Synopsis

Keywords: Contrast mechanisms: fMRI, Neuro: Brain function, Neuro: Cerebrovascular

Since its demonstration in the early 90's, the blood oxygen level-dependent (BOLD) contrast has proved to be a revolutionary tool to probe brain function non-invasively. But what lies under the hood? Rather than a direct measure of neuronal activity (or any single physiological parameter), BOLD signals reflect a complex interplay of neuronal, vascular and metabolic factors. In this talk, we will introduce the basic physiology and physics that underlie the BOLD contrast, and which govern the spatial and temporal properties of the signal we measure with fMRI.

fMRI for all: Basic BOLD physiology

Since its demonstration in the early 90's, the blood oxygen level-dependent (BOLD) contrast has proved to be a revolutionary tool to probe brain function non-invasively, and to this date remains by far the most popular choice for functional fMRI (fMRI). But what lies under the hood? Rather than a direct measure of neuronal activity (or any single physiological parameter, for that matter), BOLD signals originate from a complex interplay of neuronal, vascular and metabolic factors. It is crucial to be aware of these mechanisms, as well as their influence on the spatial and temporal properties of the measured signals, in order to design effective experiments, avoid biases, and interpret the results correctly.

In the spirit of its session, “fMRI for all”, this educational talk is intended for a broad audience, and aims to provide a first introduction to the physiology and physics that underlie the BOLD fMRI contrast, including:

• The different tissue structures and processes involved in brain function;
• The mechanisms that originate fluctuations in the measured BOLD MRI signal;
• How neuronal activity is coupled to vascular and metabolic changes;
• Other factors that can affect the BOLD signal (e.g. blood concentration of CO2);
• Spatiotemporal properties of the BOLD response, linked to its sources and generation mechanisms.

This introduction should provide a useful basis and intuition for researchers interested in BOLD fMRI, and provide valuable background to learn how to design effective fMRI experiments, understand and reduce potential biases, and draw better informed interpretations of the results.

Acknowledgements

I acknowledge funding from the Swiss National Science Foundation through grant PZ00P2_185909, and support from CSEM – Swiss Center for Electronics and Microtechnology.

References

No reference found.