Things that were science fiction 20 or more years ago are reality now. Brain-computer interface (BCI) technology has made it possible for people with disabilities to see, hear, and feel sensory inputs. With BCI technology, disabled people, such as those with ALS can manipulate computers and machinery by their thoughts. For instance, a person who is unable to move his arms could control a robotic prosthetic arm and hand with his/her thoughts.
In order to grasp how BCI works, it is essential to understand how the brain works to process thoughts into action. The brain is full of neurons; these neurons are connected to each other by axons and dendrites. Your neurons – as you think about anything or do anything – are at work. Your neurons connect with each other to form a super highway for nerve impulses to travel from neuron to neuron to produce thought, hearing, speech, or movement. If you have an itch and you reach to scratch it; you received a stimulus (an itch) and reacted in response to the stimulus by scratching. The electrical signals that generated the thought and action travel at a rate of about 250 feet per second or faster, in some cases.
Note: Different sources give different speeds that impulses travel. Some say they travel at 250 miles per hour and other sites give other speeds. The speed impulses travel depends on the kind of neurons and the type of stimulus. Impulses that tell you that your hand is on a hot stove may move faster than impulses to scratch an itch.
Biochemistry of the brain
There are ions on the membrane of every neuron that carries an electric potential. The membranes on the neurons have sodium, potassium, calcium and chloride ions which keep the signals going in the right direction through the synapses. A synapse is a tiny space between the axon and dendrite of a nerve cell. Chemical reactions take place within the synapse to send the impulse on through each of the neurons. The neurons are covered with a fatty substance called myelin. Myelin acts as an insulator; thus, the neurons, ions and myelin sheath act something like an electrical wire. Electrical impulses are able to travel through the network of neurons, similarly to the way electrical current passes through an electrical wire.
Types of BCI technology
Scientists have had great success in capturing brain signals and directing them to a computerized electronic device. The least invasive type of BCI technology uses an electroencephalograph (EEG), which consists of a set of electrodes that attach to the scalp. The external electrodes pick up brain signals and send them to a computer to be translated. External (non-invasive) BCI technology is good, but it isn’t as good (at present) as the same technology using internal electrodes. However, non-invasive BCI does have its drawbacks. The signals received from the external electrodes are somewhat distorted, while the signals received from internal electrodes are sharp and precise.
Right now, there are three basic types of BCI technology. There are the invasive devices that have already been mentioned. There are also partially invasive devices which require electrodes to be placed inside of the skull, but they don’t have to be attached to the surface of the brain. The final type is the non-invasive that has also been discussed.
At the present time, in order to have a high resolution signal, the electrodes must be implanted inside the skull. Thus, a craniotomy is necessary to place the electrodes on the surface of the brain. Research scientists are still working to improve upon external BCI technology, because over time, internal BCI technology may become ineffective. Why? Because the internal electrodes can cause scar tissue on the brain that can interrupt block the brain impulses from being picked up by the internal electrodes.
Thought translation devices are brain-computer interfaces that allow paralyzed individuals to communicate by accessing their electric brain potentials. In other words, a person can communicate their thoughts to control a word processor. For people who don’t have the ability to focus on a computer screen to make words, BCI neuroprosthetics have advanced to accommodate voice, sound and visual communication.