Monday, February 17, 2014

Motor Monday-Primitive Reflexes Part One

Are you calling my baby primitive?!  Do you think we are cavemen or something?  Nope, no name calling here, but when babies are first born their nervous systems are not fully developed and most of their movement is controlled by a more primitive part of the brain called the midbrain.  These movements are reflexive, in that they are in direct response to a stimulus.  You are probably familiar with some of the primitive reflexes like rooting and sucking. To me, these reflexes make sense because they are true survival instincts that help infants find and take in food.  Similarly the gag and coughing reflexes are important for survival, clearing the airway.  Some of the other primitive reflexes are not as clearly linked to survival now, but you can see how they might have been at one time. (It's already late and I need to get to bed, so I'm only going to touch on a couple of examples of other reflexes tonight!)

The Moro (or startle) reflex is a good example of a reflex that you can see being useful some time in human evolution. When you watch the video, watch how Avery's arms initially flare out to her sides and then pull back in to hug her body.  This is the baby's response to a threat, in this case being "dropped."  This reflex may have helped a baby cling to his mother if she began to fall.

Other reflexes are harder to see the "survival" value in.  If you have kiddos, or have spent a lot of time around babies, this pose probably looks pretty familiar to you.
This is classic ATNR (assymmetrical tonic neck reflex) where the babies head is turned and the arm and leg on the face side straighten and then bend on the skull side.  It's a little harder to see how this type of reflex could be survival based unless the baby can hold a sword and shout "on guard!"  (This position is often referred to as the fencer position.)  As babies get older, these reflexes get integrated into more purposeful movements or are inihibited and essentially disappear.  We still don't fully understand the purpose of these reflexes, but they are hypothesized to play a role in motor development.  ATNR, for example, may help babies see their hands and recognize that their hands are in fact theirs and may turn out to be pretty useful.  

Did you know that tiny babies can walk if you support them in standing and tip them forward a bit?!  This reflex is aptly named the stepping reflex, which may set the foundation for the general patten of walking and even for kicking that helps build the muscle strength needed to walk.  I am sooooo sad to say that I don't have a video of the stepping reflex to show you.  I had a great one of Avery when she was about a month old, thought I uploaded it to YouTube, and deleted it from my phone only to realize I'd uploaded a different video. =(  By the time I realized it, all their stepping reflexes were pretty hard to elicit.  So if any of our readers have a newborn and want to send me a video of them "walking" I would be so grateful!  

In Primitive Reflexes Part Two I'll talk a little more about what can happen if these reflexes don't integrate properly or are what we might call "obligatory" and the baby or child can't override the reflexive response.  Are there any other reflexes you've heard about and want to know more about?  If so let me know and I'll add that into part two!

1 comment:

  1. Avery is so tiny and sooo cute in that video! Good post, Mari!


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