To evaluate a multimodal functional magnetic resonance imaging (fMRI) protocol in healthy volunteers with artificially impaired vision in one eye, serving as a functional model of optic neuritis (ON).

ON is a frequent presenting manifestation of multiple sclerosis. Despite the common belief that ON is associated with good recovery of vision within several weeks, up to 40 % of patients still show abnormal visual acuity or contrast sensitivity after 10 years. In order to develop neuroprotective treatments, new sensitive imaging biomarkers of functional recovery after ON are required.

Nine healthy volunteers (5 women, age 29.7±6.9) with normal vision underwent a single fMRI session involving visual stimulation while wearing MRI compatible glasses to correct refractive errors and to blur a randomly assigned eye by additional +3.0 D. Three stimulation paradigms were designed to selectively activate different regions of the visual cortex: pattern reversal (2 Hz), low contrast radial motion onset (200 ms duration, 1 s interstimulus interval), and face presentation alternating with matched noise (2 Hz). A custom-designed MRI-compatible partition enabled alternating monocular stimulation. Imaging data were acquired using a 1.5 T scanner and processed using FSL. Resulting statistical maps were thresholded cluster-wise at Z > 3.0 and corrected p < 0.05.

There was no significant difference between eyes during pattern reversal stimulation. However, in face > noise contrast, the blurred eye was associated with lower activation in the right fusiform gyrus (face area). In motion onset stimulation, the blurred eye was associated with lower activation in the left dorsolateral occipital cortex (V2/V3).

Our comprehensive multimodal fMRI protocol illustrates possible utility of selective dorsal and ventral stream stimulation, suggesting a higher sensitivity of higher-order visual areas to visual acuity impairment.

Acknowledgements:
Supported by the Ministry of Health of the Czech Republic, grants nr. NV19-06-00216, and MH CZ – DRO (FNOl, 00098892).