The Universal Sense (25 page)

But even when you are not collecting evoked potentials, the free-running brain is never silent (unless it’s dead), nor is it chaotic (unless the subject is having a major seizure). And while an untrained person looking at a raw EEG tracing sees what looks like almost random rises and falls, buried within the mass electrical response of the brain there are five major rhythms that underlie global functions of the human cortex, all combined, but each changing under different physiological or cognitive conditions. The theta rhythm is the slowest at 4–8 Hz and seems to arise, at least in part, from the hippocampus during memory processing. The alpha rhythm, cycling 6 to 12 times per second (6–12 Hz), is generated by connections among different parts of the cortex and between the cortex and thalamus, the brain’s relay center. It is often subdivided into the lower-1 alpha band (6–8 Hz), the presence of which indicates alertness; the lower-2 or posterior alpha band (8–10 Hz), seen during changes in attentional states; and the upper alpha band (10–12 Hz) which is often triggered by external events and language-based memory
tasks. The beta rhythm (20 Hz) is generated in the motor cortex, which controls voluntary movement, and is usually only seen shortly after the subject stops moving (sort of an “off” or “end program” signal). The gamma rhythm is the fastest at 40 Hz and is one of the more interesting and controversial of the brain’s major rhythms.

Several studies have described the presence of a gamma “wave” traveling from the front to the back of the brain, sweeping across much of the cortex. This has led to the hypothesis (still unproven) that the gamma band may be involved in binding together all of the individual sensory inputs and feedback loops that let you perceive the world as a consistent place that doesn’t wobble about between blue, high-pitched, nasty-smelling, and too hot.

These rhythms are part of the basic infrastructure of the working brain. The presence of these rhythms in EEG traces are evidence of the coordinated firing of millions of interconnected neurons, underlying functions critical enough for the brain to devote large proportions of its processing power to them. Access to these functions is an opportunity for brain hacking—and for marketing of devices that use such access with highly varying degrees of effectiveness.

Trance bells, mind-brain machines, neural feedback devices, iPod brain hacks—even the most basic online search will lead to dozens of hardware or software products claiming to unlock the power of your mind using sounds beeping and lights flashing at one or more of the rhythms mentioned above. While most of them are based on less real science than a 1950s Godzilla movie, the funny thing is that a lot of them will work anyway because of user expectation. If you are out shopping for a brain-mind machine to let you supercharge your executive powers,
well, you’re already halfway convinced, and you’ve probably already spent money on sillier things, such as sleep-learning tapes to improve your dog’s self-esteem. (No, I’m not making that up. After all, you do have to worry about the self-esteem of a dog that lets its master put headphones on it. Perhaps after a while it will dream of chasing really big rabbits.) In fact, it actually is possible to induce changes in mental states by correct manipulation of sensory information at rates that use these basic rhythms.

At first it might seem easiest to just play a tone or a noise at a specific rate, say the 8–10 Hz posterior alpha rhythm, through a pair of headphones and wait for a soothing sensation to take over. Unfortunately, it’s more likely to become rapidly annoying or boring enough to drive you to think. This is because of a number of factors that we’ve mentioned before, including adaptation, habituation, and the fact that playing a single tone to both ears simultaneously will use only a very small percentage of your auditory processing power. Whether the sound uses the posterior alpha rhythm or not, it’s just going to be a rapid pinging in your ear, like a microwave that really wants your attention. This, it seems almost needless to say, is super-annoying and probably will not hypnotize you.

To get massive amounts of your brain entrained to a single rhythm, you need complicated input from a number of sources all acting in concert. One method is to use binaural beating. It’s a remarkably simple way to drag more of the brain into processing sound at desired rates. If you play, say, 440 Hz in your left ear but 444 Hz into your right ear, you will hear not two separate tones irritatingly close in pitch but rather a single tone that seems to be modulating four times per second. This is due to the action of the superior olive, an auditory nucleus in your
brain stem that lets you figure out the position of sound in space based on relative amplitude and/or on time differences between your two ears.

The superior olive is the first place in your brain that receives input from both of your ears, and it carries out mathematical analyses to determine where the sound is coming from in space. If both ears are presented with the same tone, the superior olive passes the information to the rest of your brain and you perceive a single sound in a fixed position, such as in the middle of the speakers in an open room, or in the middle of your head if you’re wearing headphones. However, if there is a slight difference in frequency between the two ears, on the order of a few Hz, you get the sensation of the sound moving back and forth between your ears at the rate of the difference between the two tones. If the frequency difference is a bit larger, around 4–12 Hz, what you hear is a single tone that seems to change in amplitude at the modulation rate. With an even greater difference (typically on the order of 20-40 Hz), you will in fact hear two separate tones and be convinced all is well; your head will be mercifully un-throbbing. So binaural beating can be a simple but effective way to entrain your brain from your brain stem up to your cortex as long as you are using simple tones and relatively low modulation rates, such as those in the alpha, theta, and delta rhythms.

If you listen to binaural beating tones, you can get some meditative or attentional effects, depending on your level of expectation and preparation for these states. But listening to single tones warbling over and over for twenty minutes can test the patience of even the most dogged pursuers of altered mind states. Most people who have tried it agree that it has an effect but they never want to do it again, preferring to have three or four mojitos to achieve an equally altered state with more potential
for dancing. So some of the more effective brain hacks use complex sounds composed of multiple frequencies (music, speech, car crashes), which in and of itself devotes more brain processing to the task, and turn up the power more by modulating not just the amplitude but the relative position as well—what sound engineers call “panning.” You’ve heard numerous examples of this technique, particularly in 1960s and 1970s classic rock, such as the opening to Pink Floyd’s “Welcome to the Machine,” where the engine-like sounds appear to move relatively slowly from one speaker (or ear) to the other by smoothly shifting the relative volume of the sounds from left to right.

