realizes is about has_specified_input has_specified_output inheres in role of has role function neuron neuron action potential evaluant role extracellular electrophysiology recording assay micro electrode cytometry assay single-unit recording An extracellular electrophysiology assay where a single microelectrode is placed in close proximity to a single neuron to measure voltage and current changes over time. This is the technicque used by Hubel and Wiesel to measure firing properties of primary visual cortex neurons in the 1950s in their original Nobel-prize winning study. A classic, old technique.