If you have ever struggled to remember the name of the streaming movie you just watched two nights ago, it may astound you that almost no one forgets how to ride a bicycle. This despite a rather steep learning curve at the outset, with plenty of skinned knees and scuffed helmets to show for it.
So why do we have to check our Netflix Watch It Again column to remember what movie we wanted to recommend, but we can drop into a bike shop and take off without a hitch even if decades have passed? The answer has to do with what kinds of memories we’re making.
Writing for Scientific American, neuropsychologist Boris Suchan explains that we have two different kinds of long-term memory: declarative and procedural. Within declarative memory are two sub-types: episodic and semantic memory. Episodic memory is the recall of an event in your life, like going to a concert or falling into a ditch. Semantic memory, also known as factual memory, is knowing that World War II ended in 1945.
But acquiring a skill is part of procedural memory. Learning how to drive, play a sport, or ride a bike are all activities that are stored in another part of the brain. It would theoretically be possible to suffer a brain injury that could rob you of your memory of riding a bike but preserve the part that knows how to ride the bike. Presuming your basal ganglia, which process nondeclarative memory, is unharmed, you’ll be able to pedal without incident.
But why is procedural memory so stubborn? That’s less clear to science, although one reason, Suchan writes, is that the regions in the brain where movement patterns are formed experience less nerve cell turnover, helping to preserve recall of those actions. That’s why you can always hop on a bike but not necessarily remember that movie. Alternately, maybe the film just wasn’t very good.
[h/t Scientific American]