But the superior olive uses amplitude differences only for relatively higher-frequency sounds (above about 1,500 Hz for humans—think of the shriek made by a small child who has just found a bug in her milk). For sounds made up of frequencies below this, the superior olive relies on differences in fine timing or phase differences between the two sounds. So if you use a complex musical piece and take care to synchronize the phase differences for low frequencies and amplitude differences for high frequencies, you can get a frighteningly realistic sense of apparent motion from the sound even just using stereo speakers or headphones. And it’s also how you can remix almost any piece of music (aside from drum solos) to evoke mind-altering states. Here’s where it starts to get fun.

What if you
don’t
synchronize the modulation rates? What if you make the high-frequency sounds go at one rate and the low-frequency sounds go at another rate and constantly change the rates in between? Then you potentially have a very serious, effective, and fun (for some people) or awful (for other people) brain hack.

Here’s an example. In my misspent youth, I got a phone call
from my old friend, Lance Massey, who asked, “What is psychophysics?” I gave him a very long lecture about sensation and perception. Then he asked the question that still is causing us trouble: “Does this mean we can do mind control with music?” My answer, based on years of study and experimentation, was, “I dunno. Let’s try it.” And so we became the frontmen for a very unusual band.

Lance composed a series of ambient musical pieces to which we applied embedded modulation rates based on best stimulation frequencies for different parts of the brain, to try to create specific psychological effects in a listener. The idea we had was to use music to elicit neuronal responses that targeted specific areas in the brain. It’s similar to how modulations of a carrier wave transmit information via radio. You’re not that interested in the carrier itself—you are just using it to carry the modulations to a receiver where it gets converted into a useful signal for the listener. This kind of sonic algorithm is several steps more complicated than simple binaural beating. The idea is to modulate amplitude, frequency, and phase characteristics of almost any musical or other complex acoustic signal at frequencies that best stimulate the parts of the brain that do certain things, such as induce emotional responses, change heart rate or blood pressure, make the listener feel as if he or she is moving, or just change the listener’s attentional states.

One of our first efforts was to use phase and amplitude changes that would make the music seem to orbit a listener’s head. At our first public concert, in a little hole-in-the-wall club in lower Manhattan, we noticed people slowly wobbling around in their seats when the piece came on—and when one guy fell out of his seat as a big virtual motion shift kicked in at one point in the music, we knew we were on to something. Just by using
this orbital position sonic algorithm, a simple ambient music piece began to do something weird: control how people thought they were moving in space. So we decided to ramp up the evil meter to 11 by slowly changing the modulation rates for different frequency bands. We thought a piece that used this algorithm would make people feel like they were moving but confuse them when some of the sound elements seemed to move one way and some the other. We lovingly titled this “The Vertigo Tour” and unleashed it as a track on our CD.

Despite the fact that I knew I was torturing my listeners, I begged and pleaded for feedback from anyone who got a copy. It broke down in an interesting fashion. After a few minutes of listening, about one-third of the listeners felt like they were moving when the amplitude and phase were synchronized, another third thought the music was moving through the sound field, and the final third got violently ill. Yay science. We had figured out how to induce auditory motion sickness. Unfortunately, the chair of my department at the time, a dedicated audiophile whose sound system was worth more than my salary, fell into the third category. The day after I handed him the pre-release CD, he emerged from the elevator while I was trying to get caffeinated, grabbed my arm, and said, “Your music made me sick!” “Then I guess we win!” I said, not too brightly. After all, just using relatively simple modulation rates, carefully applied in a complex musical piece, I managed to hack my department chair’s brain and make him almost throw up all over his expensive stereo system.

Luckily, I found another position relatively quickly, as even I realized that the financial possibilities of an acoustic vomit stimulator were rather limited. But it proved to me that acoustic brain hacking could have profound effects on the listener,
even at a physiological level. And while inducing vomiting is not really among the top ten effects you’d like to get from your listening audience, it demonstrated that it might be possible to start getting targeted, specific responses to manipulated sounds. So what about using sound to get effects that somebody might actually want to induce in a listener?

Music and sound have always been used as a means for inducing emotional and other responses in audiences, and they do it under your cognitive radar. Movies don’t put up big signs saying “shriek in fear” right before the monster taps the hero on the shoulder, and asks him to get off its tail, at least not in the same way as prompt signs tell a TV studio audience to applaud. Instead, the slithering sound, the sudden silence, the overwhelming roar go from the ears right to the parts of the brain that modulate emotional response via the sympathetic nervous system, and you find yourself scattering your popcorn. So when word first started getting out about our concert/experiments, we were approached by a British metal band called Thrush who told us they were writing a song about brutality in the legal system and wanted us to modify the song so that anyone who heard it would shriek with terror. This is not the kind of thing you normally think of as a desired outcome for listening to music, but that’s metal bands for you, and we accepted the challenge. And once again, acoustic science gave us the answer by applying sound to the emotional connections in the brain.

Working feverishly in the dark, secluded Bavarian castle of my Long Island apartment, I made a filter that would take any sound and throw our old friend the pseudo-random fingernails-on-a-blackboard envelope over it, then applied it to the metal band’s song. When we played it back for final re-recording, the studio engineer ran out of the room screaming and refused to
work with us ever again. Thus is success measured in the world of neurosensory algorithmic brain hacking. At least this time no one had to mop up.

So by reverse-engineering a sound with a known emotional and physiological effect using relatively simple algorithms, it is possible to capitalize on intrinsic brain properties to get targeted perceptual effects just using music as a carrier wave. But what about doing something both less disturbing and more specific? Something with a very specific outcome that didn’t involve vomiting or running away screaming?