Transcript The Brain and Behaviour

The Brain and
Behaviour
The central nervous system
• The central nervous system is one of the two
major divisions of the human nervous system.
• The central nervous system comprises the
brain and spinal cord. The spinal cord connects
the brain and the peripheral nervous system.
• The peripheral nervous system includes all
parts of the nervous system that lie outside the
brain and the spinal cord.
The Brain
• It is encased in a hard, protective skull and
weighs, on average, around 1.5 kg in
adults.
• It has the consistency of firm jelly and is
covered by a strong plastic like
membrane.
• There is a small gap between the brain
and the skull, which is filled with fluid.
The Cerebral Cortex
The cerebral cortex is the convoluted outer layer or covering
of the two cerebral hemispheres.
The surface area of the cerebral cortex bends and folds
inwards so that its surface area can fit into the limited
amount of space available in the skull.
If flattened out the cerebral cortex would cover about 4 A4
pages.
The cerebral cortex is involved with information-processing
activities such as perception, language, learning, memory,
thinking, problem-solving as well as the planning and
control of voluntary body movements.
Some areas of the cerebral cortex are dedicated to
specific functions.
The areas of the cerebral cortex and their main functions
can be can be organised into three broad categories:
1. The various sensory cortex areas which receive and
process information from our different senses
2. The motor cortex area which receives, processes and
sends information about voluntary body movements
3. Association cortex which integrate sensory, motor and
other information and are involved in the more complex
mental abilities, such as perceiving, thinking and
problem-solving.
It is believed that the larger the size of the cerebral cortex,
the more intelligent the organism will be.
Cerebral Hemispheres
The cerebral cortex is described as having two halves,
called cerebral hemispheres.
The cerebral hemispheres are two almost symmetrical
brain structures that appear to be separated by a deep
groove (known as the longitudinal fissure) running from
the front to the back of the brain.
Although the hemispheres appear to be separated, they are
connected at several points by strands of nerve tissue.
The largest and most important of these strands is the
corpus callosum.
The left hemisphere receives information from the right side
of the body just as the right hemisphere receives
information from the left side of the body.
Remember!! Contralateral
Organisation
•Left
hemisphere
controls
movement on
the right side of
the body.
•Right
hemisphere
controls
movement on
the left side of
the body.
Corpus Callosum
The interaction between the two hemispheres of the
brain occurs mainly through the corpus callosum.
The corpus callosum is a strand, or bridge of nerve
tissue that connects the left and right cerebral
hemispheres and serves as the main
communication pathway between them.
This means that information can be exchanged
between the two hemispheres when performing their
many functions as we think, feel and behave
throughout everyday life.
Four lobes of the cerebral cortex
The cerebral cortex of each hemisphere can be divided
into four anatomical regions called cortical lobes.
Cortical lobes are areas of the brain associated with
different structures and functions. The four lobes are
named after the bones of the skull that cover them.
•
•
•
•
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
The lobes contain areas of the cortex
that have specialised sensory or motor
functions, as well as areas of the
cortex generally referred to as
association cortex.
The sensory areas of the lobes receive
and process information from sensory
receptors in the body.
The sensory area that receives and processes
visual information is called the primary visual
cortex. It is located in the occipital lobe.
The sensory area that processes auditory
information is called the primary auditory
cortex and is located in the temporal lobe.
Sensory information from the skin and from
skeletal muscles is processed in the
somatosensory cortex located in the parietal
lobe.
The motor areas receive and process
information about voluntary body
movements; that is intentional
movements such as when you scratch
your nose.
There is only one primary motor area in
the brain. This is called the primary
motor cortex and is located in the frontal
lobe.
The association areas of each lobe integrate
information from different brain areas and are
mainly involved in complex cognitive processes
such as perceiving, thinking, learning,
remembering, reasoning and so on.
Association areas are located on all four lobes of
each hemisphere and may receive and process
information from sensory and/or motor areas, as
well as from other structures or other association
areas of the brain in other lobes.
Frontal Lobe
The frontal lobe is the largest of the four lobes and
occupies the upper forward half of each cerebral
hemisphere, right behind your forehead.
In the forward section of each frontal lobe are
association areas that receive information from other
lobes to enable us to perform complex mental
functions.
The frontal lobes are also involved in personality, the
control of emotions, and expression of emotional
behaviour.
Primary Motor Cortex
Located at the rear of each frontal lobe and running
roughly across the top of your head is a strip of
neural tissue called the primary motor cortex.
The primary motor cortex is specifically involved in
controlling voluntary bodily movements through its
control of skeletal muscles.
The motor cortex in the left frontal lobe controls
voluntary movements on the right side of the body
and vice versa.
The amount of cortex devoted to a particular body part
corresponds to the complexity or fineness of its
movements.
Broca’s Area
A specific cortical area located in the left frontal lobe next to
the motor cortex areas that control the muscles of the
face, tongue, jaw and throat is an area called Broca’s
area.
Broca’s area is responsible for the production of articulate
speech, coordinating movements of the muscles
required for speech and supplying this information to the
appropriate motor cortex areas.
