How Exactly Does The Human Brain Pay Attention To Something?

“Every moment, our brains are bombarded with information, from without and within. The eyes alone convey more than a hundred billion signals to the brain every second. … How do our brains select the relevant data? How do we decide to pay attention to the turn of a doorknob and ignore the drip of a leaky faucet? How do we become conscious of a certain stimulus, or indeed ‘conscious’ at all?”