Course 19

Quantifying Neurovascular Coupling: A Multimodal fNIRS-fMRI Workshop (Theory, Data, and Challenges)

Instructors: Antonio Maria Chiarelli, Giulia Rocco, Caterina Amendola, David Perpetuini

About this course

This educational course offers a comprehensive exploration of the physiological mechanisms behind the brain supply chain: Neurovascular Coupling (NVC). The course is divided into two modules. The first hour covers the theoretical foundations, beginning with the physiology of NVC and progressing to the biophysics of measurement. We will explain the calibrated fMRI approach, focusing on gas-free methods using Arterial Spin Labeling (ASL), and the mathematical framework of the Davis Model for the estimation of changes in cerebral metabolic rate of oxygen. Then, we shift to the fNIRS perspective, examining how multi-distance CW-fNIRS, Time-Domain (TD-NIRS), and Diffuse Correlation Spectroscopy (DCS) can provide estimates of hemoglobin oxygenation and blood flow. The second hour focuses on practical application of multimodal data, discussing key challenges such as spatial co-registration and signal synchronization. By analyzing trial-by-trial variability and fusion models, participants will learn how to integrate these data to move beyond relative signal changes toward absolute physiological measurement.

What will you learn?

• The physiology of NVC: the physiological mechanisms linking neuronal firing to vasodilation and how they relate to the observed fNIRS and fMRI signals.
• Quantitative CMRO2 mapping: how to use the mathematical framework of the Davis Model for CMRO2 calculation in calibrated fMRI imaging as a benchmark and in association with fNIRS measurements (CW-,TD-NIRS and DCS) and fusion models.
• Multimodal troubleshooting: practical strategies for signals co-registration and analysis in time and space.

Course details

Delivery plan

1:00 hr

Part 1: Theoretical Foundations

0:00–0:20 NVC & Metabolic Mapping, the Davis Model.

0:20–0:40 The fMRI Perspective: BOLD, ASL, and Gas-free (Breath-hold) calibration.

0:40–1:00 The fNIRS Perspective: HbO/HbR, intro to TD-NIRS and DCS.

1:00 hr

Part 2: Data, Challenges & Fusion

1:00–1:30 Multimodal Co-registration: Sensitivity maps (Jacobians), Signal Processing & Fusion.

1:30–2:00 Future Directions, Clinical applications & Q&A

Why should you enroll in this course?

The fNIRS and BOLD signals are an indirect proxy for neuronal activity, traditionally assumed to follow a linear relationship with cerebral blood flow (CBF). However, emerging research shows that task-activated regions may exhibit reversed oxygen metabolism. This challenges the canonical interpretation of hemodynamic signals and underscores the necessity of quantitative imaging.

The primary goals are:

• Translate fMRI calibration models and mathematical frameworks (like the Davis Model) into the fNIRS domain and evaluate inter-modal relationships.
• Standardize multimodal fusion: provide a roadmap for combining BOLD, CBF, and CMRO2-derived estimates with fNIRS-derived oxygenation measurements.
• Evaluate new fNIRS technologies: showcase how TD-NIRS and DCS can provide baseline and task-evoked physiological markers.