Crossing Midline

The human brain is a paired organ; it consists of two halves that look alike.

What is brain lateralization?
Brain lateralization is just the fact that the two halves of the brain are quite different from each other. Both sides have different jobs that they do, and each side is highly specialized in those functions.  For example, you may be aware that the left side of the brain is specialized for language.

Crossing Midline, or "cross lateralization":
We talk a lot in OT about "crossing midline".  Crossing midline simply means that a a child reaches across their body with either hand (such as to use his/her left hand to reach across to the right of their body and vice versa).  Think of it as if there is an imaginary vertical line down the center of their body, and crossing midline would mean moving a hand or foot across that line to the other side of it.

Well, what does this do in terms of brain function?  When a child crosses midline, new connections are made between the right side and the left side, and both sides then are working together, rather than independently of each other.  It integrates the 2 sides of the brain, and organizes the brain for better concentration and problem solving.  This is needed for reading and writing, as a child must cross midline when reading and printing from left to right across a page.  Many self help skills require being able to cross midline, as well as sports activities and other daily skills.

The ability to cross midline develops as bilateral coordination skills develop.  The child learns to coordinate their stronger hand (used for specialized skill) with their helper hand (the hand that they use to assist the dominant hand).  See an earlier post titled "Bilateral Integration/Coordination," dated 6-8-13 for activity ideas for improving bilateral coordination.

This is an example of a child reaching across midline.

You may notice that children who have difficulty reaching across midline often stop in mid-reach and switch hands.  Keep in mind that when a child routinely switches hands, each hand then gets equal practice, and true hand dominance does not develop or may be delayed in developing.  You may also notice that they turn their trunk to reach toward the opposite side instead of reaching across it.  This lack of trunk rotation limits crossing midline, and one way to work on this would be to work on core stability (see earlier post, "Postural Control and Shoulder Stability for Fine Motor Skills," dated 6/3/13 for more info on how to do that).  Also, they may exhibit difficulty visually tracking a moving object from one side to the other or have difficulty following along from left to right when reading.

"Right handed" child completing a coloring task.  Note that the crayons are located on the left side of the paper.

Same child- note that when he changed colors, he picked up the crayon with his left hand, because they were to the left of the paper.  This is not a child who readily crosses midline.  

The following are activities that you can do with your child to encourage crossing midline:

-Complete sorting or reaching and placing activities:  have your child pick up items that are on the right side of them with their right hand, and reach over and place them on their left side (and vice versa). Sort objects into containers in this manner, place pegs in pegboards, etc.

-Complete worksheets or draw on large sheets of paper for which the child has to draw a line from one side of the paper to the other.

-Cone or cup transfer:  Transfer/stack cones or cups with the right hand from right to left and from left to right.  Switch hands.  See top photo above for example.

-Complete cross crawls:  in standing, pick up left knee and touch right hand to it, and then right knee and touch left hand to it, and continue on in this manner, alternating back and forth for a number of repetitions.

-Place a long line of masking tape on the floor.  Have your child walk along the tape line, scissoring their legs (stand with each foot on each side of the tape line, walk along the line by crossing one foot over the other and stepping on the opposite side of the tape line).  Can also do this with their hands while in 4 point along the tape line on the floor, or up a tape line on the wall.

-Check out Brain Gym-  many of the activities that are Brain Gym based are related to crossing midline.  Find out more about this here:  http://www.braingym.org/index
Here is a link for 10 free Brain Gym Activities: http://sspw.dpi.wi.gov/files/sspw/pdf/sascevanshandouts.pdf