PROJECT ABSTRACT/SUMMARY A significant number of children with ASD remain minimally verbal even after receiving quality interventions. Previous literature has highlighted the heterogeneity of this group, confirming that while no single mechanism can explain the underlying causes of their severe communication deficits, innovative targeted behavioral interventions can lead to improvements in speech and social communication in some older minimally verbal children. The POLO project is a multidisciplinary effort to identify the motor and neural mechanisms underlying the profound spoken language impairments in young, minimally verbal children with ASD and to advance our understanding of how to optimize language outcomes in this younger population. Aim 2 of POLO intends to investigate links between language impairments and neural functioning including neural oscillatory patterns, long-range connectivity and auditory processing impairments in minimally verbal children. This supplement will take a complementary perspective to address the key aim of language impairment and neural functioning by using fNIRS instead of EEG (Project 2). While EEG provides information about timing, fNIRS is a user-friendly and (unlike fMRI) movement-tolerant modality which tells us about the localization of brain activity. Thus, we will extend Project 2’s focus on basic sound and speech to a study of naturalistic language stimuli, exploring the neural foundations of receptive language in MV children with ASD. We will include one standardized read aloud story and add one read aloud story on each child’s favored affinity based on Dr. Gabrieli’s work. This supplement addresses the following aims. AIM 1 Investigate neural activation patterns to language in read aloud stories in MV ASD children, age and sex-matched verbal ASD children (ASD-VF) and typical controls (TD) drawn from POLO. The key focus of this aim is on ASD-MV children – there is no prior research investigating this population. However, we expect a pattern of reduced activation to non-affinity stories, especially in the left frontal cortex, in comparison with VF and TD peers, which may indicate that targeted language interventions can be used to improve language comprehension when it is most important: in young, pre-school aged minimally verbal children. AIM 2: Link neural activation patterns to receptive and expressive language measures (PLS-5, Mullen/DAS, Natural Language Sample/ELSA) from POLO for the MV group. There is considerable evidence that ASD is characterized by atypical structural and functional neural connectivity. This research will address the key aims of POLO to conduct research with younger minimally verbal children with ASD and link the neural findings to behavior. This supplement extends POLO’s aims by using fNIRS to identify the brain regions activated by language stimuli in MV children with ASD.