Near-Infrared Spectroscopy (NIRS)
It may be surprising, but you can illuminate your brain’s surface by a simple halogen bulb. Of course quite a bit of the bulb’s energy will be lost on the surface of the head as you may notice when you sit under the bulb for long enough and it becomes quite warm. However, a part of the bulb’s spectrum which you cannot see will actually reach much deeper layers of your head and will be more or less absorbed depending on the colour of your brain. Since the brain changes colour depending on its activation state (basically it blushes as soon as you make it work...) you can watch the brain at work with nothing but a light bulb and some more or less refined detector, which extends your sight into the near-infrared.
This principle is termed near-Infrared spectroscopy (NIRS) a method being used to monitor oxygenation of the human cortex non-invasively. Our group has dedicated some work to explore the methodology’s potential to take part in the ‘concerted action’ to get a better image of the human brain at work and this page is an attempt to attract your attention to the less powerful, less well known brother of modern imaging techniques like Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI). Our group focuses on the potential of the method in studying neurovascular coupling but one of the major goals is also to explore the methodology’s versatility at the patient’s bed-side. The above mentionen ‘blushing of the brain’ may look quite different when the brain has turned very pale due to a prior ischemia before.
The image above was acquired by stimulating the left and right hemifield by an alternating black and white checkerboard. The difference between the two conditions is mapped. The red and blue spot are show the maximum difference and correspond to the primary visual areas of the subject. The left mage corresponds to the changes in the concentration of deoxygenated haemoglobin [ deoxy-Hb ] while the right shows the corresponding changes in oxygenated haemoglobin [ oxy-Hb ]. As is easily seen the images are roughly inverted.
Literature
Benaron, DA, Hintz SR, Villringer A, Boas D, Kleinschmidt A, Frahm J, Hirth C, Obrig H, Van HJ, Kermit EL, Cheong WF, Stevenson DK (2000) Noninvasive functional imaging of human brain using light. J Cereb Blood Flow Metab 20, 469-477.
Brandt SA, Davis TL, Obrig H, Meyer BU, Belliveau JW, Rosen BR, Villringer A (1996) Functional magnetic resonance imaging shows localized brain activation during serial transcranial stimulation in man. Neuroreport 7, 734-736.
Heekeren HR, Kohl M, Obrig H, Wenzel R, Von, PW, Matcher SJ, Dirnagl U, Cooper CE, Villringer A (1999a) Noninvasive assessment of changes in cytochrome-c oxidase oxidation in human subjects during visual stimulation J Cereb Blood Flow Metab 19, 592-603.
Heekeren HR, Kohl M, Obrig H, Wenzel R, Von PW, Matcher SJ, Dirnagl U, Cooper CE, Villringer A (1999b) Noninvasive assessment of changes in cytochrome-c oxidase oxidation in human subjects during visual stimulation. J Cereb Blood Flow Metab 19, 592-603.
Heekeren HR, Obrig H, Wenzel R, Eberle K, Ruben J, Villringer K, Kurth R, Villringer A (1997) Cerebral haemoglobin oxygenation during sustained visual stimulation--a near-infrared spectroscopy study. Philos Trans R Soc Lond B Biol Sci 352, 743-750.
Hirth C, Obrig H, Valdueza J, Dirnagl U, Villringer A (1997) Simultaneous assessment of cerebral oxygenation and hemodynamics during a motor task. A combined near infrared and transcranial Doppler sonography study. Adv Exp Med Biol 411, 461-469.
Hirth C, Obrig H, Villringer K, Thiel A, Bernarding J, Muhlnickel W, Flor H, Dirnagl U, Villringer A (1996) Non-invasive functional mapping of the human motor cortex using near- infrared spectroscopy. Neuroreport 7, 1977-1981.
Hirth C, Villringer K, Thiel A, Bernarding J, Muhlnickl W, Obrig H, Dirnagl U, Villringer A (1997) Towards brain mapping combining near-infrared spectroscopy and high resolution 3D MRI. Adv Exp Med Biol 413, 139-147.
