As you reach for your keys every morning before heading out the door, have you ever stopped to wonder how exactly those thoughts are so swiftly turned into the precise movements of your fingers?
Hoping to shed some light on this question, two Hopkins professors have devoted a great deal of energy to studying electric fish. They aim to uncover the mechanism the brain uses to send signals to the limbs by decoding how sensory inputs, such as touch, sight or other cues that stimulate the brain, are transformed into our everyday actions.
While you may take them for granted, your movements are the result of systematic commands signaled through specific links between your nervous system and muscles. In effect, there is a constant feedback loop between brain and body controlling every move you make.
Understanding these complex processes may make it possible for engineers to construct better rehabilitative options for the many patients with problems in these areas.
Noah Cowan, assistant professor in the Department of Mechanical Engineering, and Eric Fortune, assistant professor in the Department of Psychological and Brain Sciences, combined their expertise in an attempt to unite theories relevant to brain function and behavior with the laws of physics and chemistry.
Their research, published in the Jan. 31 issue of the Journal of Neuroscience, attempts to explain certain aspects of how sensory control systems of movement may function.
They set up an experiment studying the movements of a special species of fish, Eigenmannia virescens, more commonly known as the glass knifefish. This nocturnal fish is weakly electric, meaning that it is not only able to create electric fields but is also able to detect them.
With poor visibility, these fish rely on this electrical sense to orient themselves in the water and to communicate with one another. Additionally, the fish are mostly transparent, making them ideal subjects for all sorts of studies.
Cowan and Fortune designed an experiment in which a fish is placed in a tank with a rectangular tube. The fish instinctively choose to swim into the tube to hide. As the tube is moved, the fish automatically swim back and forth to remain hidden.
The researchers moved the tube back and forth at ever increasing frequencies to test the capacity of the fish to keep its position. The fish kept up with this rhythmic pattern over a fairly lengthy period of time and a wide range of frequencies, indicating its adaptability to changes in the environment.
Using its electrical sense, the fish detects changes in the tube, and uses these changes to control its motion. As the tube moves, the "electric image" of the tube moves along the fish's body. This is similar to the way our eyes can track a moving object. In effect, these fish use an electric sense to "see" and thereby keep positioned in the water.
The fish moved precisely forward or backward just enough to stay in the tube. Through careful calculations and observation, Cowan and Fortune concluded that electrical senses triggered signals in the fish's brain, which seems implicitly wired to understand Newton's laws.
The brain is able to calculate how much acceleration is necessary to find the right position without over- or undershooting the tube. These findings demonstrate that the nervous system is aware of velocity and can specify the proper amount of force with incredible precision.
Every move you make, whether conscious or automatic, is controlled quickly, precisely and in real time by signals sent from the brain to the body. Understanding how this mechanism works in model animals such as fish has tremendous implications for both basic biology and engineering.
Knowledge of the mechanisms of sensory processing and the adjustment of movement to the environment are necessary to the efforts of scientists and doctors working on alternatives for patients who have sensory-motor problems or are in need of prosthetics.
At present, artificial limbs can offer, at best, jerky and uncoordinated movement. With these findings and further research, it may become possible to design artificial limbs that would potentially function through mechanisms similar to normal motion. They would be under the conscious control of the user but could also adjust automatically to environmental cues, such as the way a hand naturally folds around a baseball.
As their research continues, Cowan and Fortune hope to gradually uncover the patterns that govern sensory control of movement in an effort to make significant advances in treatment options for the patients who have lost these functions.
Please note All comments are eligible for publication in The News-Letter.