Encoding processes influence word-stem completion priming in Alzheimer's disease: a meta-analysis.

Despite the numerous studies focused on priming performances in Alzheimer's disease (AD), the question of whether word-stem completion priming persists in AD is still prone to controversy. Methodological variations, such as encoding instructions, have been proposed to explain the discrepancy of word-stem completion priming results in AD. We conducted a meta-analysis on 678 AD patients and 640 controls to assess whether word-stem completion priming in AD differs according to instructions provided at encoding. When the data across the different encoding instructions were combined, the results showed that AD patients manifest significant completion priming, even though the magnitude of priming is reduced. Taking into account the different encoding conditions, the results suggested that whereas completion priming is impaired in AD when encoding conditions consist in reading or rating words, priming is equivalent to that of controls when encoding conditions require semantic judgments or generating words. In this latter condition in particular, self-generating a word at encoding may provide an aid to partially overcome conceptual deficits of the patients and increase the degree of adequacy between cognitive operations employed at encoding phase and those triggering implicit retrieval.