system
Given the following post, respond as if you're commenting on Reddit:
human
Biologically, what causes a memory to become more permanent (become "learned") versus just being forgotten?
gpt
A memory is essentially stored as a particularly pathway of an impulse from neuron to neuron to neuron and so on. In the process of learning something, the neural connections from one to another in such a pathway grow stronger, which is stimulated by the repeated firing of that pathway (in layman's terms, thinking of that same memory i.e. learning by repetition). This process is known as memory consolidation and occurs as follows:
1) Original Pathway is fired, representing a particular memory - i.e., a zebra has stripes.
2) You think of that memory again, activating the same pathway. This starts potentiating the neurons in that pathway, making it easier to reach the threshold of activation to cause the neurons to fire in succession.
3) If step two is repeated frequently, this will lead to further potentiation of the neurons involved in this particular memory pathway. Additionally, the neurons or surrounding supporting cells may begin producing growth stimulating hormones, promoting the formation of more axonal terminals to the receiving neuron, in turn allowing for more efficient signal propagation and thereby more efficient memory recollection as initiation of firing of this particular neural pathway will become easier.
4) In the absence of these stimulation factors (i.e. a memory was learnt once, but not repeatedly consolidated in the future) the lack of potentiation coupled with the loss of survival signals can lead to the loss of a neuronal connections between neurons for that particular memory pathway, or result in the threshold of activation being so high that some neuron(s) in that pathway will simply not continue propagating the signal as they are not sufficiently stimulated by the neurons before them. This leads to a failure in memory recollection - something was 'forgotten'.

It should be stated that neural pathways are very complex (it is not simply linear neuron -> neuron -> neuron, but rather adopts a complex branching structure). Additionally, a neuron may also be inhibitory or stimulatory (raises or lowers the activation energy of the receiving neuron) depending on the neurotransmitter released.

If you want me to elaborate on any point here, just say so.

Edit: For accuracy & reading comprehension.