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Changing the Paradigm from Neurochemical to Neuroelectrical Models
Published in Hanno W. Kirk, Restoring the Brain, 2020
At about the same time, Spanish pathologist Santiago Ramon y Cajal, using Golgi’s new staining technique, came to a completely different conclusion. He was able to identify and follow individual long axons to their termination. Through this, he demonstrated that the neuron was the principal structural and functional unit of the nervous system. This became known as the Neuron Doctrine.4 This doctrine states that each nerve cell is separate and individual, bounded like all other cells in the body by its plasma membrane. He argued that the junction (or synaptic gap) between neurons was essential in regulating the transmission of signals in the nervous system. From his discovery of the axonal growth cone, he experimentally demonstrated that the relationship between nerve cells was contiguous, rather than continuous as Golgi had supposed.5 The Neuron Doctrine was initially very controversial and was opposed by Golgi and other histologists, who continued to defend the Reticular Theory past the turn of the 20th century.6,7
The Nerve Cell Laid Bare
Published in Andrew P. Wickens, A History of the Brain, 2014
In a period barely spanning a decade, Cajal had made a number of fundamental discoveries concerning the structure and function of the nervous system. Perhaps most of all, he had helped establish the neuron doctrine, which recognised the nerve cell as the basic unit of the brain and spinal cord. However, this also led to a baffling and awkward question: how could information flow within an ‘infinitely fragmented’ nervous system, as opposed to a continuous neural reticulum? If the neuron doctrine was correct, then each nerve cell was a separate entity. In other words, the axon and dendrite did not fuse together as reticulum theory demanded (this was also sometimes called the continuity hypothesis). However, the alternative option, otherwise known as the contact hypothesis, was also problematical, since it remained to be known how the impulse travelled from one nerve cell to another across a tiny gap. In this respect, the Golgi technique could offer few clues. The strength of the Golgi stain had been its random selectivity. By only staining a few nerve cells in any tissue sample, it had made them highly visible for a microscopist to observe. This was also a weakness when it came to trying to establish their connections, because it was unlikely the stain would highlight two consecutive nerve cells. Even if this did occur, the visualisation of the contact was beyond the resolution of the light microscope. Thus, the Golgi method, even in the hands of Cajal, was not suitable for revealing how the axon endings terminated with other cells.
Mechanisms of Somatosensory Plasticity
Published in Mark J Rowe, Yoshiaki Iwamura, Somatosensory Processing: From Single Neuron to Brain Imaging, 2001
Following widespread acceptance of the neuron doctrine, the initial challenge to neurobiologists in this century was to map out the pathways within the central nervous system and thereby to draw, wherever possible, correlations between structure and function in the CNS. In order to put this strategy into practice it was necessary to focus attention on the rigidity of nervous organization — a viewpoint that naturally tends to suppress the possibility that neuronal connections may be in a state of constant flux. Today it is true to say that neither of these views of the CNS can be wholly supported but that, instead, some middle path seems to hold the greater truth. The somatic sensory system has provided an admirable model for studies of plasticity in the mature brain. In this article we will explore some of the mechanisms underlying the malleability of connections in the somatic sensory system and show some new data that indicate how the brain itself can exploit this unstable substrate. In this paper we describe experiments that have revealed connectional changes (plasticity) at the level of (a) the spinal cord, and (b) the cerebral cortex, and we outline some recent results that indicate the potential of major regulatory systems to alter functionally connectivity in the pathway between the skin and the seat of consciousness — the cerebral cortex.
La Retina de los Vertebrados
Published in Journal of the History of the Neurosciences, 2023
Santiago Ramón y Cajal (1852–1934) was a towering figure among early students of the nervous system in the late-nineteenth and early-twentieth centuries. Using only a simple microscope and specially prepared sections of neural tissues, he produced a prodigious body of work, which laid the foundations of modern functional neuroanatomy. His elegant descriptions of nerve cells, combined with intelligent and creative interpretations of their functional significance, were keys to the widespread acceptance of nerve cells as individual units—the neuron doctrine. His remarkable life and accomplishments were made known to the world of modern neuroscience through his autobiography (Ramón y Cajal 1917, 1966) and numerous scientific reviews, and recently a wonderfully readable and illuminating full-length biography (Ehrlich 2022).
The transnational move of interdisciplinarity: Ginseng and the beginning of neuroscience in South Korea, 1970–1990s
Published in Journal of the History of the Neurosciences, 2022
Park put great emphasis on the interdisciplinary characteristic of neuroscience. He stressed that “there is little mutual understanding between, for example, electrophysiologists … and molecular biologists” studying the brain (Jung 1992, 97). In this context, according to him, although “since the beginning of the Neuron Doctrine … countless numbers of neuroscientists have provided much information on the functions of the human brain and the neuronal activity, [the] present status of our knowledge on the biological basis of consciousness and the mental process by which we perceive, act, learn and remember amounts to only the tip of an iceberg” (Organizing Committee of ISCTN 1992, i).
Neuroanniversary 2023
Published in Journal of the History of the Neurosciences, 2023
Camillo Golgi (1843–1926) was an Italian pathologist known for his works on the central nervous system. In 1873, he discovered a staining technique called black reaction, which was a breakthrough in neuroscience. For this and related work, he received the Nobel Prize for Physiology or Medicine in 1906, which he shared with Spanish histologist Santiago Ramón y Cajal (1852–1934). The two men represented contrasting opinions on nervous tissue, Golgi defending the network theory and Cajal the neuron doctrine he investigated using Golgi’s staining technique.