Biopsychology Flashcards
(137 cards)
1
Q
The parts of the nervous system
A
- Central nervous system (CNS)
- Peripheral nervous system (PNS)
2
Q
The Central nervous system (CNS)
A
-consists of the brain and spinal cord.
3
Q
Function of the Central nervous system
A
-It has two main functions:
the control of behaviour
the regulation of the body’s physiological processes.
- In order to do this the brain must be able to receive information from the sensory receptors (eyes, ears, skin etc.) and be able to send messages to the muscles and glands of the body in response.
4
Q
Areas of the brain
A
- Cerebrum
- Cerebellum
- Diencephalon
- Brainstem
5
Q
Cerebrum
A
- This is the largest part of the brain.
- It has four lobes, and is spilt down the middle into two halves, called hemispheres.
- cerebrum controls voluntary movement, intelligence and memory.
6
Q
Cerebellum
A
Responsible for motor skills, balance and coordinating muscles to allow precise movement
7
Q
Diencephalon
A
Contains the thalamus (regulates consciousness, sleep and alertness) and the hypothalamus (regulates body temperature, stress response and hunger and thirst).
8
Q
Brain stem
A
Regulates breathing and heart rate
9
Q
The spinal cord
A
- The main function of the spinal cord is to relay information between the brain and the rest of the body.
- This allows the brain to monitor and regulate bodily processes, such as digestion and breathing, and co-ordinate voluntary movement.
- The spinal cord is connected to different parts of the body by pairs of spinal nerves, which connect to specific muscles and glands.
10
Q
What happens if the spinal cord is damaged?
A
Body areas connected to it by nerves below the damage will be cut off and stop functioning
11
Q
The peripheral nervous system (PNS)
A
- consists of the nervous system throughout the rest of the body (e.g. not the brain or spinal cord).
- The PNS transmits messages via neurons (nerve cells) to and from the CNS.
12
Q
Divisions of the PNS
A
- Somatic nervous system
- Autonomic nervous system
13
Q
The somatic nervous system
A
- controls voluntary movements and is under conscious control.
- It connects the senses with the CNS and has sensory AND motor pathways.
- It controls skeletal muscles.
- The somatic nervous system is controlled by the motor cortex.
14
Q
The autonomic nervous system
A
- is involuntary (i.e. not under conscious control).
- It ONLY has motor pathways and it controls smooth muscles and the internal organs and glands of the body.
- The ANS is controlled by the brain stem.
- Has two divisions
15
Q
Divisions of the Autonomic nervous system
A
- Sympathetic nervous system
- Parasympathetic nervous system
16
Q
Sympathetic nervous system
A
- This is activated when a person is stressed.
- Heart rate and breathing increase, digestion stops, salivation reduces, pupils dilate, and the flow of blood is diverted from the surface on the skin (fight or flight response).
17
Q
Parasympathetic nervous system
A
-This is activated when the body is relaxing and so conserving energy. -Heart rate and breathing reduce, digestion starts, salivation increases, and pupils constrict.
18
Q
Neurons
A
specialised nerve cells that move electrical impulses to and from the Central Nervous System (CNS).
19
Q
Parts of a neuron
A
- Cell body
- Nucleus
- Dendrites
- Axon
- Myelin Sheath
- Schwann cells
- Nodes of Ranvier
20
Q
Cell body as a part of a neuron
A
Is the control centre of the neuron
21
Q
Nucleus as a part of a neuron
A
Contains genetic material
22
Q
Dendrites as a part of a neuron
A
Receives an electrical impulse (action potential) from other neurons or sensory receptors
23
Q
Axon as a part of a neuron
A
A long fibre that carries the electrical impulse from the cell body to the axon terminal.
24
Q
Myelin Sheath as a part of a neuron
A
Insulating layer that protects the axon and speeds up the transmission of the electrical impulse
25
Schwann cells as a part of a neuron
Make up the myelin sheath
26
Nodes of Ranvier as part of a neuron
Gaps in the myelin sheath.
| They speed up the electrical impulse along the axon.
27
Three types of neuron
- Consist of similar parts but their structure, location and function are different.
- Sensory neuron
- Motor neuron
- Relay neuron
28
Where are Sensory neurons found?
Found in sensory receptors
| E.g. eyes, ears, tongue and skin
29
Sensory neuron function
- They carry electrical impulses from the sensory receptors to the CNS (spinal cord and brain) via the Peripheral Nervous System (PNS).
- Sensory neurons convert information from sensory receptors into electrical impulses.
- When these impulses reach the brain they are converted into sensations, such as heat, pain etc. so that the body can react appropriately.
- Some sensory impulses terminate at the spinal cord.
- This allows reflexes to occur quickly without the delay of sending the impulses to the brain.
30
Where are motor neurons found?
Located in the CNS but project their axons outside the CNS.
31
Motor neuron function
- They send electrical impulses via long axons to the glands and muscles so they can affect function.
- Glands and muscles are called effectors.
- When motor neurons are stimulated they release neurotransmitters that bind to the receptors on muscles to trigger a response, which leads to movement.
32
Where are relay neurons located?
Found in the CNS
33
Function of the relay neuron
- They connect sensory neurons to motor neurons so that they can communicate with one another.
- During a reflex arc (e.g. you put your hand on a hot hob) the relay neurons in the spinal cord are involved in an analysis of the sensation and decide how to respond (e.g. to lift your hand) without waiting for the brain to process the pain.
34
Synaptic transmission
- Process by which one neuron communicates with another.
- Neurons transmit electrical impulses, known as action potentials, between the pre-synaptic neuron and the post-synaptic neuron
35
What is the pre-synaptic and post-synaptic neuron?
- Pre-synaptic neuron is the neuron transferring the action potential
- Post-synoptic neuron is the neuron receiving the action potential.
36
Process of synaptic transmission
- When the action potential reaches the pre-synaptic terminal it triggers the release of neurotransmitters from sacs on the pre- synaptic membrane known as vesicles in a process called exocytosis.
- The released neurotransmitter diffuses across the synaptic cleft where it binds to specialised post-synaptic receptor sites.
37
Neurotransmitters
Chemical messengers
38
Synaptic cleft
physical gap between the pre-synaptic membrane and post-synaptic membrane
39
How long does synaptic transmission take?
Fraction of a second
40
How are the effects of synaptic transmission terminated?
- Terminated by a process called re-uptake .
- The neurotransmitter is taken back by the vesicles on the pre-synaptic neuron where they are stored for later release.
- The quicker the neurotransmitter is taken back the shorter the effects.
41
Why can information only travel in one direction in the synapse?
- The vesicles containing neurotransmitters are ONLY present on the pre-synaptic membrane.
- The receptors for the neurotransmitters are ONLY present on the post- synaptic membrane.
- It is the binding of the neurotransmitter to the receptor which enables the information to be transmitted to the next neuron.
- Diffusion of the neurotransmitters mean they can only go from high to low concentration, so can only travel from the pre-synaptic to the post-synaptic membrane.
42
Psychoactive drugs in synaptic transmission
- (medication that affects brain function to alter perception, mood or behaviour), -such as SSRIs
- work by affecting (increasing or inhibiting) the transmission of neurotransmitters across the synapse
43
Excitatory and Inhibitory neurotransmitters
Neurotransmitters can be excitatory or inhibitory (most can be both but GABA is purely inhibitory).
44
Excitatory neurotransmitters
-cause an electrical charge in the membrane of the post-synaptic neuron resulting in an excitatory post-synaptic potential (EPSP), meaning that the post-synaptic cell is more likely to fire an impulse
45
Inhibitory neurotransmitters
cause an inhibitory post-synaptic potential (IPSP), making it less likely that the neuron will fire an impulse.
46
If a neuron receives both ESPs and ISPs at the same time, how can you determine whether an impulse will fire?
- A neuron can receive both EPSPs and IPSPs at the same time.
- The likelihood that the cell will fire an impulse is determined by adding up the excitatory and the inhibitory synaptic input.
- The net result of this calculation, known as summation, determines whether or not the cell will fire an impulse.
- If the net effect is inhibitory the neuron will not fire, and if the net effect is excitatory, the neuron will fire.
47
Endocrine system
provides a chemical system of communication in the body via the blood stream.
48
Endocrine glands
produce and secrete hormones into the bloodstream which are required to regulate many bodily functions.
49
Major glands of the endocrine system
- Pituitary glands
| - Adrenal glands
50
Target cells
- The cells that are affected by hormones
- Target cells respond to a particular hormone because they have receptors for that hormone.
- When enough receptor sites are stimulated by that hormone there is a physiological reaction.
51
Where is the pituitary gland located?
Brain
52
Function of pituitary gland
produces hormones whose primary function is to influence the release of other hormones from other glands in the body.
53
What is the pituitary gland controlled by?
- Hypothalamus
| - Above the pituitary gland
54
How does the pituitary gland function?
- The hypothalamus receives information from many sources about the basic functions of the body.
- The hypothalamus then sends a signal to the pituitary gland in the form of a releasing hormone.
- This causes the pituitary gland to send a stimulating hormone into the bloodstream to tell the target gland to release its hormone.
- As levels of this hormone rise in the bloodstream the hypothalamus shuts down production of the releasing hormone and the pituitary gland shuts down secretion of the stimulating hormone.
55
Two divisions of pituitary gland
- Anterior pituitary gland
| - Posterior pituitary gland
56
Function of anterior pituitary gland
Releases hormone called ACTH which regulates levels of the hormone cortisol.
57
Function of posterior pituitary gland
Responsible for releasing the hormone oxytocin which is crucial for infant/mother bonding
58
Where are the adrenal glands located?
They are situated on top of the kidneys
59
What two parts is each adrenal gland made up of?
- Adrenal Cortex
| - Adrenal Medulla
60
Where is the adrenal cortex in the adrenal gland?
Outer section of the adrenal gland
61
Adrenal Cortex function
- It produces the hormone cortisol which is produced in high amounts when someone is experiencing chronic (long-term) stress.
- Cortisol is also responsible for the cardiovascular system, for instance it will increase blood pressure and causes blood vessels to constrict.
62
Where is the adrenal medulla located in the adrenal glands?
The inner section of the adrenal gland.
63
Function of adrenal medulla
- Produces adrenaline , the hormone needed for the fight or flight response
- Response is activated when someone is acutely stressed.
- Adrenaline increases heart rate, dilate pupils and stops digestion
64
The sympathomedullary Pathway
- The Sympathetic Nervous System (SNS) is triggered by the hypothalamus.
- The hypothalamus also sends a signal to the adrenal medulla (part of the adrenal glands), which responds by releasing the hormone adrenaline into the bloodstream.
65
What does adrenaline do?
- Adrenaline will increase heart rate, constrict blood vessels, increase rate of blood flow, raise blood pressure, divert blood away from the skin, kidneys and digestive system, increase blood supply to the brain and skeletal muscles, and increase respiration and sweating.
- All of this prepares the body for action and fight or flight by increasing blood supply, and therefore oxygen, to skeletal muscles for physical action and increasing oxygen to the brain for rapid response planning.
66
The parasympathetic nervous system
- When the threat has passed the parasympathetic nervous system dampens down the stress response.
- It slows down the heartbeat and reduces blood pressure.
- Digestion, which is stopped when the SNS is active, restarts.
67
What happens during the fight or flight response?
- Sympathtic nervous system is triggered
- Adrenal Medulla releases adrenaline into blood stream
- Adrenaline prepares body for action and fight or flight.
- Parasympathetic nervous system is triggered when threat is passed and slows down heart bear and blood pressure.
68
Strengths of the fight or flight response
- The fight or flight response makes sense from an evolutionary psychology point of view because it would have helped an individual to survive by fighting or fleeing a threat.
- Studies supports the claim that adrenaline is essential in preparing the body for stress. People who have malfunctioning adrenal glands do not have a normal fight or flight response to stress.
69
Weaknesses of the fight or flight response
- Gray (1988) states that the first reaction to stress is not to fight or flight but freeze. This involves the person stopping, looking and listening and being hyper vigilant to danger.
- Taylor (2000) found that females tend and befriend in times of stress. Tend and befriend refers to the protection of offspring (tend) and seeking out social groups for mutual defence (befriend). Women have the hormone oxytocin, which means they are more likely to stay and protect their offspring.
- Von Dawans (2012) has found that even males tend and befriend. For example, during the 2001 September 11th terrorist attacks both males and females showed tend and befriend as they tried to contact loved ones and help one another.
70
Localisation of function
Localisation of function refers to the principle that functions (language, memory, hearing etc.) have specific locations within the brain.
71
Centres and Areas in the brain
- Visual Centres
- Auditory Centres
- Motor Cortex
- Somatasensory Cortex
- Broca’s Area
- Wernicke’s Area
72
Where is the Visual Centres?
-The visual cortex is in the occipital lobe of BOTH hemispheres of the brain.
73
Function on the visual centres
- Visual processing starts in the retina where light enters and strikes the photoreceptors.
- Nerve impulses from the retina are transmitted to the brain via the optic nerve.
- The majority terminate in the thalamus, which acts as a relay station, passing the information onto the visual cortex.
74
Where is the Auditory Centres?
The auditory cortex lies within the temporal lobe in BOTH hemispheres of the brain.
75
Function of the auditory Centres
- The auditory pathway begins in the cochlea in the inner ear, where sound waves are converted to nerve impulses, which travel via the auditory nerve to the auditory cortex.
- Basic decoding occurs in the brain stem, the thalamus carries out further processing before impulses reach the auditory cortex.
76
Location of the motor cortex
Located in the frontal lobe of both brain hemispheres.
77
Function of the motor cortex
-The motor cortex is responsible for the generation of
voluntary motor movements.
-Different parts of the motor cortex control different parts of
the body.
-These areas are arranged logically next to one another.
-Damage to
this area can cause a loss of muscle function/paralysis in one or both sides of
the body (depending on which hemisphere/hemispheres have been affected).
78
Location of the Somatosensory cortex
It is located in the parietal lobe of BOTH
| hemispheres.
79
Function of the Somatosensory cortex
– This area detects sensory events arising from different regions of the body.
- Using sensory information from the skin, the somatosensory
cortex produces sensations of touch, pressure, pain and temperature, which it
then localises to specific parts of the body
80
Location of the Broca's Area
On the left hemisphere of the frontal lobe
81
Function of the Broca's area
This area is named after -Paul Broca who treated patients who
had difficulty producing speech.
-He found that they had lesions to the LEFT
hemisphere of the frontal lobe.
-Expressive Aphasia is language/speech
problems (caused by damage to the Broca’s area).
- It affects language
production but NOT understanding. Speech lacks fluency and patients have
difficulty with certain words which help sentences function (e.g. ‘it’ and ‘the’).
82
Location of the Wernicke's area
This area is in the LEFT hemisphere of the temporal lobe
83
Function of the Wernicke's area
-Carl Wernicke found that patients with a lesion to this area could speak but
were unable to understand language.
-Wernicke concluded that this area is
responsible for the processing of spoken language.
-The Wernicke area is
connected to the Broca’s area by a neural loop.
-Receptive Aphasia is an impaired
ability to understand language (this is usually a result of damage to the
Wernicke’s area).
84
Evaluation of Localisation of function
- Some functions are more localised than others. Motor and somatosensory
functions are highly localised to specific areas of the cortex. Other functions
(e.g. personality) are more widely distributed.
- Equipoteniality theory (Lashley, 1930) holds that higher mental functions are
not localised and that intact areas of the cortex take over responsibility for a
specific cognitive function following injury to the area normally responsible.
- Dronkers et al. (2007) re-examined the preserved brains of two of Broca’s
patients. MRI scans revealed that several areas of the brain had been damaged.
Lesions to the Broca’s area cause temporary speech disruption they do not
usually result in severe disruption of language. Language is a more widely
distributed skill than originally thought.
- Bavelier et al. (1997) found that there are individual differences in which
brain areas are activated when a person is engaged in silent reading. They
observed activity in the right temporal lobe, left frontal lobe and occipital lobe.
- It may be that how brain areas communicate with each other is more
important than specific brain regions. Dejerine (1892) reported a patient who
could not read because of damage between the visual cortex and Wernicke’s
area.
85
Lateralisation of function
-Lateralisation of function is the idea that the two hemispheres of the brain
have different specialisations.
-The right hemisphere of the brain is responsible
for the left hand side of the body, and the left hemisphere is responsible for
the right hand side of the body
86
What are the left and right hemispheres dominant for?
-Studies have found that the left hemisphere is dominant for language (Broca and Wernicke Areas) whereas the right hemisphere is dominant for recognising
faces.
-The two hemispheres are connected by a bundle of nerve fibres known as
the corpus callosum.
87
Evaluation of Lateralisation of function
+ An advantage of brain lateralisation is that it increases neural processing
capacity, which is adaptive. By using one hemisphere to engage in a particular
task it leaves the other hemisphere free to engage in another function. Rogers
et al. (2004) found that lateralisation in chickens is associated with an ability to
perform two tasks simultaneously (finding food and being vigilant for
predators).
- JW developed the capacity to speak using his right hemisphere, with the
result that they could speak about information presented to the left or right
hemisphere. It would appear that there are individual differences in how the
brain functions.
88
What is split-brain research?
In the past surgeons have cut the corpus callosum in order to prevent the
violent electrical activity caused by epileptic seizures crossing from one hemisphere to the other.
89
How did Sperry and Gazzaniga (1968) investigate split brain patients?
- Patients are asked to stare at a dot in the centre of a screen and then
information is presented in either the left or right visual field.
-They are then
asked to make responses with either their left hand (right hemisphere), right
hand (left hemisphere) or verbally (left hemisphere) without being able to see
what their hands were doing.
-They may be flashed an image of a dog in their right visual field and then asked
what they have seen.
-They will be able to answer ‘dog’ because the information
will have gone into their left hemisphere where the language centres are.
-If a
picture of a cat is shown in their left visual field and they are asked what they
have seen they will not be able to say because the information has gone into
their right hemisphere, which has no language centres.
