Lorente de Nó: From Neuroanatomy to Neurophysiology
ABSTRACT
Rafael Lorente de Nó (1902–1990) was the youngest and last of Santiago Ramón y Cajal's students. With Fernando de Castro, Lorente de Nó helped to transition the focus of Ramón y Cajal's School from neuroanatomy to neurophysiology. His main contributions to neuroscience concerned the cytoarchitecture of the cerebral isocortex and hippocampus, neural networks, central vestibular system anatomy, vestibulo-ocular reflex physiology, cochlear nuclei anatomy, and synaptic transmission mechanisms. This article pays tribute to the memory of Lorente de Nó by providing a comprehensive review of the life and work of this giant of neuroscience. Anat Rec, 303:1221–1231, 2020. © 2019 American Association for Anatomy
Rafael Lorente de Nó was the youngest and last of Santiago Ramón y Cajal's students (Fig. 1). He was born on 8 April 1902 in Zaragoza, Spain, to Francisco Lorente and Maria de Nó, who were an affluent family. Lorente de Nó graduated from high school in 1916. A year later, when he was at college, he published his first scientific paper entitled, Temperatura (Temperature), a mathematical essay on thermodynamics that left his audience astonished when he presented it. At the end of Lorente de Nó's presentation, Jerónimo Vecino y Varona, a Full Professor of Physics at Zaragoza University, claimed, “He would be an ingrate to God, who has given him the talent, and to the Motherland, so needed of scientists, if, guided exclusively by the idea of professionalism, he wasted these conditions that he possesses and that can well be qualified as exceptional” (Lorente de Nó, 1917).
In 1917, Lorente de Nó began to study medicine in his native city; however, although his academic record was full of honors, soon he became more interested in the laboratory than in theoretical classes. For this reason, he became a histology intern with Professor Luis del Río, who Lorente de Nó helped with publishing his lecture notes on histology. Lorente de Nó also wrote a paper on the involvement of the nervous system in rabbits with hepatic coccidiosis as well as another paper on the batrachian dorsal longitudinal fasciculus (Lorente de Nó, 1920a, 1920b).
Pedro Ramón y Cajal (1854–1950), a Full Professor of Obstetrics and Gynecology at the University of Zaragoza, advised Lorente de Nó about an opportunity to conclude his studies at the University of Madrid, where his brother, Santiago Ramón y Cajal (1852–1934), was the Chair of Histology and Pathology. Ramón y Cajal had been awarded the Nobel Prize in 1906 “in recognition of his work on nervous system structure.” When the young Lorente de Nó arrived at the laboratory, Ramón y Cajal asked him, “So, what do you think about Cajal?” and he replied, “Which one, the Master who described the structure of the nervous system, winning the Nobel Prize, or the one that has done little afterwards?” (Larriva-Sahd, 2002).
An Aragonese1 boy was newly incorporated into Cajal's School. His name was Lorente de Nó, a third-year student of medicine, who had moved his enrolment to Madrid … He had an interest in and aptitude for histology and had published a work already … nobody knew from A to Z like him and Cajal's work, especially, the monumental Texture of the nervous system. … That young memorist was an intelligent man, very promising, a true child prodigy, and for this reason, and because he was Aragonese (not a despicable circumstance) and had letters of recommendation from don Pedro Ramón y Cajal, he was welcomed with open arms by Tello and don Santiago. The latter drooled listening to him speak about nuclei and nervous tracts and when he gave his opinion as any wise person would about disputed issues (del Río-Hortega, 2015).
