"It's all in your head." You've heard that before, haven't you? Maybe someone was scoffing at a ghost story or downplaying the symptoms of depression, paranoia or madness. The message is simple: Your obsession, whatever it may be, has no basis outside your thoughts.
Yet with sufficient scientific understanding, it becomes obvious that everything is "all in your head." We don't mean that the world is one great big illusion, but rather that each individual's pool of consciousness and memory exists solely within the electrochemical processes of the brain. Self is a chemical cocktail imbued with a neurological spark, and consciousness is a peculiar parlor trick stirred up by evolution.
That person you think you are? Well, it's the product of a constantly changing equation made up of 95 to 100 billion neurons, along with synapses, neurotransmitters, genetic coding and a string of memories tailing back to the murky depths of childhood [source: Williams]. Alter any factor in this equation just a little, and you change the final sum. In fact, you do a little self tinkering every time you so much as make a simple observation or drink a cup of coffee. Each successive you is at least a slight variant on the previous incarnation. The mind is also subject to the severe alterations of emotional trauma, brain injury and disease, all capable of drastically changing the outcome of the neurological equation.
Our tools for addressing brain conditions have ranged from the sublime to the barbaric. We've treated mental illness on the therapist's couch, as well as with scalpels and electric shock. Fortunately, scientific breakthroughs continue to refine our methods.
For instance, there's neurostimulation, or electrically stimulating nerves to relieve pain or suppress tremors. Doctors accomplish these feats with the aid of tiny neurostimulators implanted near the spinal cord or a major nerve. Deep brain stimulation and vagus nerve stimulation take this concept even further and may effectively manage various psychiatric disorders and neurological diseases. The only catch is they too require painstaking surgery to position implants in the appropriate locations -- in the neck for vagus nerve stimulation and inside the brain for deep brain stimulation.
What if there were a way to stimulate nerves and portions of the human brain without drilling through skulls and implanting electrical devices? What if there were a way to remotely tinker with the neurological equation?
Seeing Inside the Human Mind with Ultrasound
If you've ever experienced an ultrasound or studied the fetal images the technique can produce, then you may have witnessed the future of neurostimulation.
Ultrasound operates like submarine sonar systems or bats, both of which emit sound waves to sense their surroundings. The waves travel until they make contact with an object, then bounce back to the source. A bat or a computer can then determine the shape and distance of the object based on this returning sound wave.
Ultrasound imaging systems transmit high-frequency sound pulses through the human body. Every time they hit a boundary between tissues, some bounce back while others keep going. The machine then calculates the distances and frequencies involved and creates a two-dimensional image of what's going on inside the body cavity -- such as the movements of a fetus in utero.
Scientists have studied the effects of ultrasound on biological tissues since the 1920s. As early as the 1950s, researchers realized that at sufficiently high frequencies (much higher than those used in prenatal care), ultrasound also had the potential to destroy specific cells, especially tumors in the brain.
High-frequency ultrasound (HIFU) promised all of this without harming surrounding tissue or drilling a hole through a patient's skull. For decades, however, researchers lacked sufficient imaging technology to really see what was specifically happening in the brain.
Modern researchers, however, have advanced magnetic resonance imaging (MRI) to glimpse the real-time interworking of the human body. Furthermore, brain-mapping technology continues to illuminate what's going on in the human mind. To return to the equation analogy, this means knowing exactly what parts of the neural equation affect which aspects of our abilities, memory and personality.
In a recent study by neuroscientists at Arizona State University, researchers discovered that low-intensity, low-frequency ultrasound (LILFU) could apply a gentler touch. Instead of destroying cells, these lower frequencies merely stimulate brain circuit activity.
Low-frequency Ultrasound: Therapy and Weapon of the Future?
To understand how low-frequency ultrasound (LILFU) stimulates brain circuit activity, you have to grasp what's going on with your gray matter when doctors aren't using high-tech gadgetry to blast it with sound waves.
Brain cells release neurotransmitters, molecules that carry information from one nerve cell to another across small gaps called synapses. When they arrive at another cell, neurotransmitters cause ion channels to open, which in turn triggers the electrical impulses that pass messages along nerve fibers. These reactions are a vital component of the brain's circuitry, and neurotransmitter disruptions are symptoms of such debilitating conditions as Alzheimer's disease, Parkinson's disease, depression and epilepsy.
The team of neuroscientists at Arizona State University found that LILFU waves boosted the release of neurotransmitters, possibly by opening up sodium and calcium ion channels enough to trigger action potentials, which in turn release neurotransmitters. This means that, without invasive surgery, physicians in the future may be able to undo the damage produced by diseases such as Alzheimer's by stimulating the production of the very neurotransmitters that the condition disrupts.
It will take years of research and development before LILFU technology is ready to alter human brain circuitry and nonsurgically repair neurological injuries and diseases.
As you might imagine, however, the effects of ultrasound on the human brain haven't inspired only therapeutic innovations. Various studies have reportedly theorized that ultrasonic weapons could be used to induce vomiting and nausea in victims -- perhaps during a riot-control scenario [source: Jauchem]. Other scientists suggest that the technology could eventually allow us to manipulate human memory.
Ultrasonic mind control is a science very much in its infancy. With enough research, we might one day live in an age where police use ultrasound to incapacitate you at a protest, while physicians optimize human brain efficiency with a little ultrasonic fine-tuning.
Explore the links on the next page to learn even more about ultrasound and the human brain.
Related HowStuffWorks Articles
More Great Links
- Chudler, Eric. H. "Neurotransmitters and Neuroactive Peptides." Neuroscience for Kids. 2008. (Aug. 21, 2009)http://faculty.washington.edu/chudler/chnt1.html
- ter Haar, Gail and Constantin Coussios. "High Intensity Focused Ultrasound: Past, present and future." International Journal of Hyperthermia. February 2007.
- Jauchem, James R. "High-Intensity Acoustics for Military Nonlethal Applications: A Lack of Useful Systems." Military Medicine. February 2007.
- "Neuroscience: Sound and no fury." The Economist. Jan. 8, 2009. (Aug. 21, 2009)http://www.economist.com/sciencetechnology/displayStory.cfm?story_id=12887217&fsrc=rss
- Song, Sora. "How Deep-Brain Stimulation Works." Time Magazine. July 16, 2006. (Aug. 21, 2009)http://www.time.com/time/magazine/article/0,9171,1214939,00.html
- "Spinal Injections Procedures: Neurostimulation." American Pain & Wellness. (Aug. 21, 2009)http://www.painandwellness.com/spinal_injections_neurostimulation.html
- "Ultrasound Shown to Exert Remote Control of Brain Circuits." Science Daily. Nov. 2, 2008. (Aug. 21, 2009)http://www.sciencedaily.com/releases/2008/10/081029104251.htm
- Williams, Robert W. and Karl Herrup. "The Control of Neuron Number." The Annual Review of Neuroscience 11. Sept. 28, 2001. (Aug. 25, 2009)http://www.nervenet.org/papers/NUMBER_REV_1988.html#1