Have you ever wanted to stimulate some part of your brain, only to be thwarted by that pesky skull ensconcing it? Don’t want to drill holes and implant electrodes? Well lucky it’s the 21st century so now you don’t have to. Let’s take a dive into the weird science of transcranial magnetic stimulation.
Over the past few years a slew of news outlets have been singing the cognitive benefits of learning to juggle. If one is to believe the hype, this ancient circus activity will increase your brain power, make your brain bigger (permanently, no less), and may even prevent Alzheimer’s disease. Dang.
Can there be any truth to these heady claims, or is it another case of the media committing that most egregious of sins: distorting science for the sake of a catchy headline? Here we plunge into the literature and investigate what has actually been shown experimentally. Continue reading
Well, maybe not your *favourite* drugs, depending what you’re into. But it’s true: the existence of many of the most popular drugs on the planet can be traced directly back to insects.
This includes nicotine, cocaine, possibly cannabis (with a fuzzy asterisk), and of course the most widely used psychoactive substance in the world: caffeine.
Coffee is the second most highly traded commodity globally, losing out only to crude oil. 500 billion cups are consumed every year – an average of 70 cups for every man, woman and child. As a species we’re junkies for it.
So why are psychoactive compounds, A.K.A. drugs, so appealing? The answer lies in how they work. Once inside our bodies, psychoactives slip mischievously inside our brains and start fiddling around with the control panel. Different psychoactives fiddle in different ways, but something the popular ones all have in common is that they tend to crank up the happiness dial.
Many of these popular drugs, from caffeine to cocaine, were invented by plants. But why did they do this? Plants don’t have happiness knobs to be twiddled by drugs, and they’re definitely not just out to give us humans kicks. And how do insects come into the picture?
To properly understand this tale, we’ll have to travel 450 million years back in time, trace the progression of a brutal conflict that has claimed more lives than the entire history of human warfare, and finish by shrinking down to gaze at the very foundations of consciousness itself.
Hold on tight, it’s going to be a bumpy ride.
In the Beginning…
The majestic Planet Earth, 450 million years ago in the late Ordovician period:
The first multicellular organisms to blob up onto land were sluggish low-lying plants that looked pretty much like modern day mosses and liverworts. And for a while, that’s all there was.
For those stunted critters, this brave new rocky world above the roiling sea must have seemed an idyllic paradise. Vast stretches of land awaited colonisation, the air was heady with CO2, and there wasn’t a predator to speak of. Alas, it wasn’t to last.
When we hear the word “herbivore”, we usually think of sizable mammals like cows and rabbits and giraffes. But plants have a far more ancient, insidious, and destructive foe. More than 200 million years before evolution wobbled out its first half-arsed proto-rat, there were insects.
By raw numbers, insects are the most successful branch of life of all time, boasting an estimated 6-10 million species. Four “super-radiations” have been particularly virile: beetles, moths, wasps and flies. These types of insect alone make up the majority of animal life on Earth.
Back in the Ordovician though, it was a different story. Much like early plants, the first insects were actually kind of crappy.
They were probably scavengers or predators, feeding on decaying organic matter and each other. They also weren’t particularly mobile. It would take evolution 70 million years to puzzle out how to build wings, so these early pioneers were stuck with crawling and walking to get around.
It wasn’t long though before something clicked, and the early insects turned their prehistoric compound eyes to the untapped treasure lying at their (numerous) feet: a delicious, stationary and completely undefended food source.
The Never-Ending War
Those first few centuries must have been a gustatory massacre: hordes of rampaging insects feasting on the soft succulent vegetation.
But plants fought back. They diversified, developing intricate vein-like vascular tissue that allowed them to grow larger and migrate inland. Insects followed, and responded by evolving Sap Suckers, fiendish vampires who could stab into the plants and drink their very fluids. This one keeps its enormous proboscis tucked back under its body:
Plants began secreting waxy coatings to make their leaves slippery and harder to penetrate. Marauding proto-aphids toppled hundreds of times their body height to the ground.
Insect forms multiplied, and one lineage decided to get into the mining business, adapting their bodies to best burrow into leaves, submerging themselves in a giddy world of pure deliciousness. Plants retaliated, developing machinery to sacrifice infected leaves and toss them scornfully to the ground, curled and brown.
The battle was well and truly under way.
Plants reinforced their critical systems – stems and seeds – with tough fibres that gradually evolved into woody bark and shells. Insects found ways to keep pace by strengthening their mandibles. Worse yet for plants, a strain of Leaf Miners mutated themselves into a grotesque new foe: Plant Borers. These creatures were able to burrow not just into leaves but directly into stems, roots and even the precious seeds.