Broca’s area is also involved in understanding the meaning
of words and the structure of speech such as adjectives,
prepositions and conjunctions. It is also involved in
understanding the grammatical structure of sentences.
Damage to Broca’s Area
Damage to Broca’s area often produces speech that
is very deliberate, consisting of a few words with
very simple grammatical structure, but damage
rarely results in the total loss of speech.
This type of speech impairment is known as Broca’s
aphasia.
Aphasia is a form of language loss or impairment due
to brain damage, injury or disease.
In Broca’s aphasia speech consists of very
short sentences, typically three or four
words, and these words are mainly verbs
and nouns.
The smaller parts of speech are often
ommitted such as to and the, as are
proper grammatical endings of words such
as ing and ed.
Parietal Lobe
The parietal lobe is located behind the frontal lobe and
occupies that upper back half of the brain, but not the
rear-most area.
The parietal lobe in each hemisphere receives and
processes sensory information from the body and skin
senses and other sensory areas in the brain. It also
sends information to other areas of the brain.
Located at the front of each parietal lobe, just behind and
parallel to the primary motor cortex in the frontal lobe,
is a strip of cortex called the primary somatosensory
cortex.
The primary somatosensory cortex receives
and processes sensory information from the
skin and body, enabling us to perceive bodily
sensations.
Different areas of the primary somatosensory
cortex are involved with sensations of touch
received from specific body parts.
Furthermore, the amount of cortex devoted to
a particular body part corresponds to the
sensitivity and amount of use of the body part.
Occipital Lobe
The occipital lobe is located at the rear-most area of each
cerebral hemisphere; that is at the back of your head.
The occipital lobe is primarily involved in vision.
Damage to the occipital lobe can produce blindness, even
if the eyes and their neural connections to the brain are
normal.
The primary visual cortex is located at the base of each
occipital lobe and this is where visual information from
the two eyes is received and processed.
Temporal Lobe
The temporal lobe is located in the lower, central, area of the
brain, above and around the top of each ear.
The temporal lobe in each hemisphere is primarily involved
with auditory perception, but also plays an important role in
memory, in aspects of visual perception such as our ability
to recognise faces and identify objects, and in our
emotional responses to sensory information and memories.
The primary auditory cortex in each temporal lobe receives
and processes sounds from both ears, receiving and
processing different features of sound and therefore playing
a vital role in the identification of sounds.
The two main features of sound are frequency (which we
perceive as pitch) and amplitude or intensity (which we
perceive as loudness).
Verbal sounds such as words are mainly processed in the
primary auditory cortex of the left hemisphere and nonverbal sounds (such as music) are mainly processed in the
primary auditory cortex of the right hemisphere.
Damage to the temporal lobe as a result of a stroke or severe
blow to the head can level a person with the ability to
describe someone’s facial features, to identify their sex,
and to judge their approximate age, but without the ability
to recognise the person as someone that they know, even if
it is their mother.
Wernicke’s Area
A specific area in the temporal lobe of the left hemisphere only, next
to the primary auditory cortex and connected to Broca’s area by
a bundle of nerves is called Wernicke’s area.
Wernicke’s area is involved with comprehension of speech; more
specifically, with interpreting the sounds of human speech.
When a word is heard, the auditory sensation is processed by the
primary auditory cortex of the left temporal lobe, but the word
cannot be understood until the information has been processed
by Wernicke’s area.
This area is also thought to be involved with not only understanding
words, but also for locating appropriate words from memory to
express intended meanings when we speak or write.
Hemispheric
Specialisation
Hemispheric Specialisation
• Overall, the two cerebral hemispheres appear to be two
replicas of each other in terms of size, shape and
function.
• The function of the sensory and motor areas of the left
and right hemispheres are generally the same, however,
each hemisphere does have some specialised functions
which are not duplicated by the other hemisphere.
• Hemispheric specialisation: The idea that one
hemisphere has greater control over a particular
function.
How do we know what we
know??
• The earliest evidence of hemispheric
specialisation came from observations of people
who had suffered a stroke or an injury affecting
one hemisphere but not the other.
• It was observed that damage to the LEFT
hemisphere often resulted in difficulties with
language related activities (VERBAL TASKS)
such as understanding speech, talking fluently,
reading and writing. It also noted that the left
hemisphere processes information in a step by
step and analytical way.
• Damage to the RIGHT hemisphere often
resulted in difficulties with visual and spatial
tasks not dependent on language (NON
VERBAL TASKS), such as reading a map.
What is each hemisphere
specialised in?
LEFT:
• Verbal Task (involve the recognition of words) eg.
Reading, writing, understanding of speech
• Analytical tasks (involve breaking down a task into its
key parts and then approaching it in a step by step way)
eg, following instructions on how to bake a cake.
• Left hemisphere receives and processes sensory
information from the right side of the body.
• Controls voluntary movement on the right side of the
body
Right:
• Non verbal tasks (tasks that are not dependent on
language skills) eg. Completing a jigsaw puzzle.
