Cognitive event-related potentials: Longitudinal changes in mild cognitive impairment

ObjectiveTo measure changes over time in the latency and amplitude of the major waves of auditory event-related potentials (AERP) and their correlation with the memory status of patients with mild cognitive impairment (MCI).MethodsAERPs were recorded in 22 MCI patients (mean ± SD age = 67.4 ± 7.8, median (interquartile range-IQR) MMSE score = 28 (27–29) in three consecutive exams and in 30 age-matched controls at baseline. During this time period, 3 patients converted to Alzheimer disease (AD). Latencies and amplitudes of N200, P300 and Slow Wave and the N200–P300 peak-to-peak amplitudes and latencies were determined, and correlation coefficients (CC) between them and MMSE scores were calculated.ResultsA significant increase in the P300 latency and a decrease in the N200 amplitude were observed between the exams. Only N200 latency correlated with baseline MMSE scores, whereas P300 and Slow Wave latencies correlated with age.ConclusionsN200 amplitude is more sensitive in identifying differences over time at the early stages of the disease, whereas P300 latency at later stages.SignificanceA new N2–P3 inter-peak index that incorporates changes in N200 and P300 latencies and amplitudes into a single parameter is introduced in order to adequately describe the gradual progress of MCI and its transition to AD.

Research highlights► Sensitivity of a new neurophysiological index in AD diagnosis. ► N200 amplitude is more sensitive in identifying differences over time at the early stages of AD, whereas P300 latency at later stages. ► Marked difference was observed in the values of ERP parameters between MCI stable patients and AD converters.