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A tendency to over-attend the left side of the space (i.e., pseudoneglect) has been repeatedly reported in Western adult populations and is supposed to reflect a right hemisphere dominance in the control of visuospatial attention. This neurobiological hypothesis has been partially challenged by growing evidence showing that pseudoneglect is profoundly triggered by cultural practices such as reading and writing habits. Accordingly, more recent theoretical accounts suggest a strict coupling between nature and nurture dimensions at the origins of such bias. To further explore this possibility, here we first administered a digitized cancellation task to right-handed Western children before and after literacy acquisition. Results showed an incremental leftward shift of attention in the cancellation of the first target and an increasing preference for a left-to-right visual search from preschoolers to second graders. Yet, despite these differences, the overall distribution of visuospatial attention was biased to the left in both groups. To explore the role of handedness in visuospatial asymmetries, we also tested a group of left-handed second graders. Results showed an impact of handedness on visuospatial performance, with an accentuated rightward-oriented visual search for left-handed children, although the overall distribution of attention was again biased to the left hemispace. Taken together, these findings do not provide support to a pure neurobiological view of visuospatial biases. Rather, our study indicates that the control of visuospatial attention is mediated by a dynamic interplay among biological (i.e., right hemisphere dominance), biomechanical (i.e., hand dominance), and cultural (i.e., reading habits) factors.

Objective: The lack of inversion effect for face recognition in congenital prosopagnosia (CP) is consistent with the hypothesis of a failure in holistic processing. However, although CPs' abnormal gaze behavior for upright faces has already been demonstrated, neither their scanning strategy for inverted faces, nor the possibility that their abnormal gaze behavior with upright faces is because of reasons other than the holistic deficit have been investigated yet. Method: We recorded the eye movements of a congenital prosopagnosic and a control group during the encoding of unknown faces, objects, and flowers. Two types of stimuli (faces and objects) were presented upright and inverted. Results: CPs explored upright and inverted faces in the same way (i.e., similar number of fixations of the same duration and similarly distributed), whereas controls increased the number of fixations and their duration during the presentation of inverted faces. By contrast, the 2 groups showed a similar inversion effect during the encoding of objects. Finally, CPs showed anomalous exploration of within-class objects (i.e., flowers) and impairment in subordinate-level object discrimination. Conclusions: Our results demonstrate that: (a) CPs use the same part-based strategy in encoding both upright and inverted faces, suggesting a possible interpretation of the lack of inversion effect in this population; (b) CPs' lack of inversion effect is face-specific and does not affect objects

In this study, we sought to demonstrate that deficits in a specific motor activity, handwriting, are associated to Developmental Dyslexia. The linguistic and writing performance of children with Developmental Dyslexia, with and without handwriting problems (dysgraphia), were compared to that of children with Typical Development. The quantitative kinematic variables of handwriting were collected by means of a digitizing tablet. The results showed that all children with Developmental Dyslexia wrote more slowly than those with Typical Development. Contrary to typically developing children, they also varied more in the time taken to write the individual letters of a word and failed to comply with the principles of isochrony and homothety. Moreover, a series of correlations was found among reading, language measures and writing measures suggesting that the two abilities may be linked. We propose that the link between handwriting and reading/language deficits is mediated by rhythm, as both reading (which is grounded on language) and handwriting are ruled by principles of rhythmic organization.

Unilateral spatial neglect (USN) is a common neuropsychological disorder following a right-sided brain lesion. Although USN is mostly characterized by symptoms involving the left hemispace, other symptoms are not left lateralized. Recently, it was shown that patients with neglect dyslexia, a reading disturbance that affects about 40% of USN patients, manifest a non-lateralized impairment of eye movement behaviour in association with their reading deficit when they read aloud and perform non-verbal saccadic tasks (Primativo et al., 2013).In the present paper, we aimed to demonstrate that the eye movement impairment shown by some USN patients reflects a more general oculo-motor disorder that is not confined to orthographic material, the horizontal axis or constrained saccadic tasks. We conjectured that inaccurate oculo-motor behaviour in USN patients indicates the presence of a reading deficit. With this aim we evaluated 20 patients, i.e., 10 right-sided brain-damaged patients without neglect and 10 patients affected by USN. On the basis of the patients' eye movement patterns during a scene exploration task, we found that 4 out of the 10 USN patients presented an abnormal oculo-motor pattern. These same four patients (but not the others) also failed in performing 5 different saccadic tasks and produced neglect dyslexia reading errors in both single words and texts. First, we show that a large proportion of USN patients have inaccurate eye movement behaviour in non-reading tasks. Second, we demonstrate that this exploratory deficit is predictive of the reading impairment. Thus, we conclude that the eye movement deficit prevents reading and impairs the performance on many other perceptual tests, including scene exploration. The large percentage of patients with impaired eye-movement pattern suggests that particular attention should be paid to eye movement behaviour during the diagnostic phase in order to program the best rehabilitation strategy for each patient.

Despite the fact that bilateral mirror symmetry is an important characteristic of the visual world, few studies have investigated its neural basis. Here we addressed this issue by investigating whether the object-selective lateral occipital (LO) cortex, a key brain region in object and shape processing, is causally involved in bilateral symmetry detection. Participants were asked to discriminate between symmetric and asymmetric dot patterns, while fMRI-guided repetitive TMS was delivered online over either the left LO, the right LO or two control sites in the occipital cortex. We found that the application of TMS over both right and left LO impaired symmetry judgments, with disruption being greater following right LO than left LO TMS, indicative of right hemisphere lateralization in symmetry processing. TMS over LO bilaterally also affected a visual contour detection task, with no evidence for hemispheric difference in this task. Overall, our results demonstrates that LO bilaterally plays a causal role in symmetry detection possibly due to symmetry acting as a strong cue in Gestalt processes mediating object recognition. © 2013 Elsevier Ltd.

A vertical line segment intersecting a horizontal one at different crossing points generates line sections. Visual perception of such line sections was investigated here in two experiments. In both experiments participants were most accurate and precise when they had to reproduce symmetrical sections. Interestingly, the different asymmetrical sections of a line were not equivalent in terms of participants' performance: constant errors changed as a function of sections and the error curve was nicely interpolated by the composition of two harmonics of the line length. In consistence with the harmonic fitting of the data, we propose that the perceptual salience of specific asymmetrical sections is a byproduct of the automatic triggering of a line midpoint identification process. Being perceptually tuned to symmetry warps our visual representation of the line, which results in systematic misperceptions. The way of bringing present and past experimental findings into a unitary whole is proposed.