Biology subjects

Weldon, K. B.

Publications and source records attributed to Weldon, K. B..

2 recordsLinked to original sources

bioRxiv2019

Foveal feedback supports peripheral perception of both object color and form

Evidence from neuroimaging and brain stimulation studies suggest that visual information about objects in the periphery is fed back to foveal retinotopic cortex in a separate representation that is essential for peripheral perception. The characteristics of this phenomenon has important theoretical implications for the role fovea-specific feedback might play in perception. In this work, we employed a recently developed behavioral paradigm to explore whether late disruption to central visual space impaired perception of color. First, participants performed a shape discrimination task on colored novel objects in the periphery while fixating centrally. Consistent with the results from previous work, a visual distractor presented at fixation ~100ms after presentation of the peripheral stimuli impaired sensitivity to differences in peripheral shapes more than a visual distractor presented at other stimulus onset asynchronies. In a second experiment, participants performed a color discrimination task on the same colored objects. In a third experiment, we further tested for the foveal distractor effect with stimuli restricted to a low-level feature by using homogenous color patches. These two latter experiments resulted in a similar pattern of behavior: a central distractor presented at the critical stimulus onset asynchrony impaired sensitivity to peripheral color differences, but, importantly, the magnitude of the effect depended on whether peripheral objects contained complex shape information. These results taken together suggest that feedback to the foveal confluence is a component of visual processing supporting perception of both object form and color.

neuroscience↗

bioRxiv2019

Defining region-specific masks for reliable depth-dependent analysis of fMRI data

In high-field fMRI research, anatomical reference information (e.g., gray matter (GM) segmentation, cortical depth delineation) is often defined in volumes acquired with pulse sequences subject to different distortions than those in functional volumes. In these cases, reliable interpretation of ultra-high resolution fMRI data depends on excellent cross-modal registration of functional volumes to reference anatomical volumes. In this paper, we describe a two-step approach to automating assessments of cross-modal registration quality for the purpose of guiding depth-dependent analysis. First, each functional/anatomical registration was scored by the ratio of the number of GM voxels in the functional data overlapping anatomical GM to the number of GM voxels in the functional data overlapping anatomical white matter (WM). This GM:WM overlap ratio provided an objective metric for determining whether an alignment algorithm had converged on a solution that would pass visual inspection. Second, surface-based maps indicating the consistency of overlap between functional and anatomical GM throughout the GM depth were generated for the entire region of cortex covered by the experiment. These maps served as a mask for the purpose of excluding regions where registration between functional and anatomical data was inadequate and thus unable to support depth-dependent analyses. We found, for both real and simulated data, that functional response profiles that were less biased toward superficial responses in regions where these metrics indicated satisfactory registration.

neuroscience↗