( Cornell University researchers have lea...)How fish hear and make sounds at same time

The study marks the first time that scientists have found a direct line of communication between the part of a vertebrate's brain that controls the vocal muscle system and the part of the ear that hears sound. The researchers believe that understanding the auditory system of the plainfin midshipman fish (Porichthys notatus ) -- a 6- to 10-inch fish found along the coastline from Alaska to California -- will offer insights into how other vertebrates -- including humans -- hear.

The general pattern of connections between neurons in the auditory system is the same in all vertebrates, including mammals. While humans hear with the cochlea of the inner ear, the midshipman uses the sacculus, a part of the ear that in humans detects acceleration or linear movement.

Because the study indicates a relationship between the ear and the auditory and vocalization systems of the brain, it could help scientists understand some of the mechanisms that contribute to deafness.

"We've studied so many things about these fish, and I never cease to be amazed by how similar the operation of their nervous system is to that of mammals," said Andrew Bass, professor of neurobiology and behavior at Cornell, and an author of the study published in the June 22 issue of the Journal of Neuroscience. "You don't need to study a mammal to understand what a mammal does."

The researchers found that as the fish's brain signals vocal muscles to make sound, a number of synchronized actions take place. The ear and brain are cued to the exact timing of a self-generated sound, distinguishing it from outside sounds. Just prior to a voicing, the brain warns the ear it should become less sensitive.

When analyzed closely, the vocalizations can be broken down into a series of impulses separated in time by only milliseconds. The syste
'"/>

Source:Cornell University News Service