• Spatial and visual thinking eg. Reading a map,
visualising a place in your mind, recognising faces.
• More involved in recognising emotions from facial cues
(signals), such as raised eyebrow and smiling.
• Right hemisphere receives and processes information
from the left side of the body and controls voluntary
movements on the left side of the body.
The Reticular Activating System
(RAS) and Thalamus
• Two other important brain structures are
involved in our ability to be awake and
alert and to attend to stimuli in our internal
and external environments.
• These are the reticular activating system
and the thalamus.
Reticular Activating System
(RAS)
• Before incoming sensory information (neural
impulses sent from outside the body to the
brain) reaches the cerebral hemispheres, it must
pass through the reticular activating system.
• The reticular activating system is a network of
neurons that extends in many directions from the
top of the spinal cord up to the thalamus. It
influences our state of physiological arousal and
alertness.
• Nerve fibres from sensory neurons have
side branches into the RAS, which filter
incoming sensory information, sorting it
into ‘important’ and ‘unimportant’
categories.
• These side branches stimulate the RAS to
send its own nerve impulses upward
toward the cortex, arousing it to a state of
alertness and activity.
• This stimulation keeps the cortex alert and
active which we then experience as being
in a state of consciousness awareness.
• Once alerted to the fact that new information is
on its way, the brain is ready to process the
sensory information.
• Unimportant information is ignored.
• This is what we know as ‘selective attention’our ability to voluntarily redirect our attention to
a specific stimulus while ignoring others.
• Eg. When you are trying to cross a busy road
without traffic lights the RAS allows you to filter
out unwanted sensory information and
concentrate on what is important.
• The RAS is not only involved in keeping us
alert when we are awake- it is also
involved in the control of sleeping and
waking, and is often referred to as the
brain’s arousal centre.
• Experiments in which researchers have
removed the RAS from animals show that
without it they cannot be awakened, due to
lack of arousal. If the RAS is electrically
stimulated in sleeping animals they will
awaken immediately.
• Damage to the RAS will profoundly disrupt
the sleep-wake cycle and can result in
coma or a vegetative state.
• Many general anaesthetics work by
reducing the activity of the RAS, making
the patient unconsciousness.
The thalamus: the sensory
switching station
• The thalamus is a structure that sits on top
of the brain stem and acts as a sensory
relay station.
• Information from all senses (except smell)
pass through this structure.
• The thalamus is a brain structure that
filters information from the senses and
transmits the information to the cerebral
cortex.
• Eg. Information from the eyes enters the
thalamus and is relayed to the primary visual
cortex in the occipital lobe.
• The flow of information is not one way- there is
a constant flow of information between the
thalamus and other cortical areas.
• In addition to incoming sensory information,
the thalamus receives information about our
state of arousal from the reticular formation.
• This means the thalamus also has a crucial
role in influencing our level of alertness.
• The thalamus also appears to play a role
in attention.
• It filters the vast amounts of information
that need to be attended to and highlights
some while de-emphasising others.
• This is crucial when we are in need of
resting the brain (eg sleep) as the
thalamus stops information from passing
through to the cortex.
The spinal cord
• The spinal cord is a long column of nerve tissue
that extends from the base of the brain and is
encased in the spinal column which runs from the
skull to the lower back.
• The bones of the spinal cord are called vertabrae.
• The two main functions of the spinal cord are:
To pass sensory
information from the
Peripheral Nervous
System to the brain.
To pass motor information
from the brain to the
Peripheral Nervous
System so that the
appropriate actions can
be taken.
• When the spinal cord is damaged, the
brain loses both sensory input from and
control over the body.
• The spinal cord is the linking ‘pipeline’ that
integrates the central nervous system and
peripheral nervous system, which work
together to transmit information around the
body.
• This information is transmitted via
NEURONS.
TYPES OF NEURONS
• There are three main types of neurons, each of which
has a different role in the nervous system.
•
-
These are:
Sensory neurons
Motor neurons
Interneuron's
• Sensory neurons and motor neurons are found
primarily in the PNS, whereas interneuron’s are only
found in the CNS.
SENSORY NEURONS
• Sensory neurons (also called afferent neurons) are
specialised cells that receive information from both the
external environment and from within the body and
transmit the information to the CNS.
• Their main role is to help us sense the external world
and changes within our body.
• Generally there are different types of sensory neurons,
each of which is specialised to respond only to a
particular type of stimulation. Eg. The sensory neurons
in the ears respond to sound waves, but not light.
MOTOR NEURONS
• Motor neurons (also called efferent neurons)
transmits messages from the CNS to the muscles,
glands and organs.
• They enable muscles to move, cause glands to
secrete chemicals and activate internal organs such
as the heart, lungs and intestines.
INTERNEURONS
• Interneurons exist only within the CNS.
• Interneurons provide neural links between sensory
and motor neurons and have a specialised role of
carrying and integrating messages between sensory
and motor neurons.