Life force battled hard against life force. Ecosystems diversified and increased in complexity as military innovation piled up upon military innovation. Bizarre alien forests rolled across the Earth as the Ordovician Period faded into the Silurian, which in turn faded into the Devonian. And all the while, inexorably, the death toll crept higher.
About 406 million years ago, insects finally mastered flight. Having wings transformed their world from essentially flatland into a rich 3-dimensional environment of endless possibilities. Migration and innovation boomed, and with it insects differentiated into a dizzying array of never-before seen forms.
During the next 60 million years most modern orders of species came into existence. Early winged arthropods included crickets and the elegant predatory dragonflies. And soon enough, there were beetles.
Beetles are so endlessly varied that they alone account for 30% of all animal species in existence. As the evolutionary biologist J.B.S. Haldane summed it up:
“The Creator, if He exists, has an inordinate fondness for beetles.”
Shortly afterwards, beetles were joined by wasps, moths and flies, and the four super-radiations were loosed upon the world – a beautiful insect evolutionary tree can be found here. It seemed that insect domination over plants was assured.
In a final twist of the plot, in this harsh prehistoric world when all seemed lost, plants stumbled upon a way to turn the tide of the war. They would transform insects’ greatest strength – mobility – into their greatest weakness. Plants invented chemical warfare.
Insects aren’t just gifted with movement; they are dependent upon it to do anything – to find food, to escape predators or to reproduce. Movement requires the coordinated use of multiple systems: powerful flight muscles, machinery for vision, advanced aerial navigation equipment. And all of these systems are plugged directly into a brain.
Plants began producing toxic compounds called allelochemicals to attack insect brains. Any insect eating a plant would have to eat its allelochemicals too. These toxins would then seep into its brain and start messing with the delicate movement systems. Insects would either have a seizure and die from energy depletion, or become paralysed and be eaten by predators.
What do these deadly allelochemicals looks like? Examples include nicotine, caffeine and cocaine.
As always in evolutionary wars, insects responded, this time by developing resistances. But the cost was great. Many species were forced to become specialists, living on only a narrow range of plants whose poisons they could tolerate. Some probably failed to adapt altogether.
Insects and plants dug into the trenches, so to speak, and gradually, over a long period, the conflict settled into a kind of equilibrium. The two ancient enemies constantly refined their poisons and resistances, their weapons and armour, but neither ever again gained a real upper hand over the other. Eventually some plants and insects even set aside their differences and, with their powers combined, forged one of nature’s all-time greatest collaborations: flowering plants and pollinators.
And what about us mammals? Millions of years passed in this period of plant-insect equilibrium; amphibians arose; reptiles arose; and finally, some time in the early Triassic, the very first mammals peeled away from reptiles to launch our own evolutionary journey of diversification and warfare. We sure were latecomers to the party though. By this point, insects and plants had been at each other for 200 million years.
Now, to finally answer the mystery about drugs, it’s time to go…
Inside the Mind Itself
To understand how brains work, it’s surprisingly useful to look at how computers are built. Computers are essentially big networks of logic gates connected by wires. If you’re not familiar with them, logic gates take in two signals and use them to output one signal. The signals can be either ‘on‘ or ‘off‘, and different types of logic gate behave differently.
An OR logic gate outputs on when either input is on.
Think: “I’ll go out with my friends if either mum or dad says I’m allowed to.”
An AND logic gate outputs on when both its inputs are on.
Think: “I’ll only clean my room if both mum and dad make me.”
With enough logic gates strung together, computers are able to carry out the endless complex operations that we tell them to.
Brains work is a remarkably similar way, using neurons instead of wires. There are two major differences though:
- Neurons aren’t limited to just two inputs, and instead can receive signals from up to hundreds of other neurons
- Neurons communicate on and off signals using neurotransmitters, tiny molecules that substitute for electricity
So really, a brain is just a (mind-bogglingly complex) tangle of neurons that form an astronomical number of logic gates. These logic gates are endlessly being bombarded with neurotransmitters carrying on and off signals. Logic gates rapidly read these inputs, process them into their own on or off signal, and fire it onwards, from neuron to neuron, logic gate to logic gate, racing and rippling and splitting and looping around, all in a vast never-ending neurotransmitter Yin-Yang sea of Dos and Don’ts, of ons and offs.
And through this process, we control every minuscule aspect of our existences: breathing, feeling, moving and consciousness itself.
Plant allelochemicals, A.K.A. psychoactive drugs, work by mimicking insect neurotransmitters. They screw up the fine Yin-Yang balance of signalling, either by sending an unregulated blast of ON, or freezing the system with a wave of OFF. Enough allelochemical and the insect dies from either seizure or paralysis.