-However, they can draw
a picture of a cat with their left hand because the right hemisphere controls
this hand.
90
Evaluation of split-brain research
- The disconnection between the hemispheres is greater in some patients than
in others, and some patients have drug therapy for their epilepsy for much
longer than others, which may affect the way in which their brain works. This
means the findings of split-brain research cannot be generalised to the target
population.
- Many studies using split-brain patients have as few as three participants,
making it hard for results to be generalised.
- In the real world a severed corpus callosum can be compensated for by the
unrestricted use of both visual fields. This means the research lacks ecological
validity.
91
What is brain plasticity?
-Brain plasticity refers to the brain’s ability to change and adapt as a result of experience.
-Plasticity allows the brain to cope better with the indirect effects
of brain damage, such as swelling or haemorrhage following a road accident, or
the damage resulting from inadequate blood supply following a stroke.
92
Plasticity and life experiences
-Nerve pathways that are used frequently develop stronger
connections, those that are rarely used eventually die.
-By developing new
connections and reducing weak ones the brain is able to adapt to a changing
environment.
-However, there is also a decline in cognitive functioning with age
attributed to these changes.
-Boyke et al. (2008) taught 60 year olds a new skill (juggling), this increased grey matter in the visual cortex.
93
Plasticity and Video games
-Kuhn et al. (2014) compared a control group to a group who had been given video game training for at least 30 minutes a day for two months on the game ‘Super Mario’.
-They found that playing video games caused a
significant increase in grey matter in the visual cortex, hippocampus, and cerebellum.
-Playing video games results in new synaptic connections in brain
areas involved in spatial navigation, strategic planning, working memory and
motor performance.
94
Plasticity and Meditation
-Davidson et al. (2004) compared eight practitioners of Tibetan
meditation with ten students who had no previous meditation experience.
-An EEG picked up greater gamma wave activity in the monks, even before they
started meditating.
-Gamma waves coordinate neural activity.
95
Evaluation on Plasticity
+ Kempermann et al. (1998) found far more new neurons in the brains of rats in
complex environments compared to those housed in laboratory cages. This
increase in neurons was most prominent in the hippocampus, which is involved in
the forming of new long-term memories and the ability to navigate.
+ Maguire et al. (2000) measured grey matter in the brains of London taxi
drivers using an MRI scan. The hippocampus in taxi drivers was significantly
larger than a control group and this was positively correlated with the amount
of time they had spent as a taxi driver (the extent of their life experience).
96
What is functional recovery?
Functional recovery is a form of plasticity. Following damage caused by trauma,
the brain can redistribute or transfer functions usually performed by damaged
areas to other, undamaged, areas.
97
Neural reorganisation
Transfer of functions from damaged areas of the brain to undamaged ones
98
Neural regeneration
Growth of new neurons and/or
| connections (axons and dendrites) to compensate for damaged areas
99
Axon sprouting
Axon sprouting is part of neural regeneration, new nerve endings grow and connect with other undamaged nerve
cells to form new neural pathways.
100
How to improve recovery?
-Spontaneous recovery from a brain injury tends to slow down after a number of
weeks so physiotherapy may be required to maintain improvements in functioning.
-Techniques can include movement therapy and electrical stimulation
of the brain to counter deficits in motor and cognitive functioning that can be experienced following a stroke.
101
Evaluation of functional recovery
+ Phantom Limb Syndrome (PLS) can be used as evidence of neural
reorganisation. PLS is the continued experience of sensation in a missing limb, as if it were still there. These sensations are often unpleasant and even painful. PLS is thought to be caused by neural reorganisation in the somatosensory
cortex that occurs as a result of limb loss (Ramachandran and Hirstein, 1998).
+ Hubel and Torten Wisel (1963) sewed one eye of a kitten shut and analysed
the brain’s cortical response. They found that the visual cortex for the shut eye
was not idle (as was predicted) it continued to process information from the
open eye. This is further evidence that brain areas can reorganise themselves
and adapt their functions.
- Schneider et al. (2014) found that patients with a college education are seven
times more likely to be disability free a year after a moderate to severe brain injury than those who did not finish secondary school. They concluded that neural reserve could be a factor in recovery from brain injury.
102
Ways to study the brain
- Post-Mortem examinations
- Functional Magnetic Resonance Imaging
- Electroencephalogram
- Event-Related Potentials
103
Post mortem examinations
- When the person dies, the psychologists look for abnormalities in
the brain that might explain their behaviour.
-Post-mortem studies have found a
link between brain abnormalities and psychiatric disorders, for instance, there
is evidence of reduced glial cells in the frontal lobe of patients with
depression.
