Brain Plasticity

Brain PlasticityPlastic: can be moulded or changed.Brain Plasticity: brain has the ability to change it’s structure and relocate functions to different areas or neuronal networks.Brain Plasticity can occur:

- At the beginning of life. - In the case of brain injury.- Throughout life when new learning and

memories are formed.

Developmental PlasticityChanges in neuronal connections during

development as a result of environmental interactions and learning experiences.

Changes in neurons and synaptic connections.

Key terms relating to developmental plasticity:

• synaptogenesis—the process of forming new synapses. When does synaptogenesis occur most rapidly?

• synaptic pruning—the process of eliminating synaptic connections. What determines which connections will be retained and which ones will be pruned?

Developmental plasticity

Adaptive Plasticity The brain can ‘rewire’ itself after some types of

brain damage. Occurs when the connections between the

synapses are altered to best suit environmental conditions, when learning something new or when re-learning something after brain injury or surgery.

At the neuronal level, the two processes for recovery arere-routing and sprouting.

Both of these processes involve forming new connections between undamaged neurons, however they do so in different ways.

What is the difference between re-routing and sprouting?

Adaptive plasticity

Types of Changes...

Over the course of a lifetime, our experiences shape, mould and remodel our brain.

- Dendrites grow longer and sprout new branches while others are ‘pruned’ away.

- Certain parts of the brain are function specific and may actually grow with learning and therefore alter in shape.

- With brain damage, the brain compensates by reorganising and forming new connections between intact neurons and in order to reconnect, the neurons have to be stimulated through activity.

Synaptogenesis• The process by which synapses are formed

(connections) between neurons.• Once neurons have positioned themselves

around the body axons (thin fibres that carry information away from the neuron’s cell body) and the dendrites (neurons that receive incoming messages)begin to grow from them.

• At the tips of the axons and dendrites structures called growth cones are found.

• These finger like extensions are called a filopodia.

‘Use it or lose it’

• Using your brain in novel or stimulating ways actually increases it’s size and the number of dendritic branches.

Neurogenesis: production of new brain cells. The brain loses cells every day but it

simultaneously grows new neurons to replace them.

Neural DevelopmentIn Learning...

• When learning takes place a physical change occurs in the synapse between neurons.

• These changes result in the laying down of new neural circuits, or neural pathways, through which information can travel around the brain.

Identify the age of the person by the amount of neural connections in their brain:

(newborn, 6 years old, 14 years old)

The transmission of neural impulses within the neuron basically involves electrical activity.

However, when the neural impulse reaches the end of the axon, the transmission of the information from one neuron to the next primarily involves a chemical process.

A neurotransmitter is a chemical substance that ismade by the neuron and enables communicationbetween neurons. Each neurotransmitter containsions that travel across the synapse from theneuron releasing it (the presynaptic neuron) to thereceptors on the dendrites of the receiving neuron(the postsynaptic neuron). The neurotransmitterworks by attaching (‘binding’) itself to thereceptor site on the receiving neuron. Generally,the neurotransmitter will have either of two effects.

• When an electrical charge in the form of a nerve impluse, or action potential, sweeps down the axon, neurotransmitters are released in to the synapse.

• (Neurotransmitters are chemicals released at the axon terminals of the pre-synaptic neuron. They carry the chemical messages across the synapse to the dendrite (receptor site) on the post-synaptic neuron.)

Sometimes, the neurotransmitter will have an excitatory effect, and consequently stimulates or activates a neural impulse in another neuron.

At other times, the neurotransmitter will have an inhibitory effect, and blocks or prevents the receiving neuron from firing.

The synaptic changes that take place within a neural pathway during learning are believed to have long-term potentiation.

Long-term potentiation (LTP) refers to the long lastingstrengthening of the synaptic connections of neurons, resulting in the enhanced or more effective functioning of the neurons whenever they are activated.

Basically, the effect of LTP is to improve the ability of two neurons—a presynaptic neuron and a postsynaptic neuron—to communicate with one another at the synapse.It is now widely believed that LTP is a crucial neural mechanism that makes learning possible in humans, as well as in all animals with nervous systems.