The performance of many tasks improves, throughout life, with repetition and practice. Even in adulthood simple tasks such as reaching to a target or rapidly and accurately tapping a short sequence of finger movements, which appear, when mastered, to be effortlessly performed, often require extensive training before skilled performance develops. What changes occur in the adult brain when a new skill is acquired through practice? When, and after how much practice, do these changes occur?"

Source; Proc Natl Acad Sci U S A. 95(3): 861–868.

Once acquired, 'muscle memory' skills (e.g. riding a bicycle, playing a piano etc) can often be effortlessly 'recalled' decades later. Precise details of the neuro-biological systems which enable the memory are unknown.

Muscle memory is almost certainly involving different parts of the brain than 'ordinary' memoryplugin-autotooltip__plain plugin-autotooltip_bigMemory

inexplicable

"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.. For example, many dementia and Alzheimer's diseaseplugin-autotooltip__plain plugin-autotooltip_bigAlzheimer's disease

"Alzheimer’s disease is a chronic progressive neuro-degenerative disorder characterised by three primary groups of symptoms. The first group (cognitive dysfunction) includes memory loss, language difficulties, and executive dysfunction (that is, loss of higher level planning and intellectual coordination skills). The second group comprises psychiatric symptoms and behavioural disturbances — for example, depression, hallucinations, delusions, agitation — collectively termed … patients who were formerly pianists and who have almost entirely lost all memories can still play the piano with ease.

Experimental studies have shown that the memory appears to be formed in two distinct phases. The 'Fast' phase and the 'Slow' (consolidation) phase. It's assumed that the two forms might utilise different areas of the brain. In fMRI studies, the Primary Motor Cortex ( M1 ) has been shown to be involved at some level.

The hypothesis is that fast learning involves processes that select and establish an optimal routine or plan for the performance of the given task. Slow learning, on the other hand, may reflect the ongoing long-term, perhaps structural, modifications of basic motor modules; it may be implemented through time-dependent strengthening of links between motor neurons as a function of correlated activity, and their recruitment into a specific representation of the trained sequence of movements."

(Source as above)

Also see: Memoryplugin-autotooltip__plain plugin-autotooltip_bigMemory

inexplicable

"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.