According to the Tatav Yog Mudra Vigyan, the five fingers represent the five elements, and the middle finger represents akash, the space or sky element. Akash enables sound and thought to travel. This happens through the placement of the fingers and has an effect on the two hemispheres of the brain. by centering your energies and assisting information to flow through both hemispheres of the brain. When used with a tongue placement is has a positive effects on the limbic system. The beneficial effects include an energy charge helpful in developing noble and elevated thoughts and reducing feelings of annoyance. It strengthens the bones, is helpful in heart disease, and is said to be a cure for toothache and reduces ear pain by relieving congestion. For those of us looking to drop a few extra pounds and add a little lost energy from long cold snowy days and heavy evening meals this mudra can be quite helpful as it detoxifies the body by the elimination of metabolic wastes (through exhaled air, sweat, urine and stools), helps overcome a feeling of fullness/heaviness in the body or body-parts, and is helpful in overcoming discomfort caused by over-eating
Akash mudra is best practiced 45 minutes every day, either at one stretch or in three parts(i.e for 15 minutes, three times a day) If this is not possible practice when in a reclined asana for as long as you can. The ideal time is between 2:00 to 6:00 am/pm although you can practice at any time of the day. Do not practice this mudra while walking or if you have a hyper thyroid.
To form the Akash mudra join the thumb and middle finger. The index, ring, and pinky fingers are extended. The tongue placement can be added by placing the tip of the tongue to the upper roof of the mouth.
Be well and a happy and healthy practice to all.