Israel H, Obrig H, Kohl M, Uludag K, Müller B, Wenzel R, Buckow C, Arnold G, Villringer A (2000) Is neuro-vascular coupling altered in interictal migraineurs?A combined visually evoked potential (VEP) and Near-Infrared-Spectroscopy (NIRS) Approach. Conference Proceedings Human Brain Mapping, Brighton, Abstract 10434, (Abstract).
Kleinschmidt A, Obrig H, Requardt M, Merboldt KD, Dirnagl U, Villringer A, Frahm J (1996) Simultaneous recording of cerebral blood oxygenation changes during human brain activation by magnetic resonance imaging and near-infrared spectroscopy. J Cereb Blood Flow Metab 16, 817-826.
Kohl M, Nolte C, Heekeren H, Horst S, Scholz U, Obrig H, Villringer A (1997) Changes in cytochrome-oxidase oxidation in the occipital cortex during visual stimulation: Improvement in sensitivity by the determination of the wavelength dependence of the differential pathlength factor. SPIE conference proceedings 18-27.
Kohl M, Nolte C, Heekeren HR, Horst S, Scholz U, Obrig H, Villringer A (1998) Determination of the wavelength dependence of the differential pathlength factor from near-infrared pulse signals. Phys Med Biol 43, 1771-1782.
Kohl M, Obrig H, Steinbrink J, Malak J, Uludag K, Villringer A (2001) Noninvasive cerebral blood flow monitoring by a dye bolus method: separation of extra- and intracerebral absorption changes by frequency domain spectroscopy. Proceedings of SPIE 4250, 296-300.
Kohl M, Obrig H, Steinbrink J, Malak J, Uludag K, Villringer A (2002) Non-invasive monitoring of cerebral blood flow by a dye bolus method: separation of brain from skin and skull signals. J Biomed Opt
Lang W, Obrig H, Lindinger G, Cheyne D, Deecke L (1990) Supplementary motor area activation while tapping bimanually different rhythms in musicians. Exp Brain Res 79, 504-514.
Obrig H, Heekeren H, Ruben J, Wenzel R, Ndayisaba JP, Dirnagl U, Villringer A (1996) Continuous spectrum near-infrared spectroscopy approach in functional activtion studies in the human adult. SPIE conference proceedings 2926, 58-66.
Obrig H, Hirth C, Junge-Hulsing JG, Doge C, Wenzel R, Wolf T, Dirnagl U, Villringer A (1997) Length of resting period between stimulation cycles modulates hemodynamic response to a motor stimulus. Adv Exp Med Biol 411, 471-480.
Obrig H, Hirth C, Junge-Hulsing JG, Doge C, Wolf T, Dirnagl U, Villringer A (1996) Cerebral oxygenation changes in response to motor stimulation. J Appl Physiol 81, 1174-1183.
Obrig H, Israel H, Kohl-Bareis M, Uludag K, Wenzel R, Müller B, Villringer A (2002) Habituation of the Visually Evoked Potential (VEP) and its Vascular Response: Implications for Neurovascular Coupling in the Healthy Adult. Neuroimage 17, 1-18.
Obrig H, Neufang M, Wenzel R, Kohl M, Steinbrink J, Einhaupl K, Villringer A (2000) Spontaneous low frequency oscillations of cerebral hemodynamics and metabolism in human adults. Neuroimage 12, 623-639.
Obrig H, Villringer A (1996) Near-infrared spectroscopy in functional activation studies. Can NIRS demonstrate cortical activation? Adv Exp Med Biol 413, 113-127.
Obrig H, Villringer A (1997) Near-infrared spectroscopy in functional activation studies. Can NIRS demonstrate cortical activation? Adv Exp Med Biol 413, 113-127.
Obrig H, Wenzel R, Kohl M, Horst S, Wobst P, Steinbrink J, Thomas F, Villringer A (2000) Near-infrared spectroscopy: does it function in functional activation studies of the adult brain? Int J Psychophysiol 35, 125-142.
