The word “paradigm” is over misused and overused, diluting its utility. Thomas Kuhn coined the term in The Structure of Scientific Revolutions to refer to an overarching explanatory system in science. Scientists, according to Kuhn, work within a paradigm during periods of “normal science,” punctuated by occasional “paradigm shifts” when the old explanatory model no longer sufficed, and a radically new explanatory system was required. The term has since come into colloquial use to mean any scientific breakthrough, which marketers quickly overused to refer to just about any new product.
I am therefore cautious about using the term, but I think it is appropriate in this case. In medicine I would consider a new paradigm to be an entirely new approach to some forms of illness. Common treatment paradigms include nutrition, physical therapy, surgery, and pharmacology. A new paradigm is emerging in my field of neurology – directly affecting brain function through electromagnetic stimulation.
The brain is a chemical organ, with many receptors for specific neurotransmitters. This has allowed us to use a pharmacological approach in treating brain disorders – using drugs that are agonists (activators) or antagonists (blockers) of various neurotransmitter receptors, or that affect the production or inactivation of the neurotransmitters themselves. There are limits to this approach, however. First, neurotransmitters are not the only factor affecting brain function. The brain is also a biological organ like any other, and so all the normal physiological factors are in play. Further, there is only so much evolved specificity to the neurotransmitters and their receptors.
If the brain were designed top-down it might have made sense to have each specific function or circuit in the brain use a unique neurotransmitter and a unique receptor. If this were the case, then we could design drugs that would have only one desired effect. But this is not the brain we have. Our brains evolved from the bottom-up, resulting in the use of a few neurotransmitters in various circuits in the brain, with receptors that are related because they are evolutionarily derived from common receptor ancestors. Therefore, when we design a dopamine agonist to treat Parkinson’s disease, they can cause psychotic side effects because similar receptors are used in other parts of the brain.
In some cases we are already pushing up against the limits of specificity to the pharmacological paradigm in neurology. If we are going to have treatments that are dramatically more effective or specific, we need a “paradigm shift.”
Fortunately the brain is also an electrical organ. Neuron firing can be affected by electrical stimulation or magnetic fields. There is no theoretical limit to the specificity of this approach, only practical technological limits. If we could target specific neurons and directly affect their firing, we could have any level of control over brain function.
Using electrical stimulation to affect brain function is actually decades old. The first use of this approach I am aware of is electroconvulsive therapy. In its infancy, this was the crudest of interventions – shocking the whole brain to cause a generalized seizure in order to treat depression. The treatment is effective, but the side effects, including memory loss, were severe. Over the years the technique has been refined, with less and less stimulation to produce the same results.
The cutting edge of “hacking the brain” with direct stimulation is still relatively crude compared to the potential of this approach, but with very promising results. Examples include deep brain stimulation (DBS) for Parkinson’s disease. Wires are placed into specific structures in the brain, the ventral intermediate nucleus of the thalamus, the subthalamic nucleus, or the internal segment of the globus pallidus. Stimulation at specific frequencies can reduce tremors or other motor symptoms of Parkinson’s disease. This is an invasive procedure, and there are side effects, but the results can be very good for patients who are at the limit of what pharmacology can do.
Various types of stimulation, including DBS but also vagal nerve stimulation, are being used to treat epilepsy. Epilepsy might be particularly amenable to this approach, as seizures are, in fact, electrical events.
Transcranial magnetic stimulation (TMS) is another approach – using a magnetic field to disrupt specific brain circuits. TMS is being studied for a variety of applications, including epilepsy and movement disorders, but also migraines, chronic pain, anxiety, post-traumatic stress disorder, and more.
The age of electrically hacking the brain is already here, but what interests me most is the ultimate potential for this approach. Right now there are several technological limitations to this approach: the specificity of targeting smaller and smaller circuits with either external fields or implanted wires, the safety of having wires penetrating the body and entering the brain, powering and cooling implantable devices, and overall computer technology. There is also the knowledge base of which neuroanatomical structures will produce what effects and side effects.
None of these technological challenges will likely prove an absolute limit to this approach, and there is no theoretical limit. We are finding new ways to power and cool small devices. There is plenty of waste energy in a human body – more than enough to power a small, efficient electronic device.
Electronics themselves are advancing at an incredible pace. The promise of carbon nanotube circuits, for example, would use much less power and generate much less waste heat than current electronics. There is also no reason to think that advances in computer technology will not continue at their current pace for the foreseeable future.
It only requires a reasonable extrapolation from current technology and research to imagine a not-too-distant future with implantable computer chips that are capable of targeted machine-brain interface, self-powered and sufficiently cooled, that can alter brain function in precise ways to produce a host of therapeutic effects.
This does raise one other question: are there any theoretical limits to the computer-brain interface? I have discussed this question at length on my other blog, Neurologica. The short answer is that there does not appear to be any significant theoretical limits to such an interface. Brain plasticity seems to allow for a seamless integration of computer and brain, and all the proofs of concept have already been achieved.
Just this week scientists at Harvard reported that they were able to implant a computer chip into the brain of one monkey that allowed it to control the movements of a second sedated monkey (two monkeys were used so that they did not have to paralyze one monkey for the experiment). The implanted chip read the activity of about 100 neurons and learned their activity in relation to physical movements. The second monkey had 36 electrodes implanted in their spinal cord, and when connected the “master” monkey could control the movements of the second sedated monkey.
Opposing pseudoscience in medicine is often a negative endeavor — pointing out that claims are not based upon adequate science or evidence. We have collectively made a conscious effort not to fall into the trap of being naysayers and only focusing on the negative. Science-based medicine is a positive endeavor, promoting good science in medicine. But science itself has a huge negative component: when you separate the wheat from the chaff, you have to discard the chaff.
It is important to occasionally focus on what does work in medicine, and on legitimate scientific advances. Claiming that we are on the threshold of a new paradigm in medicine, one in which we can use a variety of technologies to manipulate brain function to treat a variety of neurological diseases and disorders, may sound like the very kind of hype we generally deconstruct on this blog. This one, however, turns out to be true.
No one can predict exactly how much time it will take to develop specific applications, but the pathway seems clear and we are making steady progress.