The processing of spatial frequencies through time in visual word recognition.

This study examined the temporal profile of spatial frequency processing in a word reading task in 16 normal adult readers. They had to report the word presented in a 200 ms display using a four-alternative forced-choice task (4AFC). The stimuli were made of an additive combination of the signal (i.

The oscillatory features of visual processing are altered in healthy aging.

The temporal features of visual processing were compared between young and elderly healthy participants in visual object and word recognition tasks using the technique of random temporal sampling. The target stimuli were additively combined with a white noise field and were exposed very briefly (200 ms). Target visibility oscillated randomly throughout exposure duration by manipulating the signal-to-noise ratio (SNR).

Stereopsis provides a constant feed to visual shape representation.

The contribution of stereopsis in human visual shape perception was examined using stimuli with either null, normal, or reversed binocular disparity in an old/new object recognition task. The highest levels of recognition performance were observed with null and normal binocular disparity displays, which did not differ. However, reversed disparity led to significantly worse performance than either of the other display conditions.

Oscillatory visual mechanisms revealed by random temporal sampling.

It is increasingly apparent that functionally significant neural activity is oscillatory in nature. Demonstrating the implications of this mode of operation for perceptual/cognitive function remains somewhat elusive. This report describes the technique of random temporal sampling for the investigation of visual oscillatory mechanisms.

Cognistat: normes francophones pour les 60 ans et plus.

Cognistat is a cognitive screening test that is widely used in English-speaking countries. Its French adaptation is now available. The present study aims to establish norms for a population aged 60 and over.

A surface-based code contributes to visual shape perception.

Considerable uncertainty remains regarding the types of features human vision uses for shape representation. Visual-search experiments are reported which assessed the hypothesis of a surface-based (i.e.

Increased flanker task and forward digit span performance in caudate-nucleus-dependent response strategies.

One of two memory systems can be used to navigate in a new environment. Hippocampus-dependent spatial strategy consists of creating a cognitive map of an environment and caudate nucleus-dependent response strategy consists of memorizing a rigid sequence of turns. Spontaneous use of the response strategy is associated with greater activity and grey matter within the caudate nucleus while the spatial strategy is associated with greater activity and grey matter in the hippocampus.

Decoding the Locus of Covert Visuospatial Attention from EEG Signals.

Visuospatial attention can be deployed to different locations in space independently of ocular fixation, and studies have shown that event-related potential (ERP) components can effectively index whether such covert visuospatial attention is deployed to the left or right visual field. However, it is not clear whether we may obtain a more precise spatial localization of the focus of attention based on the EEG signals during central fixation. In this study, we used a modified Posner cueing task with an endogenous cue to determine the degree to which information in the EEG signal can be used to track visual spatial attention in presentation sequences lasting 200 ms.

Stereo and shading contribute independently to shape convexity-concavity discrimination.

The present study examined the joint contribution of shading and stereopsis to the perception of shape convexity-concavity. The stimuli were the images of a synthetic convex 3-D shape seen from viewpoints leading to ambiguity as to its convexity. Illumination came from either above or below, and from either the right or the left, and stimuli were presented dichoptically with normal binocular disparity, reversed disparity, or no disparity.

A crowdful of letters: disentangling the role of similarity, eccentricity and spatial frequencies in letter crowding.

The present study investigated the joint impact of target-flanker similarity and of spatial frequency content on the crowding effect in letter identification. We presented spatial frequency filtered letters to neurologically intact non-dyslexic readers while manipulating target-flanker distance, target eccentricity and target-flanker confusability (letter similarity metric based on published letter confusion matrices). The results show that high target-flanker confusability magnifies crowding.

Subjectively homogeneous noise over written text as a tool to investigate the perceptual mechanisms involved in reading.

In an effort to understand the factors influencing text legibility in natural reading, we adapted the visual spread method (Poirier, Gosselin, & Arguin, 2008) to natural text. Stimuli were sentences conforming to MNREAD standards (Legge, Ross, Luebker, & LaMay 1989) mixed with dynamic probabilistic noise-i.e.

Human visual processing oscillates: evidence from a classification image technique.

Recent investigations have proposed that visual information may be sampled in a discrete manner, similarly to the snapshots of a camera, but this hypothesis remains controversial. Moreover, assuming a discrete sampling of information, the properties of this sampling-for instance, the frequency at which it operates, and how it synchronizes with the environment-still need to be clarified. We systematically modulated the signal-to-noise ratio of faces through time and examined how it impacted face identification performance.

