Neurophilosophy

The Best of Neurophilosophy

For the benefit of new readers, I’ve selected what I think are the best posts from this blog.


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Wilder Penfield, Neural Cartographer: The patient lies on the operating table, with the right side of his body raised slightly. The anaesthetist sterilizes his scalp and injects it with Nupercaine to produce analgesia – the patient will remain fully conscious throughout the procedure. Behind the surgical drapes, three large incisions are made in his scalp. A large flap of bone is then cut from his skull, and turned downward to expose the surface of his brain. The ultraviolet lights which illuminate the operating theater and keep the air sterile are positioned in such a way that they do not shine directly upon the cortex.

Using an atomizer, the surgeon sprays a small amount of Ringer’s solution onto the brain substance, to keep it moist. He then manoeuvres an electrode attached to a special holder which is clamped to the margin of the opening in the skull, so that it comes into direct contact with the brain. He adjusts a dial on the stimulator to 0.5 volts, and a current with a frequency of 60 cycles per second is applied to the patient’s cortex. After asking the patient if he feels anything, and getting a negative response, the surgeon reaches for the stimulator again. He turns the voltage dial up a notch so that it reads 1 volt, and applies another current. This time, the patient reports a tingling sensation in his face and, when asked to indicate exactly where, raises an arm and points to his left cheek and temple.


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Cannibalism & the shaking death: Kuru belongs to a class of progressive neurodegenerative diseases called the transmissible spongiform encephalopathies (TSEs), which also includes variant Creutzfeldt-Jakob Disease (vCJD) and bovine spongiform encephalopathy (BSE, more popularly known as “Mad Cow Disease”). TSEs are fatal and infectious; in humans, they are relatively rare, and can arise sporadically, by infection, or because of genetic mutations. They are unusual in that the infectious agent which transmits the diseases is believed to a misfolded protein. (Hence, the TSEs are also referred to as the prion diseases, “prion” being a shortened form of the term “proteinaceous infectious particle”).

BSE first appeared in the U.K. in 1986. A decade later, a young man from Wiltshire who had eaten contaminated beef became the first victim of vCJD. Health officials realized that the disease was spreading among livestock because of the practice of feeding them offal. They warned that tens of thousands of people could be at risk and subsequently more than 200,000 cattle were culled in order to prevent this, at a huge expense to the British economy.

To date, though, only 156 people in the U.K., and a much smaller number in other countries, have died from vCJD. However, a longitudinal study of the Fore people, published 2 years ago, suggests that kuru and related diseases may have an incubation period of up to 50 years, leading some researchers to argue that we may yet face an epidemic of vCJD. And in July 2008, neurologists reported a previously unidentified prion disease which has killed 10 people in the U.S. and infected 6 others.


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Synapse proteomics & brain evolution: When it comes to human brain evolution, it is often said that size matters. The human cerebral cortex is much larger than that of other primates, and therefore its expansion must have been a vital feature of human evolution. Researchers have therefore emphasized the importance of encephalization, the process by which brain mass increased dramatically in relation to total body mass that occurred in the human lineage.

However, a new study which used bioinformatics to compare the synapses of distantly related species suggests that size may not be the most important factor in human brain evolution after all. Instead, the new findings, which were published online in Nature Neuroscience on Sunday, suggest that it is an increase in the complexity and number of synapses that was crucial for the emergence of complex behaviours and cognition.


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The discovery of the neuron: For most of the nineteenth century, there was an on-going debate among researchers about the organization of the nervous system. One group of researchers, the so-called reticularists, believed that the nervous system consisted of a large network of tissue, or reticulum, formed by the fused processes of nerve cells. The other group, the neuronists, argued that the nervous system consisted of distinct elements, or cells.

Both groups used the same methods to study nerve cells, but came to different conclusions about the fine structure of the nervous system, which could not yet be seen in detail because of the low magnification and poor resolution of the microscopes available to them at the time. Just as the observable universe increased in size with the development of increasingly powerful telescopes, so did understanding of the organization of the nervous system improve with advances in microscopy. (As featured in OpenLab 2006.)



