The human brain is incredibly skilled at adjusting our perception of sounds based on various factors such as the environment we are in or our current focus. However, the specific mechanisms by which the brain processes, filters, and reacts to sounds remain a mystery. Recently, biologists have made progress in unraveling this mystery. Through studies using an animal model, researchers have identified the orbitofrontal cortex (OFC), a brain region primarily associated with decision-making rather than hearing, as playing a crucial role in aiding the auditory cortex (a key hearing center in the brain) in adapting to changing contexts or stimuli.
Have you ever noticed how certain sounds suddenly become more prominent when you consciously focus on them, like the hum of a refrigerator or hearing your name in a noisy crowd?
The human brain is remarkably adept at adjusting what we hear based on contexts, like our current environment or priorities, but it’s still unknown how exactly the brain helps us detect, filter and react to sounds.
Now, researchers at the University of Maryland have made progress in solving this puzzle. Using an animal model, they discovered that the orbitofrontal cortex (OFC), a brain region known for decision-making but not traditionally associated with hearing, plays a critical role in helping the auditory cortex (a primary hearing center of the brain) adjust to changing contexts or situations. The findings of this study were published in the journal Current Biology on July 11, 2024.
“Our hearing is not only influenced by the sounds around us but also by our ongoing activities and priorities at that moment,” explained UMD Biology Assistant Professor Melissa Caras, the senior author of the study. “Understanding the neural mechanisms behind these adjustments could provide insights into and potential treatments for neurodevelopmental disorders such as autism, dyslexia, or schizophrenia, where sensory processing is disrupted.”
To investigate the brain circuits involved in hearing, researchers studied gerbils, whose hearing systems are similar to humans. The gerbils were exposed to sound patterns in different contexts: passively listening or actively responding to the sounds. By observing and manipulating the brain activity of the gerbils, the researchers found that the OFC helped the animals transition between passive and active listening modes.
“In essence, the OFC signals the auditory cortex when it’s time to pay close attention to sounds,” Caras explained. “While it’s unclear whether these signals are direct or relayed through another brain region, the OFC’s activity is crucial in the behavior of the gerbils during our experiments.”
When the OFC was deactivated, the gerbils’ auditory cortex failed to switch between passive and active listening, impacting their ability to focus on and respond to relevant sounds.
“To illustrate this in a human context, it would be like asking you to suddenly focus on the hum of your refrigerator in the background,” Caras stated. “If your OFC was inactive and unable to signal your auditory cortex, you might struggle to do so as your ability to adapt your sound perception would be hindered.”
Although this study was conducted with animals, Caras suggests that the findings could have significant implications for human health. The capacity to swiftly shift attention to important sounds is crucial for daily activities like communication and navigating challenging environments.
“We are just beginning to comprehend how the brain adjusts hearing sensitivity in response to changes in behavior. Our goal is to delve into how the OFC communicates with the auditory cortex and explore methods to enhance this connection to improve hearing abilities,” Caras emphasized. “This research sets the foundation for developing enhanced strategies to boost hearing capabilities in both healthy individuals and those with sensory issues.”
This research received support from the National Institutes of Health under Award Nos. R00DC016046 and R01DC020742.
