EyeProprio

This is a heads-up about an opening for a postdoc in my lab while we are preparing the formal advert.

Applications are sought for a committed Post-doctoral Research Fellow to work with the group led by Dr Daniela Balslev conducting research for an MRC-funded project entitled: The role of oculoproprioception in the neural control of ocular alignment: Understanding disease mechanisms in strabismus.  Co-Investigators and Partners are Prof Malinda Carpenter (School of Psychology and Neuroscience, University of St Andrews), Dr Alessio Fracasso (School of Psychology and Neuroscience, University of Glasgow) and Dr Nikki Hall (Children’s Orthoptic Unit, NHS Fife).

Strabismus (squint or crossed eyes) is one of the most common and debilitating eye disorders in childhood. Individuals with this condition cannot align the two eyes to look at the same object. To precisely control where we look, the brain has access to information about the rotation of each eye in the eye sockets. One source of such information is called proprioception. We ask whether the misalignment of the eyes in some types of strabismus might be caused by inaccurate proprioception. To answer this question, we will use eye tracking in 4- to 5-year-old children and functional magnetic resonance imaging/transcranial magnetic stimulation in adults.

The primary duties will be to:

• Assess whether the sense of eye position is impaired in children with strabismus (using eye tracking with 4- to 5-year-olds)
• Investigate how the human brain coordinates the movement of the two eyes (using ultra-high field functional magnetic resonance imaging and transcranial magnetic stimulation with adults)

The successful applicant will have (or be near the completion of) a PhD in cognitive neuroscience or a related discipline and a strong interest in human vision or oculomotor control. You will already have experience with some of the following methods: eye tracking, behavioural data collection in young children, functional magnetic resonance imaging or transcranial magnetic stimulation, and will be willing to learn from the investigators those methods that you do not yet master.

The post is available for 36 months starting on February 1^st, 2025, or as soon as possible thereafter.

Further details of the project can be found by contacting Dr Daniela Balslev (daniela.balslev@st-andrews.ac.uk). 

I’m delighted to share that Pei Wu has joined the lab to conduct research towards a PhD with me and Dr Tom Otto.

She will investigate the neural mechanisms underlying motor eye dominance.

Poster:

Cortical and subcortical proprioceptive contribution to oculomotor control in humans
Daniela Balslev¹, Graeme A. Keith², Ross Hardaker³, Frances Crabbe³, and Alessio Fracasso^3
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!) .

Gaze and attention: mechanisms underlying the therapeutic effect of optokinetic stimulation in spatial neglect by Chan, Mitchell, Sandilands and Balslev, Neuropsychologia, 2024 (in press)

I am delighted to announce that our paper has just been accepted for publication. The contributions from Hilary Chan and Eilidh Sandilands, who were undergraduate students at the University of St Andrews when they completed this research, deserve a special recognition.

In brief, we investigated how left optokinetic stimulation, which is a rehabilitation method in spatial neglect works. Spatial neglect is a common and disabling neuropsychological condition after a right hemisphere lesion characterised by inattention to people and objects in the contralesional space. Optokinetic stimulation is the exposure to large field visual motion, for instance when watching dots that move in the same direction on a computer screen in the lab (or in real life, when looking out of the window from a moving train). Optokinetic stimulation induces a type of eye movements called optokinetic nystagmus.

We found that in healthy participants optokinetic stimulation altered the proprioceptive (stretch) input from the extraocular muscles. The misperception of own gaze direction was associated with a bias in spatial attention. Both changes outlasted the period of optokinetic stimulation.

We are therefore proposing that the change in the eye position signals underlies the therapeutic effect of optokinetic stimulation. If so, then the effect of left optokinetic stimulation in spatial neglect could be improved by combining it with other interventions that affect eye proprioception, such as repetitive transcranial magnetic stimulation over the somatosensory cortex.

I have uploaded our accepted-for-publication manuscript here.

We could not fill this position so I am re-advertising the project.

A PhD studentship (competition funding, EASTBIO/BBSRC) is available with start on September 2024. The project investigates the neural substrate of motor eye dominance (the stable preference for one of the two eyes when sighting).

A full project description and information about the application process are available here.

You can contact me at daniela.balslev@st-andrews.ac.uk if you have questions.

Extraocular muscles graffiti, on my way to Imaging Excellence Center, Queen Elizabeth University Hospital, Glasgow for a pilot project on the 7T scanner (cortco-subcortical interaction in the control of ocular alignment). No, it wasn’t me, I’m not that talented 🙂

Proprioceptive coupling between the two eyes. A brief, passive stretch of the right eye’s lateral rectus muscle in humans is associated with an increase in the BOLD response in the left oculomotor and abducens nuclei, which innervate the extraocular muscles of the left eye. In complete darkness the left eye’s active movement mirrors the passive movement of the right eye, suggesting a role of extraocular muscle proprioception in ocular alignment (Cover illustration based on Balslev, Mitchell, Faria, Priba, Macfarlane. Proprioceptive contribution to oculomotor control in humans  https://onlinelibrary.wiley.com/toc/10970193/2022/43/16)

Proprioceptive contribution to oculomotor control in humans

We have a new paper accepted for publication at Human Brain Mapping. We argue that in humans the afferent input from the extraocular muscles (EOM proprioception) facilitates yoked movements of the two eyes.

Thanks go to my co-authors Jen Macfarlane, Lukasz Priba, Alexandra Mitchell, and Patrick Faria. Shout-out to Patrick who was only a Masters student at the time he completed a very demanding eye-tracking experiment.

The highlights are:

• A brief, passive stretch of the right eye’s lateral rectus muscle in humans was associated with an increase in the BOLD response in the left oculomotor and abducens nuclei, which innervate the extraocular muscles of the left eye.
• The left eye’s active movement mirrored the passive movement of the right eye.
• Both neuroimaging and eye tracking suggest a proprioceptive coupling between the two eyes.

I will add a link to the open-access paper and the publicly available dataset as soon as I get a free moment.

Here is a 3-minute video presentation of this research (presentation at the Annual Conference of the Organisation for Human Brain Mapping in June 2022)