Tugging at the earstrings.

Tugging at the earstrings

The deepest part of the mammalian ear doesn't just sit around listening, according to new anatomical research. Scientists at the University of North Carolina in Chapel Hill now report finding tension-generating cells in the inner ear that contain the same contractile proteins found in muscle. "We think this opens up a whole new way of thinking about the changing mechanical properties of the inner ear," says O.W. Henson.

The unusual cells were first discovered in the ears of bats by Henson and his colleagues. The cells appear able to change the way structures in the inner ear vibrate when stimulated by sound. "We thought initially that these cells might be unique to bats because bats hear very high-frequency sounds," Henson says. But the cells also were found in laboratory mice, and the scientists found descriptions of similar cells, whose function had not been recognized, in human anatomy publications. The scientists suggest that the contractile proteins within these unusual cells pull on external fibers that are attached to the long, spiraling inner-ear structure called the basilar membrane. The motion of the basilar membrane, a crucial element in hearing, would be modified by the tension applied by the fibers. Henson likens the effect to that of pulling on threads attached to the sides of a waving ribbon.