From his initial work in Ramón y Cajal's lab, the young student, Lorente de Nó, published various papers in Trabajos del Laboratorio de Investigaciones Biológicas, which was the journal of Ramón y Cajal's lab. In 1922, Lorente de Nó graduated from the University of Madrid and became a Ph.D. student in the Ramón y Cajal laboratory. That year, Ramón y Cajal retired, and Lorente de Nó contributed to a book to honor him with a paper about trigeminal nerve anatomy (Lorente de Nó, 1922). When Lorente de Nó was only 20 years old, he published a seminal study on the mouse cerebral cortex (Lorente de Nó, 1923). This paper contains detailed descriptions of many types of neurons based on Golgi staining of what is now known as the primary somatosensory cortex or, more specifically, the barrel field (Fig. 2A; Kruger and Woolsey, 1990; Fairén, 1993; Woolsey, 1993, 2001; Fairén, 2007; Larriva-Sahd, 2014). These investigations were his debut into this particular field and would culminate in 1938 with the publication of a chapter on cerebral cortex architectonics and structure in John Fulton's treatise on the Physiology of the Nervous System (Lorente de Nó, 1938a). Lorente de Nó postulated “that the cortex is composed of an enormous number of elementary units, which are not simply juxtaposed, but overlapping” (Fig. 2B). His findings were the basis of hypotheses on the columnar organization of the somatic sensory cortex developed by Vernon Mountcastle and later on the organization of the visual cortex by David Hubel and Torsten Wiesel (Mountcastle, 1957; Hubel and Wiesel, 1962). Lorente de Nó's elementary units of operation are now called cortical minicolumns (Buxhoeveden and Casanova, 2002). In 1981, Wiesel and Hubel received the Nobel Prize “for their discoveries concerning information processing in the visual system,” which they shared with Roger W. Sperry “for his discoveries concerning the functional specialization of the cerebral hemispheres.”
In December 1923, Lorente de Nó returned to Zaragoza to attend a 12-day course on vestibular physiology and exploration, which included surgical demonstrations. This course was taught by Robert Bárány (1876–1936) at the Zaragoza University School of Medicine. This was a momentous event in the life of Lorente de Nó as Bárány had been awarded the Nobel Prize in Physiology or Medicine in 1914 “for his work on the physiology and pathology of the vestibular apparatus.” Immediately after the first talk, Lorente de Nó approached Bárány to ask him some questions. Bárány was astonished when the young Spaniard explained how he could remove the fast component of nystagmus by making a short and exceedingly narrow incision along the midline of the brainstem. The next morning, Lorente de Nó performed an experimental demonstration in rabbits, and Bárány posed a question about which ocular muscles were involved in the slow component of nystagmus. Afterwards, Bárány dissected the six eye muscles and removed the eyeball to observe that only the external rectus muscles were involved in the slow phase of nystagmus provoked by rotation or caloric stimulation. Bárány asked Lorente de Nó if there was equipment in Madrid that could record the responses of individual eye muscles. Because it was impossible to get such equipment in Spain, Bárány proposed that Lorente de Nó continue his investigations in Uppsala, where he could be provided with the necessary materials. Next, they traveled to Madrid, where Bárány had been invited to give some lectures, and visited the retired Ramón y Cajal, who approved of Bárány's plan. Subsequently, both of the Nobel laureates visited the Prime Minister of Spain to request military leave for Lorente de Nó as well as a grant for him to work in Sweden with Bárány, which he later received through the Junta para la Ampliación de Estudios e Investigaciones Científicas (Council for the Extension of Studies and Scientific Research; Lorente de Nó, 1987).
Consequently, Lorente de Nó embarked on a journey to Uppsala in April 1924. However, he first stopped in Utrecht where he visited the Pharmakologist Institute directed by Rudolf Magnus (1873–1927). Although Magnus was a Professor of Pharmacology, he worked on the physiology of postural reflexes and had published in that same year his famous work entitled, Körperstellung (Posture) (Magnus, 1924). There, Lorente de Nó learned experimental methods from the otorhinolaryngologist A. de Kleijn, surgeon G. G. J. Rademaker, and C. Versteegh. In Utrecht, he also visited the eminent neuroanatomist Cornelis Winkler who was a Professor of Neurology and Psychiatry. Winkler had studied the central course of the eighth cranial nerve and had published two beautiful cat and rabbit brain atlases based on experimental research (Winkler, 1907; Winkler and Potter, 1911). Lorente de Nó also visited Jan van der Hoeve, a Professor of Ophthalmology at Leiden University. Finally, by the end of April 1924, Lorente de Nó reached Uppsala, where he worked for three years in a laboratory provided by Professor Gustaf Göthlin and was completely dedicated to studying the physiology of the labyrinth.
