Command neuron
Encyclopedia
A command neuron is a single neuron
(or small set of neurons) whose stimulation
results in the evocation of an endogenous
, specific, naturally occurring behavior pattern (Carew, 2000). Command neurons act as neural decision making cells
; push buttons that can trigger a complete, coordinated behavioral
act and are often the sole determinant of whether an action is performed or not. Command neurons receive a convergence of integrative and sensory
input and output to a multifarious group of pattern generating efferent cells. Stimulation of the command neuron triggers a lower level central pattern generator
whose motorneurons
and interneuron
s produce a particular fixed action pattern
.
nerve cord caused the crayfish to execute a tail-flip escape response
. This concept came to epitomize the general neurobiological principle that complex information can be encoded on the level of individual neurons. Soon, researchers were finding command neurons in multiple invertebrate
and vertebrate
species
, including: teleosts, crickets, cockroaches, and lobsters.
, an archetypal command cell, has been criticized as being neither necessary nor sufficient for the initiation of the C-start response it supposedly governs. Command decisions are increasingly seen as being governed by networks of interacting and redundant cells, not simply by single neurons. Critics believe that the less restrictive category of "command-like" neurons would repair the flaws in the overly strict Kupfermann and Weiss definition while more accurately classifying the role of single neurons in command decisions.
Despite Kupfermann and Weiss' scathing critique of the loose fashion with which the command neuron concept was being used in the late 1970s and the resultant abandonment of the concept by some, the command neuron concept is still extant in the most current neurobiological literature. Some accept the revisionist "command-like" neuron concept--believing that no neurons exist which can satisfy the strictures outlined in "The Command Neuron Concept". Others cling to use of the original command neuron concept as useful, rejecting the Kupfermann and Weiss strictures, and using less stringent definitions of the term (. Most seem to believe that there is a spectrum of pre-motor command organization: from parallel distributed networks on the one end, to command neurons on the other (Edwards et al. 1999)
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 small set of neurons) whose stimulation
Stimulation
Stimulation is the action of various agents on nerves, muscles, or a sensory end organ, by which activity is evoked; especially, the nervous impulse produced by various agents on nerves, or a sensory end organ, by which the part connected with the nerve is thrown into a state of activity.The word...
results in the evocation of an endogenous
Endogenous
Endogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...
, specific, naturally occurring behavior pattern (Carew, 2000). Command neurons act as neural decision making 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....
; push buttons that can trigger a complete, coordinated behavioral
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....
act and are often the sole determinant of whether an action is performed or not. Command neurons receive a convergence of integrative and sensory
Sensory system
A sensory system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory receptors, neural pathways, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing, somatic...
input and output to a multifarious group of pattern generating efferent cells. Stimulation of the command neuron triggers a lower level central pattern generator
Central pattern generator
Central pattern generators are neural networks that produce rhythmic patterned outputs without sensory feedback. CPGs have been shown to produce rhythmic outputs resembling normal "rhythmic motor pattern production" even in isolation from motor and sensory feedback from limbs and other muscle...
whose motorneurons
Motor neuron
In vertebrates, the term motor neuron classically applies to neurons located in the central nervous system that project their axons outside the CNS and directly or indirectly control muscles...
and interneuron
Interneuron
An interneuron is a multipolar neuron which connects afferent neurons and efferent neurons in neural pathways...
s produce a particular fixed action pattern
Fixed action pattern
In ethology, a fixed action pattern , or modal action pattern, is an instinctive behavioral sequence that is indivisible and runs to completion...
.
History
The term command neuron first appeared in a 1964 paper "Interneurons Commanding Swimmeret Movements in the Crayfish" by CAG Wiersma and K Ikeda in volume 12 of Comparative Biochemistry and Physiology vol 12 on pp 509–525. Wiersma and Ikeda used the term to describe how a single action potential in any of the four giant fibers that run along the dorsal margin of the crayfishCrayfish
Crayfish, crawfish, or crawdads – members of the superfamilies Astacoidea and Parastacoidea – are freshwater crustaceans resembling small lobsters, to which they are related...
nerve cord caused the crayfish to execute a tail-flip escape response
Escape response
Escape response, escape reaction, or escape behaviour is a possible reaction in response to stimuli indicative of danger, in particular, it initiates an escape motion of an animal...
. This concept came to epitomize the general neurobiological principle that complex information can be encoded on the level of individual neurons. Soon, researchers were finding command neurons in multiple invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
and vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, including: teleosts, crickets, cockroaches, and lobsters.
Criticism
In 1978, Kupfermann and Weiss' "The Command Neuron Concept" proposed a more rigorous definition of the command neuron than had previously been used. They suggested that for any neuron to qualify as a command neuron, its activity had to be both necessary and sufficient for the initiation of the behavior it was purported to command. This article initiated a torrent of tumultuous debate about which neurons, if any, could fit the new, more rigorous definition proposed by Kupfermann and Weiss.Modern view
Many believe that the command neuron concept needs to be reworked in light of the subtleties uncovered by Kupfermann and Weiss' careful methodology. Even the Mauthner cellMauthner cell
The Mauthner Cells are a pair of big and easily identifiable neurons located in the rhombomere 4 of the hindbrain in fish and amphibians that are responsible for a very fast escape reflex...
, an archetypal command cell, has been criticized as being neither necessary nor sufficient for the initiation of the C-start response it supposedly governs. Command decisions are increasingly seen as being governed by networks of interacting and redundant cells, not simply by single neurons. Critics believe that the less restrictive category of "command-like" neurons would repair the flaws in the overly strict Kupfermann and Weiss definition while more accurately classifying the role of single neurons in command decisions.
Despite Kupfermann and Weiss' scathing critique of the loose fashion with which the command neuron concept was being used in the late 1970s and the resultant abandonment of the concept by some, the command neuron concept is still extant in the most current neurobiological literature. Some accept the revisionist "command-like" neuron concept--believing that no neurons exist which can satisfy the strictures outlined in "The Command Neuron Concept". Others cling to use of the original command neuron concept as useful, rejecting the Kupfermann and Weiss strictures, and using less stringent definitions of the term (. Most seem to believe that there is a spectrum of pre-motor command organization: from parallel distributed networks on the one end, to command neurons on the other (Edwards et al. 1999)