Alzheimer's diseaseMild cognitive impairmentTheta-gamma phase amplitude couplingPhase locking valueOlfactory stimulationOddball taskBrain oscillationsSynchronizationElectroencephalogramMILD COGNITIVE IMPAIRMENTPHASE-LOCKING VALUEGAMMA OSCILLATIONSTHETA-OSCILLATIONSWORKING-MEMORYNEURAL OSCILLATIONSEEG SYNCHRONIZATIONHIPPOCAMPAL THETAAMNESTIC MCIFREQUENCY