Double-barreled electrode for simultaneous iontophoresis and single unit recording during movement in awake monkeys

A double-barreled electrode for simultaneous glutamate iontophoresis and chronic single unit recording from cortical neurons in awake monkeys during voluntary movement is described. Electrode assembly consists of pulling a heated, partitioned capillary tube over a sharpened tungsten rod. Glutamate iontophoresis increased the firing rates of wrist movement related cells an average of 34 Hz during the agonist phase of movement and 27 Hz during the antagonist phase of movement. However, in no case did glutamate iontophoresis alter the detailed structure of the cell's response pattern during wrist movement. This electrode is well suited to chronic recording applications that involve methods such as cross-correlation requiring overlapping activity of neurons and/or muscles. Other applications might involve activation of totally 'silent' neurons to avoid possible sampling bias or to detect effects in post-stimulus time histograms that would otherwise be subliminal.