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The incredible case of Phineas Gage: Phineas Gage (1823-1860) is one of the earliest documented cases of severe brain injury. Gage is the index case of an individual who suffered major personality changes after brain trauma. As such, he is a legend in the annals of neurology, which is largely based on the study of brain-damaged patients.

Gage was foreman of a crew of railroad construction workers who were excavating rocks to make way for the railroad track. This involved drilling holes deep into the boulders and filling them with dynamite. A fuse was then inserted, and the entrance to the hole plugged with sand, so that the force of the explosion would be directed into the boulder. This was done with a crow bar-like tool called a tamping iron.

On 13th September, 1848, 25-year-old Gage and his crew were working on the Rutland and Burlington Railroad near Cavendish in Vermont. Gage was preparing for an explosion by compacting a bore with explosive powder using a tamping iron. While he was doing this, a spark from the tamping iron ignited the powder, causing the iron to be propelled at high speed straight through his skull. It entered under the left cheek bone and exited through the top of the head, and was later recovered some 30 yards from the site of the accident.



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Alois Alzheimer’s first case: On November 4th, 1906, during a lecture at the 37th Conference of South-West German Psychiatrists in Tubingen, the German neuropathologist and psychiatrist Alois Alzheimer (1864-1915, left) described “eine eigenartige Erkrankung der Hirnrinde” (a peculiar disease of the cerebral cortex). In the lecture, he dicussed “the case of a patient who was kept under close observation during institutionalisation at the Frankfurt Hospital and whose central nervous system had been given to me by director Sioli for further examination”. This was the first documented case of the form of dementia that would subsequently bear Alzheimer’s name.

Alzheimer was born on June 14th, 1864, in the small Bavarian town of Marktbreit. He attended Aschaffenburg, Tubingen and Berlin universities before obtaining his medical degree from Wurzburg University in 1887. In the same year, he completed his Ph.D. thesis on the wax-producing glands of the ear, based on experiments he had carried out in the laboratory of Rudolf Albert von Kolliker, the Swiss physiologist who made valuable contributions to our undertanding of the organization of the nervous system.

Within months of obtaining his medical degree, Alzheimer began working at the Stadtische Heilanstalt fur Irre und Epileptische (Hospital for the Mentally Ill and Epileptics) in Frankfurt. There, Alzheimer studied psychiatry and, with Franz Nissl, who had developed a method for staining nervous tissue, undertook a comprehensive investigation of the pathology of the nervous system.



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The rise & fall of the prefrontal lobotomy: Lobotomy (from the Greek lobos, meaning lobes of the brain, and tomos, meaning cut) is a psychosurgical procedure in which the connections the prefrontal cortex and underlying structures are severed, or the frontal cortical tissue is destroyed, the theory being that this leads to the uncoupling of the brain’s emotional centres and the seat of intellect (in the subcortical structures and the frontal cortex, respectively).

The lobotomy was first performed on humans in the 1890s. About half a century later, it was being touted by some as a miracle cure for mental illness, and its use became widespread; during its heyday in the 1940s and ’50s, the lobotomy was performed on some 40,000 patients in the United States, and on around 10,000 in Western Europe. The procedure became popular because there was no alternative, and because it was seen to alleviate several social crises: overcrowding in psychiatric institutions, and the increasing cost of caring for mentally ill patients.



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Diagnosing Dostoyevsky’s epilepsy: Dostoyevsky was, perhaps, the most famous epileptic in history. The condition had a major influence on his philosophy and his conception of life. A recurring theme in his writing, epilepsy is something he analysed in great detail in many of his novels. Some have speculated that the course of the illness was reflected in how his writing changed throughout his life.

In Dostoyevsky, neurologists have a rich source of information about epilepsy. Some of this information is first-hand, in the form of the writer’s own descriptions of his seizures and symptoms, as related in his various correspondences. There are also numerous second-hand descriptions of Dostoyevsky’s condition, provided by his second wife, physicians who treated him, and friends. And, of course, there are the accounts of epileptic characters in his novels, which one can safely assume are based on his own experiences.



