This isn’t actually about brain control. Not really, anyway. If I really knew anything about brain control, I’d be out taking over the world, not writing blog posts (and mark my words, I’d be making Jake Gyllenhaal my number one minion. Yum). It’s really about a technique called Transcranial Magnetic Stimulation, how amazing it would be if speculations that it might happen in nature were true, and why I’m not 100% convinced that they are.
I read this article the other week in New Scientist. It describes a (not so*) new idea suggesting that the elusive phenomenon of ball lightning may in fact be a hallucination brought on by transient powerful magnetic fields caused by (ordinary) lightning strikes. The mechanism suggested to be behind this is the same one that is exploited by Transcranial Magnetic Stimulation (TMS), which I had the joy of playing with as part of my undergraduate research project. The principles of TMS are fairly simple.
Firstly, it’s important to understand that neurons (brain cells) communicate chemically, not electrically**. But the signal within individual neurons that generates this chemical communication is electrical. The process of neurotransmission is an endlessly fascinating one, but one I’m not going to go into here, for reasons of brevity and because there is a pretty good summary on the ever marvellous wikipedia. You’ll probably remember from your schooldays that if you pass an electric current through a coil of wire, a magnetic field is generated around that wire. Placing a ‘conductor’ within that magnetic field causes electric current to flow in loops perpendicular to the magnetic field, and parallel to the coil itself. If that conductor is a human head, that electric current is being induced in neurons close to the brain’s surface in the region of the coil. If this all sounds complicated, it’s probably because I haven’t explained it very well; I’m no physicist! A much nicer
explanation can be found in box 1 of this article. Anyway, the upshot of all this is that by sending brief pulses of current through such a coil, TMS can be used to externally evoke temporary neuronal activity, and we can observe the behavioural results. So, if we do this with the coil placed over motor cortex – the part of our brain that sends movement instruction to our muscles – we can make the arms or legs twitch, for example. As someone who has been subject to this bizarre procedure, I can tell you it’s both hilarious and a little unsettling to watch your hand flail about wildly seemingly of its own volition. It’s a bit like watching your dad dancing to The Mavericks; amusing, but a bit unnatural and there’s nothing you can do to stop it.
I digress. Now, what I find super interesting is that by placing the TMS coil over the occipital cortex, which includes our visual cortex, people often report seeing visual artifacts such as flashes of light, or pale shapes like ovals or lines. Awesome stuff. So, what this article was suggesting was that something similar is going on when ball lightning is perceived. The idea is that a bolt of lightning creates fluctuating magnetic fields similar to those used in TMS. If an observer happens to be about the right distance away from that lightning, this magnetic field will be strong enough to induce electrical activity in that person’s visual cortex, causing hallucinations just like those artifacts we get with TMS. This idea totally blows me away. This idea of a kind of naturally occuring TMS is just amazing – I mean lightning being able to make you see things?! It’s one of those flukey little quirks of nature that make science so interesting. I just love it.
I’m certainly no expert on lightning, so I am holding my hands up and admitting that the next couple of paragraphs are at least 73.87% speculation on my part, but I’m not entirely convinced by this idea. Let’s, for a start, write off all the supposed photographs of ball lightning. I’m fairly certain you can’t photograph a hallucination, but you can do some remarkable things with photoshop, and other phenomena like St. Elmo’s Fire can be mistaken for ball lightning. Let’s also ignore all those reports coming from groups of people who all claim to have seen the same instance of ball lightning. Social pressure and the desire to conform can cause people to say all sorts of things. So far, no solid evidence that ball lightning even exists, suggesting the hallucinations idea is actually quite plausible. But there are a couple of things that bother me about it. Firstly, the remarkable consistency in descriptions of ball lightning. As far as I have been able to find out, there don’t seem to be reports of lines, or squares, or lights of different colours. Always a glowing, sometimes moving orb. This seems quite bizarre to me, as such consistent effects would surely require a really focused, specific region of effect of the magnetic field. We might expect that a generalised magnetic field could affect any number of brain regions, causing all sorts of different effects. Not only might we expect a wider variety of visual hallucinations, but we might also expect to hear unusual sounds, or experience twitching of the limbs like I described above.
Secondly – though this is related to the first point – the fact that people seem to be able to choose to watch this lightning. Our visual cortex is mapped out in a similar way to our retina, such that picking a particular point on the visual cortex is like picking out a corresponding point in the visual field. If the perception of ball lightning really were a result of abnormal brain activity, we might expect that this ball lightning would stay firmly in the same part of our visual field. What I mean by this is that if the induced activity were in a part of the brain that corresponded to the left half of the visual field, it wouldn’t matter how far left we tried to look, the image would remain to the left of our point of focus. If you’ve ever suffered a visual aura, you’ll understand what I mean by this. It should also be perceptible with the eyes closed. I have no idea if this has been documented either way though.
Finally, the authors themselves suggest that only around half of all instances of ball lightning might be explained by this type of hallucination. Which not only leaves the obvious question of what is causing the others – but also the question of the quite astounding coincidence that hallucination-ball lightning would result in the same visual experience as non-hallucination-ball lightning. The reports just seem to consistent to be able to draw a divide between those instances that are likely to be hallucinations, and those that aren’t.
Given that ball lightning has effectively defied explanation for centuries, far be it from me to undermine what might be a really strong theory. Of course, I only really know about the brain stuff, so my questions about this idea might be totally misguided. I don’t know much about lightning or electromagnetic induction. I think this highlights why it’s really important for scientists of different disciplines to collaborate and debate more; it’s only then that the really interesting ideas and discussions come about. So on that note, if anyone has any more ideas about this, or has any response to the questions I’ve raised, I’d be really interested to hear them, and please feel free to leave comments below!
* This has actually been suggested in the past by Cooray and Cooray, 2008; paper available here, though the paper doesn’t appear to have been cited, and I couldn’t even find the (obscure) journal’s impact factor.
** Usually. There are exceptions.