A team of researchers from the University of Houston has developed an algorithm that allowed a 56 year-old man whose right hand had been amputated to grasp objects with a high-tech bionic hand powered by his thoughts. The innocuous technique monitors the activity in the brain to determine the regions involved in controlling hand movement. The work demonstrated for the first time the possibility of electroencephalogram (EEG)-based brain-machine interface (BMI) control of a prosthetic hand.
The team created a BMI program that adopted the amputated man’s intentions and allowed him to successfully grab objects. The success rate of thought-connected grasps was 80% (1). Researchers said that past studies involving either surgically embedded electrodes or electrically conducted impulses in the arm muscles have shown similar achievements.
Five fully functional subjects in their 20s and the 56 year-old amputee were tested using a 64-channel active EEG. Brain activity was recorded in areas such as the motor cortex and occurred between 50 milliseconds and 90 milliseconds before the hand began to grasp. Researchers then recorded the brain activity and hand motion in functional subjects as they picked up different objects ranging from a soda can to a screwdriver. The recorded data were used to convert neural activity into motor signals that then was translated into grabbing movements. They then fitted the amputee subject with a computer-controlled bionic hand and instructed him to think as if the hand were his as he grasped at various objects. The amputee subject’s EEG along with the information about prosthetic hand movements from the functional subjects were used to build the algorithm.
The non-invasive technique is advantageous in that it avoids the risks of surgically implanting electrodes by measuring brain activity via scalp EEG. Small and flat electrodes are attached to the scalp to measure voltage fluctuations resulting from ionic current flows within the neurons of the brain. The technique also serves as an alternative to the myoelectric control systems because the myoelectric systems require neural activity from muscles associated with hand grasping to remain intact. The team claims that the work offers a new understanding of the neuroscience of grasping and will be applicable for fixing other types of injuries including stroke and spinal cord injury.
But the researchers acknowledged the limitations of the thought-powered prosthetic hand. They claimed that the “current upper limb neuroprosthetics restore some degree of functional ability but fail to approach the ease of use and dexterity of the natural hand, particularly for grasping movements” (1). But the researchers remained optimistic about the potential of the thought-powered bionic hand and expect to increase the grasping success rate to 100% by refining the current algorithm.
References
- University of Houston. (2015, March 31). Non-invasive technique allows amputee to use bionic hand, powered by his thoughts.ScienceDaily. Retrieved from www.sciencedaily.com/releases/2015/03/150331131336.htm
Image courtesy of Integrum
