Have you ever wondered how realistic was the mind control technology presented in Kingsman: the secret service? I can’t claim to go to many Hollywood parties, but I may have an idea.
In a lesser-known series of experiments, in the 1960s a Yale University Professor, Jose Delgado, demonstrated that direct electrical stimulation of the brain is able to elicit various emotional states and reactions from a range of animals, including humans (1). The stimulation and recording of electrical activity was also achieved using radio waves. Doesn’t it sound just like a recent film?
However cool (and perhaps disturbing) this line of enquiry was, it was soon abandoned. One reason for this may be that the technology of the time wasn’t quite advanced enough to establish which specific neural pathways were responsible for which state or reaction. However, in an interesting turn of events, a new technique has come along, which has the capacity to do precisely that.
The technique, by the name of optogenetics, doesn’t use radio waves but rather controls cells in the brain using light. Before you get too worried about the effects of light on your brain, I should explain that only cells that have been genetically modified to have light-sensitive proteins will be influenced by light of a specific frequency (2). These light-sensitive proteins can be limited to a particular part of the brain and a particular cell type using genetic manipulation.
So, what can optogenetics tell us about the neural basis of specific behaviours? A recent paper by Han et al. (2017) focused on defining the neural pathways that are responsible for different aspects of hunting behaviour.
Step one: the authors injected a virus carrying the genes necessary to have light-sensitive proteins into the amygdala of mice. This is the part of the brain known to be involved in reward and fear processing (3). The genetic background of the mice and the genes in the virus interacted in such a way that only inhibitory neurons (neurons that restrict or ‘inhibit’ activity), are affected. The researchers then implanted the mice with small optical fibres that could shine light of certain frequency onto the amygdala.
Step two: the mice’s amygdala was exposed to the light resulting in the inhibitory neurons being active in the amygdala. As a result, the mice showed increased jaw muscle activity (one could argue that jaws are quite important for capturing prey) and they were faster to chase and capture crickets (their natural prey).
What’s interesting is that they also bit and ate inedible objects such as wooden sticks and attacked artificial robotic bugs (you can purchase these, like anything else, from Amazon), which rarely happens in the real mouse world. And if you don’t believe me, you can see for yourself in the video below:
Using this technique, the researchers were also able to uncover the projection pathways from the amygdala to a part of the brainstem called the reticular formation (responsible for biting the prey), and to part of the midbrain called the periaqueductal grey (responsible for pursuing prey).
Even though we may still be quite far away from the mind-controlling techniques like those used by the villain in the Kingsman, current technology offers interesting opportunities for uncovering the workings of mouse and human brains.
- Delgado JMR. Free Behavior and Brain Stimulation. In: Neurobiology CCP and JRSBT-IR of, editor. Academic Press; 1964. p. 349–449.
- Deisseroth K, Feng G, Majewska AK, Miesenbock G, Ting A, Schnitzer MJ. Next-Generation Optical Technologies for Illuminating Genetically Targeted Brain Circuits. J Neurosci [Internet]. 2006;26(41):10380–6.
- Han W, Tellez LA, Rangel MJ, Motta SC, Zhang X, Perez IO, et al. Integrated Control of Predatory Hunting by the Central Nucleus of the Amygdala. Cell. 2017;168(1–2):311–324.e18.