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Chapter 1

NROC69H3 Chapter Notes - Chapter 1: Insomnia, Dementia, Cognitive Deficit


Department
Neuroscience
Course Code
NROC69H3
Professor
d
Chapter
1

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of 4
Chapter 1
The Origins of Neuroscience
Evidence suggests that even our prehistoric ancestors appreciated that the brain was vital to life
o There are archeological records with examples of hominid skulls bearing signs of fatal
cranial damage
o As early as 7000 years ago, people were boring holes in other’s skulls in attempts to
cure headaches and disorders as they assumed it was a method to allow evil spirits to
depart from the brain
Recovered writings from physicians of Ancient Egypt indicate that they were well aware of many
symptoms of brain damage.
o However, it was the heart that was considered to be the seat of the soul and the
repository of memories.
Views of the Brain in Ancient Greece
o Hippocrates (460 379 B.C.), the father of western medicine, stated his belief that the
brain only was involved in sensation but also was the seat of intelligence.
o Not universally accepted.
o Aristotle still believed that the heart was the center of intellect and believed the brain
was a radiator for cooling the blood that was overheated by the heart.
Views of the Brain During the Roman Empire
o Greek physician and writer Galen embraced the Hippocratic view of the brain function
o His views were influenced by the many sheep brains he had dissected
o Two major parts are evident in a sheep brain: the cerebrum (front) and the cerebellum
(back).
o He assumed that the soft cerebrum was responsible for memory, receiving sensation
and that the cerebellum is responsible for commanding muscle movement
o Also saw many ventricles in the brain and assumed the old the theory of four vital fluids
(humors) responsible for movements was correct.
Views of the Brain From the Renaissance to the Nineteenth Century
o Galen’s view prevailed for nearly 1500 years
o The notion that fluid is used to pump the muscles was still prevalent
o A chief advocate of this fluid-mechanical theory was Rene Descartes.
o However, he also reasoned that unlike animals, humans possess intellect and a God-
given soul.
He proposed that the brain mechanisms for a human are similar to that of a
beast only to a certain extent.
He believed that the mind is a spiritual entity that receives sensations and
commands movements by communicating with the machinery of the brain via
the pineal gland.
o Scientists began to break away from Galen’s views
o On closer observations, the brain was noticed to have gray and white matter
White matter, because it was continuous with the nerves of the body, was
correctly believed to contain the fibers that bring information to and from the
gray matter.
o By the end of the eighteenth century, the nervous system had been completely dissected
and scientists realized that it has a central division, consisting of a brain and spinal cord, and
a peripheral division with networks of nerves that course through the body.
o An important breakthrough was the observation that the same general pattern of
bumps (gyri) and grooves (sulci and fissures) could be identified on the surface of the
brain in every individual
This pattern enables the parceling of the cerebrum into lobes; the basis of
speculation that different functions might be localized to the different bumps
on the brain.
Nineteenth Century Views of the Brain
o Summary
o Injury to the brain can disrupt sensation, movement, and thought and can cause death
o The brain communicates with the body via the nerves
o The brain has different identifiable parts, which probably performs different functions
o The brain operates like a machine and follows the laws of nature
o Nerves as Wires
In 1751, Benjamin Franklin published a pamphlet which heralded a new
understanding of electrical phenomena
Italian scientist, Luigi Galvani and German biologist Emil du Bois-Reymond had
shown that muscles can be caused to twitch when nerves are stimulated
electrically and that the brain itself can generate electricity.
This discovery replaced the idea that nerve communication with the brain was
controlled by the movement of fluid.
Scottish physician Charles Bell and French physiologist Francois Magendie
discovered that by cutting the ventral roots of the nerve fibers caused muscle
paralysis and Magendie showed that the dorsal roots carry sensory information
into the spinal cord.
o Localization of Specific Functions to Different Parts of the Brain
Bell and Magendie employed to identify the functions of the spinal roots: to
destroy these parts of the brain and test for sensory and motor deficits
experimental ablation method
Marie-Jean-Pierre Flourens used this method in many animals and showed that
the cerebellum does indeed play a role in the coordination of movements. He
also concluded that the cerebrum is involved in sensation and perception.
An Austrian medical student, Franz Joseph Gall, believed that the bumps on the
skull reflected the bumps on the brain. Flourens thought this was an idiot and
he was right.
A French neurologist, Paul Broca, was known for tilting the scales of scientific
opinion firmly toward localization of function in the cerebrum.
He was presented with a patient who could understand language but
could not speak.
Following that person’s death, Paul examined his brain and found a
lesion in the left frontal lobe.
Based on this case and several others, he deduced that region of the
human cerebrum was specifically responsible for the production of
speech
Many other experiments on the brain favoured the notion of brain localization
o The Evolution of Nervous Systems
1859, Charles Darwin stated in his book that species of organisms evolved from
a common ancestor through a process of natural selection.
He also included that behaviour among the heritable traits that could
evolve.
Thus the idea that the nervous systems of different species evolved
from common ancestors and may have common mechanisms is the
rationale for relating the results of animal experiments to humans.
o That’s why many neurologists today use animal models to
examine the process they wish to understand in humans (e.g.
rats show clear sign of addiction when they are exposed to
cocaine)
o The Neuron: The Basic Functional Unit of the Brain
In 1839, German Zoologist Theodor Schwann proposed what came to be known
as the cell theory: All tissues are composed of microscopic units called cells.
Scientists contemplated on whether or not the neuron was really the basic unit
of the brain because it had many projections that extend from the central body.
NEUROSCIENCE TODAY
Levels of Analysis
Molecular Neuroscience
Cellular Neuroscience
Systems Neuroscience
Behavioural Neuroscience
Cognitive Neuroscience
Neuroscientists
Explains the job of a neuroscientist
The Scientific Process
Observation: typically are made during experiments designed to test a particular
hypothesis
Replication: Whether the observation is experimental or clinical, it is essential that it be
replicated before it can be accepted by the scientist as a fact. It simply means repeating
the experiment on different subjects or making similar observations in different
patients, to rule out any possibility of chance.
Interpretation: Interpretations depend on the state of knowledge at the time the
observation was made and on the preconceived notions of the scientist who made it.
Verification: This is step is distinct from replication performed by the original observer.
It means that the observation is sufficiently robust that it will be reproduced by any
competent scientist who precisely follows the protocols of the original observer.
The Use of Animals in Neuroscience Research
The Animals.
Neuroscience experiments are conducted using many different species
The choice of animal species is generally based on the question under
investigation, the level of analysis, and the extent to which the knowledge
gained at this level can be related to humans
The more basic the process under investigation, the more distant can be the
evolutionary relationship with humans
Animal Welfare:
Today neuroscientists accept certain moral responsibilities toward their animal
subjects: