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The Korea Institute of Science and Technology (KIST) announced that a research team led, by Dr. Hyungmin Kim at the Center for Bionics, Biomedical Research Institute of the KIST, found a strong correlation between a ultrasonic stroke rehabilitation method for treating damaged brain and a change in delta waves, which is a type of brain waves.

A stroke is the result of a cerebrovascular hemorrhage/infarction and is a disease with a high mortality rate. Even when a stroke does not lead to death, it results in the blockage of the affected person's blood supply and damage to the nerve cells, causing the impairment of physical movement. Many researches are underway on post-stroke rehabilitation methods that can be used to repair damaged brain.

Dr. Hyungmin Kim of the KIST recently published a study on hemiparalysis treatment for motor function recovery, a treatment in which the deep cerebellum is stimulated using low-intensity focused ultrasound stimulation (Neurorehabil Neural Repair. 2018 Sep;32(9):777-787). This treatment method, which can be used to treat stroke patients with various brain lesions, has received much attention as it does not require surgical procedures and can be used to selectively stimulate deeper parts of the brain areas.

To apply this method for various stroke treatments, a 'stimulation guide' is required. This can be used to assess the patient's prognosis after brain stimulation and to optimize the intensity and frequency of the stimulation for maximizing motor function recovery.

In order to develop such a guide, the KIST research team observed changes in the brain waves of the nerve cells of stroke lesions during treatment. In particular, the research team observed and analyzed changes in delta waves (1-4 Hz), which abnormally increase in brain lesions, in both the normal cerebral hemisphere and the cerebral hemisphere affected by the legion.

The KIST research conducted the ultrasound stimulation treatment on the deep cerebellum of mice for three days. On the first day, the motor functions of the mice improved almost three-fold, and on the fourth day, the mice were able to retain their improved motor functions. During the experiment, changes in the delta waves were observed, which increased up to three times, confirming that interhemispheric balance was retained and held steady at a normal level in the ultrasound stimulation group.

The study found that ultrasound stimulation can suppress delta waves and induce a change in damaged brain, signifying the improvement of motor functions. If a patient-specific ultrasound stimulation method can be developed by monitoring brain waves, this type of treatment can be translated from animal experimentation to actual patient treatment.

"Given that ultrasound brain stimulation progresses at a rapid pace and given that it is being studied in relation to various brain diseases, it will likely be used as an effective stroke treatment in the near future," said Dr. Hyungmin Kim of the KIST. "In order to develop an ultrasound stimulation treatment, it is essential to verify the safety of such treatment based on the careful observation and long-term tracking of various stimulation conditions."

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The research, supported by the Ministry of Science and ICT (MSIT), was conducted as part of the Creative Conversion Research Project of the National Research Council of Science & Technology (NST). A journal article explaining the results of the research was published in the latest issue of IEEE Transactions on Neural Systems & Rehabilitation Engineering, an international journal on rehabilitation.