We all know the maddening experience of not being able to think of a certain word that is undoubtedly in our repertoire. Now researchers have discovered an association between a specific region in the neural language system and these tip-of-the-tongue (TOT) experiences, which are a normal part of aging. Deborah Burke of Pomona College and her team found that TOT moments became more frequent as gray matter density in the left insula declined. This area of the brain has been implicated in sound processing and production. The findings support a model proposed by Burke and her colleagues, which predicts that when we do not often use a word the connections among all its various representations in the brain become weak. “Words aren’t stored as a unit,” Burke says. “Instead you have the sound information connected to semantic information, connected to grammatical information, and so on. But the sounds are much more vulnerable to decay over time than other kinds of information, and that leads to the TOT experience.”