A retrofitted neural recording system with a novel stimulation IC to monitor early neural responses from a stimulating electrode

Extracellular electrical stimulation is increasingly used for in vitro neural experimentation, including brain slices and cultured cells. Although it is desirable to record directly from the stimulating electrode, relatively high stimulation levels make it extremely difficult to record immediately after the stimulation. We have shown that this is feasible by a stimulation system (analog IC) that includes the feature of active electrode discharge. Here, we piggybacked the new IC onto an existing recording amplifier system, making it possible to record neural responses directly from the stimulating channel as early as 3 ms after the stimulation. We used the retrofitted recording system to stimulate and record from dissociated hippocampal neurons in culture. This new strategy of retrofitting an existing system is a simple but attractive approach for instrumentation designers interested in adding a new feature for extracellular recording without replacing already existing recording systems.