Neural Language Processing in Adolescent First-Language Learners

Abstract

The relation between the timing of language input and development of neural organization for language processing in adulthood has been difficult to tease apart because language is ubiquitous in the environment of nearly all infants. However, within the congenitally deaf population are individuals who do not experience language until after early childhood. Here, we investigated the neural underpinnings of American Sign Language (ASL) in 2 adolescents who had no sustained language input until they were approximately 14 years old. Using anatomically constrained magnetoencephalography, we found that recently learned signed words mainly activated right superior parietal, anterior occipital, and dorsolateral prefrontal areas in these 2 individuals. This spatiotemporal activity pattern was significantly different from the left fronto-temporal pattern observed in young deaf adults who acquired ASL from birth, and from that of hearing young adults learning ASL as a second language for a similar length of time as the cases. These results provide direct evidence that the timing of language experience over human development affects the organization of neural language processing.

Neural stages of spoken, written, and signed word processing in beginning second language learners

“…While prior studies have not found right IPS to be modulated by language proficiency, the participants in those studies have typically possessed higher proficiency in L2 (Leonard et al, 2010, 2011). In case studies of deaf signers with scant proficiency in any language, we have observed right IPS activation later at 300–350 ms (Ferjan Ramirez et al, 2013a). It is possible that modality and proficiency interact in parietal regions, perhaps reflecting a neural processing strategy that is uniquely useful for the dynamic visual linguistic content of sign languages.…”

Language evolution to revolution: the leap from rich-vocabulary non-recursive communication system to recursive language 70,000 years ago was associated with acquisition of a novel component of imagination, called Prefrontal Synthesis, enabled by a mutation that slowed down the prefrontal cortex maturation simultaneously in two or more children – the Romulus and Remus hypothesis

“…Without PFS, their communication system could include nouns, verbs, adjectives, numbers, color and size modifiers, but was void of spatial prepositions, verb tenses, nesting, and other recursive elements. Neanderthal communication system was similar to the communication system used by contemporary individuals who have fluid speech combined with PFS disability: individuals with prefrontal aphasia (Cole et al 2014, Fuster 2008, specific brain damage (Ditunno and Mann 1990, Gläscher et al 2009, Heremans et al 2012, Kosslyn et al 1985, Waltz et al 1999, late first-language learners (Emmorey et al 1993, Martin 2009, Martin et al 2013, Pyers et al 2010, and verbal low-functioning individuals (Matson andShoemaker 2009, Vyshedskiy et al 2019).…”

“…PFS disability is not limited to individuals with LPFC damage. Individuals without any brain injury exhibit PFS disability if they were not exposed to recursive language in early childhood (Emmorey et al 1993, Martin 2009, Martin et al 2013, Pyers and Senghas 2009). In our meta-analysis of published research, ten out of ten individuals linguistically deprived until puberty suffered lifelong PFS disability despite learning significant vocabulary through intensive post-pubertal language therapy (Vyshedskiy et al 2017b).…”

“…The FOXP2 protein sequence is highly conserved. There is only one amino acid difference in the chimpanzee lineage going back some 70 million years to the common ancestor with the mouse (Enard et al 2002 .…”

“…Its neural infrastructure has to be laid down in early childhood. Perhaps this neural infrastructure is related to cortical functional specialization established through competition mechanisms similar to that of monocular deprivation (Ferjan Ramirez et al 2013, Hinkley et al 2016 and development of long frontoposterior fibers, such as arcuate fasciculus and superior longitudinal fasciculus (Wilson et al 2011). The exact mechanism of the strong critical period for PFS acquisition remains to be determined.…”