Ultrasonic energy is used for treating degenerative dementia. A focal point of an ultrasonic transducer beam is directed at a target area of the brain to promote removal of substances that accumulate in the interstitial pathways that are at least partially responsible for the degenerative dementia. In one example, the target area of the brain may comprise the hippocampus and the degenerative dementia may be Alzheimer's disease. The ultrasonic beam may stimulate brain tissue at a frequency that corresponds to a naturally occurring deep sleep burst frequency of neurons and subsequent astrocyte activation patterns that drive a convective process responsible for brain solute disposal. For example, the transducer may generate a burst frequency of between 1-4 hertz to stimulate deep sleep brain functions that help remove amyloid plaque.