Referential framework for transcranial anatomical correspondence for fNIRS based on manually traced sulci and gyri of an infant brain.

Functional near infrared spectroscopy (fNIRS), which is compact, portable, and tolerant of body movement, is suitable for monitoring infant brain functions. Nevertheless, fNIRS also poses a technical problem in that it cannot provide structural information. Supplementation with structural magnetic resonance images (MRI) is not always feasible for infants who undergo fNIRS measurement. Probabilistic registration methods using an MRI database instead of subjects' own MRIs are optimized for adult studies and offer only limited resources for infant studies. To overcome this, we used high-quality infant MRI data for a 12-month-old infant and manually delineated segmented gyri from among the highly visible macroanatomies on the lateral cortical surface. These macroanatomical regions are primarily linked to the spherical coordinate system based on external cranial landmarks, and further to traditional 10-20-based head-surface positioning systems. While macroanatomical structures were generally comparable between adult and infant atlases, differences were found in the parietal lobe, which was positioned posteriorly at the vertex in the infant brain. The present study provides a referential framework for macroanatomical analyses in infant fNIRS studies. With this resource, multichannel fNIRS functional data could be analyzed in reference to macroanatomical structures through virtual and probabilistic registrations without acquiring subject-specific MRIs.