The action of light on the retina: Translation and commentary of Holmgren (1866).

In 1866, Holmgren published an account of the physiological action of light on the retina. The article is taken as the origin of research on the electroretinogram, although the term was not introduced until much later. We present a translation of the article into English and provide a commentary on its reception and significance.

Neuroscience without borders: Preserving the history of neuroscience.

Over the last 50 years, neuroscience has enjoyed a spectacular development, with many discoveries greatly expanding our knowledge of brain function. Despite this progress, there has been a disregard for preserving the history of these discoveries. In many European countries, historic objects, instruments, and archives are neglected, while libraries and museums specifically focusing on neuroscience have been closed or drastically cut back.

Alexander von Humboldt: galvanism, animal electricity, and self-experimentation part 1: formative years, naturphilosophie, and galvanism.

During the 1790s, Alexander von Humboldt (1769-1859), who showed an early interest in many facets of natural philosophy and natural history, delved into the controversial subject of galvanism and animal electricity, hoping to shed light on the basic nature of the nerve force. He was motivated by his broad worldview, the experiments of Luigi Galvani, who favored animal electricity in more than a few specialized fishes, and the thinking of Alessandro Volta, who accepted specialized fish electricity but was not willing to generalize to other animals, thinking Galvani's frog experiments flawed by his use of metals. Differing from many German Naturphilosophen, who shunned "violent" experiments, the newest instruments, and detailed measurement, Humboldt conducted thousands of galvanic experiments on animals and animal parts, as well as many on his own body, some of which caused him great pain.

Alexander von Humboldt: galvanism, animal electricity, and self-experimentation part 2: the electric eel, animal electricity, and later years.

After extensive experimentation during the 1790s, Alexander von Humboldt remained skeptical about "animal electricity" (and metallic electricity), writing instead about an ill-defined galvanic force. With his worldview and wishing to learn more, he studied electric eels in South America just as the new century began, again using his body as a scientific instrument in many of his experiments. As had been the case in the past and for many of the same reasons, some of his findings with the electric eel (and soon after, Italian torpedoes) seemed to argue against biological electricity.

The frog's dancing master: science, séances, and the transmission of myths.

Myths are not uncommon in the history of neuroscience and their tenacity even when faced with suitable correctives is impressive. The possible origins and transmission of one such myth is examined: the oft repeated quotation, attributed to Luigi Galvani, that he was the "frog's dancing master." The statement does not occur in Galvani's writing and appears to have accrued features in the early nineteenth century, largely from French writers.

Discovering the African freshwater "torpedo": legendary Ethiopia, religious controversies, and a catfish capable of reanimating dead fish.

The electric catfishes of African rivers and lakes, once depicted on Egyptian tomb art, have been largely overlooked in histories and reviews of electric fish biology and animal electricity. This article examines how Westerners, especially Dominican and Jesuit missionaries, discovered them in Ethiopia and other parts of Africa at the beginning of the seventeenth century. What transpired took place against the backdrop of tales involving the Bible, Prester John's mythical empire, and imaginary animals with fabulous powers.

Giuseppe Moruzzi: a tribute to a "formidable" scientist and a "formidable" man.

Giuseppe Moruzzi was born one century ago; he was an outstanding Italian neurophysiologist, who was particularly famous for his contributions to the study of the mechanisms underlying the control of the sleep-waking cycle in mammals. In 1990, Rita Levi-Montalcini, Moruzzi's great friend and admirer, used the occasion of an invitation by the University of Parma, where Moruzzi graduated in medicine in 1933, to celebrate Moruzzi's scientific achievements. She wished to pay a tribute to Moruzzi's human and ethical qualities by portraying him as a "perfect model" for the young generation wishing to pursue scientific research.

Galileo's eye: a new vision of the senses in the work of Galileo Galilei.

Reflections on the senses, and particularly on vision, permeate the writings of Galileo Galilei, one of the main protagonists of the scientific revolution. This aspect of his work has received scant attention by historians, in spite of its importance for his achievements in astronomy, and also for the significance in the innovative scientific methodology he fostered. Galileo's vision pursued a different path from the main stream of the then contemporary studies in the field; these were concerned with the dioptrics and anatomy of the eye, as elaborated mainly by Johannes Kepler and Christoph Scheiner.

Galileo Galilei's vision of the senses.

Neuroscientists have become increasingly aware of the complexities and subtleties of sensory processing. This applies particularly to the complex elaborations of nerve signals that occur in the sensory circuits, sometimes at the very initial stages of sensory pathways. Sensory processing is now known to be very different from a simple neural copy of the physical signal present in the external world, and this accounts for the intricacy of neural organization that puzzled great investigators of neuroanatomy such as Santiago Ramón Y Cajal a century ago.

