Generalization in perceptual learning across stimuli and tasks.

Perceptual learning, known to improve visual perception, demonstrates the plasticity of brain processes underlying vision. Early studies, using the backward-masked texture discrimination task (TDT), focused on the lack of generalizing learning to stimulus features, relating learning specificity to the selectivity of the brain networks involved in the visual task. Learning was found to be highly specific to the stimulus features, as expected from the processing selectivity found in early visual areas as well as to the task employed in training, pointing to top-down effects.

Motion-induced blindness as a noisy excitable system.

Perceptual disappearance of a salient target induced by a moving texture mask (MIB: Motion-Induced Blindness) is a striking effect, currently poorly understood. Here, we investigated whether the dynamics of MIB qualify as an excitable system. Excitable systems exhibit fast switches from one state to another (e.

Isolating objective and subjective filling-in using the drift diffusion model.

Spatial context is known to influence the behavioral sensitivity (d') and the decision criterion (c) when detecting low-contrast targets. Of interest here is the effect on the decision criterion. Polat and Sagi (2007) demonstrated that, for a Gabor target positioned between two similar co-aligned high-contrast flankers, the observers' reports of seeing the target (Hit and False Alarm) decreased with increasing target-flanker distance.

Contrast adaptation improves spatial integration.

The effects of contrast adaptation and contrast area summation (spatial integration) were investigated using a contrast discrimination task. The task consisted of a target of variable size, and a pedestal with a fixed base contrast. Discrimination performance was examined for a condition in which the pedestal size was fixed, equal to the largest target size, and for a condition in which the pedestal size matched the target size and thus varied with it.

A decision-time account of individual variability in context-dependent orientation estimation.

Following exposure to an oriented stimulus, the perceived orientation is slightly shifted, a phenomenon termed the tilt aftereffect (TAE). This estimation bias, as well as other context-dependent biases, is speculated to reflect statistical mechanisms of inference that optimize visual processing. Importantly, although measured biases are extremely robust in the population, the magnitude of individual bias can be extremely variable.

Interaction of contexts in context-dependent orientation estimation.

The processing of a visual stimulus is known to be influenced by the statistics in recent visual history and by the stimulus' visual surround. Such contextual influences lead to perceptually salient phenomena, such as the tilt aftereffect and the tilt illusion. Despite much research on the influence of an isolated context, it is not clear how multiple, possibly competing sources of contextual influence interact.

Perceptual bias is reduced with longer reaction times during visual discrimination.

Fast and slow decisions exhibit distinct behavioral properties, such as the presence of decision bias in faster but not slower responses. This dichotomy is currently explained by assuming that distinct cognitive processes map to separate brain mechanisms. Here, we suggest an alternative single-process account based on the stochastic properties of decision processes.

Orientation-selective adaptation improves perceptual grouping.

The role of visual pattern adaptation, and learning, in spatial integration was investigated. Observers reported whether a grid of identical tilted bars was perceived as rows or columns (perceptual grouping task). Performance was measured multiple times during a session to determine effects of repeated exposure to the stimuli.

Real-time visual interactions across the boundary of awareness.

Recently, using Motion Induced-Blindness (MIB), we have shown that two visual stimuli, one consciously experienced and one not, interact as a function of feature and object similarity, pointing to preserved visual representations of objects, and their constitutive features, in the absence of perceptual awareness. Here we investigated whether these representations preserve the memory of the previously perceived stimulus by testing interactions with the unperceived stimulus modified while it is invisible. Observers performed the MIB task, wherein an object 'Target' (a plaid object) was morphed into one of its features (an oriented Gabor patch) once its disappearance was reported.

Visual learning with reduced adaptation is eccentricity-specific.

Visual learning is known to be specific to the trained target location, showing little transfer to untrained locations. Recently, learning was shown to transfer across equal-eccentricity retinal-locations when sensory adaptation due to repetitive stimulation was minimized. It was suggested that learning transfers to previously untrained locations when the learned representation is location invariant, with sensory adaptation introducing location-dependent representations, thus preventing transfer.

Expectations and visual aftereffects.

The tilt aftereffect (TAE) is traditionally regarded as a consequence of orientation-selective sensory adaptation, a low-level stimulus-driven process. Adaptation has been recently suggested to be the outcome of predictive coding. Here, we tested whether the TAE is modulated by predictability, and specifically, whether TAE depends on the congruency of adapted and expected orientations.

A dissociation between consolidated perceptual learning and sensory adaptation in vision.

Perceptual learning refers to improvement in perception thresholds with practice, however, extended training sessions show reduced performance during training, interfering with learning. These effects were taken to indicate a tight link between sensory adaptation and learning. Here we show a dissociation between adaptation and consolidated learning.

Asymmetric visual interactions across the boundary of awareness.

A salient visual object can disappear from conscious perception when surrounded by a moving texture, a phenomenon known as MIB, Motion-Induced Blindness (Bonneh, Cooperman, & Sagi, 2001). Here we tested the information available in the brain from such stimuli that do not access awareness by examining interactions across the boundary of awareness between stimuli that reach awareness and those that do not. Observers performed the MIB task in which a "Cue" was presented next to the "Target" after observers reported the perceptual disappearance of the target (Kawabe, Yamada, & Miura, 2007).

Target-selective tilt aftereffect during texture learning.

Sensory adaptation and perceptual learning are two forms of plasticity in the visual system, with some potential overlapping neural mechanisms and functional benefits. However, they have been largely considered in isolation. Here we examined whether extensive perceptual training with oriented textures (texture discrimination task, TDT) induces adaptation tilt aftereffects (TAE).

Binocular summation of chance decisions.

Seeing with two eyes usually helps one respond faster. Here we show that with ambiguous stimuli, binocular viewing can paradoxically slow down reaction time. This is explained by the observers basing their decision on a noisy neuronal representation within the visual system, with the added noise breaking the symmetry between the two possible interpretations.

Tilt aftereffect due to adaptation to natural stimuli.

The human visual system continuously adjusts to the current environment. To investigate these adjustments, biases in observers' perceptions owing to changes in the visual environment are measured (visual aftereffects). Typically, the stimuli used are synthetic and are composed of oriented patterns such as lines or gratings.

Perceptual learning in autism: over-specificity and possible remedies.

Inflexible behavior is a core characteristic of autism spectrum disorder (ASD), but its underlying cause is unknown. Using a perceptual learning protocol, we observed initially efficient learning in ASD that was followed by anomalously poor learning when the location of the target was changed (over-specificity). Reducing stimulus repetition eliminated over-specificity.

Visual perception of order-disorder transition.

Our experience with the natural world, as composed of ordered entities, implies that perception captures relationships between image parts. For instance, regularities in the visual scene are rapidly identified by our visual system. Defining the regularities that govern perception is a basic, unresolved issue in neuroscience.

Effects of spatiotemporal consistencies on visual learning dynamics and transfer.

Spatiotemporal interactions affect visual performance under repeated stimulation conditions, showing both incremental (commonly related to learning) and decremental (possibly sensory adaptation) effects. Here we examined the role of spatiotemporal consistencies on learning dynamics and transfer. The backward-masked texture-discrimination paradigm was used, with stimulus onset asynchrony (SOA) controlling the observers' performance level.

Two-stage model in perceptual learning: toward a unified theory.

Training or exposure to a visual feature leads to a long-term improvement in performance on visual tasks that employ this feature. Such performance improvements and the processes that govern them are called visual perceptual learning (VPL). As an ever greater volume of research accumulates in the field, we have reached a point where a unifying model of VPL should be sought.