Arnold B. Scheibel

Arnold Bernard Scheibel (January 18, 1923 – April 3, 2017) was an American neuroscientist, professor of psychiatry and neuroanatomy, and the former director of the Brain Research Institute at the University of California, Los Angeles. He is well known for his research regarding the anatomy of the spinal cord, brain stem, and cerebral cortex. He introduced the concept of modular organization in the nervous system. His Golgi studies of human brain tissue extended the knowledge about the nature of neuronal changes in senile brain disease and in schizophrenia. He demonstrated the correlations between human cognitive activity and structural change, and also emphasized the role of plasticity in the living reactive brain."

Early years Scheibel was the only son of Ethel and William Scheibel. He was born on January 18, 1923, and raised in Manhattan and the Bronx. His mother, Ethel, was from old southern Germany, while his father, William, was from the old Austria-Hungary. When Scheibel was 5 years old, his aunt died in childbirth, leaving behind her newborn son, Milton, to be raised by his parents. His cousin Milton became "in every sense [his] brother". It was here that he began to realize that "the study of living things was more interesting than [he] could have guessed".

The second paper was on the inferior olive (Scheibel and Scheibel, 1955). This research was the basis for a Master of Science degree in anatomy from the University of Illinois awarded to him in 1953.

Overseas After being awarded a Guggenheim Fellowship in 1953, Scheibel went to Pisa to work with Giuseppe Moruzzi. His project, in collaboration with Amilcare Mollica, was to characterize inputs upon brainstem reticular cells using extracellular microelectrode recording techniques.

They discovered that each reticular neuron was the center of a widespread convergent pattern of idiosyncratic inputs, from ascending sensory systems, brainstem and cerebellar neurons, and cerebral cortex(Scheibel, Scheibel, Moruzzi, Mollica 1956).

Life in California At UCLA, Scheibel had joint appointments in the Departments of Neurobiology and Psychiatry.

After moving to UCLA, Scheibel began to establish the major features of reticular formation neurons. He was surprised at the axonal organization of large reticular cells, as some had bifurcating axons projecting both into the spinal cord as well as the diencephalon. Another surprise was the extreme degree of rostro-caudal compression of dendrite systems of reticular neurons (Scheibel and Scheibel, 1958). Since this organization resembled stacked poker chips, these discoveries eventually gave rise to the concept of modules in the nervous system.

Scheibel began to branch out from anatomy to physiology, and he used postnatal kittens as a model for investigating cortical and subcortical electrical rhythms. This research showed that individual reticular neurons quickly habituated to the familiar signal of repetitive stimulation. Scheibel could tell that this observation was not due to simple fatigue, since he also saw that a slight change to the input restored the original intensity and thus it was clear that these reticular neurons were excited by novelty and were turned off by the familiar (Scheibel and Scheibel, 1965a). Additionally, since the cyclical patterns between periods of sensitivity and insensitivity were mutually exclusive, Scheibel hypothesized that this might be a mechanism to prevent "individual neurons from being drawn increasingly into the input-output transactions of single neural domains" (Scheibel and Scheibel, 1965b). Due to Mila's health complications, this was the last study that they were able to share together.

In 1962, the Brain Research Institute at UCLA was created and with Mila's continued illness, Scheibel started doing all of his research at home, having a technician provide all the Golgi stained material.

Research on motor neurons John Eccles hypothesized that Renshaw cells were short-axoned cells in the CNS that had an inhibitory role, but the Scheibels found that there were no such cells. The only possible candidates for the Renshaw role were collateral extensions of typical long-axoned projecting interneurons. Eccles was so troubled by this finding that he refused to speak to them ever again (Scheibel, 1971a).

By 1970, it was already well known that motor neuron soma were grouped muscle by muscle. Dendrites on the other hand, seemed to seek contact with dendrites from other nuclei as they streamed rostrally and caudally, so it was thought that dendrites were not bundled like the soma. However, through comparing samples of the reticular core of neonatal rats with those of adult rats, Scheibel found that although the dendrites of neonatal neurons are spine covered and project to the surrounded neuropil, the dendrites of mature neurons are spineless and are grouped into bundles just like motor neuron soma. Both the dramatic loss of spines as well as the reorganization into complex bundles indicated a fundamental change in how these dendrites were wired (Scheibel and Schiebel, 1973). Due to this demonstration of extraordinary plasticity, Scheibel later even hypothesized that these dendrite bundle complexes were a possible site of memory storage (Scheibel, 1975).

Research on the thalamus The thalamus is made of twelve nuclei, and each has a different neuropil pattern. Thus, studying the thalamus presented "some of the most enjoyable and most challenging" problems Scheibel faced in his research. The landmark research published on the thalamus at the time included structural descriptions by Cajal (1911), connective studies by Walker (1938), O'Leary on the lateral geniculate (1940), and Herrick on the diencephalon of the tiger salamander (1948)

The thalamic intralaminar systems were already recognized as a neural basis of sleep-wakefulness, but histological studies done of them were minimal. Through thousands of Golgi stains, Scheibel was able to picture both the thalamocortical and corticothalamic tracts of the system.

