A new study has shown that a region linked to working memory and multisensory integration may significantly influence the brain's processing of social signals.
The ventrolateral prefrontal cortex (VLPFC) is home to neurons integrating voices and faces.
However, recent research reveals that these neurons are also involved in processing the identity of the "speaker" and the expression expressed through vocalizations and facial gestures.
We still don't fully understand how facial and vocal information is combined and what information is processed by different brain regions.-Lizabeth Romanski, senior author
Humans and macaques are among the primates whose brains have an expanded region known as the VLPFC. The Romanski Lab played brief films of other macaques in this study, making friendly, hostile, or neutral vocalizations or emotions toward rhesus macaques.
The activity of almost 400 neurons in the VLPFC was recorded for the study and published in the Journal of Neuroscience. It was discovered that, taken as a whole, the cells did not show any significant categorical reactions to the identities or expressions of the macaques in the films.
Nevertheless, a machine learning model could be trained to decipher the identity and expression in the movies based only on the patterns of brain activity when the researchers merged the neurons as a population, indicating that neurons were responding to these characteristics together.
We used dynamic, information-rich stimuli in our study and the responses we saw from single neurons were very complex. Initially, it was difficult to make sense of the data.-Keshov, lead author
He goes on to say that the scientists only discovered a cohesive structure once they looked at the relationship between population activity and the social information in our stimuli.
One of the main goals of the Romanski lab is to comprehend how the prefrontal cortex processes information from both the visual and auditory senses. This procedure is needed for both auditory and visual object recognition, as well as for efficient communication.
The VLPFC was shown to be part of the brain in earlier studies conducted by the Romanski Lab to be in charge of preserving and combining voice and facial recognition during working memory.
Numerous studies indicate the significance of this brain area in the broader circuit that supports social communication.
Romanski concludes that by understanding the characteristics that neuronal populations extract from facial and vocal stimuli and how these characteristics are typically integrated, our society can better understand what may be altered in speech and communication disorders, such as autism spectrum disorders, wherein the optimal combination of multiple sensory stimuli may not occur.
- Journal of Neuroscience. Neuronal Population Encoding of Identity in Primate Prefrontal Cortex.
- Evolution of Nervous Systems. Ventrolateral Prefrontal Cortex.