• When information from a sensory neuron arrives at the
CNS, an interneuron receives, organises and
integrates the information. They also connect with the
motor neurons to send messages back through the
PNS.
Neurons
• The major difference between sensory and
motor neuron activity is the direction of the
neural impulse and what happens at their
destinations.
STUDIES ON COGNITIVE
PROCESSES OF THE BRAIN
• The brain is not always perfect as shown
through perceptual anomalies or
‘irregularities’ like when we perceive
motion that doesn’t actually occur (motion
after effect), when we fail to notice
changes that are occurring (change
blindness) and when we involuntarily
experience sensations that do not have a
physical basis at that time (synethesia).
• When looking at the irregularities of the brain
we examine these phenomena, which are all
experienced by people with intact,
undamaged brains.
• Other people with brain damage experience
the world very differently to those without
damage.
• We will also look at this and the way this
effects a persons life.
- Aphasia
- Spatial neglect
- Split-brain studies
APHASIA
• The word ‘aphasia’ is a general term used
for clinical purposes to describe individuals
with a language disorder.
• Aphasia refers to a language disorder
apparent in speech (comprehension or
production), writing or reading, produced
by injury to brain areas specialised for
these functions.
• Aphasia is often classified into three main areas:
- Fluent aphasias in which there is fluent speech but
there are difficulties in either auditory verbal
comprehension or the repetition of speech spoken
by others
- Nonfluent aphasias in which there are difficulties in
articulating clearly but auditory verbal
comprehension is good
- Pure aphasias in which there are specific
impairments in reading, writing or the recognition of
words.
• The most common cause of aphasia is stroke,
causing loss of blood supply to areas of the brain
associated with language.
• Some aphasia sufferers can speak fluently
but they cannot read, others may
understand what they read but cannot
speak, some can write but not read, some
can read but not write, some can read
numbers but not letters, and others can
sing but not speak.
Broca’s aphasia
• In the late 1800’s, French physician Paul
Broca studied patients with damage to the
lower left frontal lobe, close to the motor
cortex.
• This later became known as Broca’s area.
• He discovered that while patients with
damage to this area could understand
what was said to them and knew what
they wanted to say in response, they
simply could not say it.
• In Broca’s aphasia a person has difficulty in
speaking, although they continue to
understand speech.
• A typical patient will speak slowly and
laboriously, and use simple sentences.
• Usually only the concrete words (verbs and
nouns) are pronounced and the connecting
words are omitted (to, the or –ing).
• Eg. ‘Boy went beach’ instead of ‘The boy went
to the beach’.
• The sentence is not articulate and incomplete.
• Some patients cannot speak at all.
• Broca’s aphasia:
http://www.youtube.com/watch?v=f2IiMEbM
nPM
Wernicke’s aphasia
• Around the same time, German physician
and psychiatrist Carl Wernicke studied
patients with a different language disorder.
• This was the inability to understand
speech or to produce coherent language.
• He identified a part of the brain in the left
temporal lobe close to the primary auditory
cortex as being the area responsible for
language comprehension- Wernicke’s
area.
• Wernicke’s aphasia is a type of aphasia
in which a person has considerable
difficulty comprehending speech and
speaking in a meaningful way.
• Unlike Broca’s aphasia, speech is often
fluent and grammatically correct, but what
is said is nonsense.
• Words are used inappropriately and
sometimes made up words are used.
• The patient often is not even be aware that
what they are saying does not make
sense.
• Eg. When describing a picture of a woman
washing the dishes and her two children
stealing cookies from the cookie jar behind
her the patient says:
“Well, this is…mother is always here
working her work out of here to get her
better, but when she’s looking the two
boys looking in the other part. One their
small tile into her time here. She’s working
another time because she’s getting to. So
two boys work together and one is
sneaking around here making his work
and further funnas his time he had.”
• Tono man:
http://www.youtube.com/watch?v=Fw6d54gj
uvA
• Wernicke’s aphasia:
http://www.youtube.com/watch?v=aVhYN7N
TIKU
Language functions
• There are other areas of the brain that have been
linked to language that complement the functions
outlined in Broca and Wernicke’s areas.
• It has also been found that the right hemisphere
may also have a role in language.
• Some patients with major destruction to the left
hemisphere may be capable of swearing or using
emotionally charged words, or singing, and
learning well known phrases.
• Some can sing phrases that they are unable to
say, thereby making use of the right hemisphere’s
musical function.
Spatial neglect
• Read intro page 217.
• Spatial neglect is an attentional disorder in
which individuals fail to notice anything either on
their left or right side.
• They tend to behave as if one side of their world
does not exist.
• Most commonly observed in stroke victims or
accident victims who have extensive damage to
the rear area of the parietal lobe of the right
hemisphere.
• They mostly neglect the left side of their world.
• Read studies pg 218.
• Spatial neglect is widely considered to be a
disorder involving failure of attention, and not
due to impairment of memory processes, the
visual system or any other sensory system.
• Its much greater occurrence with damage to
the right rather than the left parietal lobe
highlights the importance of this lobe in
attention and spatial recognition.
• Many patients insist that there is nothing
wrong with their perception of the world.
• Some do however, make a gradual recovery.
Split brain studies
• Much of our knowledge on hemispheric
specialisation comes from researchers
Roger Sperry (1914-1994) and Michael
Gazzaniga (1939-).
• These researchers demonstrated that
there is more to hemispheric specialisation
than just language functions.
• How is it possible to test only one side of
the brain?
• One way is to work with people who have
had a split-brain operation.
• Split brain surgery involves surgically
cutting the corpus callosum thereby
disconnecting one hemisphere of the brain
from the other.
• Another less common procedure is the
WADA test in which a sedative is injected
into an artery which sedates only one side
of the brain.
Split brain surgery
• In the 1940’s there was very little remedy
for people who suffered from severe
epileptic seizures (10-15 a day).
• In recognising the need for new
treatments, American neurosurgeon
William Van Waganen decided to contain
seizure activity by cutting the corpus
callosum and stopping the communication
between the two cerebral hemispheres.
• Animals studies showed that there were no obvious
effects of this surgery and in the 1940’s the first of
the human split-brain surgeries began.
• There was little evidence of impairment and patients
appeared to remain ‘normal’, however there was
little or no improvement in the occurrence of the
seizures.
• The surgery was abandoned until the 1950’s when
Sperry and a student of his, Roger Myers conducted
successful split brain operations with cats.
• Through this experimentation it was found that the
earlier split-brain operations may have been
unsuccessful because the corpus callosum and
other neural connections had not been completely
severed.
• The split-brain surgeries were conducted
on 11 epileptic patients, completely cutting
the corpus callosum and other nerves,
leaving some patients virtually seizure free
afterwards and with minimal side-effects.
• Sperry and Gazzaniga however
discovered that the surgery had left some
patients with a unique condition.
Effects of having a split brain
• Surgery that cuts the corpus callosum interrupts
the exchange between the two cerebral
hemispheres, so information registered in one
hemisphere is unable to be transferred to the
other.
• This means the brain cannot integrate
information registered separately in each
hemisphere.
• Eg. Information registered in the right
hemisphere cannot be transferred to the left
(language centres) and therefore cannot be
verbalised.
• Problems arise for split-brain patients when a
response requires information from one hemisphere
to be integrated with information from the other
hemisphere.
• Eg. When registering visual information, it is
registered on the retina of each eye and travels to
each hemisphere. Info from the right portion of a
persons vision (right visual field) goes to the left
hemisphere where the speech centre allows you to
articulate this information verbally. If you receive
information only to your left visual field, the
information will only travel to your right hemisphere
and if you had a split-brain operation it would be
unable to pass to the left hemisphere and therefore
be unable to be articulated verbally.
Perceptual anomalies
• Perception occurs when sensory information
reaching the brain is meaningfully interpreted.
• Touch, taste, smell, sight, hearing.
• This allows us to make sense of the world.
• However sometimes we make errors in our
perceptions and this can lead to perceptual
anomalies.
• Perceptual anomaly refers to an irregularity in
perception. It usually involves an inconsistency
or mismatch between the perceptual experience
and physical reality.
• Eg. When driving along a highway you
may see a puddle on the road ahead. As
you drive the road stays dry and the
puddle remains in the distance. In reality
there is not puddle it is a layer of hot air
beneath cool air but the brain misinterprets
it and you see it as a puddle.
• Three types of anomalies:
- Motion after-effect
- Change blindness
- Synesthesia
Motion after-effect
• Motion after-effect refers to the
phenomenon that occurs when, after
staring at a moving image for a period of
time and then looking immediately at a
stationary one, we perceive the stationary
image to be moving in the opposite
direction to the moving image.
• http://www.michaelbach.de/ot/mot_ada
ptSpiral/
• One explanation for motion after-effect is
that the neurons in the visual cortex that
respond to the motion become fatigued
over time. When you stare at a moving
object, these cells signal movement in one
direction. When you shift your attention to
something else, these neurons fail to fire.
However, as neurons that signal
movement in the opposite direction are
more active they therefore interpret the
movement as the opposite direction.
Change blindness
• Change blindness refers to a failure to
notice changes in a visual scene.
• This failure to notice is usually because
the changes occur at the same time as a
disruption to our vision and, in particular, a
disruption to our attention.
• Change blindness illustrates the
importance of attention in cognitive
processes and the important roles of the
RAS and thalamus as a sensory filter.
• http://www.youtube.com/watch?v=vBPG_
OBgTWg
Inattentional blindness
• Inattentional blindness is the failure to notice
an object in the environment, because attention
was not focused on it.
• There is no visual disruption or reliance on
memory.
• It is possible that these phenomena occur
because of a failure to store the information in
the first place. It may also occur because we are
unable to compare the new information with the
old information.
• http://www.youtube.com/watch?v=IGQmdoK_Zf
Y&feature=related
Synesthesia
• Synesthesia is a perceptual experience in
which stimulation of one sense produces
additional unusual experiences in another
sense.
