Can the banal and transient forgetfulness that we all experience at some point in our lives give us clues about the neural mechanisms underlying the onset of severe dementia, such as Alzheimer´s disease (AD)? The hypothesis we propose suggests an affirmative answer. If access to the memory system (MS) depends on matching key input patterns to appropriate contexts, we postulate that if the matching does not occur, the MS is blocked by a neural gate. From empirical observations, we shift to neural models of memories and their modulation by contexts. Our approach provides a possible explanation for transient memory failures but also suggests that the memory gate (MG) can be a crucial neural module that triggers a cascade of events leading to conditions where AD becomes irreversible and catastrophic. This hypothesis suggests ways to slow down the progression of this disease and may be explored with currently available techniques.