Hearing the world around us and acting upon the information those sounds give us is one of the most basic things we do as humans. Today researchers published experimental results in the journal Nature exposing how these sounds get transmitted through the brain, and how mammals make decisions based on these sound cues.

Researchers at Cold Spring Harbor Laboratory (CSHL) sought to discover what happens between the auditory cortex - the part of the brain that translates sound into information that the brain can use - and the parts of the brain that make decisions and issue commands to muscles. They trained rats to listen to high and low frequency sounds. When a high-frequency sound was played, the rats were rewarded if they moved left. When it was low, they were given a reward for moving right.

CSHL Professor Anthony Zador and Dr. Petr Znamenskiy were surprised by what they found happening.

"It turns out the information passes through a particular subset of neurons in the auditory cortex whose axons wind up in another part of the brain, called the striatum," Zador said in a media release from CSHL.

Zador had expected the information that went into the auditory cortex to end up in another part of the cortex; an analogical conclusion that was based on another experiment involving the visual system of primates done at Stanford University.

Instead, what he found was that although neurons in the auditory cortex are "tuned" to low or high frequencies, only some of them transfer information to the striatum. These neurons that transfer the information make the decisions for the other ones.

Zador likened it to the US voting system and the Electoral College.

"The neurons registering 'high' and 'low' are represented by a specialized subset of neurons in their local area, which we might liken to members of Congress or the Electoral College: these in turn transmit the votes of the larger population to the place - in this case the auditory striatum - in which decisions are made and actions are taken."