Document Detail

Linear aspects of changes in deoxygenated hemoglobin concentration and cytochrome oxidase oxidation during brain activation.
MedLine Citation:
PMID:  11170817     Owner:  NLM     Status:  MEDLINE    
We used near infrared spectroscopy (NIRS) to investigate the vascular and metabolic response to brain activation in human primary and adjacent secondary visual cortex. NIRS is able to measure concentration changes in deoxygenated hemoglobin ([deoxy-Hb]) (which mainly contribute to the blood oxygenation level-dependent (BOLD) signal in functional magnetic resonance imaging (fMRI)) as well as concentration changes of oxygenated hemoglobin ([oxy-Hb]) and corpuscular blood volume ([total-Hb] = [oxy-Hb] + [deoxy-Hb]) and changes in the redox status of the cytochrome c oxidase ([Cyt-Ox]), a putative parameter for cellular oxygenation. A sound understanding of the transfer functions between stimulus parameters, neuronal activity, and vascular/metabolic parameters is important for interpretation of data acquired with indirect neuroimaging techniques like fMRI, especially in event-related design studies. In the present study we tested whether the vascular/metabolic response to stimulation can be described as a linear and time invariant system. Since linearity is a property attributed to systems that satisfy the scaling and superposition properties, as a first simple test, superposition of the responses obtained from short duration visual stimuli was used to predict the responses of longer duration stimuli. Our results showed that the predictions of [deoxy-Hb] and [Cyt-Ox] responses to stimuli of 6- to 24-s duration were satisfactory whereas predictions of [oxy-Hb] and [total-Hb] were insufficient. In a second step, a calculated convolution function of an assumed impulse response function and the stimulus function was fitted with the measured [deoxy-Hb] and [Cyt-Ox] curves to obtain amplitude, time delay, and time constant parameters. We show that predictions of cellular and vascular oxygenation responses to visual stimulation are good for 6- to 24-s stimuli duration under the assumption of a linear transfer characteristic. This model is not valid for corpuscular volume changes which affect mainly the [oxy-Hb] response. Noninvasive NIRS is shown to be a suitable method to get more direct information about neuronal-activity-associated changes in cerebral parameters which are partly reflected in BOLD signal but are not fully understood yet.
P Wobst; R Wenzel; M Kohl; H Obrig; A Villringer
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  NeuroImage     Volume:  13     ISSN:  1053-8119     ISO Abbreviation:  Neuroimage     Publication Date:  2001 Mar 
Date Detail:
Created Date:  2001-02-22     Completed Date:  2001-05-17     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9215515     Medline TA:  Neuroimage     Country:  United States    
Other Details:
Languages:  eng     Pagination:  520-30     Citation Subset:  IM    
Copyright Information:
Copyright 2001 Academic Press.
Department of Neurology, Charité, Humboldt-University, Berlin, Germany.
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MeSH Terms
Arousal / physiology*
Brain Mapping
Electron Transport Complex IV / metabolism*
Energy Metabolism / physiology
Fourier Analysis
Hemoglobins / metabolism*
Image Processing, Computer-Assisted
Magnetic Resonance Imaging*
Oxyhemoglobins / metabolism*
Pattern Recognition, Visual / physiology
Spectroscopy, Near-Infrared*
Visual Cortex / physiology*
Visual Pathways / physiology
Reg. No./Substance:
0/Hemoglobins; 0/Oxyhemoglobins; 9008-02-0/deoxyhemoglobin; EC Transport Complex IV

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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