Effects of Reading Direction on Visuospatial Organization: A Critical Review

Over the past decades, a growing literature on perceptual bias has investigated the factors that determine normal performance in simple visuospatial tasks, such as line bisection and aesthetic preference. Normal right-handed participants may exhibit spatial asymmetries in these tasks with a tendency to bisect to the left of the objective middle in line bisection and a preference for images with the center of interest in their right half in aesthetic preference tasks. These patterns of performance have mostly been attributed to hemispheric imbalance. Other explanations have also been put forth to explain the spatial asymmetries seen in the normal population. Here we review studies that target the role of reading direction on visuospatial tasks. In addition to presenting several of our studies that investigated differences in line bisection and aesthetic preference performances between left-to-right readers (French) and right-to-left readers (Israeli), we present a discussion of the existing literature on reading direction, culture and visuospatial processing. The findings are discussed regarding the interaction between cultural factors, such as reading habits, and biological factors, such as cerebral lateralization, in visual perception

Intelligence collective anticipative pour dirigeants d\u27entreprise. Retours d\u27interventions

Cet article fait état d\u27une suite de recherches action pour un système d\u27intelligence col-lective anticipative pour dirigeants d\u27entreprise. On y présente les retours de quatorze in-terventions, les facteurs critiques de succès qui s\u27en dégagent et la proposition d\u27un systè-me qui les incorpor

Influence d'une lésion occipitale sur le traitement de l'information visuelle. Approche comportementale et fonctionnelle (IRMf) de la réorganisation corticale

La répercussion d'un trouble visuel sur le traitement de scènes naturelles a été abordée selon trois approches : 1) une approche comportementale dans le but d'étudier la perception visuelle en champ central et en champs latéralisés, chez les participants sains et chez les patients hémianopsiques à la suite d'une lésion occipitale unilatérale ; 2) une approche fonctionnelle à l'aide d'une étude en IRMf afin d'évaluer tout d'abord l'incidence de la demande cognitive sur une tâche visuelle, chez les participants sains et chez les patients hémianopsiques, en champ central, puis d'observer l'impact d'une lésion occipitale droite et gauche sur la réorganisation corticale ; 3) enfin, une approche neuropsychologique dans le but d'étudier l'effet d'un entraînement visuel dans le champ aveugle des patients HLH, en utilisant les capacités visuelles inconscientes. Nous avons observé un impact différent sur le traitement visuel en champ central selon la latéralisation de la lésion occipitale (droite ou gauche). L'analyse visuelle est plus perturbée à la suite d'une lésion occipitale droite. Les données acquises en IRMf ont permis également de constater une différence des patterns d'activation selon la latéralisation de la lésion occipitale. Enfin, nous avons observé que l'entrainement dans le champ visuel aveugle des patients HLH, en utilisant les capacités de perception implicite : blindsight, permet d'obtenir une amélioration du champ visuel de manière quantifiable.Visual processing of natural scenes images was investigated in healthy individuals and patients with homonymous hemianopia (after a unilateral occipital damage) using three methods : 1) behavioral studies where stimuli were presented in the central and lateralized visual fields; 2) fMRI paradigm to assess the cerebral network underlying natural scenes processing in the central visual field and to assess consequences of right or left occipital lesion on brain reorganization ; 3) a neuropsychological study where the efficiency of visual training in the blind visual field of hemianopics patients, using blindsight, was investigated. Results showed that occipital lesion side selectively modulates visual performances and pattern of cortical activation. In patients with right occipital damage, performances were severely altered although both hemlispheres were recruited. Yet, in patients with left brain damage, performances were less degraded and the right hemisphere was recruited whatever the visual task. Finally, we observed that explicit (conscious) visual detection can be restored (at least partly) in the blind visual field by using implicit (unconscious) visual capacities.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Long Lasting Egocentric Disorientation Induced by Normal Sensori-Motor Spatial Interaction

Perception of the cardinal directions of the body, right-left, up-down, ahead-behind, which appears so absolute and fundamental to the organisation of behaviour can in fact, be modified. Perhaps unsurprisingly, it has been shown that prolonged distorted perception of the orientation of body axes can be a consequence of disordered sensori-motor signals, including long-term prismatic adaptation and lesions of the central nervous system. We report the novel and surprising finding that a long-lasting distortion of perception of personal space can also be induced by an ecological pointing task without the artifice of distorting normal sensori-motor relationships.Twelve right-handed healthy adults performed the task of pointing with their arms, without vision, to indicate their subjective 'straight ahead', a task often used to assess the Egocentric Reference. This was performed before, immediately, and one day after a second task intended to 'modulate' perception of spatial direction. The 'modulating' task lasted 5 minutes and consisted of asking participants to point with the right finger to targets that appeared only in one (right or left) half of a computer screen. Estimates of the 'straight-ahead' during pre-test were accurate (inferior to 0.3 degrees deviation). Significantly, up to one day after performing the modulating task, the subjective 'straight-ahead' was deviated (by approximately 3.2 degrees) to the same side to which subjects had pointed to targets.These results reveal that the perception of directional axes for behaviour is readily influenced by interactions with the environment that involve no artificial distortion of normal sensori-motor-spatial relationships and does not necessarily conform to the cardinal directions as defined by the anatomy of orthostatic posture. We thus suggest that perceived space is a dynamic construction directly dependent upon our past experience about the direction and/or the localisation of our sensori-motor spatial interaction with environment

Retinotopic and lateralized processing of spatial frequencies in human visual cortex during scene categorization.

