Download Week 1 Notes History of the Brain

Unit 1 Psychology
Area of Study 1: How does the brain function?
Key knowledge: Dot point 1
“The influence of different approaches over time to understanding the role of the brain, including the brain
vs heart debate, mind-body problem, phrenology, first brain experiments and neuroimaging techniques.”
The Brain
The human brain weighs approximately 1.5kg and is the heaviest organ in the human body. It’s appearance
is folded and wrinkled to allow for more surface area. If the brain was flattened out it would cover
approximately two A3 sheets of paper.
The brain is made up of 86 billion neurons. Each neuron is connected to somewhere between 1000-1500
other neurons.
The outer layer of the brain is known as ‘grey matter.’ Although it appears pinkish due to the blood flow in
and around the surface of the brain, it is made up of neuron cell bodies that connect to each other. If you
were to slice into the brain, you would encounter ‘white matter.’ White matter is the nerve fibres that
connect brain areas and it is white due to the insulating, fatty substance known as ‘myelin’ that coats the
fibres.
The grey matter of the brain is also called the cerebral cortex. This is the area where all higher mental
functioning occurs, such as language, memory, learning and problem solving.
Advances in brain imaging and recording technologies during the past 30 years or so have dramatically
increased understanding of brain function.
The Brain versus Heart Debate
Throughout history, there has been divided opinion on where our thoughts, feelings and behaviours come
from. The ancient Egyptians believed the brain had no purpose and it was removed and discarded during
mummification. They removed the liver, lungs, intestines and stomach and placed them in Canopic jars.
The organs were removed to assist the mummification process as they held a lot of fluid which would
cause the body to putrefy.
The heart held the mind and soul and was the source of all wisdom, memory, emotion, personality and the
life forces. It was left in place inside the body.
The Ancient Greeks furthered the debate with Alcmaeon and Empedocles taking opposing sides of the
argument.
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Alcmaeon (500BCE) is considered the first person to identify the brain as the source of mental processes.
He was known to dissect organs in dead animals and discovered the optic nerve connecting the eyes to the
brain. This furthered his assumption that the brain was the centre of all thinking processes and if damaged,
mental processes could be disrupted.
Empedocles (490-430BCE) believed that every living and non-living thing was made of the four elements:
earth, fire, air and water. The proposed that the heart was the centre of the body’s blood vessel system
and therefore the human soul is blood, with our thoughts located within the blood, particularly around the
heart. The composition of the blood related to the intelligence of a person.
Other Ancient Greek philosphers and physicians weighed in on the debate. Aristotle took the heart side of
the debate, whereas as Galen took the brain side of the debate. Many of Galen’s theories and explanations
around behaviour and the brain, even those that have been proved false, remained up until the 19 th
Century.
Whilst it is now agreed that the brain is the source of all mental processes and behaviour, the heart cannot
be forgotten, as changes to the function of the heart can affect thoughts, feelings and behaviour.
The Mind-Body Problem
Are our mind and body two separate entities, or are they parts of the one whole?
Ancient Greek philosophers debated this problem for many years, with most agreeing that the mind and
body were separate. The mind could control the body, but the body could not influence the mind.
René Descartes (1596-1650) challenged this assumption with his theory known as “Dualism.” He agreed
that the mind and body were two separate entities, but described the mind as being spiritual (the soul) and
the body as the physical structure (matter). Hence the saying “Mind over matter.”
According to Descartes, the mind and body interacted through the Pineal Gland. A tiny structure located in
the middle of the brain. This allowed the mind and body to work together to produce sensations, thoughts
self-awareness and other conscious experiences.
Descartes proposed that the mind influenced the body, but that the body could also influence the mind.
Descartes is most famous for his saying, “I think, therefore I am.”
We now know that the Pineal Gland is part of the Endocrine System and secretes Melatonin. Melatonin is a
hormone that is released when it gets dark to make a person sleepy. It follows a circadian rhythm and
allows people to have a regular sleep-wake cycle.
