A simple and reliable method for construction of parallel multibarrel microelectrodes

A modification to the method of construction of parallel or "piggy-back" electrodes for extracellular single-unit recording combined with iontophoresis is described that facilitates the alignment of the two components of the array. The method involves the use of an orthogonal viewing device (a pair of mirrors mounted symmetrically at 45 degrees to the horizontal), which produces a pair of virtual images of the electrode components that can be viewed with a microscope. A slight displacement between the electrodes is easily detected as an uneven separation between the electrode images. The positions of the electrode components are adjusted until there is no visible separation of the electrodes or their virtual images.