The role of the nucleus reticularis thalami, referred to as "noyau grillage" by Cajal, was uncertain, until Scheibel's Golgi studies found that reticularis cell axons projected caudally into thalamic and mesencephalic neurons. Furthermore, it appeared that all thalamocortical and corticothalamic axons going down the nucleus reticularis made collateral connections with these cells. These connections were hypothesized to be the substrate for an inhibitory feedback control system between the thalamus and cortex.

Mila died on December 31, 1976.

Neurobiology of higher cognitive functions In the 1970s, scientists began to take a greater interest into the effects and process of brain aging due to the growing aging population, resulting in the formation of the geriatric medicine specialty. Without prior experience in this area, Scheibel was able to effectively fill his gap in knowledge and further the field's understanding of human age-related cerebral cortical changes through careful examination of brain tissues (Scheibel et al., 1975). He, interestingly, noticed areas of new growth in regions of degenerated brain tissue from Alzheimer's patients that he had not observed elsewhere, calling this growth a "last gasp" of the dying cells (Scheibel and Tomiyasu, 1978). He continued to utilize Golgi techniques during his time at UCLA to study temporal lobe epilepsy, where he published his findings that supported the hypothesis that the disease was progressive (Scheibel, 1980)

Scheibel also spent time working as a psychiatric consultant for Camarillo State Hospital, at which he encountered primarily patients diagnosed with schizophrenia. He was able to obtain brain tissue samples from people with schizophrenia that were about to be discarded from the hospital, and he then focused his research around studying this disease using Golgi techniques. Despite new findings regarding diseased-cell morphology, Scheibel set his work aside to focus on the severe progression of Mila's illness. These findings were then presented several years later at the Society for Biological Psychiatry Meeting in Chicago (Scheibel and Kovelman, 1981). Prior to the presentation, in 1979, Scheibel was invited to give a talk at the University of California, Berkeley by Professor Marian Diamond, a scientist whom he had never met. Scheibel found it difficult to forget "Marian's dynamic personality and sensitivity," and as a result, their relationship grew for several years. They then married each other in 1982 and continued to work at their respective universities.

Scheibel and his colleagues also found that dendritic branching varied in length and complexity between Broca's area (and its corresponding region in the right hemisphere) and bilateral motor areas. Furthermore, they found that, in comparing the language region bilaterally, the left (Broca's area) contained neurons with longer dendrites. (Scheibel et al., 1985). These findings inspired further study into bilateral differences of the cortical hemispheres.

Other aspects of academia In 1987, Scheibel became the acting director of the Brain Research Institute at UCLA, followed by promotion to Director by 1990 until 1995. Prior to these appointments, Scheibel had already been a faculty member at UCLA, teaching his own graduate neuroscience courses as well as conducting research in his laboratory at the university. (http://www.bri.ucla.edu/about-us/past-directors/arnoldscheibel) He also established Project Brainstorm at UCLA, an outreach program that teaches neuroscience concepts to K-12 students across the Los Angeles Unified School District (LAUSD). Additionally, Scheibel created the Ethel Scheibel Endowed Chair in Neuroscience in the Department of Neurobiology at the David Geffen School of Medicine as well as the William Scheibel Endowed Chair in Neuroscience at the Brain Research Institute, each named after one of his parents. (https://newsroom.ucla.edu/dept/faculty/in-memoriam:-dr-arnold-scheibel-helped-shape-ucla-s-neuroscience-community ) Scheibel's passion for increasing exposure and accessibility to neuroscience even led him to create The Human Brain Coloring Book with Marian.

After Scheibel's active research ended, his commitment to teaching continued to flourish. Indeed, in 1997, he received the UCLA Distinguished Teaching Award. It is reported that "His lectures were captivating, guided tours through the nervous system: a stream of effortless narratives with fluid, blackboard illustrations serving as familiar landmarks. He could draw any brain structure, any cross section, at any angle with ease. A 2-hr lecture would be over before one realized it, and the students would have 20 pages of detailed notes in front of them. Lectures were linked together with the intricacy and fluidity of pastels blended on a canvas as Arne would reintroduce previous structures by referring to them as "our old friends."'

"A retrospective examination of Arne's teaching at UCLA estimated that he had taught over 700 graduate students, 1,200 undergraduates, 800 medical students, 200 psychiatric residents, and guided many research students."

He was a fellow of the Norwegian Academy of Science and Letters from 1983.

Personal life Scheibel died on April 3, 2017, in Oakland, California, at the age of 94. 3 months later, his wife Dr. Marian Diamond also died, at the age of 90.