During his time in Uppsala, Lorente de Nó frequently corresponded with Ramón y Cajal. Their remote, but strong, relationship was maintained when Lorente de Nó eventually went to America and until Ramón y Cajal's death in 1934. In fact, the letters Ramón y Cajal sent to and received from Lorente de Nó, together with those he exchanged with Gustav Retzius, represent the bulk of his written correspondence preserved to date (Fernández Santarén, 2014). In these letters, most of which consisted of scientific content, Lorente de Nó reported on his research progress, Ramón y Cajal gave him advice on staining methods, and they both exchanged offprints of their publications. Lorente de Nó often fiercely criticized the work of other researchers, sparing no one. Moreover, they exchanged opinions about the future of the Cajal Institute as well as the performance of different Spanish Neurological School members. Lorente de Nó also encouraged Ramón y Cajal to prepare a new edition of his opus magnum, Histologie du système nerveux de l'homme et des vertébrés (Ramón y Cajal, 1909). In these letters, one notices not only the feelings of mutual respect and admiration but also the fondness that both men had for each other.
Lorente de Nó and Fernando de Castro (1896–1967), who discovered carotid body chemoreceptors, were the youngest students of Ramón y Cajal and had a brotherly relationship with each other. De Castro and Lorente de Nó coauthored a paper criticizing del Río-Hortega's hypothesis concerning the similarities between oligodendroglia and Schwann cells (del Río-Hortega, 1922; de Castro and Lorente de Nó, 1923); however, this hypothesis was confirmed by electron microscopy decades later (de Robertis et al., 1958). Both students had a filial devotion and veneration toward their dear mentor, Ramón y Cajal. In a letter to de Castro, Lorente wrote, “Do not stop giving me news of the health of don Santiago. In your letter, when you call him our father, you express a great truth. What we owe him personally and scientifically cannot be repaid. I trust that he will have time to see how we two can be his continuators” (Rafael Lorente de Nó to Fernando de Castro. 25 June 1926. Letter. Archivo Fernando de Castro, Censo-Guía de Archivos de España e Iberoamérica #ES.28079.AFC; Madrid, Spain).
With Bárány's approval, Lorente de Nó interrupted his work in Uppsala between October 1926 and February 1927 for a research stay at the Kaiser Wilhelm-Institut für Hirnforschung und Neuro-Biologisches Institut der Universität in Berlin. At that time, the Kaiser Wilhelm Institute for Brain Research, which was founded in 1914, was the world's largest and most modern brain research institute. There, Lorente de Nó worked with the married couple Oskar Vogt (1870–1959) and Cécile Mugnier (1875–1962) on the anatomy of the medulla oblongata and cytoarchitecture of Ammon's horn. In September 1927, Lorente de Nó returned to Spain to fulfill a 10-month compulsory military service, but he was able to return to Uppsala one year later. From September to November 1928, Artur Blohmke (1888–1957) and Lorente de Nó worked in Uppsala on electrically induced nystagmus and then continued their investigations for another two months at the Physiological Institute in Königsberg, East Prussia, which is now known as Kaliningrad, Russia.
Lorente de Nó said that he was received with open arms at Bárány's home. During his time in Uppsala, Lorente de Nó had dinner every Sunday with the Báránys, and, almost every night, after having dinner in a nearby restaurant, he conversed with Bárány for a couple of hours. Lorente de Nó stated that “our numerous discussions on the cortex were always very lively and at times quite noisy” (Lorente de Nó, 1987). Years later, when Bárány died in 1936, Lorente de Nó wrote an obituary for The Laryngoscope (Lorente de Nó, 1936). Lorente de Nó reminisced about Bárány, but he declined to write about Ramón y Cajal.
As a result of his work in Uppsala, Lorente de Nó published numerous papers in several languages on the anatomy and physiology of the eighth cranial nerve and vestibular reflex mechanisms (Fig. 3) (Lorente de Nó, 1925a, 1925b, 1926, 1927, 1928a, 1928b, 1928c). He also published an over 200-page book entitled, Die labryrinthreflexe auf die augenmuskeln nach einseitiger labyrinthexstirpation (Labyrinthine reflexes of the eye muscles after unilateral extirpation of the labyrinth), in which he detailed his experiments on rabbits (Lorente de Nó, 1928d). He first studied the normal labyrinthine reflexes of each ocular muscle and then studied these reflexes after damage by extirpating one labyrinth or experimentally producing lesions in the vestibular pathways, nuclei, and nuclei central projections. Lorente de Nó concluded that the quick phase of nystagmus depends on substantia reticularis integrity and stated that “the nucleus ruber cannot be the center of origin of righting reflexes or of the normal apportionment of tone in the extremities” as was previously confirmed by Magnus and Rademaker.
