14 DAY TRIAL // British researchers from the University of Bristol recently conducted a study that finally revealed how locusts distinguish between different sounds. The way this mechanism works has eluded scientists for a long time, but its intricate workings have finally been exposed.
The group determined that nanoscale structures inside the eardrum of the insects are responsible for mechanically processing various sounds, and creating the necessary impulses that allows the locusts' brains to distinguish between different pitches.
A deep understanding of how this process works could open up the way to several new applications, including the development and manufacture of signal processing devices that can be inserted in micro-scale microphones. Doing so has thus far proven to be very difficult.
One of the first things the UB team found was that the locust eardrum did not behave like any other eardrum out there. Additionally, the receptor was found to have nothing in common to the way microphone membranes function. A complicated sound information processing structure was discovered.
Since locusts swarm, it is very important for them to distinguish between the sounds made by thousands, perhaps millions of other insects, and the echolocation noises that a bat produces. This difference can mean the difference between life or death for the locusts.
Using lasers to accurately measure the deformations of the eardrum revealed concentric waves of vibrations that traveled across it like tsunamis over an ocean. Lower-pitched sounds were found to travel all the way to the extremities of the ear drum, where the nerve cells coding for these frequencies were located.
Conversely, higher-pitched sounds only produced deformations that traveled across half the eardrum, to points where neurons coding for high frequencies were located. The investigation was led by UB School of Biological Sciences investigators, Dr. Rob Malkin.
“It rapidly became evident that the distribution of the vibrational energy was odd […] quite unlike what normal materials do when waves travel through them,” explains Malkin, who is an aerospace engineer by profession.
The team found that the locusts did not have the complex hearing apparatus that higher species have. A single structure is responsible for sound capture, local amplification and frequency analysis, minimizing operational requirements and boosting efficiency.
“This is a feat of miniaturisation and simplification; we now need to make a similar sensor and test it,” Malkin concludes.