Implicit learning of new auditory and visual knowledge in patients suffering from Alzheimer’s disease

Responsible : Hervé Platel et Karine Lebreton

Post-doctoral : Mathilde Groussard

Collaborations : Odile Letortu, Caroline Mauger and Biéville-Beuville care home

Learning songs in two patients with Alzheimer

Patients with Alzheimer’s disease have a severe and early impairment of declarative memory (especially episodic memory). However, we have shown that repeated exposure enables patients to learn and then spontaneously produce new songs, in the absence of all explicit recollection of the learning sessions.

This research program presents a fundamental interest for a better comprehension of the mechanisms of the human memory, questioning the ascending relations between implicit and explicit memory processes, and offers also a clinical interest in developing new strategies of cognitive stimulation and care of Azheimer patients at various stages of evolution of the illness.

This is a two-phase study.Phase 1, which is already underway, involves the collection of behavioural data using several types of ecological information (linguistic, musical and pictorial, plus photographs of objects). Two previous experiments (Samson S, Dellacherie D, Platel H (2009). Emotional power of music in patients with memory disorders: clinical implications of cognitive neuroscience. Ann N Y Acad Sci 1169 : 245-255), showed that these patients have excellent implicit learning abilities for musical and pictorial material, but very poor ones for stimuli that are purely linguistic (short texts, poems). Following on from these, we have developed several behavioural protocols, adapting existing methodologies to the patients’ levels of impairment.

Increased sense of familiarity in 12 AD patients (MMS between 5 and 19) for six unknown paintings of paintings exhibited 8 times.

Phase 2 will comprise a fMRI neuroimaging experiment which will be conducted with those AD patients in the moderate to severe stages of dementia who manifested a feeling of familiarity during the exposure sessions. Given the severity of their cognitive disturbances (Mini-Mental State Examination (MMSE) ≤ 20), the measurement of brain activity will simply consist in showing them 1) old familiar stimuli (e.g., portrait of the Mona Lisa), 2) stimuli that have become familiar to them in the course of the preceding sessions, and 3) unfamiliar stimuli. By comparing brain activity for these three different categories of stimuli, we should be able to delineate the neural networks responsible for this preserved learning ability. A population of healthy age-matched controls will perform the same task, along with a “control” musical familiarity test for which we have already collected data from healthy young individuals (Groussard M, Rauchs G, Landeau B, Viader F, Desgranges B, Eustache F, Platel H (2012). The neural substrates of musical memory revealed by fMRI and two semantic tasks. Neuroimage 53:1301-1309. IF: 5.739. Groussard M, Viader F, Hubert V, Landeau B, Abbas A, Desgranges B, Eustache F, Platel H (2010). Musical and verbal semantic memory: two distinct neural networks ? Neuroimage 49:2764-2773. IF: 5.739.)