Tip-of-the-tongue states and lexical access in dementia.

We induced tip-of-the-tongue (TOT) states in elderly participants with probable Alzheimer's disease (AD). We found that they experienced TOTs but, unlike control subjects, were unable to provide any information about the target word for which they were searching. The related words produced by the AD participants were almost all semantically related to the target, with very few phonological relatives. (Adults normally produce more phonological relatives than semantic.) We examine the relationship between the target and non-target words produced in terms of their syntactic category, frequency, and imageability. The results are discussed with regard to their implications for speech production models. We interpret the results in terms of a two-stage interactive account where the retrieval deficit in dementia lies between the semantic and lexical levels.