The mind-body problem remains. Whilst it is well established that mental processes occur in the brain,
does it follow that the ‘mind’ is simply part of the activity of the brain? Or is the mind separate from the
brain?
We consider the mind as being our consciousness, so where does that consciousness come from?
Continued research through ever more sophisticated neuro-technologies, allow us to learn more about the
mind and brain every day. Hopefully, leading to an answer sometime in the future.
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Phrenology
Phrenology: the study of the relationship between the skull’s surface features and a person’s personality
and behavioural characteristics (faculties).
German physician Franz Gall (1758-1828) proposed that different parts of the brain were used for different
functions. He believed that all the parts of the brain were completely separate.
According to Gall, personality and mental abilities were located on the outer surface of the brain. The more
they were used, the more that part of the brain would develop and it would ‘push out’ the skull creating a
lump that could be felt externally.
Gall observed his classmates at school and noted particular facial and skull features, similar shaped heads
and lumps in the same areas on each head, correlated with a type of personality or academic ability.
For example, bulging eyes suggested a well-developed memory ability that was just behind the eyes.
Gall collected a number of skulls and skull casts from people with extreme personalities and particular
talents and included writers, criminals and the mentally ill.
This research led to the creation of a map of the skull and the areas associated with abilities and
personality. Gall called these ‘faculties.’
Gall’s work was never taken seriously in scientific circles as it lacked scientific evidence. There was no way
to empirically (objectively) test his theory.
However, it was taken up by many people who created their own maps and used it to ‘read’ people and
offer advice, much like psychics.
Due to the lack of scientific evidence, phrenology is known as a pseudoscience.
Pseudoscience: a fake or false science.
Other pseudosciences include astrology, numerology and graphology.
Despite the scientific community discrediting Gall’s work, he did lead to further research into the brain. His
theory of brain regions controlling particular functions/abilities is now a well-established fact.
The first brain experiments
FLOURENS – BRAIN ABLATION
Brain ablation involves disabling, destroying or removing selected brain tissue followed by an assessment
of subsequent changes in behaviour.
Ablation involves permanent damage to the brain and is unethical to perform on humans, for the sake of
scientific research, as it causes lasting harm to individuals. Although, it is used to remove brain tumours.
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Pierre Flourens (1794-1867) is considered the first person to experiment with brain ablation. He worked
mainly on rabbits and pigeons, removing brain tissue and observing the effects on behaviour.
Despite his important findings on the brain, Flourens was criticised. His surgical technique was imprecise,
which may have led to damage beyond that intended within in the brain. His notes also made it difficult to
replicate his experiments.
FRITSCH, HITZIG AND PENFIELD – ELECTRICAL STIMULATION OF THE BRAIN (ESB)
The first experiments using electrodes to stimulate brain areas were performed by German physicians
Fritsch and Hitzig. They stimulated the motor cortex in the brain of a dog and observed movements on the
opposite side of the dog’s body. This demonstrated contralateral movement (the left hemisphere of the
brain controls the right side of the body and vice versa).
Research using ESB continued with Penfield, who used it as a way to map the brain. Penfield operated on
patients with Epilepsy. In some patients medication did not effectively treat the seizures and the only way
to prevent them was to remove the brain tissue. To ensure that Penfield created no lasting damage he
used ESB to map the brain. This ensured that when treating the epilepsy, he didn’t accidentally remove
areas of the brain such as the speech centre.
ESB is regularly used on patients undergoing brain surgery, but never for purely research purposes.
BROCA AND WERNICKE – APHASIA
Studies conducted by Paul Broca and Carl Wernicke identified two important language centres in the brain.
Their research led to these areas being named after them.
Broca’s area is located in the left frontal lobe and is involved in speech production.
Wernicke’s area is located in the left temporal lobe and is involved in language comprehension.
Damage to either of these regions leads to ‘Aphasia.’
Aphasia: a language disorder caused by brain damage.
Aphasia is a common occurrence in people who have suffered strokes.
