Theodore Berger, a professor of engineering at the University of Southern California, is ready for the era of the bionic brain. He has spent 30 years developing computer chips that can link with neurons in an effort to compensate for memory loss. The chips that can do it exist. Most of the software exists. The challenge is to make a reliable, long-term connection between the hardware and the wetware—one that is unaffected by corrosion, scar tissue, or the shifting and dying of cells in the brain. “That’s the big showstopper,” Berger says.
He is part of a growing movement of researchers struggling to perfect neural prostheses, devices that employ electrodes to receive signals from and transmit them to the brain. Cyberkinetics, a company cofounded by neuroscientist John Donoghue at Brown University, has begun clinical trials on an implant that can transmit signals from a paralyzed person’s motor cortex to a computer or to a prosthetic limb. Several groups, including one led by Ali Rezai of the Cleveland Clinic Center for Neurological Restoration, have tentatively shown that stimulation of the thalamus can relieve chronic pain, obsessive-compulsive disorder, and depression. Similar devices may be able to treat blindness, epilepsy, and Parkinson’s disease. All these applications will depend on solving the connection problem.
Groups at the University of Arizona and elsewhere have crafted arrays containing 500 or more electrodes, trying to maintain a good link through sheer numbers. Other strategies include building electrodes out of conducting polymers, which are more compatible with neural tissue than are silicon or metal, or coating electrodes with molecules that adhere to brain cells. A team at Emory University is embedding electrodes in glass cones filled with nerve-growth factors that encourage brain cells to sprout more dendrites and axons. Several paralyzed patients using the Emory device have learned to control a computer with their thoughts. But the ideal fix would be an electrode that constantly moves to maintain connections.
