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Related Concept Videos

First Pass Effect01:12

First Pass Effect

Presystemic elimination, or the first-pass effect, is the metabolism of drugs that reduces their effective concentration at the site of action. Apart from the first-pass effect, the systemic bioavailability of the drug is also reduced by other factors, including incomplete absorption or chemical degradation of drugs.
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Buffer Effectiveness

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Position-effect Variegation

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Law of Effect

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Related Experiment Video

Updated: May 29, 2026

A Naturalistic Setup for Presenting Real People and Live Actions in Experimental Psychology and Cognitive Neuroscience Studies
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The BOLD effect.

Joan M Greve1

  • 1Biomedical Imaging, Genentech, Inc., South San Francisco, CA 94080, USA. greve.joan@gene.com

Methods in Molecular Biology (Clifton, N.J.)
|August 30, 2011
PubMed
Summary

This chapter explains blood oxygen level dependent (BOLD) contrast in NMR imaging. It details how deoxyhemoglobin concentration affects magnetic susceptibility and influences BOLD MRI signals.

Area of Science:

  • Magnetic Resonance Imaging (MRI)
  • Neuroimaging
  • Biophysics

Background:

  • Blood oxygen level dependent (BOLD) contrast is a key technique in functional MRI (fMRI).
  • It relies on the magnetic properties of hemoglobin, specifically the difference between oxygenated and deoxygenated states.
  • Understanding BOLD contrast is crucial for interpreting brain activity via MRI.

Purpose of the Study:

  • To introduce novice NMR imagers to BOLD contrast principles.
  • To provide a comprehensive overview of factors influencing the BOLD signal.
  • To highlight the elegant simplicity and applications of BOLD MRI.

Main Methods:

  • Exploration of magnetic susceptibility as the source of BOLD contrast.
  • Discussion of deoxyhemoglobin concentration and its role in signal changes.

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  • Analysis of interactions between anatomical factors (vessel size) and imaging parameters (pulse sequences).

    • Main Results:

    • BOLD contrast originates from variations in blood magnetic susceptibility due to deoxyhemoglobin levels.
    • These susceptibility effects create local magnetic fields altering NMR signal intensity.
    • Signal changes are influenced by blood vessel anatomy and MRI pulse sequence choices.

    Conclusions:

    • BOLD MRI offers an elegant method for detecting functional brain activity.
    • Understanding the interplay of magnetic susceptibility, anatomy, and imaging is key to BOLD signal interpretation.
    • BOLD contrast has significant clinical and preclinical applications in neuroscience research.