a wireless transmitter. The occurrence of measured LFP was in synchronizing with the optical stimulation which was averaged to show the LFP template. The developed wireless system is proven to be a useful experimental tool for the continuous monitoring of LFP and DA. A miniature FSCV module might be feasible using ASIC approach in the future. The proposed wireless system will be extended as an experimental platform for Parkinson disease experiment in an ongoing project.