Different Electrophysiology Methods

Electrophysiologists measure signals from different sources; different tissues (brain, heart, muscles), different cells (excitatory, inhibitory), sometimes from a single neuron and sometimes from large populations of cells. The table below lists some of the major types of extracellular electrophysiology, including typical signal amplitudes and the appropriate electrode type.

Table 1: Overview of Extracellular Electrophysiology Methods

Technique	Signal	Electrodes	Typical amplitude
ECG/EKG	Heart: Depolarisation/repolarisation of cardiac tissue	Surface electrodes	mV range
EMG	Skeletal muscle: A train of motor unit action potentials.	Surface electrodes placed on skin above muscle, reference electrode on skin above bone.	mV range
EEG	Brain: Summations of neural activity	Surface electrodes on scalp	50 µV
LFP	Brain: Summations of neural activity	Intracranial electrode	100-1000 µV
‘Spike’ recording	Brain: Action potentials (‘spikes’) in individual neurons	Intracranial electrodes, e.g. tetrodes (4 insulated wires twisted together), Single-wire electrodes, Silicon probes.	20-200 µV