Chapter 9: Mechanisms of Learning Unit 4 – AOS 1 Learning Pages 422-451 1.

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Chapter 9: Mechanisms of Learning

Unit 4 – AOS 1LearningPages 422-451

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Study Design Content• behaviours not dependent on learning including

reflex action, fixed action patterns and behaviours due to physical growth and development (maturation)

• mechanisms of learning:– areas of the brain and neural pathways involved

in learning, synapse formation, role of neurotransmitters

– developmental plasticity and adaptive plasticity of the brain: changes to the brain in response to learning and experience; timing of experiences

– use of imaging technologies in identification of localised changes in the brain due to learning specific tasks

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Defining LearningLearning is such an integral part of

daily living that without the ability to learn, people would be unable to live independently and would need constant care in order to survive.

Learning can be defined as a relatively permanent change in behaviour that occurs as a result of experience.

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Defining LearningIt is an ongoing process which continues

throughout the lifespan, enabling us to adapt and cope with an ever-changing world.

Learning can occur intentionally or unintentionally.

Learning can also occur actively or passively.

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Defining LearningThe notion of change is an important

part of the definition of learning because something must be different about the organism after learning has taken place.

The change in behaviour may be immediate (ie changing your golf swing after a coach suggests an improvement).

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Defining LearningThe change also may be delayed and

actually occur some time after learning has taken place (ie changing your golf swing the next time you play golf after watching an instructional video).

Consequently, learning refers to a change in behaviour potential as well as behaviour which is observed to take place.

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Defining LearningLearned

behaviour is also defined as being relatively permanent because it cannot simply be present at one moment and then disappear the next.

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Behaviour not Dependent on Learning

Although learning accounts for most of the behaviour of people and animals, not all behaviour has to be learned.

Reflexes, fixed-action patterns and maturation also account for certain behaviours.

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Reflex ActionsAutomatic or involuntary behaviour

which does not require prior experience and is basically the same each time is called a reflex.

We are born with a large number of reflexes, with each one allowing us to deal with certain stimuli that are important for our protection and survival.

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Reflex ActionsSome reflex actions that we have include:

The suckling reflexThe gripping reflexBlinkingThe knee jerk reflexThe Babinski reflexPeripheral vision reflexGagging reflexFainting

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Fixed Action PatternsA fixed-action pattern of behaviour

occurs when different members of the same species produce and identical response to the same specific environmental stimuli.

This type of behaviour is also referred to as species-specific behaviour.

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Fixed Action PatternsThe mechanisms that controls the

behaviours are ‘fixed’ in that they are genetically programmed into the animals nervous system and appear to be unable to be changed as a result of learning.

The term ‘fixed-action’ is used to describe behaviour that is inherited by every individual member of a species.

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Fixed Action PatternsFixed-action behaviour can also be sex-

specific.

Sex-specific behaviours are linked to courtship, sexual behaviour and nesting by male and/or female members of the species.

Fixed-action patterns differ from reflexes in that they are more complex consisting of a sequence of responses.

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MaturationOther unlearned behaviour is the result of

maturation.

Maturation is a developmental process leading towards maturity based on the orderly sequence of changes that occur in the nervous system and other bodily structures controlled by genetic inheritance.

Learning Activity 9.1 – Learned versus non-learned behaviour, pg. 426

Learning Activity 9.2 – Review questions, pg. 427

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Neural Basis of Learning When neurons communicate with each other, they

do so by sending a neurotransmitter comprising of electrochemical messages across a tiny space between the neurons

The gap between the axon terminal of one neuron (which releases the neurotransmitter) and the dendrite of another (which receives the transmitter is known as the synaptic gap

The synapse contains three components;◦ The synaptic gap◦ The axon terminal of the presynaptic neuron◦ The dendrite of the postsynaptic neuron

The synapse is the site of communication between adjacent neurons and the act of sending neurotransmitter across the synaptic gap can actually change the synapse

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Neural Basis of Learning

A – Presynaptic NeuronB – Postsynaptic Neuron2 – Neurotransmitter4 – Synapse

Direction of neural impulse

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Neurotransmitters The site of chemical communication between neurons is, as

we know, the synapse

This small gap between the pre and post synaptic neurons is where electrical energy is converted into chemical energy to allow the impulse to continue

When a neural impulse reaches the axon terminal in the presynaptic neuron, neurotransmitters (a chemical substance that enables communication between neurons) are released into the synapse from the axon terminal

Each type of neurotransmitter has a distinctly different shape and role – there are believed to be over 100 different neurotransmitters

Two of these are believed to involved in learning – glutamate and dopamine

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Neural Basis of LearningDendrites can grow longer and ‘sprout’

new branches while others can be ‘pruned’ away if not used – everyday we form and lose millions of synaptic connections

