Although it is commonly accepted that learning and memory occur via enduring changes in neuronal properties such as synaptic strength within a network of neurons, many details of these processes remain unknown, including the mechanisms responsible for the persistence and maintenance of memory over long periods of time.

Source : Learning & Memory journal (special issue) 2021. 28:

On a macro scale, neuroscientists now know (more or less) where memories are 'stored' in the human brain. The brain's hippocampus, the amygdala, the striatum and the mammiliary bodiesplugin-autotooltip__plain plugin-autotooltip_bigMammilary bodies

The Mammilary Bodies are a pair of small round structures located on the underside of the brain at the end of the Fornix - which is connected to the Hippocampus. ( see diagram at Wikipedia )

They are believed to be associated with memory recall, as damage, which can occur as a result of physical injury, or due to (for example) are known to be involved in some way, because individuals who suffer damage (either by injury or disease) to those areas are prone to memory loss of various kinds.

Different modes of memory (short-term, long-term, motor memory etc) have been extensively classified and described, but researchers aren't yet in complete agreement about the models.

In 2024, researchers studying the way that neuronal connections can be strengthened and maintained over time - known as Long-Term Potentiation (LTP) - discovered some details of the operational modes of a highly specific molecule involved in memory reinforcement, called PKMzeta.

How molecules lasting only hours to days can maintain memory that persists weeks to years is a long-standing fundamental question in neuroscience."

See : Science Advances, Vol. 10, No. 26.

To recap, a full description of the neuronal mechanisms by which complex memories are stored, maintained and retrieved is still lacking.

Note : It's now known that electrical activity in neurons can cause breaks in their DNA, which are later repaired. Some research groups have suggested that these DNA breaks and re-splicing could somehow be involved in the 'coding' of memories.(ref.)

Further reading: Wikipedia

Also see: Age-related memory declineplugin-autotooltip__plain plugin-autotooltip_bigAge-related memory decline

"Normal aging is associated with a decline in various memory abilities in many cognitive tasks; the phenomenon is known as age-related memory impairment (AMI) or age-associated memory impairment (AAMI). The ability to encode new memories of events or facts and working memory shows decline in both cross-sectional and longitudinal studies. and Forgettingplugin-autotooltip__plain plugin-autotooltip_bigForgetting

"Although it is commonly accepted that learning and memory occur via enduring changes in neuronal properties such as synaptic strength within a network of neurons, many details of these processes remain unknown, including the mechanisms responsible for the persistence and maintenance of memory over long periods of time."

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