International audienceUsing large natural scenes filtered in spatial frequencies, we aimed to demonstrate that spatial frequency processing could not only be retinotopically mapped but could also be lateralized in both hemispheres. For this purpose, participants performed a categorization task using large black and white photographs of natural scenes (indoors vs. outdoors, with a visual angle of 24° × 18°) filtered in low spatial frequencies (LSF), high spatial frequencies (HSF), and nonfiltered scenes, in block-designed fMRI recording sessions. At the group level, the comparison between the spatial frequency content of scenes revealed first that, compared with HSF, LSF scene categorization elicited activation in the anterior half of the calcarine fissures linked to the peripheral visual field, whereas, compared with LSF, HSF scene categorization elicited activation in the posterior part of the occipital lobes, which are linked to the fovea, according to the retinotopic property of visual areas. At the individual level, functional activations projected on retinotopic maps revealed that LSF processing was mapped in the anterior part of V1, whereas HSF processing was mapped in the posterior and ventral part of V2, V3, and V4. Moreover, at the group level, direct interhemispheric comparisons performed on the same fMRI data highlighted a right-sided occipito-temporal predominance for LSF processing and a left-sided temporal cortex predominance for HSF processing, in accordance with hemispheric specialization theories. By using suitable method of analysis on the same data, our results enabled us to demonstrate for the first time that spatial frequencies processing is mapped retinotopically and lateralized in human occipital cortex

Bisecting the mental number line in near and far space

Much evidence suggests that common posterior parietal mechanisms underlie the orientation of attention in physical space and along the mental number line. For example, the small leftward bias (pseudoneglect) found in paper-and-pencil line bisection is also found when participants "bisect" number pairs, estimating (without calculating) the number midway between two others. For bisection of physical lines, pseudoneglect has been found to shift rightward as lines are moved from near space (immediately surrounding the body) to far space. We investigated whether the presentation of stimuli in near or far space also modulated spatial attention for the mental number line. Participants bisected physical lines or number pairs presented at four distances (60, 120, 180, 240 cm). Clear rightward shifts in bias were observed for both tasks. Furthermore, the rate at which this shift occurred in the two tasks, as measured by least squares regression slopes, was significantly correlated across participants, suggesting that the transition from near to far distances induced a common modulation of lateral attention in physical and numerical space. These results demonstrate a tight coupling between number and physical space, and show that even such prototypically abstract concepts as number are modulated by our on-line interactions with the world

A rightward shift in the visuospatial attention vector with healthy aging

The study of lateralised visuospatial attention bias in non-clinical samples has revealed a systematic group-level leftward bias (pseudoneglect), possibly as a consequence of right hemisphere dominance for visuospatial attention. Pseudoneglect appears to be modulated by age, with a reduced or even reversed bias typically present in elderly participants. It has been suggested that this shift in bias may arise due to disproportionate aging of the right hemisphere and/or an increase in complementary functional recruitment of the left hemisphere for visuospatial processing. In this study, we report rightward shifts in subjective midpoint judgement relative to healthy young participants whilst elderly participants performed a computerized version of the landmark task (in which they had to judge whether a transection mark appeared closer to the right or left end of a line) on three different line lengths. This manipulation of stimulus properties led to a similar behavioural pattern in both the young and the elderly: a rightward shift in subjective midpoint with decreasing line length, which even resulted in a systematic rightward bias in elderly participants for the shortest line length (1.98° of visual angle). Overall performance precision for the task was lower in the elderly participants regardless of line length, suggesting reduced landmark task discrimination sensitivity with healthy aging. This rightward shift in the attentional vector with healthy aging is likely to result from a reduction in right hemisphere resources/dominance for attentional processing in elderly participants. The significant rightward bias in the elderly for short lines may even suggest a reversal of hemisphere dominance in favour of the left hemisphere/right visual field under specific conditions

Connectivity Analysis Reveals a Cortical Network for Eye Gaze Perception

Haxby et al. (Haxby JV, Hoffman EA, Gobbini MI. 2000. The distributed human neural system for face perception. Trends Cogn Sci. 4:223–233.) proposed that eye gaze processing results from an interaction between a “core” face-specific system involved in visual analysis and an “extended” system involved in spatial attention, more generally. However, the full gaze perception network has remained poorly specified. In the context of a functional magnetic resonance imaging study, we used psychophysiological interactions (PPIs) to identify brain regions that showed differential connectivity (correlation) with core face perception structures (posterior superior temporal sulcus [pSTS] and fusiform gyrus [FG]) when viewing gaze shifts relative to control eye movements (opening/closing the eyes). The PPIs identified altered connectivity between the pSTS and MT/V5, intraparietal sulcus, frontal eye fields, superior temporal gyrus (STG), supramarginal gyrus, and middle frontal gyrus (MFG). The FG showed altered connectivity with the same areas of the STG and MFG, demonstrating the contribution of both dorsal and ventral core face areas to gaze perception. We propose that this network provides an interactive system that alerts us to seen changes in other agents’ gaze direction, makes us aware of their altered focus of spatial attention, and prepares a corresponding shift in our own attention