Intra- and Intersession Reproducibility of Artificial Scotoma pRF Mapping Results at Ultra-High Fields.

Functional magnetic resonance imaging (fMRI) combined with population receptive field (pRF) mapping allows for associating positions on the visual cortex to areas on the visual field. Apart from applications in healthy subjects, this method can also be used to examine dysfunctions in patients suffering from partial visual field losses. While such objective measurement of visual deficits (scotoma) is of great importance for, e.g., longitudinal studies addressing treatment effects, it requires a thorough assessment of accuracy and reproducibility of the results obtained. In this study, we quantified the reproducibility of pRF mapping results within and across sessions in case of central visual field loss in a group of 15 human subjects. We simulated scotoma by masking a central area of 2° radius from stimulation to establish ground-truth conditions. This study was performed on a 7 T ultra-high field MRI scanner for increased sensitivity. We found excellent intra- and intersession reproducibility for the pRF center position (Spearman correlation coefficients for x, y: >0.95; eccentricity: >0.87; polar angle: >0.98), but only modest reproducibility for pRF size (Spearman correlation coefficients around 0.4). We further examined the scotoma detection performance using an automated method based on a reference data set acquired with full-field stimulation. For the 2° artificial scotoma, the group-averaged scotoma sizes were estimated at between 1.92 and 2.19° for different sessions. We conclude that pRF mapping of visual field losses yields robust, reproducible measures of retinal function and suggest the use of pRF mapping as an objective method for monitoring visual deficits during therapeutic interventions or disease progression. Significance Statement Population receptive field mapping using functional magnetic resonance imaging is perfectly suited for the investigation of the retinotopic organization on the visual cortex. Expanding its influence from neuroscience toward more clinical areas of applications in patients suffering from visual field loss requires the assessment of the accuracy and reproducibility of the method. Within this work, we demonstrate the robustness of the method within as well as between two scanning sessions. This will lay the foundation for any future pRF mapping research in patients suffering from retinal disease.