Cortical mapping of gait in humans: a near-infrared spectroscopic topography study.

While we have a fair understanding of how and where forelimb-hand manipulative movements are controlled by the neocortex, due to functional imaging studies, we know little about the control of bipedal movements such as walking because of technical difficulties. We succeeded in visualizing cortical activation patterns of human gait by measuring relative changes in local hemoglobin oxygenation using a recently developed near-infrared spectroscopic (NIRS) topography technique. Walking activities were bilaterally associated with increased levels of oxygenated and total hemoglobin in the medial primary sensorimotor cortices and the supplementary motor areas. Alternating foot movements activated similar but less broad regions. Gait imagery increased activities caudally located in the supplementary motor areas. These findings provide new insight into cortical control of human locomotion. NIRS topography might be also useful for evaluating cerebral activation patterns during pathological gait and rehabilitative intervention.

Analysis of nonlinear relation for skin hemoglobin imaging.

This paper discusses the accuracy of the optical determination of the oxygenated and deoxygenated hemoglobin content of human skin under the influence of a melanin layer for a multi-wavelengths imager. The relation between the nonlinear results by Monte Carlo simulation (MCS) and the modified Lambert Beer's law (MLB) is also clarified, emphasizing the importance of the absolute values of skin pigments and their influence on the mean path-length used in MLB. The fitting procedure of the MCS data to the actual skin spectra is shown to obtain the absolute values. It is also shown that once the proper mean path-lengths have been determined, MLB can be used fairly well within an accuracy of 80% compared with MCS. Images of oxygenated hemoglobin with a newly-developed fourwavelength camera are presented to demonstrate the advantages of a multiwavelength system.

Optical tomography by the temporally extrapolated absorbance method.

The concept of the temporally extrapolated absorbance method (TEAM) for optical tomography of turbid media has been verified by fundamental experiments and image reconstruction. The TEAM uses the time-resolved spectroscopic data of the reference and object to provide projection data that are processed by conventional backprojection. Optical tomography images of a phantom consisting of axisymmetric double cylinders were experimentally obtained with the TEAM and time-gating and continuous-wave (CW) methods. The reconstructed TEAM images are compared with those obtained with the time-gating and CW methods and are found to have better spatial resolution.