BRAIN DEVELOPMENT FROM INFANCY THROUGH ADOLESCENCE Media Article

BRAIN DEVELOPMENT FROM INFANCY THROUGH ADOLESCENCE

Media Article Discussion

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Plasticity of the brain ¡The brain is capable of learning because of its flexibility in being able to adjust to changes in environmental input. ¡Experience associated with learning causes changes at the synapse, including the establishment and strengthening of connections between neurons that form neural pathways within the brain. ¡The brain’s structure is constantly remodelled by experience. ¡This fundamental but very important ability to change is referred to as plasticity ¡Plasticity is the ability of the brain’s neural structure or function to be changed by experience throughout the lifespan.

Brain plasticity in infancy: Developmental plasticity ¡Generally, an infant or a child’s brain will have more plasticity than an adult’s brain. ¡This is referred to as developmental plasticity – the ability of synapses to be modified ¡Although changes to the brain occur more frequently in the foetal stage, as well as in babies, children and adolescents (developmental plasticity), these changes continue throughout life as learning takes place (adaptive plasticity).

Brain plasticity in infancy: Developmental plasticity ¡Developmental plasticity refers to changes in the brain’s neural structure in response to experience during its growth and development. ¡The brain of a developing individual is even more plastic than that of an adult, particularly at specific times in development when it seems that the brain is more responsive to certain types of experiences. ¡This is one reason why infants learn a new language more quickly than do adults. ¡Similarly, infants recover more quickly from brain damage than do adults due to the greater plasticity of their brain.

Brain plasticity in infancy: Developmental plasticity ¡Prior to birth and for the first years of life, a child’s neurons are quite flexible in terms of their function. ¡The development of the nervous system starts before birth when the brain and spinal cord are formed. Development then goes through five stages: Ø Proliferation Ø Migration Ø Circuit formation Ø Synaptic pruning Ø Myelination

Plasticity and effects of experience on the brain ¡Developmental plasticity and adaptive plasticity ¡Developmental plasticity

Expert activity: ¡Students are placed into groups and each group researches one of the five stages of development: proliferation, migration, circuit formation, synaptic pruning and myelination. After studying their allocated developmental stage, one member from each group moves to another group to ‘teach’ them about the stage.

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Brain plasticity in infancy: Developmental plasticity ¡

Brain plasticity in infancy: Developmental plasticity ¡

Plasticity and effects of experience on the brain ¡Developmental plasticity and adaptive plasticity ¡Developmental plasticity ¡One of the significant developmental changes after birth is that the infant brain forms far more synaptic connections than it will ever use. ¡The process of forming new synapses is called synaptogenesis.

Plasticity and effects of experience on the brain ¡Developmental plasticity and adaptive plasticity ¡Developmental plasticity ¡Synaptogenesis occurs so rapidly within the first year of life that the total number of synapses increases tenfold. ¡Synaptogenesis during early development is believed to allow the brain to initially have the capability to respond to the constant stream of new environmental input ¡However, following the proliferation in forming new synaptic connections, the brain undertakes a process of eliminating synaptic connections.

Plasticity and effects of experience on the brain ¡Developmental plasticity and adaptive plasticity ¡Developmental plasticity ¡This process of eliminating synaptic connections is called synaptic pruning. ¡Synaptic pruning occurs in different areas of the brain at different times. ¡For example, in humans, it is complete in the visual cortex by about age ten but continues in the cortex of the frontal lobe until about age 14.

Plasticity and effects of experience on the brain ¡Developmental plasticity and adaptive plasticity ¡Developmental plasticity ¡What is constant across different areas of the brain, however, is that the number of synapses in an adult is about 40% less than the number in a three-year-old. ¡Experience determines which connections will be retained and strengthened and which will be pruned. ¡The connections that are frequently used are retained and those that are not decay and disappear. ¡Have you heard of the phrase ‘use it or lost it’?

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Brain development during adolescence ¡During adolescence in humans, there is a large amount of development in structures of the brain: Ø Cerebellum: there is an increase in the number of neurons and synapses in the cerebellum, the part of the brain responsible for balance, muscle tone, and the performance of motor skills. This might explain why some teenagers are more physically uncoordinated than older adults. Ø Amygdala: the amygdala becomes more active in adolescence Ø Corpus callosum: the corpus callosum thickens and there is an increase in the number of connections (or nerve fibres) between the two hemispheres Ø Frontal lobe (including prefrontal cortex): motor movement and higher-order thinking

Brain development during adolescence

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Review Questions 6. 1 page 132

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Juggling Activity ¡Right, Left, Catch ¡Right, Left, Right, Catch, Catch

Frontal lobe development ¡Studies of adolescents’ brains show a huge amount of development around puberty. ¡As unused connections developed throughout an adolescent’s life so far are pruned, other useful connections are strengthened. ¡The process of myelination continues through adolescence or later, with the highest brain levels myelinating last ¡The last part of the brain to develop is the prefrontal cortex, which is responsible for problem solving, complex planning, impulse control, risk management and critical thinking – perhaps a possible reason why adolescents can be very impulsive!

Frontal lobe development ¡Neuroscientists have found that during this time, when the prefrontal cortex is still in development, the adolescent brain may rely instead on the amygdala, a part of the limbic system, which plays an important role in processing our emotions. ¡The hyper-emotional states we might experience and bad decisions we might make during our teenage years could therefore be attributed to our brain relying on our amygdala to process information rather than our prefrontal cortex.

Class debate ¡Do you think we should lift the driving age from 18 to 21?

Review Questions 6. 2 page 135

Timing of experiences ¡As children and adolescents grow, their brains become less plastic and their neural pathways become more set. ¡Certain stages in development can be suited to learning particular things. ¡These periods are referred to as sensitive periods and are the best or optimum times for a developing individual to learn specific things.

Timing of experiences ¡For instance infants must be exposed to language in the first year of life to allow them to use and understand language.

Timing of experiences ¡If these skills and knowledge are not acquired during the sensitive period, they may be acquired at a later time but it will usually take more time, be more difficult and the learning may not be as successful. ¡Generally, the sensitive period for learning to speak our native language is up to the age of about 12 years, with the window gradually closing from about age seven.

Timing of experiences ¡Although we can learn to speak a second language at any time after childhood, if acquisition occurs before the ages of 5 -7 years, our competence will be like that of a native speaker. ¡Sensitive periods indicate that brain development goes through periods during which some synaptic connections are most easily made and some neural pathways are most easily formed.

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Chapter Review page 140