A comparison of the apparent gloss of rendered objects presented in the lower and upper regions of the visual field

Gloss is an aspect of surface perception that is important for understanding the material properties of the environment. Because a surface can stimulate any region of the visual field during natural viewing, it is of interest to measure the potential influence of visual field asymmetries on perceived gloss—as such asymmetries could make the perception of gloss dependent on the visual field location. Here, our aim was to compare the apparent glossiness of renderings of nondescript objects when positioned in the lower and upper regions of the visual field. In Experiment 1, participants (n=20) evaluated the glossiness of objects presented simultaneously below and above central fixation. Estimates of the specular reflectance required for perceptual gloss equality indicated little effect of the visual field location. In Experiment 2, participants (n=19) compared the magnitude of gloss differences across two pairs of objects in either the lower or the upper visual field. Estimates of the exponent relating specular reflectance to a gloss difference scale and a noise parameter again indicated little effect of the visual field location. Overall, these estimates are consistent with the existence of a high degree of gloss constancy across presentations in the lower and upper visual fields.

Feedback contribution to surface motion perception in the human early visual cortex

Human visual surface perception has neural correlates in early visual cortex, but the role of feedback during surface segmentation in human early visual cortex remains unknown. Feedback projections preferentially enter superficial and deep anatomical layers, which provides a hypothesis for the cortical depth distribution of fMRI activity related to feedback. Using ultra-high field fMRI, we report a depth distribution of activation in line with feedback during the (illusory) perception of surface motion. Our results fit with a signal re-entering in superficial depths of V1, followed by a feedforward sweep of the re-entered information through V2 and V3. The magnitude and sign of the BOLD response strongly depended on the presence of texture in the background, and was additionally modulated by the presence of illusory motion perception compatible with feedback. In summary, the present study demonstrates the potential of depth-resolved fMRI in tackling biomechanical questions on perception.