The motivational machinery of the brain in primates (composed of the anterior cingulate cortex, hypothalamus, amygdala, periaqueductal grey, lateral reticular formation, and parabrachial nucleus) has been implicated in inducing vocalizations in monkeys and humans (Hage and Nieder 2016)—which is responsible for laughing and crying in adults as well as infants and which survives neocortical damage, a finding consistent with what has been observed in hydrocephalic patients who have a severely-reduced neocortex (Merker 2007). The volitional control of vocalization in primates including humans is done by Broca’s area, premotor cortex, and M1 (Fig. 1). These regions control the symbolic aspects of vocalization, the syntax from which meaning is derived through a process called Merge (Chomsky 1965). Memorizing numbers and words is central to mathematical and language learning (e.g., Hosoda et al. 2013) but not sufficient, as a Japanese colleague of ours at MIT discovered after entering the United States armed with a vocabulary of 20,000 English words. This person could read and understand scientific papers written in English, but he was judged to be functionally illiterate for he could not generate a single English phrase using his vocal cords, as though the connections between Boca’s area/M1 and the vocal apparatus were non-existent even though that same pathway was ‘fluent’ in Japanese.
The frontal lobes (as well as other regions of neocortex) of all mammals are filled with neurons that merge information within and between different sensory modalities (e.g., Bartlett, Doty 2005; Chen and Wise 1995ab; Doty 1969; Evarts 1966; Hasanbegović 2024; Mountcastle 1978; Pavlov 1927). To have an advanced system of language production via the vocal cords it is critical that Broca’s area/M1 send direct projections to the vocal apparatus to permit for maximal dexterity (Kimura 1993; Ojemann 1991; Vanderwolf 2007): this is why monkeys cannot talk or use tools by which to build cities. Nevertheless, such dexterity via the telencephalon/brain stem is known to exist in songbirds which are adept at merging different fragments of sound for the purpose of mate selection (see Fig. 2, also: Goldman and Nottebohm 1983). Other animals that have advanced communication systems requiring information to be merged include whales, elephants, bats, and electric fishes to mention but a few (Tehovnik, Hasanbegović, Chen 2024). In all these animals, the neural connections between the telencephalon and the vocal apparatus must be ‘direct’ for the telencephalon to have optimal control over communications, which is an expression of an animal’s thinking ability (but see Chomsky 2012). And what differentiates humans from other animals is not in that they communicate, but rather in the way they use tools, such as the tools for writing for record keeping, which has allowed them to navigate the world and beyond. Some believe that Homo erectus was a master navigator (Everett 2016).
Figure 1: Neocortical innervations of the subcortex of circuits mediating vocalization and respiration in monkeys and humans are compared. Homologous regions exist in both species, but with a major difference. In humans, the M1 pyramidal fibres innervate directly the motor neurons that move the fingers and vocal apparatus thereby providing humans with a superior dexterity for both sign and vocal language utterances (Kimura 1993; Ojemann 1991; Vanderwolf 2007). As well, humans some 500,000 years ago were endowed with a skeletal structure to house a vocal apparatus to support speech production (Kimura 1993). The illustration is from figure 1B of Hage and Nieder (2015).
Figure 2: Telencephalic pathways in the songbird for the production of songs. Notice the direct projection between the telencephalon (i.e., RA) and cranial nerve nucleus XII (shown in red), which controls the muscles employed for singing. From figure 1C of Schuppe, Chakraborty et al. (2022).
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