AI Summary
The article discusses a study on how the ventrolateral prefrontal cortex (VLPFC) in primates responds to social stimuli, specifically faces and voices. The researchers examined whether neural responses in the VLPFC were driven by categorical features such as identity and expression. They recorded single neurons in the VLPFC of two macaques while they viewed videos of unfamiliar conspecifics making different facial expressions. They found that some neurons showed a response to identity, expression, or the interaction between the two. However, decoding the expression and identity using single-unit firing rates had low accuracy. When decoding from populations of neurons, the accuracy increased with population size, suggesting that population activity contained information relevant to both variables. Principal components analysis showed that populations of neurons responded similarly to the same identity, allowing for segregation from other identities. These findings contribute to our understanding of the role of the VLPFC in social behavior.
The ventrolateral prefrontal cortex (VLPFC) shows robust activation during the perception of faces and voices. However, little is known about what categorical features of social stimuli drive neural activity in this region. Since perception of identity and expression are critical social functions, we examined whether neural responses to naturalistic stimuli were driven by these two categorical features in the prefrontal cortex. We recorded single neurons in the VLPFC, while two male rhesus macaques (Macaca mulatta) viewed short audiovisual videos of unfamiliar conspecifics making expressions of aggressive, affiliative, and neutral valence. Of the 285 neurons responsive to the audiovisual stimuli, 111 neurons had a main effect (two-way ANOVA) of identity, expression, or their interaction in their stimulus-related firing rates; however, decoding of expression and identity using single-unit firing rates rendered poor accuracy. Interestingly, when decoding from pseudo-populations of recorded neurons, the accuracy for both expression and identity increased with population size, suggesting that the population transmitted information relevant to both variables. Principal components analysis of mean population activity across time revealed that population responses to the same identity followed similar trajectories in the response space, facilitating segregation from other identities. Our results suggest that identity is a critical feature of social stimuli that dictates the structure of population activity in the VLPFC, during the perception of vocalizations and their corresponding facial expressions. These findings enhance our understanding of the role of the VLPFC in social behavior.