Cortical and subcortical proprioceptive contribution to oculomotor control in humans
Daniela Balslev1, Graeme A. Keith2, Ross Hardaker3, Frances Crabbe3, and Alessio Fracasso3
1School of Psychology and Neuroscience, University of St. Andrews, Scotland, UK 2Imaging Centre of Excellence, University of Glasgow, Scotland, UK 3School of Psychology and Neuroscience, University of Glasgow, Scotland, UK

Our poster reports the results of a small pilot study using ultra-high field (7 Tesla) functional magnetic resonance imaging (fMRI). We show the feasibility of parallel, brain and brainstem data acquisition.

We did this research because we have previously observed that stretching the extraocular muscles of the right eye is associated with an increase of neural activity in the brainstem extraocular motor nuclei that move the left eye (Balslev et al., Human Brain Mapping, 2022). Understanding the proprioceptive coupling between the two eyes is important, because it may shed light on the disease mechanisms of strabismus, a common and disabling condition in children characterised by misaligned ocular axes. The objective is to find out which brain or brainstem structure drives this proprioceptive coupling between the two eyes. Is this a short reflex via the brainstem (like a crossed stretch reflex in the skeletal muscles) or does it reflect a longer feedback loop via the brain?

One can answer this question using fMRI connectivity. The first step in this research, however, is to acquire fMRI data from both brain and brainstem at the same time. This was not possible in our previous study at 3 Tesla where we had to zoom in on the brainstem. Imaging the brainstem is challenging because of the small nuclei and the proximity of the pulsating blood vessels. Most studies tackle this challenge by limiting the field of view to the structure of interest. Our innovative approach was to use the higher streghth of the magnetic field to increase signal-to-noise ratio. We replicate previous results, and this time around, we manage to image both brain and the brainstem at the same time, enabling future connectivity analyses.

The poster is scheduled for presentation on Wednesday June 26 and Thursday June 27 13:45-15:45 at COEX Seoul, South Korea. This small pilot was funded by the University of St Andrews (LIFTS award to Daniela) and the University of Glasgow. We are now applying for funds to complete this research (UPDATE 1.07.2024 – I just heard that the UK Medical Research Councils funded this project. I’m so happy and grateful that we get to finish this research!) .