1. Applications of Plasticity :
Sensitive Periods for Learning
Developmental Plasticity
Adaptive Plasticity

2. Sensitive & Critical Periods for Learning
Definition: refers to a very narrow period of time in an animal’s development in which the animal is pre-programmed for learning to occur.
For example, ethnologist Konrad Lorenz studied how young birds imprint (form an immediate attachment) to the first moving object they see after they hatch from the egg.
Lorenz found that greylag geese hatchlings imprinted on him and followed him wherever he went.
For these geese, the critical period was the first few moments of their life (Lorenz 1937).
In humans these critical periods are often referred to as sensitive periods because the time in which they occur is more flexible and broad than critical periods for non-human animals.

3. Sensitive Periods
Definition: Time an organism is more responsive to certain stimulation
Lack of stimulation can lead to long term deficit
E.g. closed eye from birth leads to later blindness even when eye eventually opened
Language acquisition has a sensitive period (0 – 12 years)
Learning a new language in teen years can lead to the development of a second Broca’s area!

4. Review: Developmental Plasticity
Changes as a result of experience and maturation
Synaptogenesis – new neural connections
Synaptic pruning – removal of synaptic connections that are no longer needed
Adults have less neural connections than a 3 year old!

5. Review: Adaptive Plasticity
The brain reorganises the way neurons in different regions operate in response to a deficit
Deficits can occur from birth or as a result of brain damage
Brain plasticity
Neuroplasticity

6. Damage from Birth - Congenital
Congenital – E.g. People who are blind from birth may have occipital lobes that are used for senses other than vision
This may explain why people who are blind from birth have very good hearing or tactile sensitivity

7. Damage from Injury
When a particular brain area is damaged e.g. stroke other brain areas can ‘take up the slack’
This is what happens when people ‘recover’ from brain damage
Nerve cells do not regrow, rather other neurons take over the functions of the damaged cell
Rerouting – neurons near damaged area seek new active connections with healthy neurons
Sprouting – new dendrites grow
May occur near damaged area of in other parts of brain
Allows shifting of function from damaged area to healthy area
‘Relearning’ tasks like walking, eating etc. helps these new connections form

8. Adaptive Plasticity and Experience
Why is it so?
Musicians have enhanced motor and sensory areas
Taxi drivers have enhanced functioning of their parietal lobes
Dancers motor areas are enhanced