Implicit/explicit memory dissociation in Alzheimer's disease: the consequence of inappropriate processing?

Dual-process theories of recognition posit that perceptual fluency contributes to both familiarity-based explicit recognition and perceptual priming. However, the priming-without-recognition dissociation, as observed through the intact mere exposure effect and impaired recognition in patients with Alzheimer's disease (AD), might indicate that familiarity and perceptual priming are functionally distinct. This study investigated whether the AD patients' processing strategies at testing may explain this priming-without-recognition dissociation. First, we replicated the priming-without-recognition effect in 16 patients who exhibited intact exposure effects despite null recognition. Second, we showed that, under identical conditions, inducing a holistic processing strategy during recognition testing increased AD patients' recognition--performance was similar for AD patients and healthy control participants. Furthermore, prompting analytic processing during both priming and recognition tasks decreased AD patients' performance in both tasks. These findings suggest that the extent to which AD patients use perceptual fluency in priming and recognition tasks is contingent on their processing approach. The choice of processing strategy may depend on how difficult patients perceive the task to be.