Grabbing that morning cup of coffee may not seem like much at first, but with every movement, the brain sends thousands of neurological signals between it and the moving limb. Biological engineering researchers at N.C. State is working to harness these signals with electroencephalography, or EEGs, and use them to interpret the intent of patients with prosthetic limbs.

Knowing this intent will allow the prosthetic limb to move exactly where the user wants it to, essentially creating a bionic limb that mimics the natural control of the body part it replaces. Helen Huang, an associate bioengineering professor at N.C. State and UNC-Chapel Hill, is very involved in working with this technology. She said her aim is to integrate brain signal detection into prosthetic limbs.

According to Huang, most prosthetic limbs currently used are passive. A person must use their residual limbs to move the mechanical joints of a unit. This type of operation is less efficient than limb movement for an able-bodied person and requires much more energy. 

Recently, motorized prosthetic limbs have come into the market, providing people with the power to do more demanding activities than just walking or standing. These tasks could range from stepping upstairs to rising from a fall. The powered, robotic limb takes less energy to use than the more popular passive limbs.

However, motorized devices can be expensive, fragile, difficult to charge and don’t currently offer a user-friendly format of operation, according to Huang. 

“The problem we are trying to solve is control,” Huang said. “Whether it is passive or motorized, the person does not have that intuitive link with the device. We are trying to connect the user with the robotic device. If the person wants to bend the knee, the knee will bend. If the person wanted to switch from level walking to stair ascent, the knee and ankle could know right away.”

However, there are a few features that remain to be developed in this technology. The interpretation of neurological signals for upper bionic limbs is much easier than that of lower bionic limbs. According to Huang, this is because the motion of a leg is different than that of an arm.

When walking, the human brain is not actively thinking to put one foot in front of the other. It is a repetitive activity that takes an insignificant amount of thought, but once more complex activities are performed, such as lifting the body from a seated position, the brain becomes more conscious of the motion.

Due to this, Huang said it’s important to keep the low level control, which is needed for walking, as an autonomous action and include neurological controls only when conscious action is necessary in lower limbs. Figuring out which situations require someone’s intentions and which need only automatic movement of the device is the next step in the development of this technology. 

“Reading EEGs to decode intent is very difficult, especially during walking,” Huang said. “During the sequence, it is too noisy. The brain involves a lot of functions other than just walking. We have a lot of sensory signals. We see things. We think about things. So how do we detect anything that is correlated with a person’s intent to moving the lower limb? That is a question we are starting to look at.” 

Huang said she and her colleagues realize how robust the technology must be before sending it to the market, but in the future, it is possible that these new bionic limbs could give amputees the most efficient and user-friendly replacement limbs available.

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The above story is based on materials from Technician online . 
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