A method and apparatus for providing objective assessment of the brain state of a subject using a field portable device. The method includes placing an electrode set coupled to a handheld base unit on the subject's head, acquiring electrical brain signals from the subject through the electrode set, processing the acquired electrical brain signals using a feature extraction algorithm, classifying the extracted features into brain states, computing brain abnormality indices reflecting the probability of correct classification of brain state, and graphically displaying the classification result and the abnormality indices on the handheld base unit.
