Fascinatingly, the Church of Scientology uses similar technology in its ‘E-meter’, a pastoral counselling device that is stated to measure ‘the electrical characteristics of the static field surrounding the body’ and detect the subject’s mental state. The E-meter became the subject of a major Food and Drug Administration investigation in 1963, following concerns that the Church of Scientology was using it to practise medicine without a licence, and that false claims were being made for its efficacy in treating various physical and mental illnesses. After prolonged litigation involving trial, appeal and retrial, the verdict was that the E-meter could only be used for religious counselling and that it should carry a warning stating it was not useful for the diagnosis, treatment or prevention of any disease. Not surprising, perhaps, since it is, after all, only a device for measuring skin resistance.
Mind Control
Electrical devices may have been used to kill, incapacitate or as instruments of torture and coercion, but they have also been used for good. Sometimes, as in the case of electroconvulsive therapy, the effects are controversial. But electrical devices are getting more sophisticated. Once we understand what the electrical activity of a cell or tissue looks like, it is often possible to provide an artificial stimulus that is an exact replica of the normal waveform to replace or correct a defective signal. Heart pacemakers have enabled many thousands of people to lead normal lives and implantable defibrillators have helped hundreds more.
The ability to control another person’s brain remotely, to force them to behave in a specific way, is the stuff of nightmares, albeit perhaps the Pentagon’s dream. Yet it is not impossible to control another creature’s behaviour simply by stimulating the correct bit of the brain. José Manuel Rodriguez Delgado was sufficiently confident of this idea that in 1963 he stepped into a bullring in Cordoba in front of an aggressive fighting bull. As it charged towards him, Delgado stood his ground and calmly twiddled a button on a remote control device that sent a signal to a transceiver connected to an electrode implanted in the animal’s brain. Electrical stimulation of the caudate nucleus stopped the bull in its tracks: it skidded to a halt within a few feet of the scientist.
Similarly, stimulating the brain of a fruit fly either with electric current or by photoactivation of light-sensitive ion channels can affect its course of action: as we saw in Chapter 11, it can cause a female fly to behave like a male one. Direct electrical stimulation of the human brain can have equally dramatic effects. Surgeons operating on the brain to remove a tumour, or tissue that is responsible for triggering an epileptic seizure, sometimes apply a small electric current to test that the tissue they are about to remove is not of vital importance for the patient. Such stimulation can provoke memories, sensations and even feelings of pleasure or fear. The right amount of current applied at the correct place can even be of immense therapeutic value. In some cases, the effects are so beneficial that electrodes have been permanently implanted in the patient’s brain.
Parkinson’s disease is a debilitating condition in which patients develop an involuntary tremor, muscle stiffness and difficulty in walking and talking. In some people the tremor is so bad that their arms windmill around wildly. Deep brain stimulation is now widely used to alleviate tremors that cannot be controlled by drugs. It involves electrically stimulating specific groups of nerve cells deep within the brain, usually in an area known as the subthalamic nucleus that is involved in controlling movement. The device used to do this is similar in concept to a cardiac pacemaker, and involves an electrode implanted in the brain connected by insulated wire to a small stimulating unit outside the body. A small hole is drilled in the skull and an electrode is inserted into the brain of an awake patient under local anaesthesia. The patient actively helps the surgeon decide whether the electrode is placed in the correct position by reporting what he feels when the stimulator is switched on and electrical pulses are applied to the brain. Once the electrode is in the correct position, the matchbox-sized stimulation unit is implanted under the skin, near the collarbone. Electrical impulses can then be sent from the stimulator to the electrode within the brain: usually continuous stimulation at a frequency of 150 pulses per second is used.
Deep brain stimulation suppresses the activity of the subthalamic nucleus of the brain. Quite how it does so is debated. One idea is that it stimulates the firing of inhibitory neurones that switch off overactive nerve cells: another is that it disrupts pathological brain rhythms. However it works, it is remarkably effective. Patients whose bodies are shaking uncontrollably appear normal the instant the device is switched on. Michael Holman, a journalist with the Financial Times, described it thus: ‘It could not have been simpler or starker. At the touch of a button, the battery-operated stimulator implanted in my chest was turned off by the doctor in charge of my assessment. My tremor returned within seconds, steadily gathering force. In a couple of minutes I was shuddering and flopping hopelessly. Another touch of the button, and I was restored to my tremor-free state.’
Bionic Ears
Electricity has been used to power hearing aids for years, but these are no more than simple amplifiers that boost the sound. If the sensory cells in your ear are damaged you will be unable to hear, no matter how loud the stimulus. Normally, the hair cells in the cochlea of your inner ear sense sound signals and translate them into electrical impulses that are sent to the brain via the auditory nerve. In deaf people who have an auditory nerve that is at least partially intact it is possible to bypass the damaged hair cells and stimulate the auditory nerve directly. This is what cochlear implants do.