At the end of 1928, Lorente de Nó returned to Spain. However, his lack of financial support and difficulties achieving a full-time position at the Cajal Institute led him to accept an appointment proposed by Ramón y Cajal as the Head of the Otorhinolaryngology Department at a newly founded hospital called Casa de Salud Valdecilla in Santander, Spain. In 1929, Lorente de Nó started his otorhinolaryngology specialization with Professor Antonio García Tapia (1875–1950), a prestigious laryngologist and Chair of Otolaryngology at the School of Medicine of Madrid. After spending a few months working in the clinics of Tapia, he completed his training as an otorhinolaryngologist and spent short periods in Berlin, Königsberg, and Frankfurt am Main, as well as Uppsala, where he benefited from his reputation as an otologist trained by Bárány. At the start of 1930, Lorente de Nó arrived in Santander, which is on the north coast of Spain. The Casa de Salud Valdecilla, which was the most modern hospital in Spain at the time, had a superb vestibular system anatomy and physiology laboratory, which was created especially for Lorente de Nó. During his 11-month period there, he treated over 1,100 patients and performed 933 surgical procedures, including thyroidectomies, laryngectomies, radical mastoidectomies, and nasosinusal procedures (Anales de la Casa de Salud Valdecilla, 1930). This heavy clinical burden in addition to only having two assistants interfered with his research. Many years later, Lorente de Nó stated, “I soon discovered two disturbing things, the practice of otolaryngology is repetitious and, consequently, often boring, and as long as I had to take care of the clinical department, I would not have the energy, nor the desire, nor the time, to carry out scientific research” (Lorente de Nó, 1987).
At the time, Bárány advised him stating, “I believe you have already lost too much time with the clinical work. Nevertheless, your task, I insist, should be scientific work. We are still in debt regarding the publication of your last investigations in Uppsala” (Rafael Lorente to Santiago Ramón y Cajal, July 1930. Letter. Ms 22112–151. Biblioteca Nacional de España, Madrid, Spain).
De Nó is only 27. He has had 4 years with Ramón y Cajal and 3 years previously with Cajal's brother. He has furthermore had 4 years of work with Bárány, and his knowledge of labyrinth function and disease is probably unequalled by a man of his generation. Vogt told me that he has all the earmarks of a genius (Alan Gregg to R.M. Pearce, 19 September 1929. Letter. Rockefeller Archive Center).
Following this, Lorente de Nó received an offer to become the Research Director of the Neuro-Anatomical Research Laboratory of the CID. In the summer of 1930, he decided to resign from his position at Valdecilla.
Dear friend, Lorente:
Your letter fills me with stupor. To leave to Yankeeland,2 the country in which the Spanish are considered to be beings of a low and despicable race! Moreover, to leave Spain and the Council for Further Studies that have made enormous sacrifices, so you could get away from the military service and acquire a complete scientific education!
But, all in all, if your resolution is firm there is nothing to object.
…
Prepare yourself to speak English, if you are completely determined, because, in America, French is not spoken and few know German, and none Spanish. Think it well before taking such a radical agreement.
In any case, I am sorry for your expatriation, and I only wish you would be OK in those lands so inhospitable to the Spanish.
You know you are loved by your old friend (who is passing a disastrous senescence between some things and others) who really loves you (Santiago Ramón y Cajal to Rafael Lorente de Nó, ca. June–July, 1930. Letter. Ms. 22112-150. Biblioteca Nacional de España, Madrid, Spain).
… nor have I still lost completely the hope to be able to, one day, work in Spain. … I accepted the position because the time in Santander was becoming long to me, where, overwhelmed by the clinical work, it was impossible to realize any scientific labor and so with one thing and another, for almost three years, I have left my studies. … I become an expatriate thinking that a return to Spain to “do science" would have to be under conditions in which the need for “making money” would be excluded. … In Spain nowadays, in medicine, there is still no scientific atmosphere and most of the talented people who return are lost (Rafael Lorente de Nó to José Castillejo, 7 January 1931. Letter. Exp 88-335. Archivo Junta de Ampliación de Estudios, Residencia de Estudiantes, Madrid, Spain).
