Friday, December 13, 2013

Like Riding a Bike

The expression, "It's like riding a bike." is commonly used to indicate an activity that once learned is easily repeated regardless of how much time has passed.  But what makes some activities such as bike riding easily retained while other activities such as basketball rapidly deteriorate without practice?

A recent paper published in the "Proceedings of the National Academy of Sciences of the United States of America" explored a possible root cause of this phenomenon. The paper, co-authored by Robert Ajemian, Alessandro D'Ausilio, Helene Moorman and Emilio Bizzi deals with neuroplasticity and how motor skills are learned.  In brief, the researchers posit that motor skills are encoded in the brain by a large number of neurological pathways which are all equivalent.  These pathways are refined via feedback during skill learning and largely maintained due to a constant babble of neurological "noise" (neuron to neuron signaling that does not serve a specific purpose) that is found in all complicated brains.

The question of skill or memory retention is one that has proven difficult for researchers to solve.  Clearly the human brain has a relatively high level of plasticity or else we would be unable to learn new skills.  However, too much plasticity would cause existing skills to rapidly deteriorate whenever we weren't using them. Clearly some middle ground exists wherein we can learn and retain, but the exact mechanism for this ideal state has generally remained mysterious.

The co-authors of the aforementioned paper have presented a model of learning and retention that seemingly is a viable explanation for how our brains manage to acquire new skills without losing those we already know.  During skill acquisition the brain establishes many pathways which correspond to a given activity.  Riding a bike for example.  These pathways are all equivalent in that they all have the same end result of causing the muscle movements which propel a bike forward.  During bike riding many of these pathways are utilized and reinforced by feedback mechanisms. When we take part in some other unrelated activity, cooking for example, the pathways are largely inactive.  However, even while inactive these pathways are still receiving a great deal of traffic from the surrounding neurons.  It's this neurological noise which continues to reinforce the pathways and limits skill loss.  Although over time many of the neurological paths will breakdown for biological reasons a large portion will remain allowing for the retention of previously learned skills.

So why do some skills stay with us longer than others?  The researchers of the study conjecture that it has to do with how unique a skill is as compared to other daily activities.  Bike riding doesn't have a great deal of overlap with anything else most people do in their daily lives, therefore it tends to be retained for a long while. Proficiency in video games tends to rapidly deteriorate however as each game is similar to the next in terms of motor function (they all essentially amount to pressing buttons).  When skills utilize movements which are not commonly applied to other purposes it seems they are maintained far longer than skills which use more generic movements.

The researchers new model is interesting insofar that it nicely deals with common questions surrounding skill acquisition and retention.  However, it's important to note that there is little experimental evidence to directly support the model at this point.  The researchers have simply proposed an interesting idea which merits exploration, not proven anything experimentally.  Still, all experiments have to begin with a hypothesis and this one seems promising.

That's all for this week. Until next time stay safe and rationale.

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