Evolution of Neurology as a science:
For a long time, it was believed that brain was nothing but an organ for cooling the body. None would have believed, had anyone said that the inanimate custard like substance inside our skull sparked with thoughts. If anything could be the seat of the ‘soul’ it had to be the most vital organ of the body-the heart.
What understanding we have today of the brain, is due to the pioneering effort of the 17th century English physician Thomas Willis. After his discovery that the brain, through the nerves, was responsible for the movement of the human body, the field of neurology was established. But due to the lack of knowledge about electricity as a form of energy, and due to the lack of proper techniques to analyze the cell structure of the nerves, neurology took considerable amount of time to evolve. It was late 19th century before the cellular structure of the brain had been fully mapped.
The 20th century brought with it an array of imaging techniques like the X-rays, CT, and MRI, which made it possible for us to observe the living brain. Today we know that the brain is not only the centre for control but also for thought and memory. Control is obtained through the nervous system which runs throughout our body. Small electrical pulses coursing through the nerves stimulate the muscles into contraction, thus causing motion. Different regions of the brain have been mapped and recognized to be associated with specific emotions or feelings.
Neuroelectronics:
Once it was established that the brain communicated using electrical pulses, there began an effort to correlate the nature of these pulses to the though process from which these pulses originated. In 1870, Richard Carton, a British psychologist concluded through his experiments with surgically exposed animal brains, that the electrical currents of the gray matter have a relation to its function. That is each activity/thought initiated by the brain was accompanied by electrical activity.
In 1929, Hans Berger invented the electroencephalogram, commonly known as EEG, which could measure the surface electrical activity of the brain and represent it as waves. Using the EEG, different wave patterns could be linked to specific mental states. EEG was even successfully used to diagnose those patients with epilepsy, using a pronounced wave pattern characteristic to the disease.
Published in 1943, the combined work of Warren McCulloch and Walter Pitts, neurologist and mathematician, on how the neurons might work laid the foundation for neural networks – the electronic modeling of the nervous system. Work on “thinking machines” and “man-machine interfaces” started then, to achieve the heights envisioned by science fiction writers like Isaac Asimov.
The invention of the EEG, and the continuing research in neural networks resulted in a new branch of study called Neuroelectronics. Neuroelectronics is that field of study which deals with the electrical properties of the nervous system. It encompasses electrical analysis, electrical modeling and electrical interfacing of the nervous system.
There started the effort to “fully decipher” the EEG signals, and to further use them for sending commands to a computer. But this turned out to be more difficult than initially imagined. EEG signals give the combined electrical effect of thousands of nerve cells firing at the same time. It is equivalent to listening to a crowd of people. It is very much possible to make out the general mood of the crowd or even segregate the crowd based on what one section as a whole is trying to communicate as compared to another and so on. But it would indeed be very difficult to listen to one particular person. One would have to focus on the voice of that person, and try to “tune out” the noise from the rest of the crowd.
Similarly with an EEG, it is easy to tell the general mood of the person. One can even classify the waves to be associated with different types of actions like physical movement, sleep, or seeing things. But trying to read a specific thought like- moving a mouse pointer to the right for one inch- would be very difficult to pick up, especially when the mind is clamored with other conscious and sub-conscious thoughts. To achieve that, the noise of the other thought pattern needs to be tuned out. And before we do that the specific thought pattern corresponding to the action required needs to be identified.
Some level of success has been achieved in this respect. The P300 test has been developed as a lie detector, using the EEG pattern of an unconscious thought occurring after witnessing an unexpected event. Interfaces have been developed which can be used by locked-in patients (patients with active minds, but no control of the body) to select one character after another from a stream of flashing characters, and thus compose words and sentences.
Invasive Technology:
The limitation of using the distorted signals of the EEG led scientists to use invasive methods for reading the thoughts. Electronic probes are implanted to read signals from a small set of neurons, thus getting a highly focused reading. Another advantage to this approach is that the implants could also be used to feed signals to the nervous system. Using this method, far greater results have been achieved, though at its own cost.