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An illustrated history of trepanation: There is a great deal of speculation about why ancient civilizations used trepanation, as it was – and still is – carried out in the absence of head trauma. However, it is almost certain that all those who used it did so because they somehow linked the brain with behaviour. Some anthropologists suggest that trepanation was performed as part of tribal or superstitious rituals. Other researchers believe that the procedure was used as a treatment for conditions such as headaches, epilepsy, hydrocephalus and mental disorders. These were presumably attributed to possession by evil demons, such that a hole in the skull would have provided the spirits a passage for escape. Although the reasons for trepanning and the instruments used for the procedure differ with time and from culture to culture, the result is always the same: a hole in the head, usually made when the individual was fully conscious and, often, unanaesthetized. (As featured in OpenLab 2007.)



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The psychology of Alfred Hitchcock: Alfred Hitchcock (1899-1980) was one of the most outstanding filmmakers of the twentieth century. In a career spanning six decades, Hitchcock made 53 films, the best of which are at once suspenseful, exciting, disturbing, funny and romantic.

The ‘master of suspense’ pioneered many of the techniques of the thriller genre, and remains highly influential to this day. He was, for example, one of the first directors to portray psychological processes in film narrative.

Hitchcock once remarked that “television has done much for psychiatry by spreading information about it, as well as contributing to the need for it.” During much of Hitchcock’s career, Freud’s ideas were dominant, and although Hitchcock was skeptical of psychoanalysis (as he was of other explanations for human behaviour), Freudian concepts and motifs recur in many of his films.



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Avian intelligence: In the English language, the term “bird brain” is often used in reference to intellectually challenged individuals. This is, of course, based on the notion that birds are dim-witted creatures whose behaviour is largely based on instinct. The main assumption is that a six-layered neocortex, like that of humans, is a prerequisite for anything that might be classed as intelligent, and even ornithologists have generally believed that, because they have a “smooth” brain, birds aren’t too clever. However, it has in recent years become clear that we have grossly underestimated the cognitive abilities of birds. Some of the behaviours observed in birds are just as complex, if not more so, than those seen in non-human primates – and “birdbrain” no longer seems so much of an insult.



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Old brains, new ideas: The French anatomist, anthropologist, and surgeon Pierre Paul Broca (1824-1880) is best remembered for his descriptions of two patients who had lost the ability to speak after sustaining damage to the left frontal lobe of the brain. Broca’s observations of these patients, and the conclusions he reached after his post-mortem examinations, would lead to major advances in the understanding of the brain, and laid the foundations for modern neuropsychology.



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On the peculiarities of the Negro brain: Black peoples’ brains are, of course, no more or less peculiar than those of any other people. The human brain is an extraordinarily complex organ, and there are just as many differences between the brains of people from the same ethnic group as there between the brains of people from different groups.

Some racial peculiarities of the Negro brain is the title of a long and technical paper by the anthropologist Robert Bennett Bean, published in the American Journal of Anatomy in 1906. It is one of a series of scientific papers written by Bean in the early 20th Century, in which he tried to provide scientific evidence of the inferiority of black people.

A descendant of Thomas Jefferson, Bean was born on March 24th, 1874, in a town called Gala in Virginia County. He graduated from Johns Hopkins Medical School in 1904, and, between the years of 1905-1907, was an instructor in anatomy at the University of Michigan. It is during this period of his life that Bean began his investigations into “the Negro brain”.



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Remembering Henry M.: The single most famous case study in the history of neuropsychology is that of an anonymous memory-impaired man usually referred to only by the initials H. M. This patient has one of the most severe cases of amnesia ever observed; he has been followed for over 40 years by more than 100 researchers, and is the subject of dozens of research papers and book chapters. The early studies of H. M. provide a basis for modern neuropsychology, and the findings of those who have studied him are today a cornerstone in memory research.

H. M. (sometimes referred to as Henry M.) was born in Hartford, Connecticut, in 1926. His amnesia was the result of neurosurgery performed on him in an effort to alleviate the symptoms of his epilepsy. The origins of H. M.’s epilepsy are unclear. His condition is sometimes attributed to a bicycle accident he had the age of 9 – he sustained a head injury when he was knocked down by someone on a bicycle, and subsequently lost consciousness for about 5 minutes. Soon afterwards, he began suffering from minor epileptic seizures, and had his first major seizure on his 16th birthday.



