Crossing the Midline: What’s the Big Deal?

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Crossing the midline.

That’s a goal (or objective) frequently used in music therapy sessions. I have used it for children with autism, children with developmental disabilities, and for trauma-influenced children. It also seems to be a common therapeutic goal for occupational therapists.

There’s an intervention I use in my weekly sessions with trauma-influenced kids. I borrowed it from a music therapist who works exclusively with children on the spectrum (e.g. children with autism). I (very cleverly) call it the “Right-Left Song”:

Right and left and right and left Susie’s playing the drum

She’s going right and left and right and left she’s playing the drum. (Repeat)

As I sing, Susie uses mallets to play two drums, alternating using her right hand to play the drum on the left side of her body and her left hand to play the drum on the right side of her body. All in time to the music. It’s a crossing the midline experience, but it also integrates auditory, visual, and proprioceptive sensory information. I’ve also found this particular intervention to be a great assessment tool. I can tell on any given day if a child is feeling calm and regulated or stressed and dysregulated. It’s also easy for me to “assess” a new child, to know generally where this child is developmentally.

But I digress. My real question is: What’s the big deal about crossing the midline? Why is this such an important skill to develop? Between my own experiences (and some quick Google searches), here is what I’ve found:

1. My infant daughter just had her 6 month well visit appointment. Prior to this appointment, her pediatrician asked me to fill out an assessment tool to make sure she is meeting her developmental goals. What was one of the goals this month? Crossing her midline. Reaching across her body to pick up a toy on the opposite side (and, yes, she passed).
2. Crossing the midline is an indicator of bilaterial coordination, meaning the “ability to use both sides of the body at the same time.” This is an important skill for many of our daily tasks: climbing stairs, walking, typing on a computer (Yay! I can cross my midline), riding a bicycle, picking up our children, catching a beach ball, climbing ladders, etc.
3. The development of bilateral coordination is also important for the development of cognitive skills, such as the ability to read, write, and learn. Both skills utilize both hemispheres of our brain. Crossing the midline, a skills devloped in infancy, may be an important precursor to a child’s ability to learn.
4. Here is a good article about the relationship between dominance and crossing the midline. The author says that the ability to cross our midline is a “prerequisite for appropriate lateralisation.” Most people have one hemisphere that is more dominant (e.g. lateralised) than the other (You may have heard people referred to as “right brained” or “left brained”; although not entirely wrong, this is a grossly simplified generalization). If lateralisation is not established, a person may have difficulties in various areas: making decisions, organizing, fine and gross motor organization, writing, reading, and language development, among others.

So it seems that crossing the midline is an important, basic prerequisite skill required for the appropriate development of various motor and cognitive skills. To me it seems akin to developing sustained attention or developing the ability to self-regulate (future posts, perhaps?). Both are basic, prerequisite skills needed for other learning and development to take place.

So I have learned something new; it now makes sense to me why we so often work on crossing the midline in our music therapy sessions.

And I’m glad my trauma-influenced clients like the “Right-Left Song” – we’ll be doing it for awhile!