• It is involuntary and occurs automatically
and is consistent across time.
• Grapheme-colour synesthesia is the most
common form and is when the experience
of viewing letters or numbers actually
produces the experience of colours.
• Although the causes of synesthesia are yet to
be clearly determined, there are some factors
that are associated closely with synesthesia:
- It is most likely to run in families, suggesting
a genetic link
- It is most common in drug users (LSD)
- People with one type of synesthesia are more
likely to have another form
- Creative people are more likely to have
synethesia
- Synesthesia can develop over the course of a
lifetime, not everyone is born with it.
• http://www.youtube.com/watch?v=veoN1m
h7RME
Brain research methods.
• Neuroimaging can capture detailed
images of the living intact brain as people
engage in different mental processes or
make behavioural responses.
• Functional neuroimaging refers to
scanning techniques that provide views of
some particular aspect of brain function by
showing images of the brain at work.
Brain research methods
Summarising brain research methods.docx
Ethical principals in brain
research
• Psychologists are not medically qualified
and therefore are not legally or ethically
permitted to administer any medical
procedures.
• Any neuroimaging device involves medical
procedures and can therefore not be
administered by a psychologist.
• A psychologist may work on a team with
medical experts to administer these kinds
of treatments.
THE HUMAN NERVOUS
SYSTEM
Central Nervous System
The Central Nervous System (CNS) comprises the brain and spinal
cord. The spinal cord connects the CNS with the Peripheral Nervous
System.
The roles of the CNS are to integrate and coordinate all incoming
neural information and to initiate messages sent to different parts of
the body, the CNS does not have direct contact with the outside
world.
The CNS relies on the Peripheral Nervous System to provide it with
information about both the external world and the body’s internal
environment, and to carry messages from the CNS to various parts
of the body.
Peripheral Nervous System
The Peripheral Nervous System (PNS) is the entire network of
nerves located outside the Central Nervous System.
It extends from the top of the head, throughout the body to the tips
of the fingers and toes and to all parts of the skin.
The PNS has two main functions:
1.
To carry information from the sensory organs to the CNS
2.
To convey information from the CNS to the muscles, organs
and glands.
It enables communication to occur between the CNS and all other
parts of the body outside the brain and spinal cord.
Human Nervous System
In the human nervous system, messages can only travel in one
direction along the neuron. To accommodate this, the PNS has two
different pathways for communicating information to and from the
CNS.
One of these pathways consists of a set of neurons- the sensory
neurons- that carry information from the sensory organs, muscles
and glands to the CNS.
The other pathway consists of a set of neurons- motor neurons- that
carry instructions or messages from the CNS to muscles, organs
and glands.
You are able to feel the heat of a wood fire because of the
coordination of the
and the
. The heat
given from the fire is received by the
neurons of the skin, which are part of the
. The
sensory neurons then transmit the information to the
. The brain then organises and interprets the
information in a meaningful way, which enables you
to know how hot the flame is. If you decide it is too hot, the
brain sends messages via the
neurons which
are part of the
to the muscles in your legs to move a
few steps away from the fire.
The peripheral nervous system can be subdivided into two quite
distinct nervous systems, each of which has different functions- the
somatic nervous system and the autonomic nervous system.
THE SOMATIC NERVOUS
SYSTEM
The Somatic Nervous System is a network of sensory (afferent)
nerves that carry information received by sensory receptors in the
body to the CNS, and motor (efferent) nerves that carry information
from the CNS to control voluntary movements of skeletal muscles.
The Sensory function of the SNS is activated when you sense or
feel something on your skin for example and the SNS sends
signals from that point to your brain via the spinal cord, resulting in
you experiencing the sensation.
The motor function of the SNS is demonstrated whenever you
voluntarily move a body part.
THE AUTONOMIC NERVOUS SYSTEM
The Autonomic Nervous System is a network of nerves that connects
the CNS to the body’s internal organs and glands providing
feedback to the brain about their activities.
The ANS is called autonomous because many of the organs, glands
and processes under its control are self-regulating and not usually
under voluntary control.
Eg. Heartbeat, digestion, perspiration.
Regardless of our level of awareness or alertness, the ANS keeps the
vital organs and systems of our body functioning thus maintaining
our survival.
Divisions of the ANS
The ANS is made up of two distinct divisions, the sympathetic and
parasympathetic nervous systems.
The sympathetic nervous system is responsible for increasing the
activity of most visceral muscles, organs and glands in times of
vigorous activity, stress or threat.
The parasympathetic nervous system is responsible for decreasing the
activity of most visceral muscles, organs and glands, and keeping
the body functioning in a normal state.
While the two nervous systems are both active at the same time, one
system usually dominates the other at any given time.
The Sympathetic Nervous System
Enhances survival by providing an immediate response, in a split
second, to any kind of emergency.
