STIMULUS-LOCKED LATERALIZED READINESS POTENTIAL AND PERFORMANCE: USEFUL MARKERS FOR DIFFERENTIATING BETWEEN AMNESTIC SUBTYPES OF MILD COGNITIVE IMPAIRMENT

BACKGROUND: The findings of previous studies, in which event-related potentials (ERPs) related to stimulus evaluation were measured, do not fully explain the behavioral decline observed in amnestic mild cognitive impairment (aMCI; prodromal stage of Alzheimer’s Disease). OBJECTIVES: Motor ERPs were evaluated in this study with the aim of discovering complementary explanations and identifying aMCI biomarkers. DESIGN: Cross-sectional study. SETTING: Santiago de Compostela, Galicia, Spain. PARTICIPANTS: Nineteen healthy control (52-81 years old), 21 single-domain aMCI (sdaMCI; 51-87 years old) and 12 multi-domain aMCI (mdaMCI, 62-85 years old) adults. MEASUREMENTS: Reaction times (RTs), percentage of hits, and stimulus-locked and response-locked lateralized readiness potentials (sLRP and rLRP, indexes of response selection and preparation) were evaluated. RESULTS: mdaMCI participants showed longer RTs than control adults and less hits than control and sdaMCI participants. In addition, the mdaMCI group showed lower sLRP amplitudes than the control participants, and the sdaMCI group showed longer sLRP peak latencies. CONCLUSIONS: Control and sdaMCI groups did not differ in relation to RTs or hits, although sLRP peak latencies (sensitivity and specificity >.73) were longer in the sdaMCI group, which may be a sign of compensatory mechanisms or early indication of a decline in motor control. RTs were longer and sLRP amplitudes were smaller in the mdaMCI than in the Control group, and mdaMCI scored fewer hits than control and sdaMCI participants, indicating behavioral and neurocognitive deficits. The combination of hits and RTs discriminated mdaMCI from control adults (sensitivity and specificity >.82); and the combination of sLRP peak latency and hits discriminated mdaMCI from sdaMCI adults (sensitivity=1.00, specificity=.88).