Currently, they come with both internal and external components, the former being implanted under the skin of the head and the other being worn behind the ear. The outer device, which is about the size of a small hearing aid, consists of a microphone, a speech processor and a transmitter. The microphone picks up sounds from the environment and converts them to electrical signals, the speech processor filters out background noise and the transmitter forwards the signals to a receiver mounted close to it, but inside the body. The receiver then sends the electrical signals to an array of tiny electrodes that lie alongside different regions of the auditory nerve. The array is introduced into one of the fluid-filled chambers of the cochlea during surgery, so that it lies close enough to the auditory nerve fibres to stimulate them externally.
The hair cells of the cochlea are arranged along its length according to the tones (frequencies) to which they are sensitive, with those that respond to high notes at one end and those responsive to bass notes at the other, much like the keys of a piano. The brain is able to discriminate pitch because different branches of the auditory nerve innervate hair cells that respond to different frequencies. Thus if a branch of the nerve is artificially stimulated the brain will detect it as a note of a particular pitch. The number of electrodes in a cochlear implant varies, with current devices having from sixteen to twenty-four. The more you have, the wider the range of frequencies you will be able to detect. This is why present devices cannot compare with the ear itself, which has more than 3,000 inner hair cells, enabling a far finer discrimination of pitch and the ability to hear musical composition.
Cochlear implants are currently only used in severely deaf people with damaged hair cells. They work best for adults who have lost their hearing and for very young children who are born deaf. There is a critical window for acquisition of language skills and it is important that children receive implants within that time period – two to six years is the typical age. The use of implants is still in its infancy and current devices do not provide people with entirely normal hearing: the British politician Jack Ashley once famously described it as sounding like a ‘croaking Dalek with laryngitis’. It takes practice and training to understand the sounds that are heard, and it is particularly difficult for tonal languages like Mandarin in which pitch discrimination is essential. Nevertheless, many people who were once completely deaf can now hear, and even use the telephone. Understand
ing speech in noisy situations, like a busy restaurant or bar, however, remains a challenge.
Cochlear implants work only if a few auditory nerve fibres remain intact, which is not the case in all deaf individuals. To get round this problem, electrode arrays have been designed that are implanted into one or other of the hearing centres of the brain. While these work even less well than cochlear implants, they hold some promise for providing otherwise totally deaf individuals with a crude sense of hearing. Not all deaf people are interested in devices to help them hear, however. They resent the implicit implication that they are disabled, and prefer to rely on sign language, which enables them to communicate easily and fluently with one another.
Gripping Stuff
Every morning Christian Kandlbauer gets up, eats breakfast, climbs into his car and drives off to work. Nothing remarkable about that you may think, except that Christian lost both his arms at the age of seventeen in an accident. He now has two prosthetic arms: a conventional one and one that is controlled by his brain. The nerve that once controlled one of his lost limbs was surgically redirected to his chest and different branches of the nerve implanted in different muscle groups. Over time, new nerve terminals innervated the chest muscles so that now when Christian wishes to move his arm, his brain sends a signal down the nerve that excites the chest muscles. The tiny electrical impulses in the muscles are then picked up by an amplifier placed on the surface of his chest and translated into movements of his prosthetic arm. Prosthetic limbs controlled by thought alone are still in the development stage and Christian was one of the first people to be fitted with one.
Currently, most electrically powered artificial arms are controlled by electrical signals picked up from muscles of the residual limb, and the amputee must learn which muscles to contract to control the arm and then consciously do so. In general, such arms only allow a single movement – such as opening the fingers or rotating the wrist – at a time. They are also rather slow and not suitable for people who have lost the whole of their arm or leg. The more advanced type of limb, like the one that Christian possesses, enables far more complex movements that are controlled intuitively – as one patient said, ‘I just think about moving my hand and elbow and they move.’ But even these advanced artificial arms suffer from the drawback that there is no sensory feedback to indicate, for example, just how much force to apply to pick up an object – that needed to grasp a heavy jug might break a fragile egg. Bionic arms are also expensive and must be replaced every few years due to wear and tear. There is thus a pressing need to develop even better prostheses. As is so often the case with medical advances, war is the spur, and considerable investment in new prosthetic technologies has been stimulated by the large number of young US soldiers who lost one or more of their limbs while fighting in Iraq or Afghanistan.
A future dream is to enable the paralysed to walk by mimicking the pattern of electrical activity normally supplied to our limb muscles by our nerves. This is simple to state but extremely difficult to do, for walking is a highly complex task. It is not just that the artificial electrical signals must be supplied in the correct pattern and at the right rate to many different muscles, but that our movements are constantly adjusted by feedback from our limbs. Deep within our muscles lie sensors known as muscle spindles that detect the position of our limbs and the extent of muscle contraction. The information they supply is needed not only to enable us to walk properly, but also to cope with difficulties such as uneven ground or stairs. Thus some sort of feedback system may be essential if an artificial device is to send the correct electrical signals to the muscles.
