Non-invasive brain stimulation techniques can reveal early synaptic dysfunction, characterise pathophysiological changes in cortical circuits and predict disease progression in Alzheimer disease

Motta and coworkers ( in their JNNP paper1) used a non-invasive repetitive transcranial magnetic stimulation (TMS) protocol to evaluate brain plasticity in patients with Alzheimer disease (AD). More than 15 years ago, we showed for the first time that a TMS test based on coupling motor cortex stimulation with peripheral nerve stimulation, termed short latency afferent inhibition (SAI), can probe central cholinergic pathways in humans2 and reveal cholinergic dysfunction in patients with AD.3 Several studies confirmed these findings in the following years and showed that SAI may contribute to (1) diagnosis of other forms of cholinergic dementia such as dementia with Lewy bodies; (2) differential diagnosis of different forms of dementia that present …