Visual recognition memory (VRM) is impaired early in Alzheimer's Disease (AD), but would rely on two processes: familiarity (mere feeling that an item has been seen previously) and recollection (retrieval of details associated to the item at encoding). If recollection is clearly impaired in early AD, results concerning familiarity remain contradictory. Supposed to be faster than recollection, familiarity should be better understood using a temporal approach. Its possible impairment in AD could then be better understood. In order to test this, a behavioural procedure was designed: the SAB (Speed and Accuracy Boosting). Revealing different properties of VRM (its speed-limit, Articles 1 and 2; its "bottom-up" nature, Article 3) and some of its processes (familiarity appears indeed faster than recollection, Article 1), results showed that the SAB procedure was mainly assessing familiarity (Article 1). In patients at risk of AD, an unexpected dissociation within familiarity processes was evidenced, with an impairment of late signals of familiarity (as used for classical judgements), but a preservation of the first signals (supporting fast detection assessed with the SAB) (Article 4). Last, manual segmentation of MRI images of the medial temporal lobe (first cerebral regions affected in AD, known for their key role in VRM) was also used to assess age effect at the early stage of AD (Article 5). Independently, both methods allowed understanding better the VRM and its impairment in early AD; their combination appears very promising.
