PSY2071 Lecture Notes - Lecture 2: Synaptic Pruning, Myelin, Survival Function

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Week 2
Infant Development
Major Principles governing growth
-Cephalocaudal : Growth follows a pattern that begins with the head and upper body
parts and then proceeds to the body. Based on Greek & Latin ‘head to tail’!
-Proximodistal: Development proceeds from the centre of the body outward!
-Principle of Hierarchal integration: Simple skills typically develop separately and
independently. Later they integrate into complex ones!
-Principle of the Independence Systems: Different body systems grow at different rates
The synaptic Pruning
-There is an overproduction of synapses in infancy and through experience the obsolete
connections are pruned!
-Unused neurones are selectively eliminated, this allows established neurones to build
more elaborate communication networks wot other neurones!
-Connections that are used become strength and survive while the unused once are
replaced by other pathways!
*Result is increased efficiency of neural transmission in the network!
-Synaptic pruning is a non-linear development process
Myelination
-Axons of neurones are coasted with myelin a fatty acid that provides protection and
speeds the transmission of nerve impulses
-Contributes to increased weight of the brain
-Even though many neurones are lost the increasing size and complexity of the
remaining ones contribute to brain growth!
*Infants brain triples in weight during the first two years of life!
*By age 2 years brain weight reaches more than 3/4 of its adult weight and size by age
Environmental Influences on Brain Development
-Plasticity - degree to which a developing structure or behaviour is a modifiable due to
experience
-Sensitive period - specific (but limited) time, usually early in life, when the individual is
particularly susceptible to environmental influences relating to some aspect of development
-Infants sensory experiences affect both the size of neurones and the structure of their
connections
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Document Summary

Cephalocaudal : growth follows a pattern that begins with the head and upper body parts and then proceeds to the body. Based on greek & latin head to tail". Proximodistal: development proceeds from the centre of the body outward. Principle of hierarchal integration: simple skills typically develop separately and independently. Principle of the independence systems: different body systems grow at different rates. There is an overproduction of synapses in infancy and through experience the obsolete connections are pruned. Unused neurones are selectively eliminated, this allows established neurones to build more elaborate communication networks wot other neurones. Connections that are used become strength and survive while the unused once are replaced by other pathways. *result is increased ef ciency of neural transmission in the network. Synaptic pruning is a non-linear development process. Axons of neurones are coasted with myelin a fatty acid that provides protection and speeds the transmission of nerve impulses. Contributes to increased weight of the brain.

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