Justin M. Ales

TL;DR: The purpose of this article is to describe the fundamental stimulation paradigms for steady-state visual evoked potentials and to illustrate these principles through research findings across a range of applications in vision science.

TL;DR: Forward models of cortical areas V1, V2 and V3 were generated that were based on realistic estimates of the 3-D shape of these areas and the shape and conductivity of the brain, skull and scalp and showed that sources in V1 do not fully conform to the cruciform sign-reversal.

TL;DR: This first application of the sweep VEP approach to high-level vision provides a sensitive and objective method that could be used to measure and compare visual perception thresholds for various object shapes and levels of categorization in different human populations, including infants and individuals with developmental delay.

TL;DR: Fly and human visual systems encode the combined direction and contrast polarity of moving edges using triple correlations that enhance motion estimation in natural environments, arguing that statistical structures in natural scenes have greatly affected visual processing.

Abstract: We used source imaging of visual evoked potentials to measure neural population responses over a wide range of horizontal disparities (0.5–64 arcmin). The stimulus was a central disk that moved back and forth across the fixation plane at 2 Hz, surrounded either by binocularly uncorrelated dots (disparity noise) or by correlated dots presented in the fixation plane. Both disk and surround were composed of dynamic random dots to remove coherent monocular information. Disparity tuning was measured in five visual regions of interest (ROIs) [V1, human middle temporal area (hMT+), V4, lateral occipital complex (LOC), and V3A], defined in separate functional magnetic resonance imaging scans. The disparity tuning functions peaked between 2 and 16 arcmin for both types of surround in each ROI. Disparity tuning in the V1 ROI was unaffected by the type of surround, but surround correlation altered both the amplitude and phase of the disparity responses in the other ROIs. Response amplitude increased when the disk was in front of the surround in the V3A and LOC ROIs, indicating that these areas encode figure–ground relationships and object convexity. The correlated surround produced a consistent phase lag at the second harmonic in the hMT+ and V4 ROIs without a change in amplitude, while in the V3A ROI, both phase and amplitude effects were observed. Sensitivity to disparity context is thus widespread in visual cortex, but the dynamics of these contextual interactions differ across regions.