Project Summary This grant will develop a wireless wearable high-performance, high-density diffuse optical tomography (DOT) instrument for mapping of brain function in naturalistic settings. Functional neuroimaging of healthy adults has enabled mapping of brain function and revolutionized cognitive neuroscience. Increasingly, functional neuroimaging is being used in younger age groups, and as a diagnostic and prognostic tool in the clinical setting. Its expanding application in the study of both health and disease necessitates new, more flexible tools. The logistics of traditional functional brain scanners (e.g., fMRI) are ill-suited to many subjects. In particular, fMRI is not suited for imaging subjects who cannot lie sufficiently still in MRI scanners. In addition to young children (i.e. under 5 years old) in general, this requirement also excludes children with disorders of voluntary movement, such as moderate to severe cerebral palsy. A majority of patients with CP have either spasticity and/or dyskinesia, movement disorders that prohibits successful fMRI due to motion artifacts. A subset of CP subjects can be considered to have effectively a pediatric form of a “locked-in-syndrome”, in the sense that, while intelligence can be spared entirely, motor system dysfunction prevents the ability to speak or sign. Not uncommonly, the intellectual capacities of these children are never recognized by care-providers, educators, and family members. Thus, there are many intriguing questions in the CP population that could be addressed with functional neuroimaging, such as questions of motor plasticity and learning, perhaps the most compelling is identifying and characterizing the cognitive and neuroanatomical architecture of children with CP who are locked in. Such work could provide a path to unlocking the cognitive capacities of children with severe motor dysfunction. These studies cannot be done with fMRI. Optical imaging has long held promise as a naturalistic neuroimaging technique. Recent development of high- density diffuse optical tomography (HD-DOT), a tomographic version of fNIRS, has improved image quality dramatically. When matched within subjects against fMRI, HD-DOT now can obtain localization errors <5mm, and point spread functions <15 mm FWHM, sufficient to localize functions to gyri. While initial HD-DOT reports have been confined to simpler sensory networks (visual and motor), recent results demonstrate the feasibility of mapping distributed cognitive networks, including the dorsal attention and default mode networks. Despite these advances, application of HD-DOT to naturalistic studies has been limited by a barrier imposed by a tradeoff between coverage and wear-ability. The central photonic challenges are optical sensitivity - which would bias design towards larger/heavier fibers, and coverage - which would bias design towards a larger number of fibers. In this proposal, Aims 1-2 address the technological challenges of developing a l...