You lose access to critical thinking, or the problem-solving area of your brain.
You retain access to the muscle-memory, or trained area of your brain.
Your body increases your ability to perform Gross Motor Skills, but this reduces your ability to perform fine motor skills, such as dialing a phone
Your brain tries to help you focus on what it thinks is most important for you to hear, and it filters out noises that it deems unnecessary for you.
Your vision shrinks or reduces to what is right in front of you, restricting your peripheral vision.