Why must a recording electrode be insulated everywhere but its tip? · Lobeworks/17

So that it reads the voltage at one point instead of an average along its whole length.

Why must a recording electrode be insulated everywhere but its tip?

So that it reads the voltage at one point instead of an average along its whole length. A bare shaft would touch tissue all the way down and pick up every neuron it passes; insulating it confines the contact to the tip, near one or a few cells. The shafts of the Utah array are coated in parylene-C with only the tips left bare, and the slow failure of that coating in the body is one of the ways implants lose their signal over years.