Surgically implanting an array of electrodes, directly into the brain or any other nerve cluster, enables us to read the electrical signals directly from the nervous system. Nerves can also be electrically excited through these electrodes, and thus desired signals can be generated and relayed through the nervous system. These electrodes could be connected through a wire or a wireless transmitter to the signal processor which analyzes the signals picked up by the electrodes. The processor also generates the signals required to be transmitted through the electrodes into the nervous system. This electrode and signal-processor combination forms the Neuroelectronic interface.
Various types of interfaces have been developed and tested successfully on animals. One scientist developed an interface for a monkey, which would allow it to move a robotic arm and feed itself. It would move the arm to the exact location of the food, and pick it up. Another developed an interface that would allow a rat to operate a water dispenser by thought alone.
While these are phenomenal advances, they can not yet be developed into tools used by humans. Most of these interfaces have bulky apparatus that limit mobility. Others use interfaces that are not permanent –scar tissue develops around the implant and eventually cuts off the nerve impulses that it receives. All require a lot of training to be imparted to the users of the interface. The way the signals are processed and used to control the mechanism needs to be customized to each user, and then again the signals sent by the same set of nerves, for the same action don’t remain the same. They change over time due to many factors and this makes the interface all the more unreliable.
Neuroelectronics is steadily progressing towards achieving this goal of developing more reliable interface technology. We now have commercially available cochlear implants. People with severe hearing impairment can have this device surgically implanted, and regain a sense of hearing.
The cochlear implant directly connects to the auditory nerve, and transmits electronic pulses into it. Far from being perfect, this implant doesn’t restore normal hearing but merely gives the person a representation of the sounds in the environment, and therapy is needed for them to make use of this representation. There are thousands of people using this implant, and they have been able to learn to hear using this device.
Deep Brain Stimulation is a technique in which a surgically implanted electrode in the brain is used to produce periodic signals which suppress some unwanted signals in the target region. This “brain-pacemaker” is now used successfully as a treatment for neurological disorders such as Parkinson’s disease and primary dystonia.
There is intensive research going on developing a retinal implant similar to the cochlear implant, which would in turn enable people to see. It is expected to be in market within a year.
These implants require a one way transmission of signals – from the implant to the nervous system. And in case of the cochlear implant, the signals generated are not the same as the natural signals generated by the ear. Further these implants need no conscious control – they continuously stream signals related to the sensory perception into the nervous system. All this makes the implants relatively simple interfaces.
All human movements, grabbing a glass of water for example, are a feedback controlled processes. The brain sends a signal to the hand to move the relevant muscles in order to make it grab the glass. Once it is perceived by the brain that the hand has moved enough, through the sense of touch (pressure, tension within the muscles, etc.) and sight, it stops signaling the muscles for further movement. Emulating any such functions would require developing a two way interface.
Developing a two way interface, which can be controlled by conscious thought, is much more complex. And if these signals need to be picked up from the nerve cell clusters involved in other functionality (as is the case with most conscious actions), a lot of signal processing needs to be done in order to identify the exact triggering signals.
Feasibility:
Most of the implants of the past have been developed by hit and trial methods. Implants were simply placed in various locations in the brain, whereas this can not be done for human subjects. There still seems to be a lot of controversy over which exact locations in the brain would be useful for what functions. And unless the meaning of the nerve signals has been more accurately discerned, feasible implants can not be developed for humans.
Further, safety measures built into these implants. Any implants relaying signals through a wire has a possibility of relaying an undesirable electric pulse/shock into the nervous system which could be quite dangerous. If wireless implants are used, thermal effects and effect of long term exposure to electromagnetic radiation needs to be considered. Issues like interference need to be handled. All these make the process of developing Neuroelectronic implants for humans extremely complicated.
Though there are formidable obstacles yet to be overcome it won’t be long before Neuroelectronics a widely and commercially applied field. Neuroelectronics will one day be able to restore any physical impairment, through artificial body-parts that emulate natural functions fully – including their control with the mind. Most of today’s science fiction – controlling electronic equipment through thought, communication through thought or telepathy etc. would be made possible through this technology. Neuroelectronics will soon dawn a new era in human life.
