Investigação da expressão de egr-1 nos gânglios da base durante a produção e percepção vocal em Callithrix jacchus

Abstract

A fundamental aspect of human communication is flexible speech, which has long been believed to be exclusive to humans among primates. However, recent findings suggest that some non-human primates, such as marmosets, also exhibit vocal plasticity. Investigating the neural correlates of vocal flexibility in marmosets may provide insight into its origins in humans due to brain homologies. Among the brain areas related to vocal behavior, much is known about cortical contributions, but the function of subcortical regions is much less known. In particular, the basal ganglia are related to the choice/initiation of actions, fine motor control and the learning of motor sequences; therefore, it is likely that they are relevant to vocal flexibility. Here, using previously collected histological data and stereological methods, we tested the hypothesis that the caudate nucleus and putamen in the basal ganglia are activated during vocal communication and used the expression of the immediate early gene egr-1 to map their activation in three groups of marmosets. The first group did not vocalize during the test (C), the second group heard playback vocalizations but did not vocalize (H/O), and the third group heard playback calls and vocalized (H/V). We observed an increase in erg-1 expression in both areas in the H/O condition compared to the C condition and an even more significant increase in erg-1 expression in the same areas in the H/V condition compared to the H/O condition. To ensure the specificity of the changes observed, we compared the cells expressing erg-1 in the primary sensory and motor areas, finding no significant difference between the three conditions. In addition, we quantified locomotion during the hour before the end point of the experiment to rule out movement discrepancies as an explanation for the differences observed between the groups in erg-1 expression, without finding a correlation between locomotion and expression variation. Our results indicate activation of the basal ganglia during hearing and vocalization production, independently of other brain areas and body movements, which corroborates our hypothesis. The relevance of the basal ganglia in vocal learning in songbirds, together with our findings in marmosets, suggests their importance in understanding the evolution of vocal learning.