From where to what: a neuroanatomically based evolutionary model of the emergence of speech in humans [version 1; referees: 3 approved with reservations]

Abstract

In the brain of primates, the auditory cortex connects with the frontal lobe via the temporal pole (auditory ventral stream; AVS) and via the inferior parietal lobule (auditory dorsal stream; ADS). The AVS is responsible for sound recognition, and the ADS for sound-localization, voice detection and audio-visual integration. I propose that the primary role of the ADS in monkeys/apes is the perception and response to contact calls. These calls are exchanged between tribe members (e.g., mother-offspring) and are used for monitoring location. Perception of contact calls occurs by the ADS detecting a voice, localizing it, and verifying that the corresponding face is out of sight. The auditory cortex then projects to parieto-frontal visuospatial regions (visual dorsal stream) for searching the caller, and via a series of frontal lobe-brainstem connections, a contact call is produced in return. Because the human ADS processes also speech production and repetition, I further describe a course for the development of speech in humans. I propose that, due to duplication of a parietal region and its frontal projections, and strengthening of direct frontal-brainstem connections, the ADS converted auditory input directly to vocal regions in the frontal lobe, which endowed early with partial vocal control. This enabled offspring to modify their Hominans contact calls with intonations for signaling different distress levels to their mother. Vocal control could then enable question-answer conversations, by offspring emitting a low-level distress call for inquiring about the safety of objects, and mothers responding with highor low-level distress calls. Gradually, the ADS and the direct frontal-brainstem connections became more robust and vocal control became more volitional. Eventually, individuals were capable of inventing new words and offspring were capable of inquiring about objects in their environment and learning their names via mimicry. Oren Poliva ( ) Corresponding author: polivaoren@gmail.com Poliva O. How to cite this article: From where to what: a neuroanatomically based evolutionary model of the emergence of speech in 2015, :67 (doi: ) humans [version 1; referees: 3 approved with reservations] F1000Research 4 10.12688/f1000research.6175.1 © 2015 Poliva O. This is an open access article distributed under the terms of the , which Copyright: Creative Commons Attribution Licence permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Data associated with the article are available under the terms of the (CC0 1.0 Public domain dedication). Creative Commons Zero "No rights reserved" data waiver The author(s) declared that no grants were involved in supporting this work. Grant information: Competing interests: No competing interests were disclosed. 13 Mar 2015, :67 (doi: ) First published: 4 10.12688/f1000research.6175.1 Referee Status:

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@inproceedings{Poremba2016FromWT, title={From where to what: a neuroanatomically based evolutionary model of the emergence of speech in humans [version 1; referees: 3 approved with reservations]}, author={Amy Poremba and Josef P. Rauschecker and Oren Poliva}, year={2016} }