Neurophysiological techniques (e.g., electroencephalography, EEG, transcranial magnetic stimulation, TMS) allow an informed investigation of the brain overexcitability underpinning the typical difficulty of maintaining a stable level of vigilance or experiencing a regular sleep-wake cycle in patients living with Alzheimer’s disease (AD). Importantly, this difficulty has a significant impact on the level of consciousness of patients, affecting patients’ ability to follow TV programs and social conversation during the daytime and preventing a deep sleep at night. As an important advantage, neurophysiological techniques can be applied in preclinical and clinical research models of the disease, its progression, and the effects of pharmacological and non-pharmacological interventions.