Monopolarly

Slow wave phase reversals between two zygomatic leads used monopolarly are often seen as such artifacts.

Source: wiktionary

Cortical evoked responses are commonly recorded monopolarly by placing a single electrode wire, ball, or wick on the surface of the cortex and measuring against a distant indifferent such as an alligator clip on the cut skin edge.

Source: wiktionary

It is usually recorded from electrodes on the scalp. It can be recorded bipolarly from two electrodes placed over the same part of the cortex, or monopolarly with one “active” electrode over the cortex and a second “reference” electrode on some other part of the head.

Source: wiktionary