"...one of the major revolutions in neuroscience..."
Individually identifiable nerve cells are those neurons which "can be individually named, and distinguished from any others in the same animal, and can be identified with individual neurons in other specimens of the same species... The gradual recognition of the widespread reality of identifiable neurons and their consistent connectivity and dynamic properties - in the mid- and late 1970s - must be reckoned as one of the major revolutions in neuroscience" [emphasis in original].
Quotes above are from: Theodore H. Bullock (2000) Revisiting the Concept of Identifiable Neurons. Brain, Behavior and Evolution 55:236-240. [https://doi.org/10.1159/000006657]
Also see Theodore H. Bullock (1984) Comparative Neuroscience Holds Promise for Quiet Revolutions. Science 225: 473-478.I was introduced to the concept of identifiable individual nerve cells in 1970, during my first "rotation" as a graduate student in Ted Bullock's laboratory at UCSD / Scripps Institute where I was assigned to record electrical activity from one particular nerve cell (the "parabolic burster," R15) in the abdominal ganglion of Aplysia. The concept of identified individual nerve cells was central to my dissertation and has remained as an inspiration to most of my subsequent work.
Individually identifiable neurons are found in a wide variety of species, including at least some vertebrates. They have been most extensively studied in molluscs, crustaceans, and insects.
This concept can be extended beyond the identity of cells in different individuals of the same species, to include unique cells which can be recognized as individually identifiable homologues in related species (e.g., see discussion in On Neuronal Homology, King & Valentino, 1983).
Individually identifiable neurons not only provide a striking demonstration of the exquisitely intricate organization of nervous tissue. They also put into sharp focus the extent to which genetic information (and hence evolution) can shape specific details of unique individual cells (e.g., see What can giant axons tell us? and Evolution of neural circuits).
Also see Establishing Identified Neuron Databases (1994).The extent of neuronal differentiation is still being explored. In 2024, a whole-brain connectome of the laboratory fruit fly, Drosophila melanogaster, annotated 8,453 different cell types in a brain encompassing roughly 140,000 nerve cells in total. See Nature 634:139-152 (2024), https://doi.org/10.1038/s41586-024-07686-5. The New York Times also ran an article by Carl Zimmer on Oct. 2, 2024.
Comments and questions: dgking@siu.edu
SIUC / Zoology / David King
https://dgkinglab.siu.edu/IDneuron.htm
Last updated: 17 October 2024 / dgk