104
Evaluation of post mortem examinations
+ Post-mortem studies allow for more detailed examination of anatomical and
neurochemical aspects of the brain than would be possible with other methods
of studying the brain. They have enabled researchers to examine deeper
regions, such as the hippocampus and hypothalamus.
- Studies using post-mortems may lack validity due to small sample size (as
special permission needs to be granted) and because people die in a variety of
circumstances and at varying stages of disease. Similarly, the length of time
between death and the post-mortem, and drug treatments, can all affect the
brain.
105
Functional Magnetic Resonance Imaging
-Functional Magnetic Resonance Imaging (fMRI) uses magnetic fields and radio
waves to monitor blood flow in the brain.
- It measures the change in the energy released by haemoglobin, reflecting activity of the brain (oxygen consumption)
to give a moving picture of the brain; activity in regions of interest can be compared during a base line task and during a specific activity.
106
Functional Magnetic Resonance Imaging Evaluation
+ fMRI captures dynamic brain activity as opposed to an MRI/post-mortem
examination which purely show the physiology of the brain.
- Interpretation of fMRI is complex and is affected by temporal resolution
(resolution of a measurement with respect to time), biased interpretation, and
by the base line task used. fMRI research is expensive leading to reduced
sample sizes which negatively impact the validity of the research
107
Electroencephalogram
-An electroencephalogram (EEG) measures GENERAL electrical activity in the
brain, usually linked to states such as sleep and arousal.
-Electrodes are placed on the scalp and detect neuronal activity directly below where they are placed; differing numbers of electrodes can be used depending on focus of the
research.
-When electrical signals from the different electrodes are graphed
over a period of time, the resulting representation is called an EEG pattern. EEG
patterns of patients with epilepsy show spikes of electrical activity.
-EEG patterns of those with brain injury show a slowing of electrical activity.
108
Electroencephalogram Evaluation
+ An EEG is useful in clinical diagnosis, for instance it can record the neural
activity associated with epilepsy so that doctors can confirm the person is
experiencing seizures. They are cheaper than an fMRI so can be used more
widely in research.
- EEGs have poor spatial resolution (refers to the smallest feature that a
measurement can detect).
109
Event-related Potentials
-Electrodes are placed on the scalp and detect neuronal activity (directly below where they are placed) in response to a SPECIFIC stimulus introduced by the
researcher.
-Event-related potentials are difficult to pick out from all the
other electrical activity being generated within the brain.
-To establish a
specific response to a target stimulus requires many presentations of this stimulus and the responses are then averaged together.
-Any extraneous neural
activity that is not related to the specific stimulus will not occur consistently,
whereas activity linked to the stimulus will.
110
Sensory ERPs
ERP waves generated in the first 100 milliseconds after a stimulus is presented.
They reflect physical characteristics of stimulus.
111
cognitive ERPs
ERPs
generated after the first 100 milliseconds reflect the manner in which the
subject evaluates the stimulus
Demonstrate information processing
112
Evaluation of Event-Related Potentials
+ ERP can measure the processing of a stimulus even in the absence of a
behavioural response. Therefore it is possible to measure ‘covertly’ the
processing of a stimulus.
- Only sufficiently strong voltage changes generated across the scalp are
recordable. Important electrical activity occurring deeper in the brain is not
recorded. The generation of ERPs tends to be restricted to the neocortex.
113
Biological Rhythms
-Biological rhythms are cyclical changes in physiological systems.
-They evolved
because the environments in which organisms live have cyclical changes e.g.
day/night, summer/winter etc.
114
Types of biological rhythyms
circadian, ultradian and infradian.
115
Circadian Rhythms
-Circadian rhythms are any cycle that lasts 24 hours.
-Nearly all organisms
possess a biological representation of the 24 hour day.
-These optimise an
organism’s physiology and behaviour to best meet the varying demands of the
day/night cycle.
116
How do Circadian rhythms work?
-Circadian rhythms are driven by the suprachiasmatic nuclei (SCN) in the
hypothalamus.
-This pacemaker (controls the rate at which something occurs)
must constantly be reset so that our bodies are in synchrony with the outside
world.
-Natural light provides the input to this system, setting the SCN to the
correct time in a process called photoentrainment.
-The SCN then uses this
information to coordinate activity of circadian rhythms throughout the body
117
The Sleep wake cycle
-Light and darkness are the external signals that determine when we feel the
need to sleep and when we wake up.
-Circadian rhythms keep us awake as long as there is daylight, prompting us to
sleep as it becomes dark. - The internal
circadian rhythm will maintain a cycle of 24-25 hours, even without natural
light.