When an emergency is perceived, neurons in the SNS activate target
organs and glands to respond in the required way. The result is that:
• heart rate and blood pressure increase,
• breathing rate increases so more oxygen can be taken in,
• sugar and fat are released from storage to provide instant energy to
the skeletal muscles,
• the pupils dilate to allow more light to enter the eye and enhance
vision,
• and sweat glands increase their production of sweat which cools the
body.
The Parasympathetic Nervous System
The PNS generally has the effect of counterbalancing the activities of
the SNS.
It has two main functions:
1. It keeps the systems of the body functioning efficiently and in times
of minimal stress and in the absence of threats, helps it to maintain
the internal body environment in a steady, balanced, state of normal
functioning (homeostasis).
2. It also restores the body to a state of calm, once the need for activity
of the SNS has passed.
The PNS dominates the SNS most of the time as it is involved in basic
everyday functioning.
Description
Function
Somatic
Network of sensory nerves that carry info
to the CNS received by sensory and motor
nerves that carry info from the CNS to
control voluntary movements of the
skeletal muscles.
Initiates all skeletal muscle activity
enabling you to perform voluntary actions
such as scratching your head, talking,
riding a bike, dancing, chewing and
wriggling your toes.
Autonomic
The Autonomic Nervous System is a
network of nerves that connects the CNS
to the body’s internal organs and glands
providing feedback to the brain about
their activities.
Heartbeat, digestion, perspiration.
Regardless of our level of awareness or
alertness, the ANS keeps the vital organs
and systems of our body functioning thus
Sympathetic
Enhances survival by providing an
immediate response, in a split second, to
any kind of emergency. When an
emergency is perceived, neurons in the
SNS activate target organs and glands to
respond in the required way
heart rate and blood pressure increase,
breathing rate increases so more oxygen
can be taken in, sugar and fat are
released from storage to provide instant
energy to the skeletal muscles, the pupils
dilate to allow more light to enter the eye
and enhance vision, and sweat glands
increase their production of sweat which
cools the body.
Parasympathetic
The PNS generally has the effect of
counterbalancing the activities of the SNS.
It dominates the SNS most of the time as
it is involved in basic everyday
functioning.
It keeps the systems of the body
functioning efficiently and in times of
minimal stress and in the absence of
threats, helps it to maintain the internal
body environment in a steady, balanced,
state of normal functioning (homeostasis).
It also restores the body to a state of
calm, once the need for activity of the
SNS has passed.
maintaining our survival.
•OLD COURSE
Research on hemispheric
specialisation:
• There are 3 main approaches to conducting
research on hemispheric specialisation:
1. Studying individuals with brain damage
2. Studying people who have had a split brain
operation.
3.Studying people with intact, and damaged
brains.
1. Studying people with brain
damage
• People who have suffered brain damage include those
who have suffered a stroke, have suffered head injuries
through a car or sporting accident, or for a medical
reason, have had to have part of their brain surgically
removed.
• This research has been crucial in localising the functions
of each hemisphere. For example, Broca's and
Wernicke’s pioneering studies on damage to the specific
parts of the left hemisphere that are involved in speech
production and speech comprehension. Their research
clearly showed that language and language- dependent
verbal tasks are a specialised function of the left
hemisphere.
• Similarly, the role of the right hemisphere in spatial
tasks is evident in people with Neglect Syndrome, a
disorder caused by damage to the right
hemisphere. Sufferers behave as if the left side of
their world does not exist. For example, they may
eat all the food on the right side of their plate.
Case Studies:
• Sometimes one of the best methods of brain
research is to conduct a case study.
Case study: A detailed account of a single
individual
• Eg. Phineas Gage, Albert Einstein
• Advantages: Rich source of information and
detail
• Disadvantages: Time consuming, problems with
generalising as cases are extraordinary.
• Phineas Gage is probably the most
famous patient to have survived severe
damage to the brain. He is also the first
patient from whom we learned something
about the relationship between personality
and the function of the front parts of the
brain.
• The tamping iron was 3 feet 7 inches long and
weighed 13 1/2 pounds. It was 1 1/4 inches in
diameter at one end and tapered over a
distance of about 1-foot to a diameter of 1/4
inch at the other. The tamping iron went in
point first under his left cheek bone and
completely out through the top of his head,
landing about 25 to 30 yards behind
him. Phineas was knocked over but may not
have lost consciousness even though most of
the front part of the left side of his brain was
destroyed. Dr. John Martyn Harlow, the young
physician of Cavendish, treated him with such
success that he returned home to Lebanon,
New Hampshire 10 weeks later.
• Some months after the accident, probably in
about the middle of 1849, Phineas felt strong
enough to resume work. But because his
personality had changed so much, the
contractors who had employed him would not
give him his place again. Before the accident
he had been their most capable and efficient
foreman, one with a well-balanced mind, and
who was looked on as a shrewd smart business
man. He was now fitful, irreverent, and grossly
profane, showing little deference for his
fellows. He was also impatient and stubborn,
yet impulsive and indecisive, unable to settle on
any of the plans he devised for future
action. His friends said he was "No longer
Gage."
2. Studying people who have had a
split brain operation.
