In the field of metacognition linked with episodic memory, the results of the study published in Cortex came as a surprise to the authors themselves. Firstly, the results went against the notion of anosognosia, a neuropsychological disorder typically described in cases of Alzheimer’s disease. Secondly, they contradict a study (2) conducted previously by a Franco-English team at the University of Leeds, in which patients over-estimated the probability of being able to carry out an episodic memory task. In any event, the nature of the experiment was not the same. In the first place, the task to be completed was not environmental: it depended on the association of words without any particular connection (“chair” and “apple”, for example). The patient had to recall the second term of a pair the first term of which was suggested to him or her. Subsequently and most importantly, the test only included some twenty items. This led Sarah Genon to offer an explanatory hypothesis: “It is probable that the first reaction of Alzheimer’s patients instructed to complete a task which they were not used to, was to overestimate their ability. In the task we designed, they often failed during the learning stage, which was arduous. They were therefore confronted with their difficulties” The researcher adds: “Several studies have revealed that, even among anosognosic patients, it is possible to induce a very temporary awareness of their memory dysfunction during the execution of a task”.

In a study not yet published, the researcher comes to a conclusion that is contrary to the one she reached in her first work. But here, once again, the task was easier and involved only 20 items. The patients only needed to recall a first name, so the test was more ludic… In short, there were fewer failures during the learning phase. In her opinion, it should be concluded from the limited data available, that Alzheimer’s patients poorly judge their memory function, in accordance with the social environment and the circumstances.

Cortical stimulation?

The article which appeared in October 2016 in Cortex demonstrates the existence of a correlation between the number of inappropriate judgements and the volume of grey matter in Alzheimer’s patients measured by Structural MRI. The more the patients make mistakes concerning their memory skills, the less grey matter is present in a certain region of the brain: the right prefrontal lateral cortex, which is known to be involved in monitoring processes such as those that enable us to control our behavior and to select relevant information, or to “manage” our memory.

What is the significance of the work conducted by Sarah Genon? “It seems to me that our study is important in terms of understanding the beliefs of Alzheimer’s patients about their memory and also to develop neuropsychological strategies”, says the CRC collaborator. “In a wider context, the study will be extended to determine how Alzheimer’s patients form their beliefs about their memory and how to improve the awareness they have of their everyday functions. In this way, their care could be improved”.

An understanding of how to proceed in order to influence the judgement a patient has about his or her own memory capability still needs to be found. Failure could theoretically be a way to fight anosognosia and its corollary, overestimation of their memory skills as demonstrated by many patients when they assess their memory capabilities (or others). “This strategy would not be appropriate because different studies(3) have revealed that failure generates negative emotions and that, in spite of everything, this experience does not change anosognosia”, says Sarah Genon.

She adds that promising approaches could involve Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (TDCS). Work conducted on young subjects revealed that their predictions regarding their memory performance can be improved by such cortical stimulations administered to median prefrontal regions, but also, according to certain studies, to the prefrontal lateral regions. For the moment, the experiments undertaken are limited to highlighting the existence of improvements in metacognition over periods of a few hours. Can we consider that the effects are lasting? It remains a mystery for now. In addition, there is no available information relative to the efficacy of these stimulations in Alzheimer’s patients. For now, we’ll have to wait and see.

(2) Souchay, C., Isingrini, M., Gil, M. Alzheimer's disease and feeling-of-knowing in episodic memory. Neuropsychologia 40: 2386-2396, 2002.
(3) Mograbi, D.C., & Morris, R. G. On the relation among mood, apathy, and anosognosia in Alzheimer’s disease. Journal of the International Neuropsychological Society 20: 2-7, 2014.