Investigating the human binocular visual system using multi-modal magnetic resonance imaging

Seeing in stereoscopic depth relies on the slight differences in the images in the two eyes resulting from their horizonal separation. As the inputs from the eyes are first combined in the primary visual cortex (V1), human brain imaging can be used to investigate the earliest stages of processing. To perceive depth, binocular neurons in V1 need balanced input from the two eyes, likely established by mutual inhibition, whereby activation of one eye inhibits the other eye. Thus, when input from the two eyes is comparable, both will contribute equally to binocular vision to promote 3D vision. However, if input from one eye is consistently weaker, the other eye may dominate, a situation that can lead to amblyopia.

I will describe MRI work using magnetic resonance spectroscopy indicating a role for inhibitory neurotransmitter GABA in binocular vision and eye dominance. This is the case for short term interventions as well as normal variability between people.

I will then present two studies that investigate how population receptive field (pRF) mapping can determine the selectivity of cortical areas to binocular disparity. In the first study we show that V1 pRFs measured with a disparity-defined stimulus are larger than those generated by stimuli that do not require binocular interaction. Secondly, using pRF mapping in the depth plane, we show a relationship between the preferred depth and width of the tuning curve, such that voxels preferring zero disparity have narrower tuning curves.

The ability to understand the mechanisms underlying human binocular vision raises the possibility of manipulating neural activity levels to improve function in those with impaired binocular vision.

Holly Bridge is a professor of Neuroscience at the Nuffield Department of Clinical Neurosciences of the University of Oxford (UK), she is one of the leading experts in clinical visual neuroscience.

The DEC is delighted to host Prof. Bridge as invited professor starting from June 17th 2024. During her visiting time, Holly will give a series of four lectures.

• 17/06/24, 14h30-16h30, salle Jaurès 

Understanding ‘blindsight’: investigating the pathways that allow those who are clinically blind to ‘see’ 

• 25/06/24, 14h30-16h30, salle Ribot 

The potential for visual rehabilitation following stroke to the visual cortex 

• 02/07/24, 14h30-16h30, salle Ribot 

Understanding the development of the human brain in the absence of vision 

• 09/07/24, 14h30-16h30, salle Ribot 

Investigating the human binocular visual system using multi-modal magnetic resonance imaging