Law of specific nerve energies
Encyclopedia
The law of specific nerve energies, first proposed by Johannes Peter Müller
in 1835, is that the nature of perception is defined by the pathway over which the sensory information is carried. Hence, the origin of the sensation is not important. Therefore the differences in sensory quality, the difference between seeing and hearing, between hearing and touch, and so on - are not caused by differences in the stimuli themselves but by the different nervous structures that these stimuli excite. For example, pressing on the eye
elicits sensations of flashes of light
because the neuron
s in the retina
send a signal to the occipital lobe
. Despite the sensory input's being mechanical, the experience is visual.
, and the auditory experience from sound coming into the ear, or from electrical stimulation of the cochlea
, arises from some different, special quality of the energy carried by the auditory nerve. In 1912, Lord Edgar Douglas Adrian showed that all neurons carry the same energy, electrical energy in the form of action potential
s. That means that the quality of an experience depends on the part of the brain to which nerves deliver their action potentials (e.g., light from nerves arriving at the visual cortex
and sound from nerves arriving at the auditory cortex).
In 1945, Roger Sperry showed that it is the location in the brain to which nerves attach that determines experience. He studied amphibian
s whose optic nerves cross completely, so that the left eye connects to the right side of the brain and the right eye connects to the left side of the brain. He was able to cut the optic nerves and cause them to regrow on the opposite side of the brain so that the left eye now connected to the left side of the brain and the right eye connected to the right side of the brain. He then showed that these animals made the opposite movements from the ones they would have made before the operation. For example, before the operation, the animal would move to the left to get away from a large object approaching from the right. After the operation, the animal would move to the right in response to the same large object approaching from the right. Sperry showed similar results in other animals including mammal
s (rat
s), this work contributing to his Nobel Prize
in 1981.
Johannes Peter Müller
Johannes Peter Müller , was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.-Early years and education:...
in 1835, is that the nature of perception is defined by the pathway over which the sensory information is carried. Hence, the origin of the sensation is not important. Therefore the differences in sensory quality, the difference between seeing and hearing, between hearing and touch, and so on - are not caused by differences in the stimuli themselves but by the different nervous structures that these stimuli excite. For example, pressing on the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
elicits sensations of flashes of light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
because the 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 in the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
send a signal to the occipital lobe
Occipital lobe
The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...
. Despite the sensory input's being mechanical, the experience is visual.
Quotation
Here is Müller's statement of the law, from Handbuch der Physiologie des Menschen für Vorlesungen, 2nd Ed., translated by Edwin Clarke and Charles Donald O'Malley:
The same cause, such as electricity, can simultaneously affect all sensory organs, since they are all sensitive to it; and yet, every sensory nerve reacts to it differently; one nerve perceives it as light, another hears its sound, another one smells it; another tastes the electricity, and another one feels it as pain and shock. One nerve perceives a luminous picture through mechanical irritation, another one hears it as buzzing, another one senses it as pain. . . He who feels compelled to consider the consequences of these facts cannot but realize that the specific sensibility of nerves for certain impressions is not enough, since all nerves are sensitive to the same cause but react to the same cause in different ways. . . (S)ensation is not the conduction of a quality or state of external bodies to consciousness, but the conduction of a quality or state of our nerves to consciousness, excited by an external cause.
Clarification
As the above quotation shows, Müller's law seems to differ from the modern statement of the law in one key way. Müller attributed the quality of an experience to some specific quality of the energy in the nerves. For example, the visual experience from light shining into the eye, or from a poke in the eye, arises from some special quality of the energy carried by optic nerveOptic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
, and the auditory experience from sound coming into the ear, or from electrical stimulation of the cochlea
Cochlea
The cochlea is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth, making 2.5 turns around its axis, the modiolus....
, arises from some different, special quality of the energy carried by the auditory nerve. In 1912, Lord Edgar Douglas Adrian showed that all neurons carry the same energy, electrical energy in the form of action potential
Action potential
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
s. That means that the quality of an experience depends on the part of the brain to which nerves deliver their action potentials (e.g., light from nerves arriving at the visual cortex
Visual cortex
The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....
and sound from nerves arriving at the auditory cortex).
In 1945, Roger Sperry showed that it is the location in the brain to which nerves attach that determines experience. He studied amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
s whose optic nerves cross completely, so that the left eye connects to the right side of the brain and the right eye connects to the left side of the brain. He was able to cut the optic nerves and cause them to regrow on the opposite side of the brain so that the left eye now connected to the left side of the brain and the right eye connected to the right side of the brain. He then showed that these animals made the opposite movements from the ones they would have made before the operation. For example, before the operation, the animal would move to the left to get away from a large object approaching from the right. After the operation, the animal would move to the right in response to the same large object approaching from the right. Sperry showed similar results in other animals including mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s (rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s), this work contributing to his Nobel Prize
Nobel Prize
The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...
in 1981.