The ability of the brain to change is commonly referred to as plasticity, a property that makes learning and memory possible and assists us to adapt to life’s every changing circumstances

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Areas of the Brain and Neural Pathways involved in LearningLike memory, many areas of the brain

are involved in learning although some areas seem to be more actively involved in certain types of learning

Learning can involve the formation and strengthening of neural connections at the synapse – for example learning to play the piano will form new neural connections while regularly playing the piano will strengthen those connections

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Areas of the Brain and Neural Pathways involved in LearningAccording to Hebb (1949), when a

neurotransmitter is repeatedly sent across the synaptic gap, the presynaptic and postsynaptic neurons are repeatedly activated at the same time

This has the effect of changing the chemistry at a synapse, leading to a strengthening of the connections between neurons at a synapse

When the connection is strengthened, this makes the neurons more likely to fire together – when the connection is disused, it weakens and the neurons become less likely to fire together

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Areas of the Brain and Neural Pathways involved in Learning The synaptic changes that take place within a neuron

during learning are believed to have long-term potentiation

Long-term potentiation refers to the long-lasting strengthening of the synaptic connections of neurons, resulting in the enhanced or more effective functioning of the neurons whenever they are activated

The effect of LTP is to improve the ability of two neurons to communicate together

Evidence of LTP – Morris and others (1982), Tsien (2000)

Learning Activity 9.4 – Review questions, pg. 433

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Plasticity and Effects of Experience on the Brain Plasticity refers to the ability of the brain’s neural

structure or function to be changed by experience throughout a lifespan (plasticity meaning flexible or pliable)

Some areas of the brain such as the sensory and motor cortices are more plastic than others but it is unclear whether all brain structures have this plasticity

The brain of a developing individual has a much higher level of plasticity than that of an adult – this is one reason why children can learn much more quickly than an adult, a new language for example

Effect of the environment on learning - Research by Roseweiz and others (1960s)

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Developmental Plasticity and Adaptive PlasticitySome psychologists distinguish

between various types of plasticity

Developmental plasticity – occurs as the brain develops according to its genetics

Adaptive plasticity – most apparent in recovery from brain trauma or injury

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Developmental PlasticityRefers to changes in the brain’s neural structure in

response to experience during its growth and development

This type of plasticity is predetermined by our genes but can also be influenced by our environment

After birth a significant developmental change occurs where the infant brain forms far more synaptic connections than it will ever use in a process known as synaptogenesis (the forming of new synapses)

Synaptogenesis during an early age is believed to allow an infant to respond to the constant stream of new environmental input

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Developmental PlasticityFollowing the development

of all these new neural connections, the brain undertakes a process of eliminating these synaptic connections in a process known as synaptic pruning

Synaptic pruning occurs in different rates in different areas of the brain but the number of synapses in an adult brain is 40% less than that of a three-year old brain

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Developmental PlasticityThe timing of experiences is also important in the

plasticity of the brain

These periods are called sensitive periods

A sensitive period is a specific period of time in development where an organism is more responsive to certain environmental stimuli or experiences

An example is in cats, monkeys and humans; if after birth one eye is kept closed or does not function properly due to an abnormality, that eye will be forever blind – this change responsible for the loss of vision occurs in the visual cortex

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Adaptive PlasticityAdaptive plasticity refers to changes occurring in

the brain’s neural structure to enable adjustment to experience, to compensate for lost function and/or to maximise remaining functions in the event of brain damage

Generally adaptive plasticity allows the brain to compensate for damage by reorganising its structure

At a neuronal level, two processes for recovery are rerouting and sprouting◦ Rerouting involves an undamaged neuron which has lost

an active connection with a neuron may seek a new connection with an active neuron

◦ Sprouting is the growth of new bushier nerve fibres with more branches to make new connections

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Adaptive Plasticity Through adaptive plasticity, functions that are assigned to

particular areas of the brain can sometimes be reassigned to other undamaged parts of the brain to compensate for changing input from the external environment

Areas of the somatosensory cortex for example, can be reassigned to receive input from other areas of the body in the event of damage or in response to the environment

The brain does not only demonstrate adaptive plasticity in response to damage – it also can be due to the environment

Neuroimaging studies show that in violinists, the area of the somatosensory cortex that represents the fingers of the left hand (requiring fine finger control) is larger than the area the represents the right hand (using the bow)

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Imagery in LearningUsing neuroimagery techniques, it is possible to

demonstrate the plasticity of the brain and brain areas

When MRI scans of London cab drivers (who find new routes daily) are compared with London bus drivers (who follow a fixed route), they show that the rear part of the hippocampus of taxi drivers, which is involved in spatial awareness and memory, is significantly larger.

Learning Activity 9.1 – Review questions, pg. 445