The human mind is quite beautiful; the intricacies in neural networks down to the minutiae of interactions is so profound. What are memories? We know there are three processes and perhaps a plausible fourth that contribute to the process we know as remembering: acquisition, storage, retrieval. The fourth is still under scientific scrutiny – it is “consolidation” – which is the solidification of memory. Our minds work through electrical impulses, and these electrical impulses then have subsequent consequences, specifically in dealing with neurotransmitters.
Neurons communicate through electrical impulse. Specifically, those impulses are called “action potentials.” They are caused by ion movement through protein channels down the soma of a neuron. Sodium ions move into the cell and slightly change the electric potential of the cell. When positively charged sodium ions move in, they make the intracellular conditions more positive. After a short time, potassium ion channels then open up, and because potassium ions are also positively charged, as they move out of the cell, they return the brain cell back to its normal resting potential, which is negative. Now, we understand that this is an electrical phenomenon. This electrical impulse will propagate down the brain cell, down its projection called an axon.
Within the end of our brain cells, called the axon terminal, are little vesicles containing molecules called neurotransmitters. When an electrical impulse reaches the end of its journey, it stimulates these vesicles to fuse with the very end of the axon and then the dumped neurotransmitters reach another cell at its sensing region, called a dendrite. The space between the axon terminal and a receiving dendrite is called a synapse. In general, neurotransmitters are dumped by exocytosis into the synaptic cleft and reach the dendrites and then have a specific function in the specialized part of your body where this event is occurring.
This was all work up to what we know as a synapse. Our memories, our recollection and story of our lives, and our experiences actually change our brain chemistry, and the synaptic efficacy (strength of transmission) is affected directly by our senses being stimulated. What comprises our memory is actually a change in our synapses, which is literally just a space between two brain cells. Brain activity and experience literally change how synapses and communication between two brain cells occurs. When you decide to recall declarative memory, the circuitry of your neural network that was changed by a specific experience is reactivated and you have your declarative memory come to your consciousness. When you can’t remember something that’s at the tip of your tongue, and you’re trying and failing, that specific neural network probably hasn’t been used for a while. Synapses and parts of your memory is strengthened as they are used more. Knowledge and their respective neural networks, if not used for a while tend to get a little dusty.
The mind is beautiful. It is simultaneously resilient as well as fragile.