Neuroscience, Exploring the Brain Notes
Ch 1
Introduction
The word "neuroscience is young
The Society of Neuroscience – founded 1970
Study of the brain is old
Neuroscience is multi-disciplined
The Origins of Neuroscience
Nerves systems are crucial for life
As early as 7000 years ago people were performing trepanation (boring holes in peoples skulls using rudimentary tools) for the purpose of trying to heal
Writings by physicians in Egypt dating almost 5000 years ago show that they were well aware of many symptoms of brain damage
However thought that it was the heart that that stored memories
While the rest of the body was carefully preserved, the brain was just scooped out of the nose
Views of the Brain in Ancient Greece
Several scholars concluded that the brain was the organ for sensation
Hippocrates (460-379 B.C.) went further to say that the brain was also responsible for intelligence
Aristotle, (384-322 B.C.) however, still thought that the heart was the seat for knowledge and the brain was responsible for cooling blood.
Views of the Brain during the Roman Empire
Galen, (A.D. 130-200) a physician to the gladiators, embraced Hippocrates ideas and performed many animal dissections (sheep where a favorite)
Concluded that the front of the brain (cerebrum) was responsible for sensation and the back (cerebellum) for muscle control
Proving that science sometimes makes mistakes
Recognized that to form memories, sensations must be imprinted into the brain
Found, via dissections, that the brain is made up of hollow spaces called ventricles, which are filled with fluid
Reasoned this fit with previous theories that the body functioned via four vital fluids (humors).
Sensation and movement were controlled by these humors via nerves
Views of the Brain from the Renaissance to the Nineteenth Century
Galen's view prevailed for almost 1500 years
Detail was added to the structure of the brain by Andreas Vesalius (1514-1564 AD) but the idea that fluids controlled neurology remained in full force
It was actually strengthened by the development of hydraulics
Rene Descartes (1596-1650) believed that uniquely human mental capabilities existed out of the "brain" in the "mind"
The mind communicates with the mechanical and sensory imputes and outputs via the pineal gland
In the 1600-1700's this view was dismissed
The brain is divided into gray and white mater
They correctly believed that white matter relayed information via fibers to and from gray matter
By the end of the 1700's, the nervous system has been completely dissected and it's gross anatomy had been described
It was found that the general pattern of bumps (gyri) and grooves (sulci and
fissures) could be found on service of every individual's brain
It was speculated that different functions are located in different bumps,
and the parceling of the cerebrum was done
To recap, these were the views at the end of the 1800's:
Injury to the brain can disrupt sensation, movement, thought, and cause death
The brain communicates with the body via the nerves
The brain has different identifiable parts, which probably perform different functions
The brain operates like a muscle and follows the laws of nature.
Nineteenth Century Views of the Brain
In this century, more was learned about the brain than all previous recorded history.
Nerves as wires
In 1751 Ben Franklin published a pamphlet which heralded a new understanding of electricity
In the turn of the 1800's Italian scientist Luigi Galvani and German biologist Emil du Bois-Reymond had shown that muscles can be electrically stimulated and that the brain can generate electricity
Around 1810, Scottish physician Charles Bell showed that cutting the nerves that attach to the front of the spinal cord (Nerves in the ventral root) causes muscle paralysis
A little later, French physiologist Francois Magendie showed that the muscles that enter in the back of the spinal cord (the dorsal root) carry sensory information
In each sensory and motor nerve fiber, information only gets transmitted in one direction
Localization of Specific Functions to Different Parts of the Brain
In 1811, Bell proposed that the origin of motor fibers is the cerebellum and the destination of sensory fibers is the cerebrum
They tested this in the same manner, by systematically destroyed to determine their functions, called the experimental ablation method
In 1823, French physiologist Marie-Jean-Pierre Flourens confirmed this using primarily birds as models
In 1809, Franz Joseph Gall proposed that certain personality traits, such as generosity, secretiveness, and destructiveness could be related to the dimensions (or bumps) of the head
The correlation of the structure of the head with personality traits was called phrenology
Flourens
was a vociferous critic of phrenology reasons he gave included:
The shape of the skull is not correlated with the shape of the brain
Particular traits are not isolated to the portions of the cerebrum specified by phrenology
His clams that the cerebrum acted as a whole and could not be subdivided have now been shown to be misguided
Paul Broca is based up the localization of function of the cerebrum.
