Clocking the conduction velocity of the visual pathway with optically pumped magnetometers

Project Information

OptiVision

Grant agreement ID: 101138983

DOI

10.3030/101138983

Project closed

EC signature date 9 October 2023

Start date 1 January 2024

End date 30 June 2026

Funded under

• European Research Council (ERC)

Total cost

No data

EU contribution

€ 150 000,00

Coordinated by

AARHUS UNIVERSITET
Denmark

Periodic Reporting for period 1 - OptiVision (Clocking the conduction velocity of the visual pathway with optically pumped magnetometers)

Reporting period: 2024-01-01 to 2026-06-30

Summary of the context and overall objectives of the project

The visual pathway provides an important window into the health of the central nervous system. Retinocortical conduction time (RCT), the time required for signals to travel from the retina to the visual cortex, has long been proposed as a potential biomarker for neurological disorders. However, current approaches rely on relatively slow electrophysiological responses, and important questions remain regarding how visual pathway conduction can be measured accurately and non-invasively.
The OptiVision project was motivated by findings from the ERC-funded OscillatoryVision programme that suggested the potential for estimating RCT from earlier neural responses than those traditionally used. To pursue this objective, the project focused on developing the methodological, technical, and anatomical foundations required for future studies.

A major component of the project involved advancing the use of optically pumped magnetometers (OPMs) for measurements of visual system activity. This included substantial efforts to improve the magnetic measurement environment, reduce environmental noise, optimize experimental procedures, and establish workflows capable of supporting challenging high-frequency recordings.

In parallel, the project investigated anatomical factors relevant to visual pathway conduction. In particular, it examined the relationship between head size and visual pathway length, providing evidence on how inter-individual anatomical variability may influence conduction delays. Understanding these anatomical determinants is essential for interpreting future RCT measurements and for developing biomarkers that can distinguish normal biological variation from disease-related changes.

The expected impact of the project is therefore twofold. First, it has established technical capabilities and measurement methodologies that strengthen the foundation for future OPM-based studies of visual system function. Second, it has improved our understanding of anatomical factors that influence visual pathway conduction, providing critical groundwork for the future development of more accurate biomarkers of visual pathway integrity. In the longer term, such biomarkers could contribute to improved assessment and monitoring of neurological disorders.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The project focused on establishing the technical and scientific foundations required for improved measurement of visual pathway conduction. This comprised development of magnetic field compensation for OPM measurements and the investigation of anatomical factors that may influence conduction delays.

A major achievement of the project was the development of a magnetic field compensation algorithm to automatically tune biplanar coils for arbitrary OPM sensor configurations. This reduces background noise and improves tolerance to movements and vibrations. These advances strengthened the laboratory’s capability to perform high-sensitivity OPM recordings and provide a foundation for future studies.

The project also investigated the relationship between head size and visual pathway length. The results demonstrated that anatomical variability can influence the distance over which visual signals travel and therefore represents an important factor to consider when interpreting conduction measurements across individuals.

Despite the improvement of OPM signal quality that was achieved, detection of retinal high-frequency responses remained difficult. To address the main neuroscientific aim, the experiment was redesigned with conventional MEG and ERG to ensure measurement of high-frequency signals. Analysis for the expected effects on retinocortical conduction time estimation remains ongoing.

Overall, the project delivered valuable technical knowledge and improvements for OPM measurements and new insights into anatomical determinants of visual pathway conduction. These outcomes reduce technical barriers for future studies and advance the long-term goal of developing improved biomarkers of visual pathway function.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The project advanced the methodological foundations for studying visual pathway conduction using emerging OPM technology. In particular, it improved the measurement environment, recording procedures, and analysis workflows required for high-sensitivity neuromagnetic recordings, providing a platform that can benefit from future improvements in high-frequency signal-to-noise ratio.

Although OPM-based detection of the targeted high-frequency retinal responses proved more challenging than anticipated, the underlying high-frequency retinocortical conduction time (RCT) concept was successfully demonstrated using conventional MEG and ERG recordings. These results support the feasibility of measuring visual pathway conduction from early neural responses.

The project therefore delivered both technical advances for future OPM-based implementations and scientific validation of the high-frequency RCT approach. Building on these results, clinical collaborations have been established to evaluate the sensitivity of high-frequency RCT measures in neurological and neuropsychiatric populations.
The key outcomes of the project are an improved OPM measurement infrastructure, enhanced expertise in low-noise magnetic recordings, new insights into anatomical variability in visual pathway length, and ongoing validation of the high-frequency RCT concept as a promising candidate biomarker of visual pathway function.