Dr Anna Hughes, a former colleague of ours in UCL who has since moved on to greener pastures, published a study in which we use stimuli defined by motion for pRF mapping. Most visual field mapping is done with solid high-contrast stimuli (moving bars or rotating wedges, etc.). Here instead we used random fields of moving dots and defined the stimulus location by means of the dot properties. The aim was to test whether stimuli defined for instance by the coherence of motion would selectively produce responses in higher visual areas that are believed to be involved in global motion processing. While our results were indeed consistent with that, we also observed similar results when using control stimuli not defined by motion. Our findings therefore instead suggest that what determines activation in visual field mapping studies is not necessarily the stimulus feature – in fact, it could simply be the signal-to-noise ratio of the mapping signal.
Hughes, AE, Greenwood, JA, Finlayson, NJ, & Schwarzkopf, DS (2019). Population receptive field estimate for motion-defined stimuli. NeuroImage In press.