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

Objective:To 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).

Methods:AERPs 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.

Results:A 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.

Conclusions:N200 amplitude is more sensitive in identifying differences over time at the early stages of the disease, whereas P300 latency at later stages.

Significance:A 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.