118
When does the strongest sleep occur in the sleep-wake cycle?
This rhythm dips and rises at different
times of the day so that the strongest sleep drives occur between 2:00-
4:00am and 1:00-3:00pm.
119
Melatonin in the sleep wake cycle
-The release of melatonin from the pineal gland is at its peak during the hours
of darkness.
-Melatonin induces sleep by inhibiting the neural mechanisms that
promote wakefulness.
-Light supresses the production of melatonin.
120
Homeostatic control of the sleep wake cycle
-Sleep and wakefulness are also under homeostatic control.
-When we have been
awake for a long time homeostasis tells us that the need for sleep is increasing
because of the amount of energy used up during wakefulness.
-This homeostatic
drive for sleep increases gradually throughout the day, reaching its maximum in
the late evening
121
Evaluation of circadian rhythms
+ One practical application of circadian rhythms is chronotherapeutics. The
time that patients take medication is very important for treatment success. It
is essential that the right concentration of drug is released in the target area
of the body at the time the drug is most needed. For example, the risk of heart
attack is greatest during the early morning hours after waking. Medications
have been developed that are taken before the person goes to sleep but are not
released until the vulnerable time of 6:00 am.
- Research on circadian rhythms has not isolated people from artificial light,
because it was believed only natural light affected circadian rhythms. However,
more recent research suggests this might not be true. Cziesler et al. (1999)
altered participant’s circadian rhythms down to 22 hours and up to 28 hours by
using artificial light alone.
- There are individual differences in the length of circadian rhythms. One
research study found that cycles can vary from 13 to 165 hours (Czeisler et al,
1999).
- Another individual difference in circadian rhythms is when they reach their
peak. ‘Morning people’ prefer to rise early and go to bed early whereas ‘evening
people’ prefer to rise late.
- Studies of individuals who live in Artic regions, where the sun does not set in
the summer months, show normal sleeping patterns despite the prolonged
exposure to light. This suggests that there are occasions where the exogenous
zeitgeber of light may have very little bearing on our internal biological
rhythms.
122
Ultradian Rhythms
-Ultradian rhythms span a period of less than 24 hours.
-An example is the five
sleep stages.
-Human sleep follows a pattern alternating between Rapid Eye
Movement (REM) sleep (which is stage five) and Non-Rapid Eye Movement
(NREM) sleep (which consists of stages one, two, three and four).
-The cycle
repeats itself every 90 minutes.
123
EEG in ultradian rhythms
Each stage shows a distinct EEG pattern. As the person enters deep sleep, their
brainwaves slow and their breathing and heart rate decreases.
-During the fifth
stage (REM sleep), the EEG pattern resembles that of an awake person.
-It is
during this stage that dreaming occurs.
124
Kleitman (1969) findings on ultradian rhythms
-Kleitman (1969) referred to the 90 minute cycle found during sleep as the Basic
Rest Activity Cycle (BRAC).
-He suggested that this 90 minute cycle continues
when we are awake.
-During the day, rather than moving through the sleep
stages, we move progressively from a state of alertness into a state of
physiological fatigue.
-Studies suggest that the human mind can focus for about
90 minutes, and towards the end of those 90 minutes the body begins to run out
of resources, resulting in loss of concentration, fatigue and hunger.
125
Evaluation of Ultradian Rhythms
+ Ericsson et al. (2006) found support for the ultradian rhythms. They studied
a group of elite violinists and found that among this group practise sessions
were limited to 90 minutes at a time. Violinists frequently napped to recover
from practise, with the best violinists napping more. The same pattern was
found among athletics, chess players and writers. This fits with the BRAC.
- Tucker et al. (2007) suggests that there are individual differences in
ultradian rhythms which are biologically determined and may even be genetic in
origin. Participants were studied over 11 consecutive days and nights in a
laboratory environment. The researchers assessed sleep duration, time taken to
fall asleep and the amount of time in each sleep stage. They found differences
in all of these characteristics.
126
Infradian Rhythms
Infradian rhythms span aperiod of longer than 24 hours; they may last weeks,
months or even a year.
127
Menstrual cycle as an infradian rhythm
-One example of an infradian rhythm is the menstrual
cycle, which lasts for about a month.
-There are considerable variations in the
length of this cycle, with some women experiencing a 23 day cycle and others a
36 day cycle (Refinetti, 2006).
-The average is 28 days.
-Hormones regulate the menstrual cycle.
-Ovulation occurs roughly halfway
through the menstrual cycle, when oestrogen levels are at their peak, and
usually lasts for 16-32 hours.
