Proper name anomia is a frequent finding among patients in the early stages of Alzheimer’s disease. The present study investigates naming of famous persons in a group of DAT patients, a group of persons with mild cognitive impairment (MCI) and healthy controls. The study is aimed at distinguishing the relative contributions of semantic and post-semantic factors to difficulties in proper name retrieval. As shown by a significantly lower score in answering semantic questions, DAT patients retrieve less biographical knowledge related to famous persons than healthy elderly subjects and persons with mild cognitive impairment. This finding is in line with the frequent observation of semantic deficits in early and moderate DAT. The high number of Tip-of-the-Tongue (TOT) answers in DAT found in relation to few spontaneously named items shows that post-semantic deficits are as important as semantic deficits in determining anomia for people names in DAT. Moreover, DAT patients were less sensitive to phonological cueing than healthy persons or persons with mild cognitive impairment. These findings suggest that proper name anomia in DAT is not only due to semantic deficits, but also to problems in accessing the phonological representation, as well as to a degradation of phonological representations. Thus, naming deficits in DAT differ not only quantitatively, but also qualitatively from the difficulties of healthy elderly persons. No significant differences were found between persons with mild cognitive impairment and healthy controls in proper name retrieval.
Difficulty in retrieving names of people is a frequent finding among patients in the early stages of Alzheimer’s disease (Perry & Hodges, 1996; Hodges, & Salmon, & Butters, 1993; Greene & Hodges, 1996; Semenza, 1997; Yasuda, Nakamura, & Beckman, 2000). Indeed, it seems to be already present at a stage where according to the standard criteria (NINCDS-ADRDA; (McKkann et al., 1984)), a diagnosis of DAT is still far from being safe. A longitudinal study on subjects suspected of DAT (Semenza, Borgo, Mondini, Pasini, & Sgaramella, in press) showed, for example, that simple tests requiring people names retrieval could effectively discriminate between those patients who eventually developed DAT and subjects who would instead receive other diagnoses (such as pseudodementia, vascular dementia, etc.) at the time where even extensive batteries for dementia screening (e.g. MODA (Brazelli, Capitani, Della Sala, Spinnler, & Zuffi, 1994)) could not.
Anomia for people names is thus an early and therefore a very important symptom of DAT. Indeed, it may be considered as a pathological increment of a phenomenon that belongs otherwise to the intrinsic characteristics of human memory and the physiological changes it undergoes with age. In fact, a widespread literature documents word finding difficulties with increasing age and it is widely accepted that proper names (of which people names are the best studied) are not only intrinsically more difficult to retrieve but also disproportionally sensitive to the age factor. Although experimental support for this view is surprisingly little and only recently produced (Cohen & Burke, 1993; Nicholas, Barth, Obler, Au, & Albert, 1997; Semenza, Nichelli, & Gamboz, 1996), it can now be safely claimed that (a) proper names are generally at disadvantage with respect to common names, (b) this disadvantage becomes larger with the age of 70, and, finally (c) in DAT the age-related disadvantage of proper names is dramatically pronounced.
The nature of the proper name deficit found in DAT remains, however, to be fully investigated. While in studies with patients after focal lesions the importance of lexical activation has been stressed (Semenza and Zettin, 1988 and Semenza and Zettin, 1989; Semenza, Zettin, & Borgo, 1998), proper name anomia in DAT would reflect primarily a loss of stored semantic knowledge about the identity of familiar people (Della Sala, 1995). This may not, though, be the whole explanation. In the particular case of DAT, other post-semantic deficits, as, for example phonological degradation, may contribute as well to proper names anomia—in which proportion remains to be established.
The present study is aimed at distinguishing the relative contributions of semantic and post-semantic factors. Semantic knowledge is tested by specific questions regarding biographic information of famous persons. The contribution of post-semantic factors is estimated by the analysis of the frequently observed Tip-of-the-Tongue (TOT) phenomenon and its sensitivity to phonological cueing. A TOT word is in the lexicon of a speaker, but is temporarily inaccessible (e.g. (Burke, MacKay, Worthley, & Wade, 1991)). Better knowledge of the processing stages at which people name anomia arises may dictate better intervention strategies to cope with a socially very embarrassing symptom. With respect to previous studies post-semantic stages will be more thoroughly investigated. The issue will also be addressed whether anomia for proper names in DAT represents indeed a quantitative increment of age-related memory changes or has qualitative differences as well.
Neuropsychological background tests evidenced multiple deficits in the DAT group, but not in the MCI group. MCI group and controls differed in two measures of verbal memory (free recall and recognition). DAT patients showed deficits in verbal learning (CERAD), in verbal and visual memory (CERAD), in naming (short form of the Boston Naming Test which is part of the CERAD), in verbal fluency (names and S-words in 2 min), in verbal intelligence (VKI), in space perception (number location, VOSP) and in an interference task (NAI). DAT patients thus showed the typical profile with multiple cognitive deficits. Both patients groups scored in the normal range in the depression screening (GDS) Table 1.
