An electrogram (EGM) is a recording of

electrical activity This is a list of electrical phenomena. Electrical phenomena are a somewhat arbitrary division of electromagnetic phenomena. Some examples are: * Biefeld–Brown effect — Thought by the person who coined the name, Thomas Townsend Brown, to ...

organs In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a f ...

such as the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

and

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...

, measured by monitoring changes in

electric potential The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is defined as the amount of work energy needed to move a unit of electric charge from a reference point to the specific point in ...

Brain

Electroencephalography (EEG)

An electroencephalogram (EEG) is an electrical recording of the activity of the brain taken from the

scalp The scalp is the anatomical area bordered by the human face at the front, and by the neck at the sides and back. Structure The scalp is usually described as having five layers, which can conveniently be remembered as a mnemonic: * S: The ski ...

. An EEG can be used to diagnose

seizures An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or neural oscillation, synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much o ...

sleep disorders A sleep disorder, or somnipathy, is a medical disorder of an individual's sleep patterns. Some sleep disorders are severe enough to interfere with normal physical, mental, social and emotional functioning. Polysomnography and actigraphy are test ...

, and for monitoring of level of anesthesia during surgery.

Electrocorticography (ECoG or iEEG)

An electrocorticogram is an electrical recording of the brain measured intracranially, that is, from within the brain.

Eye

Electrooculography (EOG)

An electrooculogram (EOG) is an electrical recording of the potential between the

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...

and the

retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...

, and does not change with

visual stimuli In physiology, a stimulus is a detectable change in the physical or chemical structure of an organism's internal or external environment. The ability of an organism or organ to detect external stimuli, so that an appropriate reaction can be mad ...

. An EOG can measure movements of the eyes and can help in diagnosis of

nystagmus Nystagmus is a condition of involuntary (or voluntary, in some cases) eye movement. Infants can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. Due to the invol ...

Electroretinography (ERG)

An electroretinogram (ERG) is an electrical recording of the electrical activity of the retina.

Heart

Electrocardiogram (ECG)

An electrocardiogram (ECG or EKG) is an electrical recording of the activity of the heart. The typical meaning of an "ECG" is the 12-lead ECG that uses 10 wires or

electrodes An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...

to record the signal across the chest. Interpretation of an ECG is the basis of a number of cardiac diseases including

myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may ...

(heart attack) and arrhythmias such as atrial fibrillation.

Cardiac electrogram

When electrical recordings are made from the

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

, it is considered to be an ECG as described above. However, electrical recordings made from within the heart such as with an

artificial cardiac pacemaker An artificial cardiac pacemaker (or artificial pacemaker, so as not to be confused with the natural cardiac pacemaker) or pacemaker is a medical device that generates electrical impulses delivered by electrodes to the chambers of the heart ei ...

or during an

electrophysiology study A cardiac electrophysiology study (EP test or EP study) is a minimally invasive procedure using catheters introduced through a vein or artery to record electrical activity from within the heart. This electrical activity is recorded when the hear ...

, the signals recorded are considered an "electrogram" instead of an ECG. These signals are not interpreted in the same manner as an ECG.

Muscle

An electromyogram (EMG) is an electrical recording of the activity of a

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

or muscle group. An EMG study can be combined with a

nerve conduction study A nerve conduction study (NCS) is a medical diagnostic test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body. These tests may be performed by medical specia ...

to diagnose neuromuscular diseases such as

peripheral neuropathy Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or or ...

and

amyotrophic lateral sclerosis Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) or Lou Gehrig's disease, is a neurodegenerative disease that results in the progressive loss of motor neurons that control voluntary muscles. ALS is the most comm ...