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The BOLD response: a new look at an old riddle
Valentine L Marcar1, Thomas Loenneker
1University of Zürich, Institute of Psychology, Department of Neuropsychology, Treichlerstrasse 10, CH-8032 Zürich. v.marcar@psychologie.unizh.ch
Neuroreport
|October 16, 2004
Summary
This review proposes separating neuronal activity into electrical discharge and population size components. These factors oppositely affect the Blood-Oxygen-Level-Dependent (BOLD) signal, clarifying functional imaging interpretation.
Area of Science:
- Neuroimaging
- Systems Neuroscience
- Biophysics
Background:
- Functional imaging techniques aim to quantify neuronal activity.
- A persistent challenge is linking measured signals to underlying neural processes.
- The Blood-Oxygen-Level-Dependent (BOLD) signal is a primary readout in functional magnetic resonance imaging (fMRI).
Purpose of the Study:
- To propose a novel framework for understanding the BOLD signal.
- To differentiate neuronal activity into distinct components influencing the BOLD signal.
- To reconcile the discrepancy between electrical neuronal activity and observed hemodynamic responses.
Main Methods:
- Review of existing literature on neurovascular coupling.
- Theoretical modeling of BOLD signal generation.
- Conceptual division of neuronal activity into electrical discharge and population size.
Main Results:
- Neuronal activity is proposed to have two components: electrical discharge and activated population size.
- These two components exert opposing influences on the BOLD signal.
- The interplay of these components is summarized within a standard model.
Conclusions:
- This two-component model offers a more nuanced understanding of the BOLD signal.
- It provides a quantitative link between neuronal activity and functional imaging signals.
- The proposed framework advances the interpretation of neuroimaging data.