Animal Models in Neuroscience

Invertebrate Models 

The squid giant axon is pretty well renowned for his its applications neuroscience research. J Z Young discovered the giant squid axon and giant squid synapse and was the first to apply it neurophysiological research. The giant squid (loligo pealii) was and is still considered to extrodinarly vital to neuroscience research because of the sheer size of its axon (<1mm). It’s size makes it easy to dissect and support. External and internal perfusion with varying saline levels allowed scientists to determine ion flows in action potential.  Using the giant squid axon, Alan Lloyd Hodgkin and Andrew Huxley won the Nobel Prize in Physiology or Medicine in 1963 for developing Hodgkin–Huxley model mathematical model that describes how action potentials in neurons are initiated and propagated.

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In electrophysiology, worms are used as a model for cellular death (apoptosis) and development and are also studied because of their relatively large axon. The C.elegans a nematoda (roundworm) is often studied because its genome, nervous system and genetic regulation of behaviour has been fully mapped. Specifically, these roundworms are an ideal model for apoptosis.

Fruit flies or drosophilia melangosaster have probably come up a fair few times if you have ever taken biology. Fruit flies are used in neuroscience for the identification of genes regulation nervous system development. In particular, the role of pax-6 in the development and evolution of the eye.

Vertebrate Models 

Frogs 

Italian physician Luigi Galvani in his frog studies showed that muscles can be caused to twitch when electrically stimulated.

German physician and physicist Hermann von Helmholtz isolated the nerve conduction velocity to be between a range of 24.6 – 38.4 meters per second.

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Ross G. Harrison was the first person to make observations of axonal growth whilst studying tadpoles in vitro.

Katz and Miledi whilst studying frogs observed the role of calcium ions in the release of neurotransmitters.

The neuropsychologist Roger W. Sperry, known for his split-brain research that lead his Nobel Prize in 1981, observed rats and frogs discovering how nerves pathfind.

Birds

The domestic chicken (gallus domesticus) have been used again and again the study of brain development because of how easy they are to study. Chickens are so easy to study because of how ‘simple’ it is for scientists to manipulate the embryo. Being able to manipulate the embryo means the scientists have been able to transplant genes, tissue and nerve growth factors to study the effects.

Konrad Lorenz an Austrian zoologist,ethologist, and ornithologist studied imprinting in chicks, which is when an animal comes to believe the first person, thing or animal they see is there mother.

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English biologist Steven Rose also used chicks to study passive avoidance learning, which is when a person or animals learns to stop doing a certain behaviour when it results in punishment.

Nichole Le Douarin transplanted regions of nervous system between quails and the domestic chicken to create a chimera, which has led to critical insights into the development of the nervous system and the immune system. Other notable researchers that have worked with the domestic chicken are Viktor Hamburger and Rita Levi-Montalcini.

Mammals and Non-Human Primates

Hitzig and Fritsch both German physicians used dogs to map out the motor cortex of dogs.

Using cats, dogs and apes English neurophysiologist, histologist, bacteriologist, and a pathologist Sir Charles S. Sherrington made huge progress to our current knowledge of reflexes, motor control and localisation in addition to coining the term synapse.

German pharmacologist Otto Loewi who discovered of acetylcholine, used dogs to study chemical neural transmissions. This discovery came from the stimulation of the vagus nerve releasing vagustoff, which caused a reduction  in the heart rate. This vagustoff was later confirmed to be acetylcholine. English neuroscientist Henry Hallett Dale later expanded on this discovery to study the release of ACh from the motor nerves in cats, dogs and frogs. He came up with Dale’s principle that individual nerves release a single neurotransmitter, which of course, was later proved false.

British physiologist John Langley named the autonomic nervous system and studied cats, dogs and rabbits to formulate the receptor theory.

American psychologist Karl Lashley searched for the engram (physical embodiment of memory) using ablations in rats to see how it would affect their memory performance in maze tasks.

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To famous psychological experiments involving mammals are those of American psychologist B.F. Skinner and Russian psychologist Ivan Pavlov. Pavlov conducted studies on dogs and coined the term what is now known as classical or passive conditioning via the pairing of stimuli. B.F. Skinner using a ‘Skinner Box’ and rats coined the term active or operant conditioning via reinforcement.

Kuffler (Hungarian-American neurophysiologist), Hubel (Canadian neurophysiologist) and Weisel (Swedish neurophysiologist) worked together on cats and monkey brains to map out receptive fields related visual processing.

Mice transgenics have also widely been used to study molecular dissection of behaviour and diseases in particular in relation to reward systems and development abnormalities.

Non-human primates are of particular interest to neuroscientists because they are of few animals with brains similar to ours, in particular they have a frontal lobe.