Saturday, April 9, 2011

A little nerve goes a long way

Phonating, articulating, and swallowing (the three main things we all do with our laryngeal, pharyngeal, and articulatory musculature) are all incredibly complex motor functions.   It should come as no surprise that the act of speech is just as complex, if not more so, and singing is an extension of the sensory-motor act of speech (the coordination of phonation and articulation).  Did you know you coordinate 30 muscles through 6 cranial nerves over the span of 1.5 seconds to every time you swallow?  It’s also a reflexive act:  i.e. you don’t consciously think about swallowing to coordinate it, it just happens.  That’s some awesome physiology right there!  Now the act of phonating itself should be a bit more like that too:  you don’t have to think that much about it, it just happens to work right when you command it and it takes 2 branches of 1 cranial nerve to enact.  The reason it’s not considered reflexive is that the command comes from higher up in your brain:  i.e. you consciously think about starting up your voice before it happens.  Phonation involves smaller, fine-tuned, movements from smaller muscles, and so it takes less nerve impulse (or “nerve-power,” if you will) to happen than the act of swallowing.  Those palatal, pharyngeal, and laryngeal elevators (along with muscles of the tongue) are involved in gross muscle movement.  They’re larger, stronger, and take more nerve impulses to function than phonation.

An interesting thing about these neural pathways from your brain to your voice and throat, these muscles that control all these lovely fine motor and gross motor movements, is the synaptic pruning that goes on.  Synaptic pruning is when certain synaptic pathways are eliminated in lieu of the ones that are being used.  This is the “use it or lose it” principle we’ve heard of.  Essentially, in this process, the pathway that gets used out of a command and gets reinforced grows stronger and the pathway that isn’t being used starts to die off.  Now, although this happens on a much more significant, large-scale, during prenatal development, childhood, and puberty, it does happen in smaller amounts throughout our life span.  (There are a whole lot of incredibly smart scientists out there currently studying something called neuroplasticity, which in essence, involves the stimulation of either new or damaged neural pathways to reconnect and rehabilitate someone from an injury, such as strokes, traumatic brain injuries, etc., which is based on this discovery.)

So here’s where I propose my theory, which at this time is more like an educated guess:   While a vocal injury like mine was not a stroke or traumatic brain injury (thank God!), having a “dysfunctioning” voice for nearly a decade really set some fairly concrete, albeit hyper-functioning, muscular coordination.  So when we say we’re working out “muscle memory,” we’re really working out “nerve memory.”  Because of my vocal fold asymmetry caused by the paresis, my brain had to actively recruit other muscles to help bring complete closure to the folds.  I had been “yelling” at my voice to not be breathy, and it had responded by calling upon the “big guns” of those more powerful gross movement muscles and pharyngeal muscles to force a clear “resonance” over that air escaping.  This occurred over and over during those 9 or 10 years of my injury.  The result was the creation and strengthening of very well-set pathways to recruit those gross-movers to force my voice to sound like I wanted it to in spite of the injury.  Those bigger muscles were recruited every single time my brain said to my larynx “sing!”  And just like someone compensating for an injured ankle, the effect was basically vocal “limping” that was so engrained as THE singing muscle coordination my body wasn’t just going to let it go when I told to sing again post-therapy. 

So here’s where the neuroplasticity thing differs with an injury like mine (still my theory at this point):  Therapies based in neuroplasticity seeks to activate pathways that either get damaged by stroke, neurodegenerative disease (Parkinson’s, etc.), or that were never there in the first place.  But, rehabilitating my voice to function optimally was NOT the process of re-activating neural pathways, it was the act of getting additional pathways to shut the heck up!  I had to find a way to get those extra muscles to stop firing when my brain said “sing.”  Therapy had retrained my voice quickly and efficiently by not requiring any manipulation or even thought on my part beyond just doing the exercises as I was taught.  My voice was truly healed up.  My lovely recurrent nerve was firing at full-force once again.  But that retraining only really worked on my speaking voice.  It didn’t magically cross-over into my singing voice.  Why?  Well, here’ s more theory on my part until I know more:  I think the coordination process of singing tends to be stored differently in the brain than that for speech.  (I mainly base that off of the fact that people who stutter can sing without stuttering and my own experience.)  My therapy exercises weren’t just a jumping-off point for how I would finally get my singing voice on track, they were the key to a complete shift in how I practice singing, how I view the process of learning to sing, and how I teach voice now.  Paradigm shifts like that don’t take place in a vacuum, but hopefully, I’ll be able to explain the process well enough for you guys out there who want to know.  But yeah, retraining “nerve memory” as I now like to call it ain’t easy, as we all know too well!

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