D.D. Schmorrow, L.M. Reeves (Eds.): Augmented Cognition, HCII 2007, LNAI 4565, pp. 30–37, 2007. © Springer-Verlag Berlin Heidelberg 2007 A Sensor Positioning System for Functional Near-Infrared Neuroimaging Ping He 1 , Betty Yang 1 , Sarah Hubbard 2 , Justin Estepp 1 , and Glenn Wilson 2 1 Department of Biomedical, Industrial and Human factors Engineering, Wright State University, Dayton, OH, U.S.A. 2 Air Force Research Laboratory, Wright-Patterson Air Force Base, U.S.A. Abstract. In cognitive studies using functional near-infrared (fNIR) techniques, the optical sensors are placed over the scalp of the subject. In order to document the actual sensor location, a system is needed that can measure the 3D position of an arbitrary point on the scalp with a high precision and repeatability and express sensor location in reference to the international 10-20 system for convenience. In addition, in cognitive studies using functional magnetic resonance imaging (fMRI), the source location is commonly expressed using Talairach system. In order to correlate the results from the fNIR study with that of the fMRI study, one needs to project the source location in Talairach coordinates onto a site on the scalp for the placement of the fNIR sensors. This paper reports a sensor positioning system that is designed to achieve the above goals. Some initial experimental data using this system are presented. Keywords: 10-20 system, brain mapping, fNIR, neuroimaging, Talairach. 1 Introduction Recent advancements in the functional near-infrared (fNIR) technique have expanded its potential applications in mapping the human brain's hemodynamic response to various cognitive tasks. In most studies reported in the literature, the optical sensors were placed over the forehead [1-3]. However, in many functional neuroimaging studies, the location nearest to the activation area in the brain may not be on the forehead [4]. In such cases, the optical sensors need to be placed at various locations on the scalp in order to optimize the reception of fNIR signals. In order to document the actual sensor location in a study, a device is needed that can measure the 3D position of an arbitrary point on the scalp with a high precision and repeatability. In addition, in cognitive studies using functional magnetic resonance imaging (fMRI), the source location is commonly expressed using the Talairach coordinate system. In order to correlate the results from the fNIR study with that of the fMRI study, one needs to project the source location in Talaraich coordinates onto a site on the scalp and then place the fNIR sensors over that site. Finally, since the most recognized standard for scalp electrode localization is the international 10-20 system used in the EEG studies [5], it may be convenient to express the fNIR sensor location in reference to the international 10-20 system, but a much higher spatial resolution is required (the typical 10-20 system has only 19 electrode locations). This paper reports a sensor