In patients suffering from Alzheimer’s disease, the first impairments generally concern episodic memory which involves personally experienced events. By conducting several studies, the Ageing and Memory group of the Cyclotron Research Centre, University of Liege has explored how memory is functioning and also how it is malfunctioning in patients suffering from this dementia. “All the experiments have shown that Alzheimer’s patients more easily use a feeling of familiarity to recognize a piece of information because their failing episodic memory does not allow them accessing to sufficient details in order to be able to remember the entire context of an event”, explains doctor Eric Salmon, coordinating neurologist at the Memory Centre and the Neuropsychology Unit of the University Hospital of Liege. Since “familiarity” is largely preserved at early stages of Alzheimer’s, its use should be promoted as it seems possible that it can be used as a compensatory mechanism enabling patients to continue to devote themselves to the fulfillment of routine daily activities.

Memory is not a single entity. Since the work of the Canadian researcher Endel Tulving (1995), many authors support the idea that it is sub-divided into several independent entities which interact with each other, supported by different cerebral networks. In the Alzheimer’s patient all forms of memory are affected, but to varying degrees. At the beginning of the condition, it is mostly episodic memory that is affected, the “receptacle” for personally experienced events whose spatial and temporal context can be identified. For example, someone will remember having run out of petrol on the Paris-Lyon motorway in August 2010 while there was a heat wave and his wife was seven months pregnant. Another will remember his godchild being photographed sitting on Santa’s lap dressed in blue in a department store in the center of Brussels.

Memory of recent events, those which are produced a few minutes, a few hours, a few days or a few months previously, seem to be the first casualties of memory loss in Alzheimer’s. Therefore such a patient will not remember having switched on his cooker ten minutes earlier and another will not remember having made a bank transfer at the beginning of the previous month.

 “We think that, in the initial phases of the illness, episodic memory of previous phenomena is relatively well preserved”, indicates Professor Eric Salmon, coordinating neurologist at the Memory Centre and Neuropsychology Unit of the University Hospital of Liege and vice-president of the Cyclotron Research Centre of the University of Liege (ULg). He goes on to explain, “It is probable that older memories are stored in regions of the brain which have been protected from the illness for a longer period, at a time when the storing mechanism was not yet failing”.

Nevertheless, the question of the quality of these “older memories” arises because everything seems to point to the fact that they frequently risk losing their episodic character and tend to drift towards the area of semantic memory which is the seat of our “general knowledge of the world”. It is this form of memory which tells us that Rome is the capital of Italy, that during a religious wedding the bride generally wears white or that when we are in a restaurant we should be seated, read the menu, eat and ask for the bill and then pay. “Alzheimer’s patients have a tendency to recall only the main currents of events which they have lived in the past, without contextual details”, confirms Eric Salmon.