Cholinergic dysfunction, neurodegeneration, and amyloid-beta pathology in neurodegenerative diseases.

•Cholinergic dysfunction measured by the Electroencephalography-Acetylcholine index correlates with reduced hippocampal volume and thinner cortex in several frontal, temporal, and occipital regions.•Cholinergic dysfunction seems to be downstream to biomarkers of amyloid-beta pathology (CSF Aβ) and neurodegeneration (CSF total tau and hippocampal volume).•The Electroencephalography-Acetylcholine index is a useful biomarker for cholinergic dysfunction in vivo, with value for differential diagnosis of dementia and monitoring patients at the dementia stage.•The Electroencephalography-Acetylcholine index could be used to monitor treatment with cholinesterase inhibitors.