Visual images in Luigi Galvani's path to animal electricity.

The scientific endeavor that led Luigi Galvani to his hypothesis of "animal electricity," i.e., of an electricity present in a condition of disequilibrium between the interior and the exterior of excitable animal fibers, is reviewed here with particular emphasis to the role played by visual images in Galvani's path of discovery.

Luigi Galvani's path to animal electricity.

In spite of the historical importance of the research that, in the second half of the 18th century, led Luigi Galvani (1737-1798) to lay down the foundation of modern electrophysiology, his scientific personality is largely misrepresented in science history and in popular imagery. He is still considered as a pioneer that by chance incurred some surprising experimental observations and was incapable of pursuing his research in a coherent way. In contrast with these views, Galvani was a high-standard scientist who succeeded, with the strength of experimental science, in demonstrating, in animals, electricity in a condition of disequilibrium between the interior and the exterior of excitable fibres.

Pre- and post-synaptic effects of manipulating surface charge with divalent cations at the photoreceptor synapse.

Persistence of horizontal cell (HC) light responses in extracellular solutions containing low Ca2+ plus divalent cations to block Ca2+ currents (ICa) has been attributed to Ca2+-independent neurotransmission. Using a retinal slice preparation to record both ICa and light responses, we demonstrate that persistence of HC responses in low [Ca2+]o can instead be explained by a paradoxical increase of Ca2+ influx into photoreceptor terminals arising from surface charge-mediated shifts in ICa activation. Consistent with this explanation, application of Zn2+ or Ni2+ caused a hyperpolarizing block of HC light responses that was relieved by lowering [Ca2+]o.

Nerves, alcohol and drugs, the Adrian-Kato controversy on nervous conduction: deep insights from a "wrong" experiment?

Edgar Douglas Adrian, a dominating figure of 20th century electrophysiology, published in 1912 a study on the effects of the conduction block induced by application of alcohol vapours to small segments of nerves from which he derived the conclusion that nerve signals regenerate along the nerve fibre during the conduction process. This conclusion was based on results of experiments in which the time required to produce a conduction block was found to decrease as the length of the nerve segment treated was increased. These results could not be confirmed when similar experiments were performed about 10 years later by Gen'ichi Kato, a leading figure of Japanese physiology and founder of one of the great schools of Japanese electrophysiology.

Fifty years of the Hodgkin-Huxley era.

Modern neuroscientists are accustomed to the detailed information on the structure and function of membrane ion channels that can be obtained by the combination of molecular biology, crystallography and patch-clamp recordings. It can be difficult for us to appreciate how hard it was for humankind to realize that physical events underlie nervous function and, moreover, to appreciate how long it took to devise a realistic model for the generation and propagation of the nerve impulse.

Drawing a spark from darkness: John Walsh and electric fish.

John Walsh's research on electric fish, carried out between 1772 and 1775, proved fundamental for demonstrating that electricity might be involved in animal physiology, and, moreover, in favouring a period of great progress in both the physiology and physics of electrical phenomena. However, Walsh is hardly known to modern neuroscientists and is largely neglected by science historians also. One of the reasons for this neglect is that he never published his 'crucial experiment', that is the production of a spark from a discharge of the electric eel.

Drawing a spark from darkness: John Walsh and electric fish.

John Walsh's research on electric fish, carried out between 1772 and 1775, proved fundamental for demonstrating that electricity might be involved in animal physiology, and, moreover, in favouring a period of great progress in both the physiology and physics of electrical phenomena. However, Walsh is hardly known to modern neuroscientists and is largely neglected by science historians also. One of the reasons for this neglect is that he never published his 'crucial experiment', that is the production of a spark from a discharge of the electric eel.

Biological machines: from mills to molecules.

Although scientific progress is usually represented as being linear, it may, in fact, have a cyclical character--some discoveries may be forgotten or lost (at least temporarily), and themes may reappear through the centuries. Consider, for example, the concept of 'molecular machines', from the exciting phase of research that flourished in the seventeenth century, to the idea of machines that is at centre stage in modern cell biology.

The bicentennial of the Voltaic battery (1800-2000): the artificial electric organ.

Alessandro Volta invented the electric battery at the end of 1799 and communicated his invention to the Royal Society of London in 1800. The studies that led him to develop this revolutionary device began in 1792, after Volta read the work of Luigi Galvani on the existence of an intrinsic electricity in living organisms. During these studies, Volta obtained a series of results of great physiological relevance, which led him to anticipate some important ideas that marked the inception of modern neuroscience.