Reading laterally: the cerebral hemispheric use of spatial frequencies in visual word recognition.

It is generally accepted that the left hemisphere (LH) is more capable for reading than the right hemisphere (RH). Left hemifield presentations (initially processed by the RH) lead to a globally higher error rate, slower word identification, and a significantly stronger word length effect (i.e.

The eyes are not the window to basic emotions.

Facial expressions are one of the most important ways to communicate our emotional state. In popular culture and in the scientific literature on face processing, the eye area is often conceived as a very important - if not the most important - cue for the recognition of facial expressions. In support of this, an underutilization of the eye area is often observed in clinical populations with a deficit in the recognition of facial expressions of emotions.

Clouds are not normal occluders, and other oddities: more interactions between textures and lightness illusions.

Identical textured disks can appear white or black depending on the luminance properties of the surrounding textured region (B. L. Anderson & J.

Spatial layout of letters in nonwords affects visual short-term memory load: evidence from human electrophysiology.

The sustained posterior contralateral negativity (SPCN) was used to investigate the effect of spatial layout on the maintenance of letters in VSTM. SPCN amplitude was measured for words, nonwords, and scrambled nonwords. We reexamined the effects of spatial layout of letters on SPCN amplitude in a design that equated the mean frequency of use of each position.

Does face inversion change spatial frequency tuning?

The authors examined spatial frequency (SF) tuning of upright and inverted face identification using an SF variant of the Bubbles technique (F. Gosselin & P. G.

Reading between eye saccades.

Background: Skilled adult readers, in contrast to beginners, show no or little increase in reading latencies as a function of the number of letters in words up to seven letters. The information extraction strategy underlying such efficiency in word identification is still largely unknown, and methods that allow tracking of the letter information extraction through time between eye saccades are needed to fully address this question.

Methodology/principal Findings: The present study examined the use of letter information during reading, by means of the Bubbles technique.

Comparing a novel model based on the transferable belief model with humans during the recognition of partially occluded facial expressions.

Humans recognize basic facial expressions effortlessly. Yet, despite a considerable amount of research, this task remains elusive for computer vision systems. Here, we compared the behavior of one of the best computer models of facial expression recognition (Z.

Orientation invariance in visual shape perception.

To assess directly the orientation-invariance of specific shape representation stages in humans, we examined whether rotation (on the image plane or in depth) modulates the conjunction and linear non-separability effects in a shape visual search task (M. Arguin & D. Saumier, 2000; D.

Attentional and anatomical considerations for the representation of simple stimuli in visual short-term memory: evidence from human electrophysiology.

Observers encoded the spatial arrangement of two or three horizontal line segments relative to a square frame presented for 150 ms either in left or right visual field and either above or below the horizontal midline. The target pattern was selected on the basis of colour (red vs. green) from an equivalent distractor pattern in the opposite left-right visual hemifield.

Perceptive fields of saliency.

Visual saliency plays an important role in early vision. Humans automatically orient to salient information, via covert attentional shifts and overt eye movements. Here, we measured saliency using a novel psychophysical method.

Features for identification of uppercase and lowercase letters.

The determination of the visual features mediating letter identification has a long-standing history in cognitive science. Researchers have proposed many sets of letter features as important for letter identification, but no such sets have yet been derived directly from empirical data. In the study reported here, we applied the Bubbles technique to reveal directly which areas at five different spatial scales are efficient for the identification of lowercase and uppercase Arial letters.

On the representation of words and nonwords in visual short-term memory: evidence from human electrophysiology.

Electrophysiological measures were used to investigate the contribution of lexical status on the maintenance of letter strings in visual short-term memory (VSTM). The sustained posterior contralateral negativity (SPCN), an electrophysiological marker of storage in VSTM, was measured for words and nonwords as well as scrambled letters. A smaller SPCN was found for words than for nonwords (independently of their pronounceability), indicating that lexical status influences storage in VSTM.

The spatio-temporal dynamics of visual letter recognition.

We applied the Bubbles technique to reveal directly the spatio-temporal features of uppercase Arial letter identification. We asked four normal readers to each identify 26,000 letters that were randomly sampled in space and time; afterwards, we performed multiple linear regressions on the participant's response accuracy and the space-time samples. We contend that each cluster of connected significant regression coefficients is a letter feature.