A device is provided, for detecting a brain response state of a subject by determining cellular variance and/or volatility of at least one neuron's evoked response. The device comprises a sound stimuli generating unit operative to repeatedly present the subject with a sound stimulus for evoking a brain response. The device further comprises a detection unit operative to detect the evoked brain response signal related to the sound stimulus and a storage unit operative to store information based on evoked brain response signal. Further the device comprises a control unit for determining a window having a time width covering at least partly an area of the one neuron's evoked response, and for calculating an average response signal over the window, and for determining the cellular variance and/or volatility for the area of said one neuron's evoked response by using the average response signal