Forward to the Future
The use of electrical devices in medicine is now routine. Deep brain stimulation has had transformative effects on the lives of people formerly incapacitated by the shakes, and its use in reducing severe depression is currently under investigation. Many people are able to lead normal lives due to cardiac pacemakers. Hearing aids have advanced into new territories. Prosthetic limbs are becoming ever more sophisticated. Devices to help the blind see and the paralysed walk are still in their infancy and there is a long way to go before commercial devices will be available, but there is no reason to think they will not exist eventually.
But it is unlikely to stop there. Functional magnetic resonance imaging (fMRI) can already be used to determine a person’s answer to a yes–no question. In the future, with more sophisticated interpretation of brain scans, it may be possible to enable patients with ‘locked-in’ syndrome to communicate more fully. Whether it will be possible to read someone’s mind, however, is a different matter. Current fMRI technology is massive, spatial and temporal resolution are limited, and how much can be interpreted from the signals produced remains controversial. Yet we should not forget that although the first ECG machine needed two rooms to house it, portable devices are now commonplace.
While pacemakers, deep brain stimulation and fMRI cause little comment, the idea of connecting your brain to a computer is far more startling. In one sense, many of us are already interfaced with our laptops and mobiles – although that connection is mediated via our eyes and fingertips rather than directly with our brain. But as I grow older, I would appreciate a more intimate connection. How wonderful to be able to access all my memories at will. To be prompted with the name of the person standing in front of me whom I taught twenty years ago and whose name now escapes me. To search the Web for information simply by thinking. Frightening though it at first appears to consider wiring your brain up to a computer, it is the nature of the connection that is the crux of the matter. Providing that it can be switched on or off at will, and that any information downloaded to a personal storage device (such as our brain) is both secure and under our own control, it seems likely that many of us will eventually succumb to its seductive lure. Thinking is, after all, faster than typing and reading.
But Mary Shelley’s story has a long reach and first we will need to overcome our fear of the unknown, of monsters such as that created by Frankenstein. We will also need to find ways to legislate and regulate the use of such technology so that the poor are not disadvantaged. Furthermore, any such radical modification of our brains will need to be invisible (for humans prefer not to stand out in a crowd), and preferably it should be possible to remove it easily when desired. Today, we routinely enhance our senses with microscopes, telescopes and night-vision goggles, to name but a few examples, but we can take them off at the end of the day. Likewise, we have calculators and computers that immeasurably enhance our mental abilities and the Internet serves as a vast, external collective memory, with far greater capacity and speed of recall than our brains and libraries. Indeed, many of us are rarely offline and our immediate response to an unknown question is usually to ‘Google’ it. It may be that some individuals will prefer to continue to access such electronic aids via their senses – their fingers, eyes and ears – rather than by a direct connection to the brain. But I for one would like a device that effortlessly stores and retrieves my personal memories, and it would obviously be invaluable for people suffering from memory loss caused by disorders such as Alzheimer’s disease.
Artificial memory aids that plug directly into our brains are, of course, currently only science fiction. But science fiction often has a way of becoming science fact, and 100 years ago few would have imagined it would be possible to control a mechanical arm simply by thinking, or stop a charging bull with a signal to its brain. Perhaps in another hundred years such memory devices may exist. It is impossible to tell, but what I do know is that understanding how the body uses electricity, and how memories are laid down, stored and retrieved by the electrical circuits in our brain will be the key to their success.
Notes
Introduction: I Sing the Body Electric
1 For those who would like a more detailed explanation, it works like this. When the KATP channel is open, potassium (K+) ions move through it, flowing out of the cell down their concentration gradient. Because K+ is positive
ly charged, its efflux makes the inside of the cell more negative. This negative membrane potential holds calcium channels closed, so preventing insulin secretion. When plasma glucose levels increase, more glucose is metabolized by the beta-cell. This generates a chemical called ATP, which binds to the KATP channel and causes it to shut. As a consequence, the membrane potential becomes less negative (as fewer K+ ions leave the cell), which in turn triggers opening of the calcium channels. Calcium rushes into the cell and causes the insulin-containing secretory vesicles to fuse with the surface membrane and release their contents into the bloodstream.
1: The Age of Wonder
1 This quotation is often attributed to Galvani (see, for example, W. W. Atkinson, Dynamic Thought (Los Angeles: The Segnogram Publishing Company, 1906, p. 179) but this is not correct. It is not Galvani’s style and he was not mocked in this way during his lifetime. The quotation was probably invented by the French astronomer Camille Flammarion as it appears in his book L’inconnu et les problèmes psychiques (Paris: Ernest Flammarion Editeur, 1862). I am indebted to Professor Marco Piccolino for this information.
2 Prometheus was sentenced by Zeus to have his liver torn out by an eagle for eternity. His liver regenerated every night so his punishment was unceasing: it is fascinating that Zeus should have chosen the liver, as it is one of the organs most capable of regeneration.
3 Anne-Robert-Jacques Turgot’s famous epigram on Franklin: ‘He snatched lightning from the sky and the sceptre from the tyrant.’
The Spark of Life: Electricity in the Human Body Page 32