Boston University Scientists Find Pattern in Cellular Activity
(Boston, Mass.)--A mathematically predictable form known as a fractal can describe the activity of individual cells as well as complex physiological systems, report Drs. Steven B. Lowen and Malvin C. Teich of Boston University's College of Engineering in a paper which appears in today's Journal of Neuroscience. Co-authors of the paper are Sydney S. Cash of Columbia University and Prof. Mu-ming Poo of the University of California, San Diego.
The scientists worked with isolated pairs of neurons (nerve cells) and muscle cells from frogs. Even at rest, the neurons continuously send out chemical signals in discrete units, called quanta, to the muscle cells. The researchers examined the rates at which the quanta fire to signal muscle cells. They found that the rate at which these quantal emissions occur can be predicted using the mathematics of fractals.
Fractals occur commonly in nature. They are objects that are made up of smaller copies of themselves. A fern, for example, is fractal because each frond is composed of sub-fronds, each a miniature, but not necessarily identical, copy of the whole. This pattern is repeated on a smaller scale over and over again. Similarly, river networks, blood supply systems and other branching systems contain smaller parts that resemble the system as a whole. These complex shapes can be described conveniently in mathematical terms.
The scientists compared the rates at which a neuron released a quantal signal to the muscle cell over various time periods. As they looked at smaller and smaller time scales, the fluctuations in the rate changed, but the overall pattern of quantal emissions remained essentially the same. These patterns can be described and predicted with the mathematics of fractals.
Previously the team had demonstrated fractal patterns in auditory and visual neurons in a variety of animals, as well as in the sequence of human heartbeats. "The importance of this study is the discovery of a common behavior at very different levels of signal transmission in the nervous system," says Teich. "It is not known why it is there, but it is clearly important since it is ubiquitous."
Lowen adds, "Our results will help us better understand normal body function and, since fractal behavior can be quantified, it can help us diagnose the health of cells and systems within the body. It also may help us learn more about how drugs act within the cells so that we can develop new, more effective drug therapies."