When You Do Not Get the Whole Picture: Scene Perception After Occipital Cortex Lesions.

Occipital cortex lesions (OCLs) typically result in visual field defects (VFDs) contralateral to the damage. VFDs are usually mapped with perimetry involving the detection of point targets. This, however, ignores the important role of integration of visual information across locations in many tasks of everyday life.

Functional connectivity of the Precuneus reflects effectiveness of visual restitution training in chronic hemianopia.

Visual field defects in chronic hemianopia can improve through visual restitution training, yet not all patients benefit equally from this long and exhaustive procedure. Here, we asked if resting-state functional connectivity prior to visual restitution could predict training success. In two training sessions of eight weeks each, 20 patients with chronic hemianopia performed a visual discrimination task by directing spatial selective attention towards stimuli presented in either hemifield, while suppressing eye movements.

Useful Field of View Performance in the Intact Visual Field of Hemianopia Patients.

Purpose: Postchiasmatic brain damage commonly results in an area of reduced visual sensitivity or blindness in the contralesional hemifield. Previous studies have shown that the ipsilesional visual field can be impaired too. Here, we examine whether assessing visual functioning of the "intact" ipsilesional visual field can be useful to understand difficulties experienced by patients with visual field defects.

Human V2A: A map of the peripheral visual hemifield with functional connections to scene-selective cortex.

Humans can recognize a scene in the blink of an eye. This gist-based visual scene perception is thought to be underpinned by specialized visual processing emphasizing the visual periphery at a cortical locus relatively low in the visual processing hierarchy. Using wide-field retinotopic mapping and population receptive field (pRF) modeling, we identified a new visual hemifield map anterior of area V2d and inferior to area V6, which we propose to call area V2A.

Eccentricity scale independence for scene perception in the first tens of milliseconds.

Visual processing of scenes in the first tens of milliseconds relies on global image summary statistics rather than localized processing. Although natural scenes typically involve our entire visual field, scenes are usually presented experimentally at limited eccentricity. Receptive-field size increases with foveal eccentricity while increasingly pooling activity from local receptive fields.

Useful field of view test performance throughout adulthood in subjects without ocular disorders.

Previous research has shown an age-related decline in Useful Field of View (UFOV) test performance, which measures the duration required to extract relevant information from a scene in three subtasks. However, these results are mostly based on data that may have been confounded by (age-related) ocular diseases. We examined UFOV performance in subjects aged 19.

Improvement in activities of daily living after visual training in patients with homonymous visual field defects using Goal Attainment Scaling.

Background: Stroke is the most common cause of homonymous visual field defects (HVFDs). Yet, there is no standard protocol for composing a rehabilitation program.

Objective: In this study we assess ADL gain of visual training for vision restoration in HVFD patients by means of Goal Attainment Scaling.

Segregation of Spontaneous and Training Induced Recovery from Visual Field Defects in Subacute Stroke Patients.

Whether rehabilitation after stroke profits from an early start is difficult to establish as the contributions of spontaneous recovery and treatment are difficult to tease apart. Here, we use a novel training design to dissociate these components for visual rehabilitation of subacute stroke patients with visual field defects such as hemianopia. Visual discrimination training was started within 6 weeks after stroke in 17 patients.

A meta-analysis of perceptual and cognitive functions involved in useful-field-of-view test performance.

The useful-field-of-view (UFOV) test measures the amount of information someone can extract from a visual scene in one glance. Its scores show relatively strong relationships with everyday activities. The UFOV test consists of three computer tests, suggested to measure processing speed and central vision, divided attention, and selective attention.

Visual Rehabilitation in Chronic Cerebral Blindness: A Randomized Controlled Crossover Study.

The treatment of patients suffering from cerebral blindness following stroke is a topic of much recent interest. Several types of treatment are under investigation, such as substitution with prisms and compensation training of saccades. A third approach, aimed at vision restitution is controversial, as a proper controlled study design is missing.

Dissociation of retinal and headcentric disparity signals in dorsal human cortex.

Recent fMRI studies have shown fusion of visual motion and disparity signals for shape perception (Ban et al., 2012), and unmasking camouflaged surfaces (Rokers et al., 2009), but no such interaction is known for typical dorsal motion pathway tasks, like grasping and navigation.

Differential responses in dorsal visual cortex to motion and disparity depth cues.

We investigated how interactions between monocular motion parallax and binocular cues to depth vary in human motion areas for wide-field visual motion stimuli (110 × 100°). We used fMRI with an extensive 2 × 3 × 2 factorial blocked design in which we combined two types of self-motion (translational motion and translational + rotational motion), with three categories of motion inflicted by the degree of noise (self-motion, distorted self-motion, and multiple object-motion), and two different view modes of the flow patterns (stereo and synoptic viewing). Interactions between disparity and motion category revealed distinct contributions to self- and object-motion processing in 3D.

Saccade target selection relies on feedback competitive signal integration.

