Researchers Pinpoint Brain’s Audiovisual Processing Center

A new study is helping scientists more precisely understand how the brain stitches together sensory information such as sound and images, insight that could shed new light on conditions such as Autism. The research, which appears in the Journal of Neuroscience, identifies an area of the brain in the frontal lobe responsible for working memory and sensory integration.

“Work in our laboratory is aimed at understanding how auditory and visual information are integrated since we know this process is crucial for recognizing objects by sight and sound, communicating effectively, and navigating through our complex world,” said Lizabeth Romanski, Ph.D., an associate professor in the University of Rochester Department of Neurobiology and Anatomy and co-author of the study.

“Our recent study demonstrates that the prefrontal cortex plays an essential role in audiovisual working memory, and when this area is switched off our ability to remember both the auditory and visual cues is impaired,” said to Bethany Plakke, Ph.D., a postdoctoral fellow in the Romanski lab and co-author of this study.

The frontal lobe is the cockpit of the human brain and is responsible for important cognitive skills, such as problem solving, planning, decision-making, working memory, and communication. While sensory inputs are collected in many different parts of the brain, the frontal lobe is where this complex information is integrated with other ongoing events. Consequently, this area of the brain is of great scientific interest not only because of its central role in human cognition, but because of its potential role in sensory integration deficits which occur in disorders such as Autism.

The researchers focused their attention on a region in the brains of primates called the ventral prefrontal cortex which comprises the lower segment of the frontal lobe. This area is anatomically similar to a region in the human brain referred to as the inferior frontal gyrus which contains Broca’s area, a region that is essential for speech and language processing.

The study involved testing the working memory of rhesus monkeys, specifically their ability to associate visual with auditory information. Using short videos, the scientists trained the subjects to remember the faces and “voices” of fellow monkeys. After a period of time, the researchers would show the videos again, this time occasionally mismatching faces and voices. When the subjects recognized the mismatch, they pushed a button and, if correct, received a reward consisting of fruit juice. During the control phase of the experiments, the subjects were able to detect mismatched faces and voices 70 to 80 percent of the time.

However, when the researchers inactivated the ventral prefrontal cortex a reversible process that is akin to putting nerve cells in this part of the brain to sleep the ability to identify the mismatched faces and voices was greatly reduced. Additionally, when it was necessary to only remember faces, performance was not impaired, suggesting that the ventral prefrontal cortex is essential in auditory and multisensory processing.

The research points to the importance of this area of the brain in the process of integrating communication information, or the ability of the brain to combine speech with gestures, facial expressions and other visual input and make sense of it all. As such, these findings may have significant implications in disorders, like Autism, where individuals have difficulty integrating auditory and visual information during communication. The failure to integrate can result in the loss of information and miscommunication and may contribute to the impaired communication and social behaviors that are the hallmark of these conditions.