A system comprising: a lead; one or more electrodes (724, 726) that are on the lead and are configured to sense bioelectrical activity of a brain; and control circuitry configured to: sense one or more local field potential signals using the one or more electrodes; measure the amplitude of the one or more LFP signals over a period of time; calculate a plurality of variance values from the amplitude of the one or more LFP 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 estimate a number of activated synapses in an area of the brain based on the plurality of variance values; and assess the relative level of neural activation of the area of the brain based on the number of activated synapses estimated and the plurality of variance values calculated, 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. a lead; one or more electrodes (724, 726) that are on the lead and are configured to sense bioelectrical activity of a brain; and control circuitry configured to: sense one or more local field potential signals using the one or more electrodes; measure the amplitude of the one or more LFP signals over a period of time; calculate a plurality of variance values from the amplitude of the one or more LFP 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 estimate a number of activated synapses in an area of the brain based on the plurality of variance values; and assess the relative level of neural activation of the area of the brain based on the number of activated synapses estimated and the plurality of variance values calculated, 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. sense one or more local field potential signals using the one or more electrodes; measure the amplitude of the one or more LFP signals over a period of time; calculate a plurality of variance values from the amplitude of the one or more LFP 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 estimate a number of activated synapses in an area of the brain based on the plurality of variance values; and assess the relative level of neural activation of the area of the brain based on the number of activated synapses estimated and the plurality of variance values calculated, 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.