14 DAY TRIAL // Investigators finally managed to gain new insight into how the complex network of neurons in the auditory cortex responds to sounds within a specific frequency band.
Discovering how this happens has been a long-standing goal for experts. Previous studies have demonstrated that our brains are capable of mapping the aural world around us based on the frequencies of the sounds we hear.
However, the exact mechanisms through which this happens remained elusive until now. Experts compare this ability of the auditory cortex to the one the visual cortex has of drawing out maps of our surroundings by spatially identifying the objects in it.
One of the most peculiar things about the auditory cortex is that it is divided into smaller modules, each of which is capable of responding to a very specific frequency band.
In the new investigations, experts at the Cold Spring Harbor Laboratory (CSHL) have made significant progress in determining precisely how this process takes place.
The team here focused its research on understanding how functional connectivity between auditory cortex neurons is responsible for creating the acoustical maps we perceive.
The study was led by CSHL professor Anthony Zador MD, PhD, who is the chair of the Neuroscience Program at the laboratory. Details of the work appear in the October 17 issue of the esteemed journal Nature Neuroscience.
“What we learned from this approach has put us in a position to investigate and understand how sound responsiveness arises from the underlying circuitry of the auditory cortex,” Zador explains.
Despite producing maps similar to that created by the visual cortex, the neural organization in the auditory cortex is very different from that underlying any other sensory input control area in the brain.
One of the main differences is that the sound receptors in the ear's cochlea are disposed in a one-dimensional pattern. Visual receptors on the retina are organized in a 2D arrangement.
“Because sound is intrinsically a one-dimensional signal, unlike signals for other senses such as sight and sensation which are intrinsically two-dimensional, the map of sound in the auditory cortex is also intrinsically one-dimensional,” Zador adds.
“This means that there is a functional difference in the cortical map between the low-to-high direction and the direction perpendicular to it,” he adds.
“However, no one has been able understand how that difference arises from the underlying neuronal circuitry,” the expert goes on to say.
CSHL experts say that their work could have practical applications as well, such as for example understanding how diseases such as autism change the way neurons are set up in various cortices.