Years later, in 1952, Lorente de Nó was offered the opportunity to return to Spain to work for six months a year at the Cajal Institute; however, his offer was not accepted (Gallego, 1990).
In my opinion, the investigators' wives have the major merit. I speak from experience and in strict justice. Who doesn't remember what Cajal wrote about his wife, the spirit of self-denial that would encourage her and her total dedication at any cost for her husband's work? I can say the same about mine. I see in Hede, that's my wife's name, a reflection of my fellow countrywoman Mrs. Silveria. Now, leaving her in New York, with our daughter for this short stage, I realized, more than ever, how she has supported me in all of the worst moments and how much I owe her for what I might have done (ABC (Madrid), 20 March 1949, p. 7).
In the autumn of 1931, the couple left Spain for St. Louis, where Lorente de Nó began to prepare his previous work for publication in English. This work was published in the next few years and mainly concerned the central structures and mechanisms involved in the generation of the fast phase of nystagmus, vestibulo-ocular reflex arc complexity, and the role of interneurons (Fig. 4A,B) (Lorente de Nó, 1932, 1933a). He also published two classic papers that provided precise and meticulous anatomical descriptions of acoustic nerve anatomy. This work described hair cell innervation and the cochlear nuclei projections preserving tonotopic organization (Lorente de Nó, 1933b, 1933c).
Furthermore, Lorente de Nó published two additional papers concerning his previous Berlin-based investigations of the entorhinal cortex and hippocampal formation (Lorente de Nó, 1934a, 1934b). These papers accurately described the cytoarchitecture and connections of the hippocampus and established a nomenclature for the fields of Ammon's horn, which is still used worldwide (i.e., CA, cornu ammonis; CA1–CA4). He also compared the entorhinal areas of the mouse, monkey, and human and concluded that they had the same basic structural plan. Finally, Lorente de Nó studied entorhinal function and proposed that entorhinal neurons work as a summation apparatus (Swanson, 1993).
When Lorente de Nó arrived in St. Louis in 1931, the CID was associated with Washington University. There, the pioneers of electrophysiology Joseph Erlanger (1874–1965) and Herbert S. Gasser (1888–1963) worked on recording action potentials from the bullfrog sciatic nerve using a cathode ray oscilloscope. In 1944, they were jointly awarded the Nobel Prize in Physiology or Medicine “for their discoveries relating to the highly differentiated functions of single nerve fibers.” Their daily contact with Lorente de Nó would be crucial for changing the direction of his research from neuroanatomy to neurophysiology. Thus, he would go one step further than his mentor Ramón y Cajal by integrating structure and function. In a letter to Ramón y Cajal, Lorente de Nó's transition from neuroanatomy to neurophysiology started to show when he stated that “the physiology of the nervous system is at a standstill” and “current physiology starts discussing problems in terms of the activity of individual neurons.” Next, he told Ramón y Cajal how he organized his work in such a way that “the mornings are dedicated to anatomy and the evenings to physiology” (Lorente de Nó to Santiago Ramón y Cajal, 28 May 1933. Letter. Archivo Fernando de Castro, Censo-Guía de Archivos de España e Iberoamérica #ES.28079.AFC; Madrid, Spain).
Anatomical research gives gloss and reputation only when physiologists find applications for it and, when one wants to live their life based on pure science, they have to do research that can be continued by other people. This is why I am dedicating half of my time to physiological experiments (Rafael Lorente de Nó to Santiago Ramón y Cajal, 10 April 1934. Letter. Ref. 7541. Cajal Legacy, Cajal Institute, Madrid, Spain).
Following this, he discussed modern methods to study the action potentials of neurons using the cathode ray oscilloscope.
Dear colleague and friend,
I am seriously sick with a colitis that has lasted nearly two months and does not allow me to leave the bed, eat, or write. This letter serves to tell you that I received your work on the Ammon's horn of the mouse, and I am thankful for the gift.
Only two observations:
- Spines. Note that they are not sharp irregular excrescences, but instead, are genuine spines ending in a ball. The pedicle [neck] is sometimes too pale.
- Ammon's horn. The mouse is not very favorable for a structural study. It is difficult to find short axon cells, and there is an excessive tendency to [stain] clumps of fibers without detailing their origin or termination.
Why have you not worked with 20- to 40-day-old rabbits? The [method of] Cox gave me magnificent isolated [axonal] arborizations of short-axon cells and a multitude of details that cannot always be seen with the method of Golgi.
