Alzheimer’s: when you don’t know that you know…
3/15/17

Alzheimer’s patients generally have a propensity to overestimate the strength of their episodic memory which is a category of memory that enables an individual to store and be aware of personally experienced events. A study conducted by researchers in the Cyclotron Research Center of the University of Liege, which was recently published in the magazine Cortex, found that the opposite was true in fact. In addition, they showed that the more the patients had a tendency to make inappropriate judgments, the less grey matter was contained in a particular region of their brain.

Alzheimer prediction FOTOLIA

Anosognosia
 describes patients who have limited or no awareness of their physical, cognitive or behavioral deficits. (see also the article “self-unconsciousness”). Hemispatial neglect is a prime, almost caricatural example of a patient’s inability to have a clear knowledge of their state. Following a cerebrovascular accident (CVA) in the right hemisphere, some patients permanently behave as though their knowledge of the left side of space has been greatly reduced or in some cases, has disappeared completely. Those patients who are most affected by the condition bump into furniture and walls located on their left side, forget to shave or make up the left side of the face, or neglect to eat food on the left side of their plate... Some even have their head permanently turned to the right.

Anosognosia is particularly frequent in cases of dementia. Thus, in the case of Alzheimer’s disease, despite some discrepancies between different studies, it is estimated that 10 to 15% of patients in the early stages of the disease are anosognosic and this figure can be as high as 40 to 50% during the more severe stages of the disease.

Sarah Genon, a doctor of psychology and a scientific collaborator at the Cyclotron Research Center (CRC) of the University of Liege, is currently working on modelling the relationships between the brain and behavior. In addition, she has conducted a study (1) at the CRC which was published in October 2016 in the magazine Cortex. This research is not unrelated to anosognosia, because it deals with the metacognition skills of Alzheimer’s patients with regard to two types of   memory: episodic memory, which is a category of memory that enables an individual to store and be aware of personally experienced events, and semantic memory, which gives us our general knowledge of the world – this type of memory enables us to know that Rome is the capital of Italy or that Donald Trump is the new president of the United States… Metacognition defines the mental activity an individual uses to control his or her own mental processes. Imagine that on a given morning you don’t have to go to your usual place of work but you have to go to a different location. If, by some automatic reflex, you follow your usual route, you will eventually realize your mistake and rectify it. This awareness of poor performance in the above situation, concerning another mental process that is lower in hierarchical order, is an example of metacognition.

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Numerous works have shown that, in the case of Alzheimer’s, episodic memory is generally altered at an early stage, while semantic memory is preserved for a longer time. The reason for this is that episodic memory involves conscious and controlled processes which are underpinned by a large number of brain regions, while semantic memory is supported by more automatic processes. The question raised by the recent article in Cortex was: how do Alzheimer patients judge their memory processes? Sarah Genon dealt with this question by examining the way in which patients, who in this case were in the early stages of the disease, predicted their own memory performance in terms of their episodic or semantic memory. “We wanted to compare the processes of metacognition for these two types of memory by means of an identical task while using the same type of material”, explains Sarah Genon. This had never been done before. Moreover, the researchers wanted to use a relatively environmental task, one that resembled daily life as much as possible.

(1) Genon S, Simon J, Bahri MA, Collette F, Souchay C, Jaspar M, Bastin C, Salmon E, Relating pessimistic memory predictions to Alzheimer's disease brain structure, Cortex 2016. Pii: S0010-9452(16)30261-1. Doi: 10.1016/j.cortex.2016.09.014.

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