The present invention is directed to a method of continuously monitoring neuronal synchronization in a subject comprising (a) determining a deviation in mean synchronization (R) from a predetermined value at rest, wherein the pre-determined value of R is 1, and the variability of synchronization H； and (b) repeating step (a) one or more times to continuously monitor synchronization R and its variability H in a subject. The invention also features methods of determining and monitoring the degree of brain excitability. The invention furthermore features methods of determining or monitoring the degree of sleep deprivation in a subject, methods of identifying subjects that are susceptible to a sleep disorder and methods of diagnosing a sleep disorder in a subject.
