A technique for microiontophoretic study of single neurones in the behaving monkey

A technique is described for the construction and use of iontophoretic electrodes suitable for extracellular single-unit work in awake behaving monkeys. The technique combines a multi-barrelled pipette for iontophoresis and an insulated tungsten electrode that is employed routinely for chronic single-unit recordings. The pipette consists of up to 11 double filamented glass barrels concentrically arranged around a large diameter glass tube. The recording electrode is extruded through the central tube under microscopic control and glued in place. This technique allows separate optimization of the shape of the recording electrode for recording in the behaving monkey, and of the iontophoretic tips. An adapted micropositioner is used to accommodate the electrode's unusual length, required in order to allow access to deep brain structures and so that a guide tube can protect the trans-dural passage of the electrode tip.