Around the time Sam moved to New Zealand, he and Dr Catherine Morgan conducted a little experiment. Seeing that we knew three individuals who would be visiting London as well as Auckland within a few months, we decided to scan them twice on a pRF mapping paradigm. The first scan was on the 1.5T scanner at BUCNI in London, the second scan on a 3T scanner at CAMRI in Auckland. Naturally, there are quite a few differences in the scanning parameters between these site and the sequences used on two magnetic field strengths. Our aim was not to test the specific effect of magnetic field strength. Rather we sought to compare pRF estimates on two different sites with different scanners, using the standard parameters at each site. We did however keep things constant, such as the voxel size, temporal resolution, and the visual field of view of the participant in the scanner.
The findings, which are now published in F1000Research, suggest that the general retinotopic map organisation, as well as pRF size and cortical magnification estimates, are all pretty similar across sites. This is in spite of the fact that the signal-to-noise ratio of the 3T scanner is undeniably superior to the 1.5T. This is an important finding because it suggests we can directly compare pRF mapping data between different sites. In turn, this further opens up the possibility of conducting multi-site collaborations. Due to the small sample size in this study, we of course cannot rule out very subtle differences that we were simply not able to detect here. Most pRF or retinotopic mapping studies tend to focus on single participants as case studies, so it is actually crucial that we observe identical results from the same participant at different sites.
Morgan, C, & Schwarzkopf, DS (2020). Comparison of human population receptive field estimates between scanners and the effect of temporal filtering. F1000Research 8: 1681.