ABSTRACT This grant application requests funding for the purchase of a high-density electroencephalography (EEG) system to reside in the Human Neurophysiology Core at Boston Children's Hospital. The EEG system offers state-of- the-art technology that will allow investigators flexibility in experimental design to incorporate event related potentials, magnetic resonance imaging (MRI) co-acquisition, transcranial magnetic stimulation (TMS) application and physiology co-registering into high density EEG collection. The equipment selected has been optimized for EEG biomarker collection in pediatric populations, including infants, young children, children with neurodevelopmental delays and neuropsychiatric symptomatology. Importantly, the equipment will be located within a Core facility staffed with experts in the design, collection and analysis of EEG data enabling users to obtain impactful results related to a broad array of NIMH funded research aims. EEG is being incorporated into an increasing number of research studies due to the capacity of this technique to yield high quality data reflecting neural function and connectivity from sensitive populations. Biomarkers of disease state, prognostics, stratification and treatment response have been identified in a number of neuropsychiatric disorders including autism spectrum disorder, ADHD, psychotic disorders and depression/anxiety. Furthermore, considerable EEG research is being undertaken specifically for therapeutic indications in combination with physiological measures (heart rate, galvanic skin response), TMS and MRI neuro- feedback. The realization of these research goals, however, is dependent on the collection of standardized, reproducible data, which is dependent on high quality equipment with built-in validation capabilities and deep technical expertise. To this end, availability of the state-of-the art equipment outlined here within a core setting makes incorporation of EEG based biomarkers and therapeutic applications possible for all investigators focused on improving mental health outcomes.