Humans are very distant cousins of insects, around 500 million years distant, and we use many of the same neurotransmitters. However, with so much time apart, our brains have obviously evolved down separate paths, and our logic gates are made somewhat differently. Because of our shared ancestry with insects, plant drugs designed to attack insects can still affect us, but only in a weak and wobbly kind of way. If allelochemicals are like a bolt of lightning to insects, we get a warm shower of sparks.
Also unlike insects, we have the unintended benefit of having evolved pleasure centres in our brains. It is one of nature’s great chemical coincidences that, just as no one predicted that aspartame would be sweet, or that angina medication would cause whopping erections, plants never imagined that their anti-insect drugs would be great at turning up the happiness dials of distant future humans.
So next time you’re enjoying your morning cup of java, maybe spare a thought for the countless poor insects who gave their lives in order that we may have our buzz.
- 24 Remarkable Caffeine Consumption Statistics
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- Insects Evolved With Earth’s First Land Plants
- Number of Living Species in Australia and the World
- Episodic Radiations in the Fly Tree of Life
- Insect-Plant Interactions
- Early History of Arthropod And Vascular Plant Associations
- Ninety-seven million years of angiosperm-insect association: Paleobiological insights into the meaning of coevolution
- Geological Time Periods
- Family-group names in Coleoptera (Insecta)
- Angiosperm-like pollen andAfropollis from the Middle Triassic (Anisian) of the Germanic Basin (Northern Switzerland)
- Insect Family Tree Maps 400-Million-Year Evolution
Back in the control room I find my friend waiting for me, all smiles as usual. She must have arrived while I was strapped in the machine.
“Hi!” she greets enthusiastically. “I just saw your brain.”
I suppose this shouldn’t be a surprise, given the situation. Yet I’m caught off guard. How do you respond to something like that? It feels awkwardly personal, like a housemate admitting that they heard you having sex. Is this more or less weird? I wonder.
On one hand, it’s just bits of lumpy grey matter. We all have them, and they don’t look like much. But on the other, it’s a part of you that no one normally gets to see, and it defines absolutely everything about your personality. Also my friend is a neuroscientist, so who knows what she might have been able to read into it. Was she judging me on the size of my hippocampus? Wait, does size even matter, or is it just how you use it?
She’s been watching my face, and maybe she can read my thoughts after all. “Well, only a bit of it,” she clarifies, sounding a little apologetic. “The prefrontal cortex. It was very… handsome.”
What’s going on? I’m at a Biomedical Imaging Research Centre, and I’ve just had a functional magnetic resonance imaging (fMRI) scan. But let me start from the beginning.
The head researcher, Paul* the PhD student, was waiting for me at reception when I arrived. I didn’t have a medical condition or any real reason to get my brain scanned. I volunteered for the study simply because how freaking cool is it to see your own brain? Pretty damn cool, if you ask me.
We went through the consent and medical forms. No history of epilepsy: check. No metallic implants or bits of shrapnel in my body: check. This last one is very important because fMRI machines create powerful magnetic fields. I assume that if you had, say metal pins in your skull, the machine would suck them right out through your face.
I followed Paul through to the control room, where I met Dave* the imaging technician. He was pleasantly spoken, and my gaydar gave a faint uncertain reading. He invited me to help myself to a platter of sandwiches and make myself comfortable. I did so. Dave returned to working away at three large computer monitors, preparing the scanning software.
Through a wide blue-tinted panel of glass I could spy the fMRI machine, looking like a giant upright donut. It was smooth and white, and very much resembled something you might find in the game Portal, or perhaps Kubrick’s 2001: A Space Odyssey.
How does MRI work? Well to begin with, the machine has to create an extremely powerful and uniform magnetic field. The strength of this field is typically about 1.5 tesla. For perspective, this is about five times the intensity of an average solar sunspot.
To achieve this, the machine is fitted with superconducting magnets which are cooled by liquid helium. The resulting magnetic field excites hydrogen atoms present in water molecules in your brain, causing them to emit a radio frequency signal. This signal is detected, and an image is assembled.
Dave asked me to remove any metal items from my person and follow him into the scanning room. We passed though a reinforced door which read “MAGNETUM” in imposing capitals. Black and yellow triangles on either side warned of “MR- Magnetic Field” and “High Frequency Field”. Yep, watch out for fields.
A series of panels on the ceiling were illuminated to show a beautiful image of blue sky, wispy clouds and tree leaves in the foreground, as if you were lying in a park looking up. “It’s to help people with claustrophobia,” Dave later explained to me, when I was back in the control room watching my friend’s brain materialise on the screen.