Warm greetings from your old friend,
Cajal (Santiago Ramón y Cajal to Rafael Lorente de Nó, 15 October 1934. Letter. Colegio Oficial de Médicos, Madrid, Spain).
Knowing Ramón y Cajal's personality, it is not surprising that, hours before expiring, he accompanied the letter's text with an anatomical drawing of the dendritic spines. The really surprising finding is that the role of spines in mediating synaptic connectivity was not confirmed until the end of the 1950s with the advent of the electron microscope.
During these years in St. Louis, Lorente de Nó became familiar with the cathodic ray oscilloscope with Helen T. Graham. Following this, he switched to electrophysiology and began recording extraocular muscle responses using electrodes placed in eye muscle motoneuron nuclei at the floor of the fourth ventricle and in the superior colliculus. He studied the refractory period and synaptic delay of oculomotoneurons and developed the concept of temporal and spatial impulse summation (Lorente de Nó, 1935a, 1935b, 1935c).
In 1935, Lorente de Nó was appointed as a Lecturer of Neuro-otology at the Washington University School of Medicine in Saint Louis. However, the effects of the Great Depression caused drastic research budget cuts, and the support Lorente de Nó received from the Rockefeller Foundation came to an end. At this time, Lorente de Nó thought about returning to Spain. Fortunately, in 1936, Gasser, who in 1935 became the second director of the Rockefeller Institute for Medical Research, invited him to join the Institute along with other neuroscientists, such as Harry Grundfest, Birdsey Renshaw, and David P.C. Lloyd, to create a major center for neurophysiology research (Chase and Hunt, 1995). Lorente de Nó accepted the offer and moved to the Rockefeller Institute, where he worked until his official retirement. Initially, he assumed the position of Associated Investigator. In 1941, Lorente de Nó became a member, and, finally, in 1953, which was the same year that Gasser retired, he became a professor after the Rockefeller Institute became a part of the University of the State of New York (Corner, 1965; Kobler, 1970).
The active neurons are arranged in convergent chains of relatively simple composition, which may be called multiple and closed chains through which impulses circulate. The multiple chain of neurons is the elementary unit of transmission; it supersedes the classical reflex arc with a fixed number of synapses (Lorente de Nó, 1938b).
These ideas would later support the neuropsychological theory of the organization of behavior postulated by Donald O. Hebb (1904–1985) as well as the neural basis of learning (Hebb, 1949). The concept of cell assembly proposed by Hebb is based on the reverberating circuits of Lorente de Nó. In a letter to Lorente de Nó dated 26 April 1949, Hebb writes, “I believe that my book will be able to show that modern ideas in neurophysiology, and particularly some of those you have developed, have a revolutionary significance for psychological theory” (cited by Brown and Milner, 2002).
As we have seen, Lorente de Nó was a pioneer of neural modeling. His discovery of neurons with recurrent axons in the brainstem is regarded as the first biological evidence for the existence of a feedback loop (Lorente de Nó, 1933a). However, a lesser known facet of his career is the role he played in the development of cybernetics. In 1948, the term cybernetics was coined by the mathematician and physicist Norbert Wiener to describe a theory of communication and control in machines and living organisms (Wiener, 1948). In 1942, a multidisciplinary meeting on “Cerebral Inhibition” took place in New York under the auspices of the Macy Foundation. This first meeting was attended by the neurophysiologists Arturo Rosenblueth, Warren McCulloch, and Lorente de Nó, among others. In 1945, Wiener organized an exclusive gathering at Princeton inviting seven people, including Lorente de Nó. During this meeting, Lorente de Nó and McCulloch spoke about how their brain model was serving as a model for the von Neumann machine, which was the first binary electronic computer with data and programs stored in the same memory. From 1946 onward, the Macy Foundation funded a series of conferences for this new field. The first conference was held in New York, and the first lecture was jointly given by Lorente de Nó and John von Neumann (1903–1957), who was the foremost mathematician at the time. Their lecture was about the correlations between artificial networks and neuronal circuits (Heims, 1993; Malapi-Nesson, 2017).
