Making the Brain Plastic: Early Neuroanatomical Staining Techniques and the Pursuit of Structural Plasticity, 1910?1970

Abstract

The concept of neuronal plasticity is widely used, but seldom defined in the neurosciences. It can signify many different occurrences, such as structural alterations of axons and dendrites (Cotman & Nadler, 1978), behavioural adaptations (Rosenzweig & Bennett, 1996), or physiological changes in synapse formation (Martin et al., 2000) at different stages of health and disease. Although there is such a wealth of research from many disciplines, the neuroanatomical aspects of plasticity are the focus of this paper. It seeks to illuminate the evolution of different concepts of plasticity concerning the structure and circuitry of the central nervous system (CNS). Early modern morphological research on de- and regeneration phenomena in the 19th- and early 20th-century is well documented. These studies, however, almost exclusively concentrated on the peripheral nervous system (PNS). It was one of the major contributions of Santiago Ramón y Cajal (1852-1934), that he applied the concept of regenerative capacities to the CNS. But the term plasticity seemed to have disappeared for about two decades after his death. The ensuing comeback of the expression may be attributed, at least in part, to new neuroanatomical staining and tracing methods. The pursuit of these techniques will serve as a guidepost through varying approaches in different times: It was the 1950s which seemed to spawn the time for new departures in structural investigations of neuronal plasticity.

Investigating rapid effects of motor training on the brain's gray matter volume: a magnetic resonance imaging study with repeated testing

“…Although it is often said that the adult brain was considered to be anatomically static a good bit into the 20th century, much work has been done to document the dynamic properties of brain cells since the beginning of the 1900s (Stahnisch, 2003). Inquiries into the relationship between neural structure and learning are older still, and animal experiments on the subject are documented as far back as 1783.…”

Engaging cognitive circuits to promote motor recovery in degenerative disorders. exercise as a learning modality

“…We are now at the stage where hundreds of publications, many utilizing a wide spectrum of neuroimaging techniques, have shown changes in activation and circuitry with physical activity in human subjects (Caproni et al, 2013; Hamaide et al, 2016). Several reviews articulate in greater detail than our present brief synopsis, the history of the scientific concept of brain plasticity and we refer interested students of the neurosciences to these, as well as the tests of aforementioned authors (Berlucchi, 2002; Berlucchi and Buchtel, 2009; Cooper, 2005; Stahnisch, 2003). …”

From ‘Nerve Fiber Regeneration’ to ‘Functional Changes’ in the Human Brain—On the Paradigm-Shifting Work of the Experimental Physiologist Albrecht Bethe (1872–1954) in Frankfurt am Main

“…Max Bielschowsky’s (1869–1940) research during this time, who referred to Bethe’s ( 1931 ) work repeatedly and was invited by the latter to also contribute to his Handbuch der normalen und pathologischen Physiologie , similarly focused on regeneration phenomena in CNS fibers (~nerve axons). With respect to his work on regeneration in the nervous system, he followed similar positions to those of Georges Marinesco (1863–1938) and Ion Minea (1878–1941) in Bucharest on peripheral nerve growth (1906), Giuseppe Levi (1872–1965) in Turin investigating sensory ganglion cell regeneration (1927), Santiago Ramón y Cajal and Jorge F. Tello (1880–1958) in Madrid on retinal regeneration phenomena (1934), who had all made pioneering contributions to the regeneration tradition in the modern neurosciences from their respective research directions (see further details in Stahnisch, 2003 ).…”

“…Most neuroscientists at the beginning of the twentieth century held the opinion that the human brain lacked any functional capacities for repair, readaptation, and response to neuronal damage following degenerative diseases (e.g., Alzheimer’s Disease or Morbus Parkinson) and cerebral injuries (such as stroke; Stahnisch, 2003 ). Only a tiny minority of neurologists and neuropathologists sought to identify cerebral repair mechanisms that allowed the neurologically severed human brain to be seen in a different physiological light.…”