Subjective memory impairment and cholinergic transmission: a TMS study.

Subjective memory impairment (SMI) is being increasingly recognized as a preclinical phase of Alzheimer disease (AD). Short latency afferent inhibition (SAI) is helpful in demonstrating dysfunction of central cholinergic circuits, and was reported to be abnormal in patients with AD and amnestic multiple domain mild cognitive impairment. In this study, we found normal SAI in 20 subjects with SMI. SAI could be a useful biomarker for identifying, among individuals with memory complaints, those in whom cholinergic degeneration has occurred.