Lorente de Nó actively participated in two scientific disputes which wasted 30 years of his life. The first controversy was about the nature of synaptic transmission and is known as “The War of the Soups and the Sparks” (Valenstein, 2006). The pharmacologists led by Henry Dale and Otto Loewi considered the transmission of nerve impulses to be a chemical process, whereas the neurophysiologists, including John Eccles, Gasser, Erlanger, and Lorente de Nó, maintained that impulse transmission was electric. By 1945, based on his own experiments, Eccles began to accept the chemical hypothesis. However, it was not until 1949 that Lorente de Nó finally accepted the chemical hypothesis at a meeting held in Stockholm, where he, Sir Henry Dale, and Corneille Heymans were invited to the inauguration of the Physiology and Pharmacology laboratories at the Karolinska Institutet. This key dispute in the history of neuroscience was “won” by the pharmacologists (Bacq, 1975). Dale and Loewi had already received Nobel Prizes in 1936. Their opponents Erlanger and Gasser were awarded in 1944 and, in 1963, Eccles received the Nobel Prize. Paradoxically, the discovery of electrical synapses at gap junctions had partially informed Lorente de Nó's view as well as that of Camilo Golgi for his reticular theory, which refuted Ramón y Cajal's neuron theory (Revel and Karnovsky, 1967; Yuste, 2016).
The investigations in peripheral nerves of the properties of nervous tissue are a direct and profitable method to study the elementary processes that take place in the nervous system. Knowledge of the properties of nerves may not result in the immediate solution of the problems offered by the central nervous system, but it supplies challenging analogies and working hypotheses.
Thereafter, Lorente de Nó decided to examine peripheral nerves with a series of experiments on the sciatic nerve of the bullfrog. This work culminated in his two-volume set A Study of Nerve Physiology (Lorente de Nó, 1947a, 1947b), which was known as the “telephone books” by physiology students. Lorente de Nó was very interested in using the mathematical theory of inert core conductors for the analysis of his experiments. Thus, when preparing A Study of Nerve Physiology, Lorente de Nó collaborated with Leverett Davis, Jr. (1914–2003), who he visited at the California Institute of Technology in 1940. During his studies on peripheral nerve impulse transmission, Lorente de Nó also synthesized tetraethylammonium, which is a quaternary ammonium cation that is widely used today to block voltage-dependent potassium channels (Lorente de Nó, 1948, 1949).
Unfortunately, this magnificent work contained significant mistakes that overshadowed Lorente de Nó's career (Kruger, 1993). He argued that the connective tissue sheath did not serve as a barrier to solute diffusion or current flow. Moreover, he stated that “the epineurium is only a relatively small part of the connective tissue sheath of the nerve” (Lorente de Nó, 1947a, 1947b, 1947c). These ideas formed the basis of Lorente de Nó's second controversy, which was known as the “Battle of the Sheath” (Fig. 6). He also argued that saltatory conduction of action potentials did not occur along myelinated axons by jumping from one node of Ranvier to the next (Huxley and Stämpfli, 1949). Moreover, he incorrectly argued that the resting potential of neurons did not depend on ionic gradients. However, he did find that the demarcation potential (i.e., the potential difference between the intact and cut ends of a nerve) and, therefore, the resting membrane potential, depend on oxidative metabolism. The ionic hypothesis postulated by Alan Hodgkin and Bernard Katz explained the ionic mechanisms underlying the initiation and propagation of action potentials (Hodgkin and Katz, 1949). The final nail in the coffin for Lorente de Nó was a series of five seminal papers published by Hodgkin and Andrew Huxley in 1952. In these studies, Hodgkin and Huxley worked with single nerve fibers dissected out of the nerve trunk of squid giant axons. Their findings disproved more than a decade of work by Lorente de Nó (Lorente de Nó, 1950). Far from capitulating, Lorente de Nó appeared to adopt the role of Don Quixote tilting at windmills by referring to the “so-called sodium hypothesis” in his lectures (Woolsey, 2001). His arguments, delivered in a passionate, combative, and stubborn manner, gained him many enemies and eliminated his chances of receiving the Nobel Prize. In the early 1950s, Lorente de Nó had been one of the strongest candidates for the Nobel Prize. According to the Nobel Prize nomination database, he was nominated in 1949, 1950, 1952, and 1953.
