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 c...

Human stereo vision can resolve remarkably small depth differences between two stimuli, but the smallest resolvable difference is usually that between stimuli located near the plane of fixation. As distance from this plane increases, so does the smallest detectable increment in disparity. We examined this loss of resolution by comparing disparity discrimination thresholds for single-scale and m...

We investigated the way in which binocular coordination in reading is affected by the spatial structure of text. Vergence eye movements were measured (EyeLink II) in 32 observers while they read 120 single German sentences (Potsdam Sentence Corpus) silently for comprehension. The similarity in shape between the neighboring strokes of component letters, as measured by the first peak in the horiz...

I. Diagnostic testing review A. Case history B. Best corrected visual acuity – use of crowding bars C. Cycloplegic refraction – emphasis on retinoscopy D. Monocular fixation 1. Visuoscopy – rule out eccentric fixation, microstrabismus 2. MITT/Haidinger’s brushes – rule out eccentric fixation E. Binocular status 1. Cover test – rule out strabismus 2. Stereopsis – random dot versus lateral dispar...

Binocular disparity is a powerful depth cue for object perception. The computations for object vision culminate in inferior temporal cortex (IT), but the functional organization for disparity in IT is unknown. Here we addressed this question by measuring fMRI responses in alert monkeys to stimuli that appeared in front of (near), behind (far), or at the fixation plane. We discovered three regio...

Older adults (65 + years) often have greater difficulty in reading than young adults (18-30 years). However, the extent to which this difficulty is attributable to impaired eye-movement control is uncertain. To address this issue, the alignment and location of the two eyes' fixations during reading were monitored for young and older adults. Older adults showed typical patterns of reading diffic...

Stereoscopic depth perception is based on binocular disparities. Although neurons in primary visual cortex (V1) are selective for binocular disparity, their responses do not explicitly code perceived depth. The stereoscopic pathway must therefore include additional processing beyond V1. We used functional magnetic resonance imaging (fMRI) to examine stereo processing in V1 and other areas of vi...

The literature on vertical disparity is complicated by the fact that several different definitions of the term "vertical disparity" are in common use, often without a clear statement about which is intended or a widespread appreciation of the properties of the different definitions. Here, we examine two definitions of retinal vertical disparity: elevation-latitude and elevation-longitude dispar...