Effect of a Dual Task on Postural Control in Dyslexic Children

Several studies have examined postural control in dyslexic children; however, their results were inconclusive. This study investigated the effect of a dual task on postural stability in dyslexic children. Eighteen dyslexic children (mean age 10.3±1.2 years) were compared with eighteen non-dyslexic children of similar age. Postural stability was recorded with a platform (TechnoConcept®) while the child, in separate sessions, made reflex horizontal and vertical saccades of 10° of amplitude, and read a text silently. We measured the surface and the mean speed of the center of pressure (CoP). Reading performance was assessed by counting the number of words read during postural measures. Both groups of children were more stable while performing saccades than while reading a text. Furthermore, dyslexic children were significantly more unstable than non-dyslexic children, especially during the reading task. Finally, the number of words read by dyslexic children was significantly lower than that of non-dyslexic children and, in contrast to the non-dyslexic children. In line with the U-shaped non-linear interaction model, we suggest that the attention consumed by the reading task could be responsible for the loss of postural control in both groups of children. The postural instability observed in dyslexic children supports the hypothesis that such children have a lack of integration of multiple sensorimotor inputs

Influence of eye dominance on oculomotor and attentional selection

International audienceThe dominant eye is the one used to perform a monocular task. There is an advantage of the hemifield controlateral to the dominant eye for both motor (higher saccade accuracy) and perceptual (faster detection) performance. The current study examines the influence of eye dominance in a dual-task paradigm. It involves a saccade and a discrimination task to one of the six locations possible, enabling the dissociation between saccade target and discrimination target. Four groups of participants are tested, according to their eye dominance and eye dominance strength. We investigate whether the higher saccade accuracy in the hemifield controlateral to the dominant eye is due to enhancement of the target location or to inhibition of the distractor locations. Preliminary results on discrimination performance suggest that eye dominance is associated to attentional asymmetries between visual hemifields

Eye dominance strength modulates the global effect on saccade accuracy

International audienceThe dominant eye is the one chosen to perform a monocular task. Vergilino-Perez et al. (2012) showed with binocular recordings that participants could exhibit weak or strong eye dominance. The dominant eye is known to be preferentially related to the ipsilateral primary visual cortex (V1). Recently, we have shown that for participants with strong eye dominance, the influence on saccade accuracy of a distractor proximal to the target ("global effect") is reduced in the hemifield controlateral to the dominant eye compared to the ipsilateral hemifield (Tagu et al., 2016). We concluded that for strong eye dominance, the relationship between dominant eye and ipsilateral V1 induces a better selection of the saccadic target in the hemifield controlateral to the dominant eye. Interestingly, this result was enhanced for strong left eye dominance and reduced for strong right eye dominance. We proposed this difference could be due to the co-occurrence of a leftward attentional bias giving more weight to the distractor because of the right hemispheric specialization for visuo-spatial attention. A way to test this interpretation is to dissociate the saccade target selection process linked to eye dominance from the leftward attentional bias. Here we examine the global effect as a function of saccade preparation duration across paradigms known to induce short (gap-200 and step) and long (overlap-600) saccade latencies. Preliminary results on 52 participants (i) confirm the controlateral advantage on saccade accuracy when eye dominance is strong (ii) show that both the saccade target selection and attentional bias increase with saccade latency

Influence of eye dominance on oculomotor and attentional selection

International audienceThe dominant eye is the one used to perform a monocular task. There is an advantage of the hemifield controlateral to the dominant eye for both motor (higher saccade accuracy) and perceptual (faster detection) performance. The current study examines the influence of eye dominance in a dual-task paradigm. It involves a saccade and a discrimination task to one of the six locations possible, enabling the dissociation between saccade target and discrimination target. Four groups of participants are tested, according to their eye dominance and eye dominance strength. We investigate whether the higher saccade accuracy in the hemifield controlateral to the dominant eye is due to enhancement of the target location or to inhibition of the distractor locations. Preliminary results on discrimination performance suggest that eye dominance is associated to attentional asymmetries between visual hemifields

Saccadic adaptation alters object size perception

International audienceBackward adaptation Control 1 st Phase 3 rd Phase 1st Phase 3rd Phase Gain 0.99 ±0.05 0.80 ±0.05 0.97 ±0.05 0.99 ±0.05 Latency 235 ±97 205 ±40 259 ±74 218 ±44 Phase 1 similar to Phase 3 for control group Saccadic parameters and difficulty of the task are stable in the control group. Overall, PSE slightly increases when saccadic amplitude decreases. An increase in PSE indicated that the size of the comparison disk in the third phase has to be larger to become perceptually equal to the standard, compared to the first phase. Psychometric functions for #21 from Backward adaptation group (left) and for #48 from Control group (right). Error bars represents confidence interval at 95%. We observed a shift of the PSE to the right for #21 and an overlap of the PSEs for #48 Paired t-test : * p0.

Presaccadic attention interferes with feature detection

Collins T, Heed T, Doré-Mazars K, Röder B. Presaccadic attention interferes with feature detection. Experimental Brain Research. 2009;201(1):111-117