In 1959, Lorente de Nó suggested that the decremental conduction of dendritic spikes might play an important role in synaptic integration by generating spikes in dendrites that would not reliably propagate to the soma (Lorente de Nó and Condouris, 1959). Therefore, the effect of dendritic spikes would be to actively amplify depolarization associated with certain synaptic inputs without necessarily triggering an action potential (Yuste and Tank, 1996; Spruston et al., 2016).
In contrast to his mentor, Lorente de Nó did not establish a school in the United States. He was more of a solitary investigator and was usually the sole author of his papers or only had a single collaborator. These collaborators included Helen T. Graham, Birdsey Renshaw, T. P. Feng, C. L. Cazzullo, Yves Laporte, James O'Leary, Antonio Gallego, G. A. Condouris, Vicente Honrubia, Makoto Matsumoto, and A. S. Marrazzi.
Lorente de Nó was naturalized as a United States citizen in 1944. He was a member of the Collegium Oto-Rhino-Laryngologicum Amicitiae Sacrum from 1926 and was also a member of the American Physiological Society, American Association of Anatomists, and American Neurological Society. In 1950, Lorente de Nó was elected as a member of the National Academy of Sciences. Later, in 1954, he was elected as a fellow of the American Academy of Arts and Sciences. In 1951, he was the first speaker to give a lecture at the annual banquet of the Cajal Club. In 1959, Lorente de Nó won the first Karl Spencer Lashley Award from the American Philosophical Society. He also received the Award of Merit from the Association for Research in Otolaryngology in 1986. He was awarded honorary degrees by the University of Uppsala (1953), Clark University, and Rockefeller University (1978).
After his official retirement in 1972, Lorente de Nó was invited by Victor Goodhill and his student Vicente Honrubia to move to the University of California in Los Angeles (UCLA) with the support of the Ahmanson Foundation and Hope for Hearing Foundation. There, Lorente de Nó was appointed as a Professor Emeritus of Anatomy at the Division of Otolaryngology - Head and Neck Surgery and Brain Research Institute at UCLA. During this period, he prepared a chapter entitled, Central representation of the eighth nerve, for Goodhill's book entitled, Ear Diseases, Deafness, and Dizziness (Lorente de Nó, 1979). This chapter was the prelude to his acclaimed book The Acoustic Nuclei (Lorente de Nó, 1981). In the preface, Lorente de Nó expressed that most of the work described was completed by 1938; however, the cost of its numerous illustrations prevented its publication, which allowed it to languish in the drawers of a cabinet for more than four decades! Actually, Lorente de Nó's cochlear nuclei studies began in 1920 in Madrid and then continued in Uppsala, St. Louis, and, finally, New York. In a letter to Ramón y Cajal written on 14 October 1930 when Lorente de Nó was working as an ear, nose, and throat surgeon at Valdecilla, he told Ramón y Cajal that “every patient I operated on was required to bring me kitties that were age-adapted for Golgi staining and, this way, I have been able to assemble Golgi preparations of more than 250 cat medulla oblongata samples” (Rafael Lorente de Nó to Santiago Ramón y Cajal, 14 October 1930. Letter. Ref. 7245. Cajal Legacy, Cajal Institute, Madrid, Spain). Over 30 years later, Goodhill encouraged Lorente de Nó to resume this work. Although most of this work, including the drawings, had been performed previously, Lorente de Nó thoroughly revised the literature and recognized his earlier mistake in which he had mislabeled the position of the basal and apical cochlear turns, where the nerve fibers penetrate the cochlear nucleus.
In 1979, Lorente de Nó retired from UCLA and moved with his daughter Edith to Tucson, Arizona, because of its dry climate, which was appropriate for the progressive emphysema that he developed as a smoker. On 2 April 1990, he died of cancer there at the age of 87.
ACKNOWLEDGMENTS
Prof. Fernando Salmón of the University of Cantabria and Mario Corral of the Marquesa de Pelayo Library, Santander, provided some relevant documents related to the work of Lorente de Nó at Valdecilla Hospital. We are also indebted to Bethany Antos of the Rockefeller Archive Center for her kind help with attaining archival documents. Fernando de Castro Soubriet generously gave us free access to the Fernando de Castro Archive, which is part of the Archives of Santiago Ramón y Cajal and Spanish Neurohistological School and is registered as a Memory of the World by the United Nations Educational, Scientific, and Cultural Organization (UNESCO). The authors thank Marisa Flook for reviewing the manuscript.