SPERRY AND GAZZANIGA – SPLIT-BRAINS
Roger Sperry and Mike Gazzaniga conducted experiments into ‘split-brains’. A split-brain occurs when a
person has their corpus callosum severed.
Corpus callosum: a bundle of nerve fibres connecting the two hemispheres of the brain, allowing
communication.
In some patients with severe epilepsy, the only way to treat it is to sever the connection between the
hemispheres. This creates two separate brains.
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BURKHARDT AND MONIZ – LOBOTOMY
Gottlieb Burkhardt and Antonio Moniz both performed frontal lobotomies on mentally ill patients in the
late 19th and early 20th centuries.
A frontal lobotomy involves inserting an ice pick through the eye socket into the frontal lobe of the brain.
The pick is then swirled around destroying brain tissue.
Both men observed patients who were once aggressive and agitated calmed after the procedure.
Lobotomies became a common practice during the 1940’s and 1950’s despite no conclusive evidence that
they actually treated mental illness.
Neuroimaging techniques
Brain Imaging Techniques: CT, MRI, fMRI, PET
Computerised Tomography (CT): takes x-rays of the brain at different angles to produce a computer-enhanced
image of a cross-section of the brain. It provides information about brain structures.
Magnetic Resonance Imaging (MRI): uses a magnetic field and radio waves to vibrate brain neurons and produce a
detailed, still, computer-enhanced 3D image of brain areas and structures. More detailed than CT. Shows brain
structure.
Functional Magnetic Resonance Imaging (fMRI): detects changes in oxygen levels in the blood flowing through the
brain and combines this data into a detailed, computer-enhanced 3D representation of the active brain. Shows
structure and function of the brain.
Positron Emission Tomography (PET): involves the injection of radioactive glucose into the bloodstream, tracking
the blood flow to the brain and combining this data into a series of computer generated colour coded images of the
level of activity in various brain areas while engaged in different tasks. Show brain function.
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BRAIN IMAGING TECHNIQUES SUMMARY
Imaging
Technique
Computerised
Tomography
(CT)
What it is useful for
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Magnetic
resonance imaging
(MRI)
Functional
magnetic
resonance imaging
(fMRI)
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Positron Emission
Tomography (PET)
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CT identifies the precise location
and extent of damage to or
abnormalities in various brain
structures or areas.
A CT scan can reveal the effects
of strokes, tumors, injuries and
other brain disorders
MRI diagnoses structural
abnormalities of the brain.
MRI detects and displays
extremely small changes in the
brain. More detail than CT.
Records the levels of activity in
different areas of the brain while
the person is involved in a
cognitive activity, such as
thinking, imagining, remembering
or talking.
One application of fMRI in brain
research has been in the study of
hemispheric specialization with
intact brains.
fMRI are more detailed than PET
images.
Records the levels of activity in
different areas of the brain while
the person is involved in a
cognitive activity, such as
thinking, imagining, remembering
or talking.
Designed to diagnose
abnormalities in the brain and is
highly effective if that area of the
brain is structurally intact.
Provides information on the brain
functioning of specific groups or
populations of research interest,
such as people with mental
illnesses.
Limitations

Shows only brain structure or
anatomy – not function.

Cannot be used with people who have
internal metallic devices such as heart
pacemakers or steel pins in bones.
Shows only brain structure, or
anatomy—not function.
Differences in levels of brain activity
of different areas may not just be the
direct result of the specific task being
undertaken.
Levels of brain activity may be
associated with other factors relating
to the research task performed by the
participant; for example, task duration
(that is, the length of time taken to do
the task) and task difficulty.
fMRI’s are not common in hospitals
and are expensive.
Requires injection of a radioactive
substance, but the radiation dosage is
harmless, and risks to the person’s
health areconsidered to be negligible.
However, the need for radiation
means that a PET session must be
kept short so that the person does not
receive too much radiation.
Furthermore, PET needs a 40-second
interval between scans, and each
individual scan takes 30 seconds to
complete. This means that PET
doesn’t necessarily pick up the very
rapid progression, or changes in brain
activity associated with different brain
functions.
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