Language processing in the brain

**Dual stream connectivity between the auditory cortex and frontal lobe of monkeys and humans.** Top: The auditory cortex of the monkey (left) and human (right) is schematically depicted on the supratemporal plane and observed from above (with the parieto- frontal operculi removed). Bottom: The brain of the monkey (left) and human (right) is schematically depicted and displayed from the side. Orange frames mark the region of the auditory cortex, which is displayed in the top sub-figures. Top and Bottom: Blue colors mark regions affiliated with the ADS, and red colors mark regions affiliated with the AVS (dark red and blue regions mark the primary auditory fields). Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.

In psycholinguistics, language processing refers to the way humans use words to communicate ideas and feelings, and how such communications are processed and understood. Language processing is considered to be a uniquely human ability that is not produced with the same grammatical understanding or systematicity in even human's closest primate relatives.^[1]

Throughout the 20th century the dominant model^[2] for language processing in the brain was the Geschwind-Lichteim-Wernicke model, which is based primarily on the analysis of brain-damaged patients. However, due to improvements in intra-cortical electrophysiological recordings of monkey and human brains, as well non-invasive techniques such as fMRI, PET, MEG and EEG, a dual auditory pathway^[3]^[4] has been revealed and a two-streams model has been developed. In accordance with this model, there are two pathways that connect the auditory cortex to the frontal lobe, each pathway accounting for different linguistic roles. The auditory ventral stream pathway is responsible for sound recognition, and is accordingly known as the auditory 'what' pathway. The auditory dorsal stream in both humans and non-human primates is responsible for sound localization, and is accordingly known as the auditory 'where' pathway. In humans, this pathway (especially in the left hemisphere) is also responsible for speech production, speech repetition, lip-reading, and phonological working memory and long-term memory. In accordance with the 'from where to what' model of language evolution,^[5]^[6] the reason the ADS is characterized with such a broad range of functions is that each indicates a different stage in language evolution.

The division of the two streams first occurs in the auditory nerve where the anterior branch enters the anterior cochlear nucleus in the brainstem which gives rise to the auditory ventral stream. The posterior branch enters the dorsal and posteroventral cochlear nucleus to give rise to the auditory dorsal stream.^[7]^: 8

Language processing can also occur in relation to signed languages or written content.

^ Seidenberg MS, Petitto LA (1987). "Communication, symbolic communication, and language: Comment on Savage-Rumbaugh, McDonald, Sevcik, Hopkins, and Rupert (1986)". Journal of Experimental Psychology: General. 116 (3): 279–287. doi:10.1037/0096-3445.116.3.279. S2CID 18329599.
^ Geschwind N (June 1965). "Disconnexion syndromes in animals and man. I". review. Brain. 88 (2): 237–94. doi:10.1093/brain/88.2.237. PMID 5318481.
^ Hickok G, Poeppel D (May 2007). "The cortical organization of speech processing". review. Nature Reviews. Neuroscience. 8 (5): 393–402. doi:10.1038/nrn2113. PMID 17431404. S2CID 6199399.
^ Gow DW (June 2012). "The cortical organization of lexical knowledge: a dual lexicon model of spoken language processing". review. Brain and Language. 121 (3): 273–88. doi:10.1016/j.bandl.2012.03.005. PMC 3348354. PMID 22498237.
^ Poliva O (2017-09-20). "From where to what: a neuroanatomically based evolutionary model of the emergence of speech in humans". review. F1000Research. 4: 67. doi:10.12688/f1000research.6175.3. PMC 5600004. PMID 28928931. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
^ Poliva O (2016). "From Mimicry to Language: A Neuroanatomically Based Evolutionary Model of the Emergence of Vocal Language". review. Frontiers in Neuroscience. 10: 307. doi:10.3389/fnins.2016.00307. PMC 4928493. PMID 27445676. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
^ Pickles JO (2015). "Chapter 1: Auditory pathways: anatomy and physiology". In Aminoff MJ, Boller F, Swaab DF (eds.). Handbook of Clinical Neurology. review. Vol. 129. pp. 3–25. doi:10.1016/B978-0-444-62630-1.00001-9. ISBN 978-0-444-62630-1. PMID 25726260.

[1] Seidenberg MS, Petitto LA (1987). "Communication, symbolic communication, and language: Comment on Savage-Rumbaugh, McDonald, Sevcik, Hopkins, and Rupert (1986)". Journal of Experimental Psychology: General. 116 (3): 279–287. doi:10.1037/0096-3445.116.3.279. S2CID 18329599.

[Geschwind_1965-2] Geschwind N (June 1965). "Disconnexion syndromes in animals and man. I". review. Brain. 88 (2): 237–94. doi:10.1093/brain/88.2.237. PMID 5318481.

[Hickok_2007-3] Hickok G, Poeppel D (May 2007). "The cortical organization of speech processing". review. Nature Reviews. Neuroscience. 8 (5): 393–402. doi:10.1038/nrn2113. PMID 17431404. S2CID 6199399.

[Gow_2012-4] Gow DW (June 2012). "The cortical organization of lexical knowledge: a dual lexicon model of spoken language processing". review. Brain and Language. 121 (3): 273–88. doi:10.1016/j.bandl.2012.03.005. PMC 3348354. PMID 22498237.

[Poliva_2017-5] Poliva O (2017-09-20). "From where to what: a neuroanatomically based evolutionary model of the emergence of speech in humans". review. F1000Research. 4: 67. doi:10.12688/f1000research.6175.3. PMC 5600004. PMID 28928931. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.

[Poliva_2016-6] Poliva O (2016). "From Mimicry to Language: A Neuroanatomically Based Evolutionary Model of the Emergence of Vocal Language". review. Frontiers in Neuroscience. 10: 307. doi:10.3389/fnins.2016.00307. PMC 4928493. PMID 27445676. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.

[pmid25726260-7] Pickles JO (2015). "Chapter 1: Auditory pathways: anatomy and physiology". In Aminoff MJ, Boller F, Swaab DF (eds.). Handbook of Clinical Neurology. review. Vol. 129. pp. 3–25. doi:10.1016/B978-0-444-62630-1.00001-9. ISBN 978-0-444-62630-1. PMID 25726260.

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