Brain Implants, often referred to as neural implants, are technological devices that connect directly to a biological subject's brain - usually placed on the surface of the brain, or attached to the brain's cortex. A common purpose of modern brain implants and the focus of much current research is establishing a biomedical prosthesis circumventing areas in the brain, which became dysfunctional after a stroke or other head injuries. This includes sensory substitution, e.g. in vision. Brain implants involve creating interfaces between neural systems and computer chips, popularly called brain-machine interfaces.
Neuroscientists have implanted a device in the motor neocortex of two people that has allowed them to operate a computer display by "thinking" about it. It has been known for many years that direct electrical stimulation of particular brain regions can elicit sensory experiences, memory recall, or motor responses. However, unlike scenes from many (oftentimes bad) science fiction movies, it has always been unclear whether or not brain cell activity could be used to control external machines.
Dr. Phillip R. Kennedy, a researcher who has worked with researchers at Georgia Institute of Technology and Emory University, developed an implant that can be used to detect that activity of neurons, and convey these signals to computers for further processing and control operations. The small recording sensor is enclosed in a glass envelope and coated with nerve growth factors that allow neurons in the region of the implant to establish functional connections with the sensor. Normally, when recording electrodes are implanted in brain tissue the region surrounding the electrode is enveloped by glial cells (Module 1; Principles of Psychobiology) that attempt to encapsulate the "foreign" material. This electrically isolates the recording electrodes from small amplitude potentials that are conveyed by individual axons, dendrites or gap junctions (Modules 1-5; Principles of Psychobiology). The key development is the application of nerve growth factors that apparently encourages the growth of functional connections to the recording electrode -- This formation of intact connections could be followed after implantation by a change in the pattern of electrical activity detected by the electrode.
Surgeries on two patients were performed by Dr. Roy Bakay from Emory, who presented the findings at the Congress of Neurological Surgeons annual meeting in Seattle. The electrodes were implanted in the motor cortex, near the arm/facial region (Module 7c; Principles of Psychobiology), and signals were routed to a computer that moved a cursor across a screen to an icon region. Both patients were paralyzed and unable to move their limbs or speak. The first patient, who had the implant for 2.5 months before dying from amyotrophic lateral sclerosis, learned to control the signals in an "on-off manner" for seven days. The second patient (J.R.), who suffered brain stem stroke after a heart attack, has had the implant for 6 months. Initially, this patient had a problem stopping his brain's electrical activity, but researchers programmed a pause into the system so that whenever the cursor landed on an icon, it stopped. Eventually, the patient was able to stop the cursor at an icon and click it to say a word or a phrase.