"All the experiments we have conducted show that Alzheimer’s patients more easily use a feeling of familiarity to recognize information, to the extent that their failing episodic memory does not give them access to sufficient details to recall the entire context of an event”, points out Eric Salmon.

As “familiarity” is largely preserved at the start of Alzheimer’s, its use should be promoted because it seems to be able to be used as a compensatory mechanism allowing patients to continue to devote themselves to the fulfillment of routine daily tasks.

The burden of error

“Familiarity” is an explicit process by means of which the individual is capable of verbally expressing a sense of “déjà vu” which he feels. But it also has a common characteristic with the implicit phenomenon of priming conveying the fact that a first confrontation with a stimulus, the “prime”, can lead us, without our knowing it, to prefer this stimulus later (4). The characteristic common to both familiarity and priming is “fluency”, that “facility” which governs the evocation of certain information.

In 2008, after a study (5) involving several phases, Sylvie Willems, Eric Salmon and Martial Van der Linden showed that perceptual fluency does not help Alzheimer’s patients to improve their performances in terms of recognition by familiarity if they concentrate on details, but that it improves the (unconscious) priming and conscious recognition if the strategy adopted is a holistic one, that is to say, if the patient deals with the visual information as a whole. “In this case, recognition is as good at the beginning of the illness as in the controlled subjects”, indicates Eric Salmon.
   
In another very recent (6) study, researchers from the Ageing and Memory group showed that Alzheimer’s patients make erroneous judgments about their recent memory and that the extent of their erroneous assessment is correlated with the degree of atrophy of their hippocampus. “This element is not insignificant because it influences the choice of memory strategy”, insists Eric Salmon.

In conclusion, strategies centred on familiarity should be encouraged in Alzheimer’s patients even though they run the risk of leading to false recollections, such as when we meet an unknown person and believe that she is familiar to us. “Although very useful in a lot of cases, learning by trial and error is to be discouraged in cognitive readaptation strategies for Alzheimer’s patients”, insists Eric Salmon. It the patients fail because we overestimated the residual recollection capacity of their episodic memory, not only is there a high risk that they will repeat their mistakes but, moreover, some of them will feel devalued and others who are anosognosic will have feelings of anger, and will be persuaded that an attempt has been made to trick them. Consequently, the quality of the neuropsychological assessment more than ever constitutes one of the keys to the treatment of the Alzheimer’s patient.

(4) For example, it is possible that, for no apparent reason, after discussing botany with someone (enticement), we would prefer to take a walk in the woods rather than drink a coffee outside a café.
(5) Willems S. et al., Implicit/explicit memory dissociation in Alzheimer's disease: the consequence of inappropriate processing? Neuropsychology 22/710-717, 2008.
(6) Genon S. et al., Specific impairment of episodic metacognitive judgements in Alzheimer's disease: the role of the hippocampus (submitted for publication).