Hering's law of equal innervation
Encyclopedia
Hering's law of equal innervation is used to explain the conjugacy of saccadic
eye movement in stereoptic animals. The law proposes that conjugacy of saccades is due to innate connections in which the eye muscles responsible for each eye's movements are innervated equally. The law also states that apparent monocular eye movements are actually the mathematical summation of conjugate version
and vergence
eye movements. The law was put forward by Ewald Hering
in the 19th century, though the underlying principles of the law date back considerably. Aristotle
had commented upon this phenomenon and Ptolemy
put forward a theory of why such a physiological law might be useful. It was clearly stated for the first time by Alhacen in his Book of Optics
(1021).
This theory is in contrast to the theory proposed by Von Helmholtz
(1911) which states that conjugacy is a learned, coordinated response and that the movements of the eyes are individually controlled.
Although for most of the 20th century, it was believed that Hering was right, recent evidence has suggested that the eye movements may be separately encoded.
Saccade
A saccade is a fast movement of an eye, head or other part of an animal's body or device. It can also be a fast shift in frequency of an emitted signal or other quick change. Saccades are quick, simultaneous movements of both eyes in the same direction...
eye movement in stereoptic animals. The law proposes that conjugacy of saccades is due to innate connections in which the eye muscles responsible for each eye's movements are innervated equally. The law also states that apparent monocular eye movements are actually the mathematical summation of conjugate version
Version (eye)
A version is an eye movement involving both eyes moving synchronously and symmetrically in the same direction.#Dextroversion / right gaze#Laevoversion / left gaze#Sursumversion / elevation / up gaze#Deorsumversion / depression / down gaze...
and vergence
Vergence
A vergence is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision..When a creature with binocular vision looks at an object, the eyes must rotate around a vertical axis so that the projection of the image is in the centre of the retina in both...
eye movements. The law was put forward by Ewald Hering
Ewald Hering
Karl Ewald Konstantin Hering was a German physiologist who did much research into color vision and spatial perception...
in the 19th century, though the underlying principles of the law date back considerably. Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
had commented upon this phenomenon and Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
put forward a theory of why such a physiological law might be useful. It was clearly stated for the first time by Alhacen in his Book of Optics
Book of Optics
The Book of Optics ; ; Latin: De Aspectibus or Opticae Thesaurus: Alhazeni Arabis; Italian: Deli Aspecti) is a seven-volume treatise on optics and other fields of study composed by the medieval Muslim scholar Alhazen .-See also:* Science in medieval Islam...
(1021).
This theory is in contrast to the theory proposed by Von Helmholtz
Hermann von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions to several widely varied areas of modern science...
(1911) which states that conjugacy is a learned, coordinated response and that the movements of the eyes are individually controlled.
Although for most of the 20th century, it was believed that Hering was right, recent evidence has suggested that the eye movements may be separately encoded.
See also
- Sherrington's law of reciprocal innervationSherrington's law of reciprocal innervationSherrington's law of reciprocal innervation, also called Sherrington's law II explains how a muscle will relax when its opposite muscle is activated. René Descartes had hypothesized as much in 1626...
- Dissociated vertical deviationDissociated Vertical DeviationDissociated Vertical Deviation is an ocular condition which occurs in association with a squint, typically Infantile Esotropia.- Mechanism :...
- Orthoptics