Optical system for selectively firing neurons

Summary form only given. When studying activity in neuronal networks it is desirable to induce arbitrary patterns of action potential activity. Neurons transduced with light-sensitive ion channels (ChR2 and NpHR) can be stimulated by incident light. Prior research has determined that irradiance of at least 1mWmm^-2 pulsed at 1kHz at 470nm (for excitation) and 590nm (for inhibition) will result in reliable stimulation of a neuron. We have used a Spatial Light Modulator (Forth Dimensions Display SXGA-3DM containing 1280x1024 voltage controlled 17.6μm x 17.6μm mirrors), synchronised with high-power blue and amber LEDs, to project arbitrary light patterns onto the neuronal culture with micrometer precision. To achieve the necessary sample irradiance high-power (100mW) LED Engin emitters were used and the efficiency of the optical system was optimised. The commercial SLM control system has been replaced with a custom circuit board and is driven by a LabVIEW program. This allows arbitrary patterns to be uploaded to the SLM without interupting display. The system delivers arbitrary stimulation patterns with power greater than 1mWmm^-2 at both 470nm and 590nm with the required spatial (1.76 μm) and temporal (1ms) precision. This system will be employed as a tool for analysis of information processing inneuronal networks.