1.+Mechanisms+of+Learning

**Dot Point 2.**
 * AOS 1**


 * Mechanisms of learning:**

**Neural Basis:**  When neurons communicate, they send a neurotransmitter (electrochemical message) across the axon ending neuron to dendrites of the next.
 * 
 * // Presynaptic- // the axon ending of ‘sending’ neuron
 * // Postsynaptic- // the dendrite of the ‘receiving’ neuron.


 * ** - Synapse formation during learning **

Synapse is the site of communication between the adjacent neurons. It comprises of the axon terminal of presynaptic neuron, the synaptic gap, and the dendrite of the postsynaptic neuron.
 * The Long term potentiation and Learning: **
 * Synapse formation involves: **
 * Creation of new neural pathways
 * Strengthening of existing neural pathways

Long-term potentiation- is the long-lasting strengthening of the synaptic connections of neurons, resulting in more enhanced functioning of neurons whenever they are activated. Dendrites that receive neurotransmitter message can grow longer and //‘sprout//’ new branches when used others are //‘pruned’// away from disuse.


 * __ Hebbian Learning (Hebbs Rule): __**
 * Learning results in the creation of cell assembles or neural networks
 * ** ‘neurons that fire together wire together’ **
 * When a neurotransmitter is repeatedly sent across the synapse this can affect the strength of these connections making it more likely to fire together more forcibly again.
 * Neurons that do not fire together weaken their connections.

- ** The role of Neurotransmitters on Learning **

There are two important neurotransmitters involved in learning; **__glutamate__** and **__dopamine__**.

When learning takes place, **glutamate** is released by the presynaptic neurons. Glutamate is the main excitatory neurotransmitter in the brain for learning. When glutamate is released by the presynaptic neuron, it acts on two types of glutamate receptors in the postsynaptic neuron:
 * The **AMPA** receptor activates the postsynaptic neuron
 * The **NMDA** receptor necessary to produce any long-lasting modifications to the synapse and helps glutamate carry its messages across to the post-synaptic neuron.

The repeated glutamate release also stimulates the release of **dopamine**, which in turn activates genes in the neuron. This prompts growth in the postsynaptic neuron of an increased number of **dendritic spines** that make the postsynaptic neuron more sensitive to future firing by other neighbouring presynaptic neurons. This process happens within 30 minutes.

**Areas of the Brain and Neural Pathways involved in Learning**

** Structures of the brain involved in learning: **
 * //__ Hippocampus- __// is involved in spatial tasks (how to navigate through space). It is crucial for forming and storing information.
 * //__ Amygdala __// : can strengthen the learning of information for declarative memories that is associated with positive/negative emotions.
 * //__ Basal Ganglia __// (located in frontal lobe), use information from motor areas and somatosensory cortex to integrate smooth bodily movements
 * //__ Cerebellum __// (little brain) - it works with the basal ganglia in learning movement sequences so that the movements can be carried out.
 * //__ Ventral tegmental area __//// - // important for learning through operant conditioning (rewarding effects of reinforcers on behaviour).





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



**Plasticity of the brain:** Neural plasticity - The brain is adaptive, it changes its neural structure and function as a result of experience (learning).

¡ **__ Developmental Plasticity __** : Changes in the brains neural structure as a result of experience during growth and maturation. It also facilitates the elimination of weak connections that are not used. The neural changes occur as a result of learning and development of the organism.

¡ **//__ Synaptogenesis __//**** (also known as circuit formation) ** – new neural synaptic connections ¡ **//__ Synaptic (or circuit) pruning __//** – removal of synaptic connections that are no longer needed. ¡ ** Sensitive period ** – time an organism more responsive to certain stimulation. Lack of stimulation can lead to long term deficit. Eg Language.

¡ **__ Adaptive Plasticity __** : The process whereby brains functions can be relocated to other areas of the brain to enable adjustment to experience or to compensate for a loss of function (damage). As a result of damage; nerve cells do not regrow, rather other neurons take over the functions of the damaged cell. ¡ **//__ Rerouting __//** – neurons near damaged area that has lost connection with its neuron seek new active connections with healthy neurons ¡ **//__ Sprouting __//** – new dendrites grow with more branches to make more connections.

**Timing of Experience: Critical Periods** __ Critical Periods __ – A time of increased sensitivity to environmental influences when the conditions are optimal for certain capacities to emerge in an organism. Evidence: 1) If a pregnant woman contracts German Measles in early pregnancy, the child may be born with heart defects, cataracts or hearing loss. If the illness is contracted later in pregnancy, the chances of these defects are greatly reduced.   2) Severe damage to the left hemisphere of a child’s brain before the age of two can result in a shift in the language processing to the right side of the brain. This is not possible in an adult

3) Lorenz work with Geese and imprinting

In humans this phenomena is often referred to as **__sensitive periods__** of development. A specific period of time in development when an organism is more responsive (or ‘sensitive) to certain environmental stimuli or experiences. There is a specific onset (‘start’) and offset (‘end’) times. They are known as windows of opportunity for learning’. Why? Brain development goes through periods during which synaptic connections are most easily made and neural pathways are most easily formed – assuming there is access to the appropriate environmental stimulus. Evidence: Vision peaks by 3 years, Language up to about 12 years.

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

Modern brain imaging technologies such as CT scans, PET scans, SPECT scans, MRI scans and fMRI scans provide clear evidence that, during learning, changes occur in neurons that can result in permanent structural and functional brain changes. CT = Computerised Axial Tomography : Structure PET = Positron Emission Tomography: Function SPECT = Single Photon Emission Computed Tomography: Function MRI = Magnetic Resonance Imaging: Structure fMRI: Functional Magnetic Resonance Imaging: Structure & Function PET, SPECT & fMRI collect information about the activity occurring in the brain during a specific task, by measuring blood flow. This information is used to monitor changes in the location of activity in the brain and provides information about learning and plasticity.

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