title: Regional changes in cerebral haemodynamics as a result of a visual stimulus measured by near infrared spectroscopy.
abstract: Near infrared spectroscopy (NIRS) is used to measure global changes in cerebral haemodynamics. We have adapted the technique to measure regional changes in response to a visual stimulus. Ten volunteers were exposed to a computer generated visual stimulus designed to activate a large area of the visual cortex, including V1, V2, V3, V4 and V5. The stimulus was on for 30 s and off for 30 s. Changes in the concentrations of oxyhaemoglobin ([HbO2]) and deoxyhaemoglobin ([Hb]) were measured using a commercial spectrometer (NIRO500), over the occipital cortex. The data were summed over ten cycles. As a control, the experiment was repeated over the frontal cortex. For each subject [HbO2] increased during stimulation, and decreased when the stimulus was off. The mean (+/- s.e.m.) change in [HbO2] was 0.54 +/0 0.14 micromol 1(-1). The change in total haemoglobin concentration, given by [HbO2] + [Hb] was 0.61 +/- 0.21 micromol 1(-1), equivalent to a rise in cerebral blood volume of 0.04 +/- 0.01 ml 100 g(-1) which is about 2% of the total cerebral blood volume. There was no significant change in [HbO2] over the frontal cortex, implying that the changes in blood volume originated in the occipital lobe. This demonstrates that NIRS provides a non-invasive method of measuring regional changes in cerebral haemodynamics as a result of visual stimulation.
authors.affiliation: Department of Paediatrics, University College London, U.K.
authors.forename: J H
authors.initials: JH
authors.lastname: Meek
authors.forename: C E
authors.initials: CE
authors.lastname: Elwell
authors.forename: M J
authors.initials: MJ
authors.lastname: Khan
authors.forename: J
authors.initials: J
authors.lastname: Romaya
authors.forename: J S
authors.initials: JS
authors.lastname: Wyatt
authors.forename: D T
authors.initials: DT
authors.lastname: Delpy
authors.forename: S
authors.initials: S
authors.lastname: Zeki
mesh_terms: D000328:Adult; D001810:Blood Volume; D002540:Cerebral Cortex / Q000098:blood supply* / Q000502:physiology*; D002560:Cerebrovascular Circulation; D005625:Frontal Lobe / Q000098:blood supply / Q000502:physiology; D006439:Hemodynamics; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D009778:Occipital Lobe / Q000098:blood supply / Q000502:physiology; D010108:Oxyhemoglobins / Q000378:metabolism*; D012016:Reference Values; D013055:Spectrophotometry, Infrared / Q000379:methods*; D014793:Visual Cortex / Q000098:blood supply / Q000502:physiology; D014796:Visual Perception
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin