Even the simple act of swallowing requires coordination of over 30 muscles. Even a small loss in function can cause severe disability. Nerve stimulation is a way for these people to regain their oral function.Researchers at Texas A&M University recently determined the minimum amount of electric currents required to produce sensation in various parts of the mouth. Researchers said that their study was a crucial step in building stimulation implants that can restore vital intraoral functions lost to brain or nerve damage.The study's results were published in the journal Institute of Electric and Electronics Engineers (IEEE) Transactions on Biomed Engineering.Sensorimotor feedback loops are responsible for many essential bodily functions. These neural circuits, as the name implies, involve the brain reading the signals from the sensory nerves and commanding motor nerves to perform a particular movement. Sensorimotor loops, for instance, play an important role in voluntary movements like walking, holding an object, or blinking.The mouth, also known as the intraoral cavity or the oral cavity, is home to a wealth of sensory and motor nerves. Sensorimotor nerves, located in the soft palate and on the tongue, coordinate intraoral movements such as swallowing, speech, and respiration. These essential functions can be compromised by damage to the motor or sensory nerve fibers from neurotrauma, or other diseases, which can lead to a decrease in quality of life for those affected.The idea of electrical nerve stimulation could be used to stimulate the nerves. This is similar to how a pacemaker can stimulate the nerves in the heart. It causes the heart muscle contraction. However, details about the frequency and amplitude required for stimulation of different parts have not been studied.Dr. Hangue Park is an assistant professor in the Department of Electrical and Computer Engineering. "Electrical stimulation may modulate nerve currents and action potentials which are the mode of communication between the brain and the body," she said. It is important to use electrical stimulation with care, as it can have undesirable side effects or even stop stimulating anything.Park and his team placed tiny metal electrodes inside a standard retainer to determine the minimal stimulation currents required. The electrodes were placed in the mouths of subjects to stimulate their soft palates or the tip and side of the tongues, which have a large supply of sensory nerves. Researchers gradually increased the stimulation current at each location, while keeping the frequency constant. Next, the researchers asked subjects to describe when they felt the sensation. The experiment was repeated for a higher current frequency.The team compiled their data and determined the discomfort thresholds and average perception of the tongue and soft palate. To replicate the electrical properties in that area, the researchers also created an identical circuit for the intraoral cavity. The researchers believe that this circuit can be used to study the effects of electric stimulation offline, without the need for human subjects.Researchers noted that the next step would be to stimulate the intraoral area with an electric current and examine how this simulations affect chewing, swallowing, and other behaviors.Park stated that "sensorimotor system can be extremely vulnerable due to neural defects and aging, neurodegenerative diseases, and aging." "In this study we have laid the foundation for electrically stimulating parts in the mouth that control voluntary and involuntary movements. This is a landmark study that will help us in the future to assist people who face huge challenges with everyday tasks we take as a given.
