(Boston, Mass.)--A team of scientists led by Dr. James J. Collins of the NeuroMuscular Research Center and the department of biomedical engineering at Boston University has demonstrated that the presence of a certain level of background "noise" can enhance an individual's ability to feel a subthreshold stimulus, one which he or she ordinarily would not feel. The finding was published in today's issue of Nature.
"Noise," as used by engineers, can be any background stimulus or unintended signal, like static on a radio, which arises in a system. In this study the noise was produced by stimulating the fingertips of the subjects with a mechanical device which slightly indented the tip. Subjects were asked to indicate when they were able to feel a separate test stimulus to their fingertip as the level of noise was varied.
The ability to enhance detection of a stimulus by introducing a specific level of noise is known as stochastic resonance. Although stochastic resonance has previously been demonstrated in the sensory neurons of rats and other animals, Collins' work is the first instance in which it has been tested in human beings by measuring the ability of an individual to detect a stimulus below their ordinary threshold level.
In the article, Collins and his colleagues demonstrate that as noise intensity was increased, the ability of the subjects to detect the test stimulus also increased until it reached an optimum level. As the noise level continued to increase beyond the optimum level the ability of the subjects to feel the test stimulus declined.
"The results of this study have possible implications for clinical treatment," says Collins. "These findings could lead to the development of noise-based techniques to improve the tactile perception of people who have experienced a loss of sensation as a result of natural aging, diabetic neuropathy or stroke. There are also possibilities for developing tactile interfaces for telerobotics and virtual environments."
Collins also collaborated in another study of stochastic resonance as part of a team led by Dr. Paul J. Cordo of the R.S. Dow Neurological Sciences Institute in Portland, Oregon. This study, reported in the same issue of Nature, found that enhanced sensitivity to a weak movement signal (in this case a slight rotation of the wrist) could be produced in muscle spindle receptors by introducing noise through stimulation of the tendon of the parent muscle.
The NeuroMuscular Research Center (NMRC) at Boston University is made up of scientists in the fields of biomedical engineering, neuroscience, rehabilitation medicine, and related fields who collaborate to increase understanding of motor control and improve the quality of health care for neuromuscularly impaired patients through basic and applied research.
The department of biomedical engineering is part of the Boston University College of Engineering. With its state-of-the-art facilities, the College of Engineering is a leader in the development and commercialization of technologies that are transforming the nation and the world. The College offers degrees in aero-mechanical; electrical, computer, and systems; and manufacturing engineering, as well as biomedical engineering. The College also offers special programs, including undergraduate and graduate degrees in environmental engineering, and joint degrees with the School of Management and the School of Medicine.