Psych U3 AOS1 Dot point 2

Neural mechanisms of memory formation and learning

Synaptic plasticity

The ability of the synapse to change in response to experience. 

Sprouting

The creation of new extensions on a neuron to allow it to make new connections with other neurons. This occurs through the growth of nerve endings (‘sprouts’) on axons or dendrites, thereby enabling new links to be made, including rerouting of existing connections.

Rerouting

Occurs when new connections are made between neurons to create alternate neural pathways. The rerouting may involve the existing synaptic connections and/or new connections from the sprouts.

Pruning

The elimination of weak, ineffective or unused synapses (and therefore connections to other neurons).

Long-term potentiation (LTP)

Refers to the long-lasting strengthening of synaptic connections, resulting in enhanced or more effective synaptic transmission. 

• LTP improves the ability of two neurons to communicate with one another at the synapse, and this improvement is stable and enduring. 

• LTP strengthens synaptic connections, which enables postsynaptic neurons to be more easily activated in the future.

Process of LTP

• The postsynaptic neurons become more and more responsive to the presynaptic neurons as a consequence of repeated stimulation by neurotransmitters. 

• The more that the connection is activated, the more it is strengthened. The more the connection is strengthened, the more the relevant neural pathway is strengthened, increasing the efficiency in transferring information along the pathway and decreasing the likelihood that what has been learned will be forgotten. 

• In addition, the more we use the information being remembered, the more the LTP process strengthens the pathway, making it easier to retrieve that information.

Long-term depression (LTD)

Is the long-lasting decrease in the strength of synaptic transmission and neuronal response (which is the opposite of LTP).

Process of LTD

• This results from a lack of stimulation of pre- and postsynaptic neurons or prolonged low-level stimulation. 

• Generally, a postsynaptic neuron becomes less responsive to the neurotransmitter released by a presynaptic neuron, and the effect is to weaken the synaptic connection and therefore weaken or even silence communication at the synapse.

• It is believed that LTD may be just as important for learning and memory as LTP. The weakening or elimination of unused synapses through LTD may prune unimportant or unwanted connections, leaving behind the important connections that have been strengthened through repeated use by LTP. 

• LTD may, for example, enable old memories or unused connections and pathways for previously learned information or skills to be cleared out. 

• LTD may be what allows us to correct our thinking when solving a problem, or to adjust our movements when learning a new motor skill.

• It may also provide the basis of blocking or erasing unwanted, inappropriate or incorrect thoughts, feelings and behaviours.