Home / Neuroscience / index.php
---------------Neuroscience----------------

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

Questions –
What are brain ventricles, and what functions have been ascribed to them over the ages?
What experiment did Bell perform to show that the nerves of the body contain a mixture of sensory and motor fibers
What did Flourens' experiments suggest were the functions of the cerebrum and the cerebellum?
What is the meaning of the term animal model?
A region of the cerebrum is now called Broca's area.  What function do you think this performs and why?
What are the different levels of analysis in neuroscience research?  What types of question do researchers ask at each level?
What are the steps in the scientific process?  Describe each one.