Extracellular field potential
Encyclopedia
The extracellular field potential is the electrical potential produced by cell
s, e.g. nerve
or muscle cells, outside of the cell. Electrophysiological studies
investigate these potentials using extracellular microelectrodes. In these experiments the extracellular field potential will be detected as an electrical potential whose source and composition is often ambiguous, making its interpretation difficult. Individual nerve cells neuron
s may produce spike
s seen as peaks of some tens to hundreds of microvolts. Contributions from neighbouring neurons may overlap, producing extracellular potentials of up to several millivolts. Spatially integrating over even larger populations of cells, i.e. lumps of nervous
or muscular tissue
, will produce signals commonly called local field potential
s (LFP) that can be recorded either in the tissue or with suitable equipment at the body surface as, e.g., electroencephalogram (EEG), electrocardiogram
(ECG), or electromyogram (EMG).
For individual cells, the time course of the extracellular potential theoretically is inversely proportional to the transmembrane current. In practice, however, this is complicated considerably by the very complex morphology
of neurons and the overlap of contributions from adjacent cells.
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s, e.g. nerve
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
or muscle cells, outside of the cell. Electrophysiological studies
Electrophysiology
Electrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart...
investigate these potentials using extracellular microelectrodes. In these experiments the extracellular field potential will be detected as an electrical potential whose source and composition is often ambiguous, making its interpretation difficult. Individual nerve cells neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
s may produce spike
Voltage spike
In electrical engineering, spikes are fast, short duration electrical transients in voltage , current , or transferred energy in an electrical circuit....
s seen as peaks of some tens to hundreds of microvolts. Contributions from neighbouring neurons may overlap, producing extracellular potentials of up to several millivolts. Spatially integrating over even larger populations of cells, i.e. lumps of nervous
Nervous tissue
Nervous tissue is one of four major classes of vertebrate tissue.Nervous tissue is the main component of the nervous system - the brain, spinal cord, and nerves-which regulates and controls body functions...
or muscular tissue
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
, will produce signals commonly called local field potential
Local field potential
A local field potential is a particular class of electrophysiological signals, which is dominated by the electrical current flowing from all nearby dendritic synaptic activity within a volume of tissue. A voltage is produced by the summed synaptic current flowing across the resistance of the local...
s (LFP) that can be recorded either in the tissue or with suitable equipment at the body surface as, e.g., electroencephalogram (EEG), electrocardiogram
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(ECG), or electromyogram (EMG).
For individual cells, the time course of the extracellular potential theoretically is inversely proportional to the transmembrane current. In practice, however, this is complicated considerably by the very complex morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
of neurons and the overlap of contributions from adjacent cells.