Novel linguistic evaluation of prefrontal synthesis (LEPS) test measures prefrontal synthesis acquisition in neurotypical children and predicts high-functioning versus low-functioning class assignment in individuals with autism

Abstract

In order to grasp the difference between "the cat on the mat" and "the mat on the cat," understanding the words and the grammar is not enough. Rather it is essential to visually synthesize the cat and the mat together in front of the mind's eye to appreciate their relations. This type of voluntary imagination, which involves juxtaposition of mental objects is conducted by the prefrontal cortex and is therefore called Prefrontal Synthesis (PFS). While PFS is essential for understanding of complex language, its acquisition has a strong experience-dependent critical period putting children with language delay in danger of never acquiring PFS and, consequently, not mastering complex language comprehension. In typical children, the timeline of PFS acquisition correlates with vocabulary expansion. Conversely, atypically developing children may learn hundreds of words but never acquire PFS. In these individuals, common tests of intelligence based on vocabulary assessment may miss the profound deficit in PFS. Accordingly, we developed a 5-minute test specific for PFS -Linguistic Evaluation of Prefrontal Synthesis or LEPSand administered it to 50 neurotypical children, age 2 to 7 years (4.1±1.3) and to 23 individuals with impairments, age 8-21 years (16.4±3.0). All neurotypical children older than 4 years received the LEPS score 7/10 or greater indicating good PFS ability. Among individuals with impairments only 9 of 23 (39%) received the LEPS score 7/10 or greater. LEPS score was 90% correct in predicting high-functioning vs. low-functioning class assignment in individuals with autism, while full-scale IQ score was only 50% correct..

Pretend play predicts receptive and expressive language trajectories in young children with autism

“…Children acquire voluntary imagination and the associated combinatorial recursive language between the age of 3 and 4 years. Based on our research experience, children younger than 3 years did not understand spatial prepositions or recursion, but children older than 4 generally understood both (Vyshedskiy, DuBois, et al, 2020). Pretend play, on the other hand, is initiated between the ages of 1.5 to 2 (Lillard et al, 2011), two years ahead of voluntary imagination acquisition.…”

Parent-reported assessment scores reflect ASD severity in 2- to 7- year-old children

“…Finally, in a 3-year study of 6454 children, children who engaged with a specialized language therapy displayed a 2.2-fold faster improvement in their combinatorial language scores when compared to children with similar initial evaluations (p<0.0001) and 1.4-fold faster improvement in their expressive language score (p=0.0144). However, differences in their sociability, sensory awareness, and health scores remained insignificant (Vyshedskiy, DuBois, et al, 2020).…”

Imagination exercises improve language in younger but not in older children with autism suggesting a strong critical period

“…MITA includes both verbal and nonverbal exercises aiming to develop voluntary imagination ability 22 in general and Prefrontal Synthesis (PFS) ability in particular 15 . The fidelity, validity and reliability of the MITA was discussed in detail in Refs.…”

“…Failure to juxtapose mental objects, called PFS paralysis, results in life-long inability to understand spatial prepositions, semantically-reversible sentences (e.g., "the cat on the mat"), and recursion. Among individuals diagnosed with ASD, the prevalence of PFS paralysis is 30 to 40% 14 and may be as high as 60% among children enrolled into special ASD schools 15 .…”

“…PFS is an internal, subjective function that does not easily manifest itself to evaluators 15 . Most receptive language tests are based on vocabulary assessment and may miss the profound deficit in PFS.…”