It is often assumed that decision making involves neural competition, accumulation of evidence "scores" over time, and commitment to a particular alternative once its scores reach a critical decision threshold first. So far, however, neither the first-to-threshold rule nor the nature of competition (feedforward or feedback inhibition) has been revealed by experiments. Here, we presented two simultaneously flashed targets that reversed their intensity difference during each presentation and instructed human subjects to make a saccade toward the brightest target.

Speed and direction response profiles of neurons in macaque MT and MST show modest constraint line tuning.

Several models of heading detection during smooth pursuit rely on the assumption of local constraint line tuning to exist in large scale motion detection templates. A motion detector that exhibits pure constraint line tuning responds maximally to any 2D-velocity in the set of vectors that can be decomposed into the central, or classic, preferred velocity (the shortest vector that still yields the maximum response) and any vector orthogonal to that. To test this assumption, we measured the firing rates of isolated middle temporal (MT) and medial superior temporal (MST) neurons to random dot stimuli moving in a range of directions and speeds.

Adjacent visual representations of self-motion in different reference frames.

Recent investigations indicate that retinal motion is not directly available for perception when moving around [Souman JL, et al. (2010) J Vis 10:14], possibly pointing to suppression of retinal speed sensitivity in motion areas. Here, we investigated the distribution of retinocentric and head-centric representations of self-rotation in human lower-tier visual motion areas.

Distance estimation is influenced by encoding conditions.

Background: It is well established that foveating a behaviorally relevant part of the visual field improves localization performance as compared to the situation where the gaze is directed elsewhere. Reduced localization performance in the peripheral encoding conditions has been attributed to an eccentricity-dependent increase in positional uncertainty. It is not known, however, whether and how the foveal and peripheral encoding conditions can influence spatial interval estimation.

Occlusion-related lateral connections stabilize kinetic depth stimuli through perceptual coupling.

Local sensory information is often ambiguous forcing the brain to integrate spatiotemporally separated information for stable conscious perception. Lateral connections between clusters of similarly tuned neurons in the visual cortex are a potential neural substrate for the coupling of spatially separated visual information. Ecological optics suggests that perceptual coupling of visual information is particularly beneficial in occlusion situations.

The role of motion capture in an illusory transformation of optic flow fields.

In the optic flow illusion, the focus of an expanding optic flow field appears shifted when uniform flow is transparently superimposed. The shift is in the direction of the uniform flow, or "inducer." Current explanations relate the transformation of the expanding optic flow field to perceptual subtraction of the inducer signal.

Multi-timescale perceptual history resolves visual ambiguity.

When visual input is inconclusive, does previous experience aid the visual system in attaining an accurate perceptual interpretation? Prolonged viewing of a visually ambiguous stimulus causes perception to alternate between conflicting interpretations. When viewed intermittently, however, ambiguous stimuli tend to evoke the same percept on many consecutive presentations. This perceptual stabilization has been suggested to reflect persistence of the most recent percept throughout the blank that separates two presentations.

Flash suppression and flash facilitation in binocular rivalry.

We show that previewing one half image of a binocular rivalry pair can cause it to gain initial dominance when the other half is added, a novel phenomenon we term flash facilitation. This is the converse of a known effect called flash suppression, where the previewed image becomes suppressed upon rivalrous presentation. The exact effect of previewing an image depends on both the duration and the contrast of the prior stimulus.

The time course of binocular rivalry reveals a fundamental role of noise.

When our two eyes view incongruent images, we experience binocular rivalry: An ongoing cycle of dominance periods of either image and transition periods when both are visible. Two key forces underlying this process are adaptation of and inhibition between the images' neural representations. Models based on these factors meet the constraints posed by data on dominance periods, but these are not very stringent.

Representation of head-centric flow in the human motion complex.

Recent neuroimaging studies have identified putative homologs of macaque middle temporal area (area MT) and medial superior temporal area (area MST) in humans. Little is known about the integration of visual and nonvisual signals in human motion areas compared with monkeys. Through extra-retinal signals, the brain can factor out the components of visual flow on the retina that are induced by eye-in-head and head-in-space rotations and achieve a representation of flow relative to the head (head-centric flow) or body (body-centric flow).

An illusory transformation of optic flow fields without local motion interactions.

The focus of expansion (FOE) of a radially expanding optic flow pattern that is overlapped by unidirectional laminar flow is perceptually displaced in the direction of that laminar flow. There is continuing debate on whether this effect is due to local or global motion interactions. Here, we show psychophysically that under conditions without local motion transparency the illusion becomes weaker but can still be observed.

Distributions of alternation rates in various forms of bistable perception.

Studying the temporal dynamics of bistable perception can be useful for understanding neural mechanisms underlying the phenomenon. We take a closer look at those temporal dynamics, using data from four different ambiguous stimuli. We focus our analyses on two recurrent themes in bistable perception literature.

Manipulating saccadic decision-rate distributions in visual search.

The Gaussian shape of reciprocal latency distributions typically found in single saccade tasks supports the idea of a race-to-threshold process underlying the decision when to saccade (R. H. Carpenter & M.