What does it mean to have a weakening of signal or input from the senses?

Several kinds of changes in people’s bodies make it difficult for their brains to represent what they hear and see as accurately as they did when they were younger. Hearing and vision rarely improve with age. In addition to the well-known declines in the function of the ear and the eye, there are declines in function in the brain systems that deal with all of the senses. As these systems decline, it becomes difficult for the brain to create crystal-clear representations of sounds and experiences–of the input from the senses. The fuzzier those representations are, the harder it is for the brain to record and store them. It is then harder to find, retrieve and manipulate them.