This is an observational study with the aim of validating, in a consistent population sample, with appropriate follow-up, whether EEG connectivity analysis combined with the neuropsychological evaluation and ApoE genotype testing in aMCI could be of help in early identification of converted aMCI as a first-line screening method in order to intercept early those subjects with a high risk for rapid progression to AD.

Primary aim of the present project is to investigate the dynamic connectivity among brain centers by using a mathematical (Small World) approach to the analysis of EEG-related neural networks. The aim is to provide reliable discrimination of amnesic-Mild Cognitive Impairment (a MCI) subjects who, on individual basis, will rapidly convert to Alzheimer Disease (AD) after a relatively brief follow-up. Moreover, keeping in mind that the epsilon-4 allele of the ApoE gene is a genetically determined risk factor for pathogenesis of late-onset AD, a secondary endpoint is introduced to investigate whether the EEG connectivity markers together with a genetically determined risk of dementia as represented by ApoE testing can reach higher sensitivity/specificity for early discrimination of MCI converting to AD

Exclusion criteria for AD will be:

• frontotemporal dementia;
• behavioural variant of frontotemporal dementia;
• vascular dementia;
• extra-pyramidal syndromes;
• reversible dementias (including pseudodementia of depression);
• Lewy body dementia.

The exclusion criteria for aMCI will be:

• mild AD, as diagnosed by standard protocols including National Institute on Aging-Alzheimer's Association workgroups (McKhann et al. 2011);
• evidence (including magnetic resonance imaging -MRI procedures) of concomitant dementia such as frontotemporal, vascular and reversible dementias (including pseudo-depressive dementia), marked fluctuations in cognitive performance compatible with Lewy body dementia and/or features of mixed dementias;
• evidence of concomitant extrapyramidal symptoms;
• clinical and indirect evidence of depression as revealed by the Geriatric Depression Scale GDS (Yesavage et al. 1982); scores lower than 14 (no depression);
• other psychiatric diseases, epilepsy, drug addiction, alcohol dependence, use of neuro/psychoactive drugs including acetylcholinesterase inhibitors;
• current or previous uncontrolled or complicated systemic diseases (including diabetes mellitus) or traumatic brain injuries.

Participants 150 aMCI will be recruited (including 90 already available EEG and clinical data recordings) in order to obtain two homogeneous sub-groups according to the clinical follow-up, classifying them as converted to AD or stable aMCI after a 12 to 24 months period from the time of baseline EEG recording.