Review of Process and Non-invasive Near-Infrared and Infrared Spectroscopy: 1993–1999

We report the first evidence of the structure of beta-amyloid protein as it exists in situ within a slice of human Alzheimer's diseased brain tissue. Using a Fourier transform infrared microspectroscopic technique, areas of interest can be selected for spectral measurements with regions of potential contamination masked. In so doing, it is possible to obtain infrared spectra only of beta-amyloid and not the surrounding grey matter within which it lies. However, to obtain spectra of high-quality signal-to-noise ratio using a conventional infrared source, we were limited to aperture sizes between 24 microns x 24 microns to 50 microns x 50 microns. Markedly improved high-quality spectra were acquired with infrared radiation provided by a synchrotron light source (National Synchrotron Light Source, Brookhaven National Laboratories), using aperture sizes as small as 12 microns x 12 microns. This allowed spectroscopic mapping of brain tissue regions containing amyloid. We observe that in situ protein of grey matter exist predominantly in an alpha-helical and/or unordered conformation, whereas within amyloid deposits a beta-sheet structure predominates. The hydrogen bonding strength of the beta-structure found in situ is different from that reported in the literature for isolated/chemically synthesized beta-amyloid peptides.

Near-infrared spectroscopy (NIRS) is a new technique for non-invasive monitoring of tissue oxygenation and its kinetics. Up to this date, it has been used solely in research for the global hemodynamic change of the brain and for rough regional activation after stimulating the brain physiologically. This paper describes functional brain mapping using multi channel (ten channel) NIRS by applying the motor stimulation in humans. Our results demonstrate that the regional hemodynamic change was detected in a small area around the motor cortex with a time resolution of 1-2 s. NIRS technique offers considerable potential for research and clinical applications with no invasion.