By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) - The weather is heating up and that means it is time for waterice, ice cream and all sorts of ways to try and be cool. But what about when you take that bite of ice cream and suffer a brain freeze.

What happens and why?

Researchers brought on brain freeze in the lab by having 13 healthy volunteers sip ice water through a straw right up against the roof of their mouth. The volunteers raised their hands when they felt the familiar brain freeze come on, and raised them again once it disappeared.

The researchers monitored the blood flow through their brains using an ultrasound-like process on the skull. They saw an increase in blood flow to the brain through a blood vessel called the anterior cerebral artery, which is located in the middle of the brain behind the eyes.

The blood rushes in and can’t be cleared quickly. The pressure inside the skull rises and induces pain that way.

As the pressure and temperature in the brain rise, the blood vessel constricts, reducing pressure in the brain before it reaches dangerous levels.