Light-Addressed Stimulation Under $\hbox{Ca}^{\bf 2+}$ Imaging of Cultured Neurons

Light addressing is an emerging and sophisticated technique that can induce pinpoint and/or patterned neuronal activation in cultured neurons. We previously developed a light-addressable electrode using hydrogenated amorphous silicon ($a$-Si:H), which was sandwiched between a tin oxide ( $\hbox{SnO}_{2}$) substrate and a passivation layer of zinc antimonate ($\hbox{ZnOSb}_{2}\hbox{O}_{5}$) dispersed epoxy. This research developed an experimental system that simultaneously implemented light-addressed stimulation and $\hbox{Ca}^{2+}$ imaging of neuronal activities. The translucent and thin laminated structure of our electrode permitted optical accesses from two directions: $\hbox{Ca}^{2+}$ imaging from above and light addressing from beneath. The submillisecond bright/dark switching property of our electrode offered light-addressed stimulation without causing interference with $\hbox{Ca}^{2+}$ imaging. To provide patterned illumination for light addressing, a digital micromirror device was installed in the system as an active photomask. The system could induce pinpoint neuronal activation at a cellular level.