Deep brain stimulation has been developed as a substitute for the classical lesioning methods previously used in stereotactic and functional neurosurgery. Recent, anecdotal cases reports suggested that electrical stimulation of the cholinergic output of the Nucleus Basalis of Meynert (NBM) may improve cognitive performances, especially the memory tasks.

The present study aims to assess the effect of bilateral electrical stimulation of the NBM on the mnesic performance [assessed by the sum of the three free recalls of the Free and Cued Selective Recall Reminding Test (FCSRT)] in patients diagnosed with probable, moderate, Dementia with Lewy Bodies.

Inclusion Criteria:

• Diagnosis of probable Lewy-body dementia according to the internationally accepted consensus criteria (McKeith, 2005)
• Outpatients, male or female, aged between 18 to 75 years
• Moderate dementia defined by a mini-mental state examination (MMSE) score between 16 and 26
• Stable dose of cholinesterase inhibitors (maximal dose tolerated) for a minimum of 1 months
• Patients receiving antiparkinsonian treatment unmodified for 3 months, if treated
• French as native language
• Written informed consent of the patient
• Written informed consent of the caregiver

Exclusion Criteria:

• Other causes of dementia (Alzheimer dementia, vascular dementia, dementia associated with Parkinson's disease)
• Other causes of extrapyramidal symptoms (Parkinson's disease)
• Patients with a history of severe psychiatric disorders, such as psychosis. Earlier episodes of depression and/or anxiety without hospitalization are not exclusion criteria
• Contraindications for MR imaging (claustrophobia, metallic foreign bodies, pacemakers, etc)
• MRI evidence of cerebral microbleeds
• Surgical contraindications: especially, hemostatic disorders, severe cortical atrophy
• Patients receiving treatments that may interfere with the cholinergic system: anticholinergics, cholinomimetics.
• Patients receiving neuroleptics
• Patients with a history of alcohol or drug abuse
• Pre-existing structural brain abnormalities (such as tumor, infarction, or intracranial hematoma)
• Previous neurosurgical intervention
• Patients with a progressively fatal disease, or life expectancy £ one year
• Asthma
• Severe visual deficit of ophthalmic origin (such as glaucoma, age related macular degeneration, cataract)
• Fertile women not using adequate contraceptive methods
• Women who are pregnant or breast feeding