Dissection was prohibited for religious reasons but Michelangelo exchanged his art for the chance to study human anatomy.
Dissection was prohibited for religious reasons but Michelangelo exchanged his art for the chance to study human anatomy.
Other ideas about the location of the mind were speculative not observation-based.
The wars of the 17th & 18th centuries provided opportunities to observe head and spine injuries.
How did heads grin after decapitation on the guillotine
Cabanis concluded all thought depends on the brain.
Robert Whytt (1714-1766) found that decapitated frogs would respond to a pinch by withdrawing the leg 15 min later.
Robert Whytt (1714-1766) found that decapitated frogs would respond to a pinch by withdrawing the leg 15 min later.
This demonstration of spinal reflexes requires an intact spinal cord.
Francois Magendie (1795-1855) showed the dorsal and ventral roots have different functions, dorsal controls sensation and ventral controls movement
Bell successfully challenged the priority of Magendie’s discoveries; today this is called the Bell-Magendie law.
Charles Bell (1774-1842) suggested that the nerve imposes sensory specificity regardless of how it is stimulated.
Charles Bell (1774-1842) suggested that the nerve imposes sensory specificity regardless of how it is stimulated.
Visual sensations can result from stimulation of the optic nerve by light or by pressing the eyeball (with eye shut)
German physiologist Johannes Peter Muller (1801-1858) said the nerves must either communicate different impressions or project to different places in the brain which impose specificity.
Now we know different projection areas are involved.
The greatest 19th century physiologist, Helmholtz published definitive works on physiological acoustics and optics and a theory of color vision.
The greatest 19th century physiologist, Helmholtz published definitive works on physiological acoustics and optics and a theory of color vision.
Helmholtz & James Clark Maxwell tested Thomas Young’s theory of trichromatic vision – that 3 distinct kinds of nerve fibers respond to primary colors.
Young-Helmholtz theory of trichromatic vision.
Helmholtz’s research on neural conduction was his most brilliant contribution to physiology.
Helmholtz invented the myograph to trace a muscle contraction on a revolving drum.
Helmholtz invented the myograph to trace a muscle contraction on a revolving drum.
Helmholtz conducted the first reaction time experiments in which human subjects pressed buttons.
Reaction times to a sensation on the thigh were faster than on the toe.
Speed was 25 meters per second.
People rejected his ideas because nerve sensations seem immediate, not delayed.
Is the impulse exclusively electrical or also chemical?
Is the impulse exclusively electrical or also chemical?
Do different nerves conduct at different speeds.
Do different people’s nerves conduct at different speeds?
Does the speed of the nerve impulse depend on the intensity of the stimulus.
Are nerves equally excitable at all times?
A great deal of progress was made after this as the brain was studied directly in the 19th century.
Phrenology taught our field a great deal about how to be scientific and how to avoid the pitfalls of pseudoscience.
Phrenology taught our field a great deal about how to be scientific and how to avoid the pitfalls of pseudoscience.
Franz Joseph Gall (1758-1828) suggested that personality can be inferred from bodily appearance, especially features of the skull.
He noticed that people with protruberant (bulging) eyes tended to have good memories, so he looked for other associations between features and abilities.
His observations were compiled into a large catalog.
Phrenologists like Gall & Spurzheim considered themselves anatomists and scientists.
Phrenologists like Gall & Spurzheim considered themselves anatomists and scientists.
Gall’s books were considered deterministic, materialistic and atheistic and placed on the Index of Prohibited Books by the Catholic church.
After Gall’s death, Spurzheim & George Combe turned phrenology into a cult, giving theatrical demonstrations, ultimately in the USA.
Ultimately, phrenology became big business.
Circularity of arguments, e.g., opium produces sleep because it has a soporific (sleep-inducing) tendency.
Circularity of arguments, e.g., opium produces sleep because it has a soporific (sleep-inducing) tendency.
This is a problem with all inductive research.
Circular predictions cannot be tested & proved false.
In 1857, phrenology did stop seeking only corroborative examples and sought contradictory instances, but these were not accepted.
“Maybe Descartes [small forebrain] was not so great a thinker as many thought him to be.” Spurzheim said.
Magendie replaced Laplace’s brain with an imbecile’s.
Flourens was a French surgeon & the foremost brain researcher of the mid-19th century.
Flourens was a French surgeon & the foremost brain researcher of the mid-19th century.
He published “An Examination of Phrenology” in 1843.
Flourens’ studies showed that the contours of the skull do not correspond to the contours of the brain.
Phrenologists had located amativeness (lust) to the cerebellum – Flourens found that ablating the cerebellum interferes with motor movements not sex.
Flourens used ablation as a technique to systematically test for localization of function.
Flourens used ablation as a technique to systematically test for localization of function.
The parts studied should be anatomically distinct.
He divided the brain into 6 separate areas.
His method was to:
First observe an animal’s behavior.
Second remove one of the brain’s units and let the animal heal.
Third, observe the animal’s behavior again.
The cerebral lobes are the seat of all voluntary actions – only reflexes exist without them.
The cerebral lobes are the seat of all voluntary actions – only reflexes exist without them.
The cerebral lobes are also the seat of perception and higher mental functions such as memory, will, judgment.
Animals can survive damage to the cerebrum and cerebellum but not to the medulla oblongata.
His Grand Principle -- the brain is an inter-connected, integrated system with a common action.
Small areas can recover from damage without loss.
The accidental damage to Phineas Gage provided empirical evidence to show that Flouren’s findings with animals apply to humans too.
The accidental damage to Phineas Gage provided empirical evidence to show that Flouren’s findings with animals apply to humans too.
After the accident, Gage became fitful, irreverent, profane, impatient of restraint or advice conflicting with his desires, obstinate, unable to plan or make decisions – “no longer Gage.”
Characteristic of
people with frontal lobe damage.
First evidence came from impairment after stroke.
First evidence came from impairment after stroke.
Based on experience with military injuries, Gall identified the regions just behind the eyes.
Gall’s student, Bouillaud offered 500 franc challenge.
Broca’s patient “Tan” seemed to be a disorder of speech without damage behind the eyes.
However, Broca’s autopsy showed a lesion to the left frontal lobe in the area specified by Bouillaud and Aubertin (his pupil).
