1. A method for assessing neural activation of a brain, comprising: sensing one or more bioelectrical signals from one or more electrodes in contact with or proximate the brain; measuring the amplitude of the one or more bioelectrical signals over a period of time; calculating a plurality of variance values from the amplitude of the one or more bioelectrical signals, each of the variance values of the plurality corresponding to the variance of the amplitude for a different interval of time of the period of time with respect to the other variance values of the plurality of variance values; and assessing the relative level of neural activation of an area of the brain based on the plurality of variance values, wherein the area of the brain is assessed to have a relatively higher level of neural activation when the variance is relatively higher and the area of the brain is assessed to have a relatively lower level of neural activation when the variance is relatively lower and wherein sensing, measuring, calculating, and assessing are each performed at least in part by control circuitry.