I lay down on a special table, with my head at one end of the donut hole. Dave stuffed earplugs into my auditory canals. You see, rapid changes in the magnetic field of the fMRI machine cause the magnets to vibrate, which creates a loud hammering sound. Foam cushioning was then crammed around my head, and a Velcro strap placed across my forehead to hold it in place. It was a bit of pressure and not overwhelmingly comfortable, but it was definitely not as restricting as I had been anticipating. Capillaries and neurons are pretty tiny, so I had assumed my head would have had to be fully immobilised to get an accurate reading. As it was, I could still move a bit.
A plastic visor was clicked into place above my eyes. It held a mirror which redirected my vision toward a monitor at the far end the donut. Wherever he was, Dave manipulated some controls and the table rose up and slid my head into the donut.
Paul came over to see how I was going. Just fine. He placed a controller with a large button into my left hand, explaining that I had to push the button whenever I saw the same image twice in a row. This was to be the experiment. In my right hand he placed a squeezy bulb, which I could use if I ever got claustrophobic and wanted to stop the experiment. Pssh, claustrophobia. I was actually feeling pretty excited and eager to start.
Everyone else left the room, and the quietness was soon replaced with Dave’s soothing voice over the intercom. He informed me that there would be a few scans of varying lengths. The first was to be a mere ten seconds, and would sound a little strange.
A harsh distorted electronic tone burst forth, like a synth from some Daft Punk song. I was glad for the earplugs. It held for a moment, rose in pitch, held for another second or two, and I anticipated the tone rising again – the sacred melody of neuroscience being revealed to me. It dropped back to the first tone instead. Then, quiet.
Dave’s voice dropped in again over the intercom, asking me how that was. He informed me that the next scan would take about four minutes. Ok.
Brand new electronic tones clicked and whirred. At some point the notes settled into regular monotonous pulses, and my thoughts drifted. Is this what life feels like for a photocopier? Stuck in one place, doomed to a single view, hearing the repetitive hum of page after page being scanned and printed. Or I felt like a person still plugged in to the Matrix in a little isolated pod, oblivious to the rest of the world out there.
I closed my eyes and started to feel warm and sleepy. The experimental explanatory statement reads:
“The radiofrequency waves we use to create the MR scans can cause your head and body to warm up slightly. This is not a problem, and you usually won’t notice it at all, as your blood flow will increase slightly to take the heat away.”
Maybe I noticed it.
My mind started to recite the “To be or not to be” soliloquy from Hamlet. Haha brain, “whether ‘tis nobler in the mind to suffer”, aren’t you clever? Then I started to worry that maybe I was causing the language centres of my brain to light up, giving a misleading reading. Quick, think about maths! No wait, probably I should just think about nothing. But I don’t seem to be able to! Argh!
Finally I decided that if it was going to be a problem, they would’ve warned me in advance not to think about anything. Surely they were just checking my neural structure now anyway.
ERRRK, ERRRK, ERRRK went the machine. Then it fell silent once more.
Dave gave me one more preliminary scan, this time lasting a minute. A softer, more constant buzz hummed for the duration of this one. I imagined the magnetic fields raging and swirling around me, like some divine battle, whipping up the water molecules in my brain and battering them one way then the other. Surely that’s got to do something to one’s perception? I focused inwardly and tried to decide whether I could feel anything. Possibly something subtle… but it could easily by placebo effect. No, probably nothing.
Finally it was time for the experiment proper.
A stream of pictures flashed by on the screen: faces, flowers, buildings, abstract tessellated patterns – repeating and repeating, faster and faster. My finger twitched nervously on the button; I cursed silently when I pressed it accidentally, but grinned with pride when I matched the abstract tessellated patterns. I started seriously doubting my skills of facial recognition.
The second task involved watching coloured dots move across the screen and involved more button-pressing. I found myself feeling strangely exhausted and having to close my eyes between rounds. At some point I remembered that they were using infrared lasers to track my eye movement, then I worried that maybe I was screwing up the experiment by closing my eyes so often.
I’m so sorry dear science.
When everything was finished, the lovely Dave burnt me a disc containing the map of my brain. It’s really quite fascinating and gross scrolling through from one hemisphere to the other, watching the cortex burst forth, swirl and evolve as it reaches the midbrain and the medulla and corpus callosum appear, then warp and recede away as you pass out the other side.
I imagine I will treasure this map until the day that my brain shrivels up from some neurodegenerative disease, and ironically I can no longer fathom what I’m looking at. But I suppose it won’t matter by that point. The pictures wouldn’t be of me anyway.
* Name in this article have been changed.