Based on an autopsy of a patient who could understand language but not speak and had lesions in there left frontal lobe, he concluded that this region of the brain was responsible for speech
German physiologists Gustav Fritsch and Eduard Hitzig showed in 1870 that applying small electrical current to circumscribed regions of the brain of a dog could cause distinct movement
Similar experiments were carried out by Scottish neurologist David Ferrier, and German physiologist Hermann Monk in monkeys
The Evolution of Nervous Systems
In 1859, English biologist Charles Darwin published On The Origin of Species which claimed that species of organisms evolved from common ancestors.
Differences among species arise by a process called natural selection but that similar species have similar traits as a result of a common ancestor
This is the reason that we can use animal models in our studies
The more specialized a trait is, the less one can use different animals as substitutes for research
The Neuron: The Basic Functional Unit of the Brain
As a result of refinements in microscopes, in 1839, German zoologist Theodor
Schwann proposed what was to be known as the cell theory:
All tissues are composed of microscopic units called cells
Neuroscience Today
Levels of Analysis
Molecular Neuroscience
The study of neuroscience at the molecular level
Cellular Neuroscience
The study of how these molecules work together to give the neuron it's cellular properties
Systems Neuroscience
The study of how constellations of neuronal cells work together perform a common function
Behavioral Neuroscience
The study of how neural systems work together to produce integrated behaviors
Cognitive Neuroscience
The study of how and whether the activities of the brain create the mind
Neuroscientists
Neuroscience research is divides into two types:
Clinical – mainly conducted by physicians
Neurologist
An M.D. trained to diagnose and treat diseases of the nervous system
Psychiatrist
An M.D. trained to diagnose and treat disorders of mood and personality
Neurosurgeon
An M.D. trained to perform surgery on the brain and spinal cord
Neuropathologist
An M.D. or Ph.D. trained to recognize the changes in nerves tissue that result
from disease.
Experimental –
Computational Neuroscientist
Uses mathematics and computers to construct models of brain functions
Developmental
Neurobiologist
Analyzes the development and maturation of the brain
Molecular Neurobiologist
Uses the genetic material of neurons to understand the structure and function
of brain molecules
Neuroanatomist
Studies the structure of the neuvas system
Neurochemist
Studies the chemistry of the nerves system
Neuroethologist
Studies the neural basis of species-specific animal behaviors in natural settings
Neuropharmacologist
Examines the effects of drugs on the nervous system
Neurophysiologist
Measures the electrical activity of the nervous system
Neurophysiologist
Studies the neural basis of human behavior
Physiological Psychologist (biological psychologist,
psychobiologist)
Studies the biological basis of animal behavior
Psychophysicist
Quantitatively measures perceptual abilities
The Scientific Process
Observation
Observations can be made during experimentation, watching the world around
us, or introspection
Replication
Repeating the observed hypothesis to rule out that possibility that it happened
by change
Interpretation
A conclusion that is derived from the observation
Conclusions do not always stand the test of time
Verification
That other scientists agree on the observation and replication done by the
fire individual and that they have performed the same tests
Reasons to study Neuroscience
Some major disorders of the nervous system
Alzheimer's Disease
A progressive degeneration of the brain, characterized by dementia and always
fatal
Cerebral Palsy
A motor disorder caused by damage to the cerebrum at the time of birth
Depression
A serious disorder of mood characterized by insomnia, loss of appetite, and
feelings of dejection
Epilepsy
A condition characterized by periodic disturbances of brain electrical activity
that can lead to seizures, loss of consciousness, and sensory disturbances
Multiple
Sclerosis
A progressive disease that affects nerve conduction, characterized by episodes
of weakness, lack of coordination, and speech disturbance
Parkinson's Disease
A progressive disease of the brain that leads to difficulty initiating voluntary
movement
Schizophrenia
A serious psychotic illness characterized by delusions, hallucinations, and
bizarre behavior
Spinal Injury
A loss of feeling and movement caused by traumatic damage to the spinal cord
Stroke
A loss of brain function caused by disruption of the blood supply, usually
leading to permit sensory, motor, or cognitive deficit