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I am a neuroscientist and physiologist, which means I get to look at a lot of brains and try to figure out how they work. As I am also a writer, I thought I would do a few posts on my particular brand of science as it applies to science fiction. To start it off, I would like to begin with an email that I received today, inviting me to a Brain Stimulation symposium (which I will not attend, but that is beside the point).

Brain stimulation is a thing. An actual thing, used in therapy and research. In its most basic form, it involves introducing a specific amount of electricity to a specific part of the brain, depending on what you want the result to be. If this sounds like ‘wiring up’ a human brain to a machine, it is because that is what it is.

The methods for doing this vary. We have external devices and implanted devices, and they operate on different principles, have different limitations and different risks. However the basics are much the same: introduce an electric current in a specific part of the brain to make the neurons in that part of the brain do what you want them to do. This typically means either exciting or inhibiting the neurons (which can, for simplicity, be thought of as turning them on or off).

Deep brain stimulation is an invasive method. It requires surgery. It is the younger and more advanced cousin of the much older electrical brain stimulation that has been used to target surface areas in the brain with various degrees of success since the mid-1800s and uses electrodes embedded deep in the brain. The surgically embedded electrodes are connected with insulated wires to a stimulator, which is usually implanted somewhere just below the neck. The stimulator controls the electrical impulses to the brain, and its settings is calibrated by healthcare personnel (or anyone with the access, know-how and equipment).

Deep brain stimulation is used in the treatment of diseases such as Parkinson’s Disease and chronic pain. It will not cure the disease, but it can take away some of the worst symptoms and improve the lives of these patients. Not without risk, of course – brain surgery is no walk in the park – but it is effective. For what else can it be used? Deep brain stimulation, depending on the regions it is implanted, might alleviate major depression and obsessive-compulsive disorder, although the jury is still out on how well it works. That is not to say it is not possible – it might merely be a case of finding the right targets and the right stimulation frequency.

Also, it does not have to be electrodes. A slightly more futuristic type of deep brain stimulation based on optogenetics is being developed. Optogenetics is a way of controlling cells (often neurons) using light. The brain’s neurons can be inserted with light-sensitive probes. This is often done using a manipulated virus, carrying the probe, which targets a specific group of cells. The modified nerve cells can now be stimulated by exposing them to light – effectively turning them ‘on’ and ‘off’ with a light switch. This technique is in use in animals, and can be powered and controlled using wireless radio signals. Different wavelengths of light can then be used to target different inserted light receptors in the cells, giving different types of response.

A less invasive method is transcranial magnetic stimulation, where a magnetic impulse is sent to a part of the brain using an external device. The change in magnetic field causes a change in electric current in the brain (which is, of course, the stuff of neurons), and hey presto: stimulation. This method is not invasive in that it does not require any surgery, but it can only penetrate so far into the brain, so its influence is limited to surface regions (as opposed to deep brain stimulation).

How far can this be taken? Can this control someone’s behaviour, or be used to manipulate someone? Well, possibly. To some extent at least. Stimulating motor regions of the brain, which are involved in controlling our movements, can trigger movement. It is possible to record signals from one person and transmit these through, for example, transcranial magnetic stimulation, to the motor regions of another person, making them do the movement of the first person. Like a puppet.

Stimulating an area of the brain called the nucleus accumbens has the potential to ‘turn off’ addictive behaviour, such as compulsive overeating, at least in animals. Similarly, targeting a region of the brain called the hypothalamus can create rage in experimental animals. In humans, stimulation of the amygdala (which is an area of the brain associated with fear processing) can trigger aggression and rage. Also, there is at least one case where stimulation of the subthalamic nucleus (often targeted in Parkinson’s Disease) caused a patient to show new, manic personality traits1, which went away when the stimulation was adjusted. Can it be used to ‘turn off’ aggression? Yes, so it seems2. So it is currently possible in humans, if rare (only by accident, or in severe medical cases), to alter personality using brain stimulation.

What about complex ideas? Can these be created or transmitted? Could you make someone agree with you politically or make them aggressive towards a certain group of people? So far, no. In theory, it should be possible, given enough knowledge about how the brain operates. It would be the same principle as recreating a motor response in the example above, but likely involve a range of brain regions (including areas associated with decision making, emotions, attention, and so on) and different stimuli (excitation, inhibition) in a precise pattern over time. That is the theory. In practice, we currently simply don’t understand nearly enough about the brain to reliably describe, much less recreate, the activation patterns of complex thoughts or behaviours using mechanical contraptions. That is still the realm of (dystopian) sci-fi.