Tetrode

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A tetrode is a two-grid vacuum tube. It has four electrodes instead of three, as in the case of a triode.

A tetrode is a group of wire bundles used in electrophysiological studies in the neurosciences to record extracellular field potentials from nervous tissue, e.g. the brain. They consist of bundles of 4 thin (e.g. 30 µm diameter) wires glued together. The idea is that the wires are spaced close enough to each other to 'see' overlapping populations of neurons, but wide enough so that the exact waveform of the signal recorded would be different on each of the wires. These differences would then be used to distinguish the contributions of different neurons based on the shape of their spikes (the extracellular correlates of their action potential) by spike sorting.

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