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Biological sonar systems: Echolocation – or biological sonar – can be thought of as an auditory imaging system that is used by organisms in environments where vision is ineffective. It involves the emission of vocalizations by the animal, and the detection of the echoes of those sounds, which are used to produce three-dimensional information about the environment.

Echolocating organisms understand the world largely via the interpretation of the acoustic reflections, and possess specialized neural circuitry that performs the computations necessary for the perceptual organization of auditory information. This information is used for complex spatially-guided behaviours, such as navigation and determining the location of prey.

In those groups of organisms that use it, echolocation evolved separately as an adaptation to a particular environment, and is essential to the survival of those species. In humans, echolocation is not so important. Echolocation research does, however, have many possible applications.



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Exorcizing animal spirits: The ancient theory of ‘animal spirits’ (pneuma psychikon in Greek; spiritus animalis in Latin) was first proposed by Alexandrian physicians in the third century BCE. Animal spirits were thought to be weightless, invisible entities that flowed through the hollow nerves to mediate the functioning of the body. The animal spirits theory was related to the notion of the four humours (blood, phlegm, and yellow and black bile), and was popularised by the Roman physician Galen (c. 129 -216) in the second century AD. Because of Galen, animal spirits dominated thinking about the nervous system for 1,500 years; they were exorcised very recently – it was only during the latter part of the 18th century that investigators began to decipher the electrochemical language of the nervous system.

Galen believed that nutrients were absorbed by the liver, which produced ‘natural spirits’. These were transported to the left ventricle of the heart, which transformed them into vital spirits; these in turn were carried to the brain by the carotid arteries, and again transformed into animal spirits when mixed with inhaled air (“pneuma”) in the cerebral ventricles, or in a plexus of blood vessels at the base of the brain which Galen called the rete mirable (‘wonderful net’). Animal spirits were thought to be stored in the ventricles of the brain until needed, and then transported through the hollow nerves to force the muscles into action, or to carry sensory impressions. Animal spirits were also believed to flow into the brain, which was by then considered the seat of intellect (which consisted of the imagination, cognition and memory).



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Interpreting hybrid images: How the brain interprets complex visual scenes is an enduring mystery for researchers. This process occurs extremely rapidly – the “meaning” of a scene is interpreted within 1/20th of a second, and, even though the information processed by the brain may be incomplete, the interpretation is usually correct.

Occasionally, however, visual stimuli are open to interpretation. This is the case with ambiguous figures – images which can be interpreted in more than one way. When an ambiguous image is viewed, a single image impinges upon the retina, but higher order processing in the visual cortex leads to a number of different interpretations of that image.

Only one of these interpretations is available to our conscious awareness at any one time. Repeated viewing of the image leads to perceptual reversal, whereby first one, and then the other, interpretation is perceived. For psychologists and neuroscientists, ambiguous figures provide a means by which the functioning of the human visual system can be investigated.



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Brainwashed by a parasite: This carpenter ant (genus Campanotus), and the bullet ant in the first film clip below (Paraponera clavata), have fallen victim to parasitic fungi of the genus Cordyceps, which manipulate the behaviour of their host in order to increase their own chances of reproducing.

The spores of the fungus attach themselves to the external surface of the ant, where they germinate. They then enter the ant’s body through the tracheae (the tubes through which insects breathe), via holes in the exoskeleton called spiracles. Fine fungal filaments called mycelia then start to grow inside the ant’s body cavity, absorbing the host’s soft tissues but avoiding its vital organs.

When the fungus is ready to sporulate, the mycelia grow into the ant’s brain. The fungus then produces chemicals which act on the host’s brain and alter its perception of pheromones. This causes the ant to climb a plant and, upon reaching the top, to clamp its mandibles around a leaf or leaf stem, thus securing it firmly to what will be its final resting place.

Comments

  1. #1 Jim
    March 16, 2008

    I am especially fond of the Hitchcock piece, as well as the Brain injury, Lobotomy, and early neurosurgery pieces. I’d be interested to know if they still perform “Third Eye” surgery in Tibet, as the the good doctor/spiritual teacher suggested.
    Well done.