1. A method for measuring brain activity of a subject comprising the steps of: (a) subjecting the subject to at least one first stimulus of interest, measuring brain activity of the subject during a first period of interest, and generating a first brain map for the subject; (b) subjecting the subject to at least one second stimulus of interest, measuring brain activity of the subject during a second period of interest, and generating a second brain map for the subject; (c) generating a first contrast brain map for the subject by subtracting a parameter of interest of the second brain map from the parameter of interest of the first brain map; (d) generating a second contrast brain map for the subject by subtracting the parameter of interest of the first brain map from the parameter of interest of the second brain map; and (e) determining if the subject responded to the first or the second stimulus of interest as follows: i) if the parameter of interest of the first contrast map is greater than the parameter of interest of the second contrast map, then the subject is determined to have responded to the first stimulus of interest; ii) if the parameter of interest of the second contrast map is greater than the parameter of interest of the first contrast map, then the subject is determined to have responded to the second stimulus of interest.