Not sure if you're still looking at this but just in case -
More info:
I just copied this off a website. There seems to be lots of sites that have info on related topics. I've copied bits from 2:
www.ccs.k12.in.us/Hbm/Topics%20in%20OT.htm
What is bilateral coordination and crossing the midline?
Bilateral coordination is the ability to use both sides of the body at the same time. This can mean using the two sides for the same action (like using a rolling pin) or using alternating movements (like climbing stairs). Bilateral coordination can also refer to using each side of your body for a different action, such as stabilizing a paper with one hand while writing with the other.
Crossing the midline, which relies on good bilateral coordination, means using part of one side of the body in the space of the other part. Some examples of crossing the midline include sitting cross-legged on the floor or drawing a horizontal line from one side of the paper to the other without switching the pencil to the other hand.
Why is bilateral coordination and crossing midline important?
Having efficient bilateral coordination enables both feet or both hands to work together. This allows you to play and work with fluid body movements. Bilateral coordination and crossing the body?s midline also support a child?s development of fine motor skills, ability to use tools, and ability to visually track a moving object.
How can I promote the development of these skills in my child?
Here are some suggested activities that you can try:
o Play Simon Says (?touch your left elbow?)
o Kick a soccer ball (balance on one foot and kick with the other)
o Blow bubbles and reach with both hands to pop them
o Pull cotton balls apart (can glue onto a picture, make a project, etc.)
o String beads to make a necklace
o Spread peanut butter on toast or frosting on cookies (and open jar first)
www.proteacher.net/discussions/showthread.php?t=1858
Some children actually have a problem "crossing the midline" of their bodies (an imaginary line down the center of the body from head to toe). They cannot reach across their body with their right hand to pick up an object that is on their left, or vice versa. They get "stuck" in mid reach & will have to switch hands. This can also apply to the legs, but is more noticeable with the hands/arms. Not being able to cross the midline may affect a child's ability to read, write, participate in sports & physical activities, etc.
As the previous poster noted, this all has to do with "brain programming", etc. Brain Gym exercises that involve crossing over to touch the opposing shoulder, elbow, knee, toe, heel, etc. can help "program " the brain to do this. You may have to physically assist the child to make the movements across the midline.
If the child is very young, you can try table exercises to cross the midline. While sitting at a table, have them pick up a marker, toy, cheerio, etc. that is placed on their right, but gently restrain the child's right arm and make them use their left. If the item they are reaching for is an item of great interest (favorite toy or treat), they will make a greater effort to get it. Again, you may have to physically assist the child to move the arm across the midline.
Another suggestion is drawing large lazy figure eights (the infinity sign, or an 8 laying down). This can be done on a chalk board, in the air or on large piece of paper.