-After ovulation, progesterone levels increase in
preparation for the possible implantation of an embryo in the uterus.
128
Evaluation of Infradian Rhythms
+ Infradian rhythms can affect behaviour. Penton-Voak (1999) found that
women express a preference for feminised male faces when choosing a partner
for a long-term relationship. However, they showed a preference for
masculinised faces during ovulation.
- The menstrual cycle is not only governed by infradian rhythms. When several
women of childbearing age live together, and do not take oral contraceptives,
their menstrual cycles synchronise. In one study samples of sweat were
collected from one group of women and rubbed onto the upper lip of another
group of women, their menstrual cycles became synchronised. This suggests
that the synchronisation is affected by pheromones. Pheromones are a chemical
substance produced and released into the environment by an animal which
affects the behaviour of others of the same species
129
Endogenous Pacemakers and Exogenous Zeitgebers
-Our internal biological rhythms must be finely tuned in order to stay in keeping
with the outside world.
- In order to achieve this we have endogenous
pacemakers (internal biological rhythms) and exogenous zeitgebers (external
cues/factors e.g. light) which reset our biological rhythms every day.
130
Endogenous Pacemakers
-The most important endogenous pacemaker is the suprachiasmatic nuclei
(SCN).
-This is a tiny cluster of nerve cells in the hypothalamus.
-The SCN plays
an important role in generating circadian rhythms.
-It acts as the master clock,
linking other brain regions that control sleep and arousal, and controlling all
other biological clocks throughout the body.
131
How does the SCN work?
-Neurons within the SCN synchronise with each other, so that their target
neurons in sites elsewhere in the body receive time-coordinated signals.
-These
peripheral clocks can maintain a circadian rhythm, but not for very long, which
is why they are controlled by the SCN.
-This is possible because of the SCN’s
built in circadian rhythm, which only needs resetting when external light levels
change.
-The SCN receives information about light levels through the optic
nerve.
-If our biological clock is running slow then morning light shifts the clock.
132
How does the SCN regulate the secretion of melatonin?
-The SCN also regulates the manufacture and secretion of melatonin in the
pineal gland via the interconnecting neural pathway.
-The SCN sends a signal to
the pineal gland, directing it to increase production and secretion of the
hormone melatonin at night and to decrease it as light levels increase in the
morning.
-Melatonin induces sleep by inhibiting the brain mechanisms that
promote wakefulness.
133
Evaluation of Endogenous Pacemakers
+ Folkard (1996) studied a university student, Kate Aldcroft, who spent 25 days
in a laboratory. She had no access to the exogenous zeitgebers of light to
reset the SCN. However, at the end of 25 days her core temperature rhythm
was still at 24 hours. This indicates that we DO NOT need the exogenous
zeitgebers of light to maintain our internal biological rhythms.
- Kate Aldcroft’s sleep-wake cycle extended to 30 hours, with periods of sleep
as long as 16 hours. This suggests that we DO need the exogenous zeitgebers
of light to maintain our internal biological rhythms.
134
Exogenous Zeitgebers
-The term exogenous refers to anything whose origins are outside of the
organism.
-Exogenous zeitgebers are environmental events that are responsible
for maintaining the biological clock of an organism.
-The most important
zeitgebers for most animals is light.
135
Exogenous Zeitgebers and light
-Receptors in the SCN are sensitive to changes in light levels during the day and
use this information to synchronise the activity of the body’s organs and glands.
-Light resets the internal biological clock each day, keeping it on a 24-hour cycle.
-A protein in the retina of the eye called melanopsin, which is sensitive to
natural light, is critical in this system
136
What happens when the zeitgebers are disrupted?
-When people move to a night shift or travel to a country with a different time
zone their endogenous pacemakers try to impose their inbuilt rhythm of sleep
(circadian rhythm), but this is now out of synchrony with the exodengeous
zeitgeber of light.
-Out of sync biological rhythms lead to disrupted sleep
patterns, increased anxiety and decreased alertness and vigilance.
137
Evaluation of Exogenous Zeitgebers
+ The vast majority of blind people who still have light perception have normal
circadian rhythms. Blind people without light perception show abnormal
circadian rhythms. This shows the vital role that the exogenous zeitgeber of
light levels play in maintaining our internal biological rhythms.
+ Burgess et al. (2003) found that exposure to bright light prior to an east-west
flight decreased the time needed to adjust circadian rhythms to local time.
- Studies of individuals who live in Artic regions, where the sun does not set in
the summer months, show normal sleeping patterns despite the prolonged
exposure to light. This suggests that there are occasions where the exogenous
zeitgeber of light may have very little bearing on our internal biological
rhythms.
