Magnetic resonance (MR) imaging-guided ultrasound, a technology that involves highly-targeted ultrasound beams and monitoring their effects through imaging, has shown to help treat symptoms of Alzheimer’s disease in mice. The treatment was found to improve brain performance in the animals and has the researchers hopeful that the technique may prove effective in improving cognitive behavior in humans.

Scientists at Toronto's Sunnybrook Research Institute were exploring the effects of the therapy on transgenic mice, a variant of mice that have increased plaque on the hippocampus (a part of the brain responsible for memory). These mice show symptoms typical of Alzheimer’s in humans, such as memory loss and learning difficulties, and are therefore used in research relating to the disease.

Using a microbubble contrast agent, the researchers found that they were able to temporarily open up the blood-brain barrier, a passageway to the brain. But only when the microbubbles travel through the high-intensity ultrasound beam do they have this effect, clearing the way for a more effective delivery of drugs.

The plaque abnormalities on untreated transgenic mice (left) and the brain of a transgenic mouse that has been treated with MR imaging-guided focused ultrasound (right)(Image: Kullervo Hynynen, Sunnybrook Research Institute)

Using this technique to treat the transgenic mice, they observed improvements in cognition and spatial learning. They say a possible reason for this is a boost in neuronal plasticity resulting from the ultrasound beam, combined with a reduction of brain plaque, the presence of which in humans correlates with symptoms of Alzheimer’s. The team also reported an increase in the number of neurons and dendrite length, the tree-like extensions of neurons that help them communicate with other neurons.

"The results are an exciting step in the search for Alzheimer’s treatments," says Steven Krosnick, Program Director for Image-Guided Interventions at the National Institute of Biomedical Imaging and Bioengineering at Nation Institutes of Health. "But there is more to be done. There are limitations on the memory tests that can be done on mice, and human cognition is significantly more complex. Hopefully these results will open doors to more research on how MR imaging-guided focused ultrasound could benefit cognition and perhaps be magnified by using other therapeutics in conjunction with this method."

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