A sensor assembly for measuring electromagnetic activity of a brain of a subject, comprising: - a support plate having first and second sides; - a plurality of electrodes orientable toward the subject's scalp, the electrodes arranged in a spaced array, one of the plurality of electrodes comprising a reference electrode; - a plurality of amplifiers, each amplifier of the plurality of amplifiers associated with one of the plurality of electrodes to receive signals from the associated ones of the electrodes indicative of electric field activity of the brain; wherein the plurality of electrodes protrude from the first side of the support plate and the plurality of amplifiers arranged on the second side of the support plate, and characterized in that the sensor assembly further comprises: - a microcontroller in communication with the amplifiers to receive signals from the amplifiers, the microcontroller including a processor operative to determine a weighted average of the signals indicative of an electric field generated by electromagnetic activity of the brain, wherein an x-component (E x) of the electric field generated by the electromagnetic activity of the brain is determined by calculating the weighted average from a sum of potential signals from each active electrode relative to the reference electrode multiplied by a square of the distance from each active electrode to a center of the spaced array, the sum divided by a further sum of the square of an x-coordinate of each active electrode with respect to the center of the array, and wherein a y-component (E y) of the electric field generated by the electromagnetic activity of the brain is determined by calculating the weighted average from a sum of potential signals from each active electrode relative to the reference electrode multiplied by a square of the distance from each active electrode to a center of the spaced array, the sum divided by a further sum of the square of a y-coordinate of each active electrode with respect to the center of the array. - a support plate having first and second sides; - a plurality of electrodes orientable toward the subject's scalp, the electrodes arranged in a spaced array, one of the plurality of electrodes comprising a reference electrode; - a plurality of amplifiers, each amplifier of the plurality of amplifiers associated with one of the plurality of electrodes to receive signals from the associated ones of the electrodes indicative of electric field activity of the brain; the plurality of electrodes protrude from the first side of the support plate and the plurality of amplifiers arranged on the second side of the support plate, and characterized in that the sensor assembly further comprises: - a microcontroller in communication with the amplifiers to receive signals from the amplifiers, the microcontroller including a processor operative to determine a weighted average of the signals indicative of an electric field generated by electromagnetic activity of the brain, - a microcontroller in communication with the amplifiers to receive signals from the amplifiers, the microcontroller including a processor operative to determine a weighted average of the signals indicative of an electric field generated by electromagnetic activity of the brain,