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Minicourse EDEP-JG05

NIRS-EEG co-registration: possibilities, challenges and solutions

Judit Gervain

with Jessica Gemignani

About this course

The aim of this mini-course is to address the challenges of NIRS-EEG co-recording both theoretically and practically. To achieve this, the course first offers a basic overview of how the hemodynamic response relates to neural activity in order to provide an understanding of the physiological mechanisms that the two techniques measure. It then exemplifies the challenges of NIRS-EEG co-recording by reviewing concrete studies from the instructors’ lab that were unsuccessful in combining the two techniques. Similarly, studies from the instructors’ lab will then be presented in detail that successfully co-registered the two techniques to illustrate possible solutions and best practices. Finally, practical guidance will be given about methodological issues, data analysis techniques such as multivariate analyses and the interpretation of the results. Ample time will be allowed for discussion, and participants will be given the opportunity to raise questions about NIRS-EEG co-registration challenges that they have encountered in their own research practice.

Learning Outcomes

Participants will learn about:

  • the physiological mechanisms that link the hemodynamic response to neural activity;
  • challenges in NIRS-EEG co-recording, e.g. in stimulation duration, experimental design, data analysis;
  • solutions to overcome these challenges.

Course Plan

Level: Introductory

Pre-Requisites: None
Course Duration: 2 hours

Delivery Plan

30 min: the physiological mechanisms linking the hemodynamic response to neural activity
30 min: illustrating the challenges of NIRS-EEG co-recording
60 min: illustrating and discussing possible solutions to these challenges with active participation from the audience: solutions for experimental designs and data analysis (e.g. multivariate analysis)

Why enrol on this course?

Multimodal brain imaging is an increasingly common approach in neuroscience, as combined methods offer more insights into neural mechanisms. Combining fNIRS with electroencephalography (EEG) is particularly promising, as the two techniques have complementary strengths: NIRS offers precise spatial localization, EEG high temporal resolution. There is no interference between the two signals, and the sensors can easily be inserted into the same headgear. Despite its relevance and ease of applicability, NIRS-EEG co-registration is not without its challenges. The two techniques measure different physiological mechanisms, NIRS assessing the hemodynamic correlates of neural activity, EEG the neural activity itself. As a consequence, the time scales of the two techniques differ by an order of magnitude, as the hemodynamic response measured by NIRS unfolds over seconds, while the neural activation recorded by EEG occurs at the millisecond range. This mismatch in time scales poses considerable challenges for experimental and stimulation paradigms, as it is hard to create stimuli and experimental designs of optimal durations. It is also a challenge for data analysis and interpretation, because responses to the same stimuli do not occur at the same time, and the two measures do not always provide converging results. The sensitivity of the two measures may also differ, depending on the experimental task, the population and the instrumentation involved.