It’s coming up Christmas time and as my thoughts turn to the music, Stanford University (California, US) researchers are focused on hearing and touch (the two are related) according to a Dec. 4, 2013 news item on Nanowerk,
Much of what is known about sensory touch and hearing cells is based on indirect observation. Scientists know that these exceptionally tiny cells are sensitive to changes in force and pressure. But to truly understand how they function, scientists must be able to manipulate them directly. Now, Stanford scientists are developing a set of tools that are small enough to stimulate an individual nerve or group of nerves, but also fast and flexible enough to mimic a realistic range of forces.
The Dec. 3, 2013 Stanford Report article by Cynthia McKelvey, which originated the news item, provides more detail about hearing and the problem the researchers are attempting to solve,
Our ability to interpret sound is largely dependent on bundles of thousands of tiny hair cells that get their name from the hair-like projections on their top surfaces. As sound waves vibrate the bundles, they force proteins in the cells’ surfaces to open and allow electrically charged molecules, called ions, to flow into the cells. The ions stimulate each hair cell, allowing it to transfer information from the sound wave to the brain. Hair bundles are more sensitive to particular frequencies of sound, which allows us to tell the difference between a siren and a subwoofer.
People with damaged or congenital defects in these delicate hair cells suffer from severe, irreversible hearing loss. Scientists remain unsure how to treat this form of hearing loss because they do not know how to repair or replace a damaged hair cell. Physical manipulation of the cells is key to exploring the fine details of how they function. This new probe is the first tool nimble enough to do it.
The article also goes on to describe the ‘nano’ probe,
The new force probe represents several advantages over traditional glass force probes. At 300 nanometers thick, Pruitt’s [Beth Pruitt, an associate professor of mechanical engineering] probe is just three-thousandths the width of a human hair. Made of flexible silicon, the probe can mimic a much wider range of sound wave frequencies than rigid glass probes, making it more practical for studying hearing. The probe also measures the force it exerts on hair cells as it pushes, a new achievement for high-speed force probes at such small sizes.
Manipulating the probe requires a gentle touch, said Pruitt’s collaborator, Anthony Ricci, a professor of otolaryngology at the Stanford School of Medicine. The tissue samples – in this case, hair cells from a rat’s ear – sit under a microscope on a stage floating on a cushion of air that keeps it isolated from vibrations.
The probe is controlled using three dials that function similarly to an Etch-a-Sketch. The first step of the experiment involves connecting a tiny, delicate glass electrode to the body of a single hair cell.
Using a similar manipulator, Ricci and his team then press the force probe on a single hair cell, and the glass electrode records the changes in the cell’s electrical output. Pruitt and Ricci say that understanding how physical changes prompt electrical responses in hair cells can lead to a better understanding of how people lose their hearing following damage to the hair cells.
The force probe has the potential to catalyze future research on sensory science, Ricci said.
Up to now, limits in technology have held scientists back from understanding important functions such as hearing, touch, and balance. Like hair cells in the ear, cells involved in touch and balance react to the flexing and stretching of their cell membranes. The force probe can be used to study those cells in the same manner that Pruitt and Ricci are using it to study hair cells.
Understanding the mechanics of how cells register these sensory inputs could lead to innovative new treatments and prosthetics. For example, Pruitt and Ricci think their research could help bioengineers build a better hair cell for people with impaired hearing from damage to their natural hair cells.
Stanford has produced a video about this work,
I find it fascinating that hearing and touch are related although I haven’t yet seen anything that describes or explains the relationship. As for anyone hoping for a Christmas carol, I think I’m going to hold off until later in the season.