Neural Correlates of Vocal Repertoire in Primates

Front Neurosci. 2018 Aug 9:12:534. doi: 10.3389/fnins.2018.00534. eCollection 2018.

Abstract

Understanding the nature of the relationship between vocal complexity and brain architecture across non-human primates may help elucidate some of the key elements underlying the evolution of human speech. Here, we report a positive correlation between vocal repertoire size and the relative size of cortical association areas (governing voluntary control over behavioural output) in non-human primates. We further demonstrate that a hominid grade shift in the relative volume of cortical association areas coincides with a similar grade shift in the hypoglossal nucleus (which is associated with the cranial nerve that innervates the muscles of the tongue). Our results support a qualitative continuity in the neural correlates of vocal repertoire, but a quantitative discontinuity in the extent to which the neural system supporting speech is innervated by cortical association areas in great apes and humans.

Keywords: brain evolution; cortical association areas; evolution of speech; language; prefrontal cortex; primate evolution; primates; vocal complexity.