Obrig H, Wolf T, Doge C, Hulsing JJ, Dirnagl U, Villringer A (1996) Cerebral oxygenation changes during motor and somatosensory stimulation in humans, as measured by near-infrared spectroscopy. Adv Exp Med Biol 388, 219-224.
Ruben J, Wenzel R, Obrig H, Villringer K, Bernarding J, Hirth C, Heekeren H, Dirnagl U, Villringer A (1997) Haemoglobin oxygenation changes during visual stimulation in the occipital cortex. Adv Exp Med Biol 428, 181-187.
Steinbrink J, Kohl M, Obrig H, Curio G, Syre F, Thomas F, Wabnitz H, Rinneberg H, Villringer A (2001a) Somatosensory evoked fast optical intensity changes detected non-invasively in the adult human head. Neurosci Lett 291, 105-108.
Steinbrink J, Wabnitz H, Obrig H, Villringer A, Rinneberg H (2001b) Determining changes in NIR absorption using a layered model of the human head. Phys Med Biol 46, 879-896.
Syré F, Obrig H, Steinbrink J, Kohl M, Wenzel R, Villringer A (2003) Are VEP Correlated Fast Optical Changes Detectable in the Adult by Non Invasive Near Infrared Spectroscopy (NIRS)? Adv Exp Med Biol 530, 421-431.
Uludag K, Kohl M, Steinbrink J, Obrig H, Villringer A (2002) Cross talk in the Lambert-Beer calculation for near-infrared wavelengths estimated by Monte Carlo simulations. J Biomed Opt 7, 51-59.
Villringer K, Minoshima S, Hock C, Obrig H, Ziegler S, Dirnagl U, Schwaiger M, Villringer A (1997) Assessment of local brain activation. A simultaneous PET and near- infrared spectroscopy study. Adv Exp Med Biol 413, 149-153.
Wenzel R, Horst S, Obrig H, Henning C, Kohl M, Villringer A (1998) Localised cytochrome-oxidase redox state and haemoglobin oxygenation response over visual area MT shown with a multilocular full-spectrum NIRS. Neuroimage 7, S258 (Abstract).
Wenzel R, Obrig H, Ruben J, Villringer K, Thiel A, Bernarding J, Dirnagl, U, Villringer A (1996a) Cerbral Blood Oxygenation Changes Induced by Visual Stimulation in Humans. J Cereb Blood Flow Metab 1, 399-404.
Wenzel R, Obrig H, Ruben J, Villringer K, Thiel A, Bernarding J, Dirnagl U, Villringer A (1996b) Cerebral blood oxygenation changes induced by visual stimulation in humans. J Biomed Opt 1, 399-404.
Wenzel R, Wobst P, Heekeren HH, Kwong KK, Brandt SA, Kohl M, Obrig H, Dirnagl U, Villringer A (2000) Saccadic suppression induces focal hypooxygenation in the occipital cortex. J Cereb Blood Flow Metab 20, 1103-1110.
Wobst P, Wenzel R, Kohl M, Obrig H, Villringer A (2001) Linear aspects of changes in deoxygenated hemoglobin concentration and cytochrome oxidase oxidation during brain activation. Neuroimage 13, 520-530.
Wolf T, Lindauer U, Obrig H, Dreier J, Back T, Villringer A, Dirnagl U (1996a) Systemic nitric oxide synthase inhibition does not affect brain oxygenation during cortical spreading depression in rats: a noninvasive near-infrared spectroscopy and laser-Doppler flowmetry study. J Cereb Blood Flow Metab 16, 1100-1107.
Wolf T, Lindauer U, Obrig H, Villringer A, Dirnagl U (1996b) Extra- and intracellular oxygen supply during cortical spreading depression in the rat. Adv Exp Med Biol 388, 299-304.
Links
Harvard BioRobotics Laboratory
UCL Biomedical Optics Research Laboratory
