Tip-of-the-tongue for proper names in mild cognitive impairment. Semantic or post-semantic impairments?

Difficulty in recalling the names of people is very common in the early stages of Alzheimer's disease and in mild cognitive impairment (MCI). However, it is not known whether the difficulty in naming people in MCI reflects problems associated with lexical access or with semantic access. The aims of the present study were to investigate semantic and phonological access to proper names by use of a Tip-of-the-tongue (TOT) task in individuals with multidomain amnestic MCI, individuals with amnestic MCI, and healthy controls, as well as to study the relationships between TOT production and performance in a free recall verbal memory test. In the individuals with multidomain amnestic MCI, the main process affected was phonological access: failures in phonological access were related to deficits in general cognitive functioning and in free recall verbal memory. Semantic access was not impaired in the either type of MCI. We interpret the findings in light of the transmission deficit hypothesis, as MCI involves a greater deficit in transmission from semantic to phonological representations than that produced by normal aging. We suggest that failure in phonological access may be the first step in the progression from MCI to AD as regards naming difficulties. (C) 2011 Elsevier Ltd. All rights reserved.