• A split brain operation involves surgically cutting the corpus
callosum, the main bundle of nerves/tissue that connects the two
hemispheres.
• This procedure was first used in the 1940’s to minimise or stop
recurring seizures in severe cases of epilepsy that could not be
treated by any other means. By severing the corpus callosum, the
seizures were unable to pass over the hemispheres.
• Important information gained from
split-brain research is how the left and
right hemisphere function when they
cannot exchange information, and
therefore cannot communicate
together. For example, Sperry (1974)
found that a split brain patient can
recognise a picture of an object but not
name it.
3.Studying people with intact and
damaged brains.
• This refers to the study of people who have not
undergone brain surgery and do not have a brain
injury or disease.
• New technology allows the study of brain functions
ie:
- Electrical stimulation of the brain (ESB)
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Electroencephalograph (EEG)
Computerised Axial Tomography (CAT)
Positron emission tomography (PET)
Magnetic Resonance Imaging (MRI)
Functional Magnetic Resonance Imaging (fMRI)
The Wada test
Electrical Stimulation of the
Brain (ESB)
• ESB involves precisely regulated
electric current to stimulate a specific
area of the brain leading to either
activation or inhibition of stimulated
area.
• Wilder Penfield mapped the brain
using numbered tags, and by eliciting
either a physical, emotional or
experiential response.
Electrical Stimulation of the
Brain (ESB)
• Advantages:
-Identifying function and location.
-hemispheric specialisation.
-Disadvantages:
-Only useful for people undergoing brain surgery.
-Invasive risks.
-Generalisation difficult.
The Wada test:
• The Wada test is used
on patients with intact
brains before surgery
to find out in which
hemisphere the
language centres are
located.
The WADA test:
• Sodium amytal (a fast acting barbiturate) is
injected into either the left or right carotid artery
(an artery in your neck)
• These arteries send blood primarily to the
cerebral hemisphere on the same side as the
injected artery
ie. Injecting the left artery results in
anaesthetising the left hemisphere (and so the
right side of the body)
The WADA test:
What happens?
• Patients are asked to put both arms in the air and count
backwards from 100.
• The arm on the opposite side of the injection will fall limp
(indicating that the anaesthesia has taken effect)
• If patients continue to count backwards the language
centre must be on the other side from the injected artery.
• If the patient stops counting, the language centre must
have been anaesthetised and is on the same side as the
injection.
Electroencephalograph: (EEG)
• EEG is a device that detects, amplifies and records
general patterns of electrical activity of the brain.
• Described in rhythms or patterns as alpha, beta, delta,
theta.
• Used to diagnose brain-related medical conditions
Electroencephalograph: (EEG)
• Advantages:
-Non invasive
-Less expensive than PET and MRI, can be used widely
and over long periods
• Disadvantages:
-Doesn’t provide detail on specific brain structures.
Computerised (axial)
Tomography (CAT)
• A CT is a neuroimaging technique that produces a
computer enhanced image of a cross section (slice)
of the brain from X-rays taken at different angles.
• Needs a radiologist.
• Contrast/iodine injected into the bloodstream to
highlight brain’s blood vessels with no ill effect.
Computerised (axial)
Tomography (CAT)
• Advantages:
-Non invasive
-precisely locates brain damage.
• Disadvantages
-Only structural, not functional information.
Positron Emission Tomography
(PET)
• PET produces a computer-generated image that
provides information about brain function and activity
during various tasks.
• Tracks blood flow and detects increased neural activity
as a result of glucose consumption.
• Harmless radioactive substance injected.
• Colour coding- red is most active
Positron Emission Tomography
(PET)
• Advantages:
-Detailed images of brain functioning.
-Use on people without brain damage
-More sensitive than CAT/MRI
-Colour coding easy to analyse.
• Disadvantages:
-Injection
-Session must be kept short
-Can’t eliminate other causes of brain activity at time of the
scan
Magnetic Resonance Imaging
(MRI)
• MRI is a neuroimaging technique that uses
harmless magnetic fields and radio waves to vibrate
atoms in the brain’s neurons to produce an image
of the brain.
• Coloured image assembled by computer indicates
high and low level activity.
Magnetic Resonance Imaging
(MRI)
• Advantages:
-Identifies structural abnormalities.
-Detects very small changes.
-Can detect prosopagnosia (identifying faces but not
objects) and akinetopsia (lack of motion perception)
-No x-rays or radioactive substances.
Disadvantages:
-No metallic devices can be present.
-Still does not assess brain function.
Functional Magnetic Resonance
Imaging (fMRI)
• fMRI is a neuroimaging technique that enables
the identification of brain areas that are
particularly active during a given task by
detecting changes in oxygen levels in the blood
flowing through the brain.
• Colour variation reflects degree of activity.
• Can take numerous images in succession
leading to more detailed, precise images.
• 3D displays.
Functional Magnetic Resonance
Imaging (fMRI)
• Advantages:
-No radiation.
-More detail than PET.
-Colour coding
• Disadvantages:
-Still cannot eliminate other influences on
brain activity of brain at a given point.