Christel Bidet-Ildei

A visual processing but no phonological disorder in a child with mixed dyslexia

The case study of Martial, a French 9-year-old boy, who exhibits severe mixed dyslexia and surface dysgraphia is reported. Despite very poor pseudo-word reading, Martial has preserved phonological processing skills as his good oral language, good phoneme awareness and good verbal short-term memory show. He exhibited a strong length effect when reading briefly presented words but no sign of mini-neglect. His letter-string processing abilities were assessed through tasks of whole and partial report. In whole report, Martial could only name a few letters from briefly displayed 5-consonant strings. He showed an initial-position advantage and a sharper than expected left-to-right gradient of performance. He performed better when asked to report a single cued letter within the string but then showed an atypical right-side advantage. The same rightward attentional bias was observed in whole report when top-down control was prevented. Otherwise, Martial showed preserved single letter identification skills and good processing of 5-letter strings when letters were sequentially displayed one at a time. His poor letter-string processing thus reflects a parallel visual processing disorder that is compatible with either a visual attention (VA) span or a visual short-term memory disorder. Martial was further engaged in a complex reaching movement task involving VA and simultaneous processing. He performed motor sequences not as a whole but as a succession of independent motor units, suggesting that his attention was not allocated in parallel to the two to-be-reached targets prior to movement execution. Against a more basic motor disorder however, he showed good performance in a task of cyclical pointing movements. The overall findings suggest that Martial suffers from a visual simultaneous processing disorder that disturbs letter identification in strings. Instead of being restricted to letter-string processing, this VA disorder might extend to non-verbal task.

Influence of handwriting skills during spelling in primary and lower secondary grades.

We sought to identify, the impact of handwriting skills on the efficiency and temporal course of word spelling across Grades 2–9. Eighty-four students, drawn from primary and lower secondary schools, were asked to perform a dictation task to assess their word spelling. They also had to write out the letters of the alphabet, as well as their firstnames and surnames, from memory to assess their handwriting skills. Handwriting kinematics were recorded using a digitizing tablet and a computer running Eye and Pen software. Results revealed that graphomotor skills (as assessed by the name writing task) influenced the success and temporal course of spelling, but only in primary grades, whereas the influence of orthographic knowledge (as assessed by the alphabet task) could still be observed in the lower secondary grades, even if it ceased to influence the temporal course and only affected errors. We discuss what these findings tell us about changes in transcription processes over the course of child development.

Preference for Point-Light Human Biological Motion in Newborns: Contribution of Translational Displacement.

In human newborns, spontaneous visual preference for biological motion is reported to occur at birth, but the factors underpinning this preference are still in debate. Using a standard visual preferential looking paradigm, 4 experiments were carried out in 3-day-old human newborns to assess the influence of translational displacement on perception of human locomotion. Experiment 1 shows that human newborns prefer a point-light walker display representing human locomotion as if on a treadmill over random motion. However, no preference for biological movement is observed in Experiment 2 when both biological and random motion displays are presented with translational displacement. Experiments 3 and 4 show that newborns exhibit preference for translated biological motion (Experiment 3) and random motion (Experiment 4) displays over the same configurations moving without translation. These findings reveal that human newborns have a preference for the translational component of movement independently of the presence of biological kinematics. The outcome suggests that translation constitutes the first step in development of visual preference for biological motion.

Handwriting in patients with Parkinson disease: Effect of l-dopa and stimulation of the sub-thalamic nucleus on motor anticipation

The present research focused on how patients with Parkinsons disease (PD) produce handwriting sequences. PD patients who were on/off medication or deep brain stimulation treatments had to write lll and lln trigrams. We evaluated their ability to anticipate on-line the last letter in the trigram. The results revealed that in PD patients, contrary to healthy participants, the percentage of time taken by the down-stroke of the second l did not vary as a function of the spatial constraints of the following letter (l or n). In other words, the handwriting of the PD patients did not exhibit any sign of motor anticipation. However, under treatment, PD patients exhibited similar results to healthy participants despite no improvement in movement variability. Taken together these results do not seem consistent with the hypothesis that PD patients do not anticipate future movements because of their movement variability. They are more in agreement with theories that postulate that PD patients have a general deficit in the parallel processing of the components of a motor sequence.

Sex Differences in the Neuromagnetic Cortical Response to Biological Motion

Body motion is a rich source of information for social interaction, and visual biological motion processing may be considered as a hallmark of social cognition. It is unclear, however, whether the social brain is sex specific. Here we assess sex impact on the magnetoencephalographic (MEG) cortical response to point-light human locomotion. Sex differences in the cortical MEG response to biological motion occur mostly over the right brain hemisphere. At early latencies, females exhibit a greater activation than males over the right parietal, left temporal, and right temporal cortex, a core of the social brain. At later latencies, the boosts of activation are greater in males over the right frontal and occipital cortices. The findings deliver the first evidence for gender-dependent modes in the time course and topography of the neural circuitry underpinning visual processing of biological motion. The outcome represents a framework for studying sex differences in the social brain in psychiatric and neurodevelopmental disorders.

Reading action word affects the visual perception of biological motion

In the present study, we investigate whether reading an action-word can influence subsequent visual perception of biological motion. The participants task was to perceptually judge whether a human action identifiable in the biological motion of a point-light display embedded in a high density mask was present or not in the visual sequence, which lasted for 633 ms on average. Prior to the judgement task, participants were exposed to an abstract verb or an action verb for 500 ms, which was related to the human action according to a congruent or incongruent semantic relation. Data analysis showed that correct judgements were not affected by action verbs, whereas a facilitation effect on response time (49 ms on average) was observed when a congruent action verb primed the judgement of biological movements. In relation with the existing literature, this finding suggests that the perception, the planning and the linguistic coding of motor action are subtended by common motor representations.

Anticipating the terminal position of an observed action: Effect of kinematic, structural, and identity information

The ability to visually identify and anticipate motor actions performed by others is thought to be an essential component of social interactions and possibly requires relating visual information with sensorimotor knowledge. Though motor theory of visual perception received convincing evidence from behavioural, neuropsychological, and developmental studies, the nature of the information used for anticipating the terminal location of an observed human action remains still an open issue. In this context, the aim of the present study was to evaluate the role of motor representations on the prediction of the terminal location of an observed manual reaching movement. The stimulus was a two-dimensional point-light display showing the top-view of a right arm moving along the sagittal plane towards targets positioned at different distances. The task was to estimate the terminal location of the reaching movement after the stimulus vanished following 60% of total movement duration. Characteristics of the point-light display could vary according to movement kinematics (biological motion, constant, inverse, or monotonically increased velocity), structural features (all joints visible or only the forefinger tip), and movement identity (self- vs. other-generated action). Results showed that spatial performances improved when presenting “self-generated” actions (identity effect) in the biological motion condition (kinematic effect). Furthermore, reducing the visual stimulus to the forefinger did not affect the performance (structural effect). Considered together, these findings provide further evidence for motor-based visual perception of biological motion and suggest that kinematic but not structural information is crucial to give sense to an observed human action and to anticipate its final location.

Influence of biological kinematics on abstract concept processing

During a random number generation task, human beings tend to produce more small numbers than large numbers. However, this small number bias is modulated when motor behaviour, such as a turn of the head, is performed during the random number generation task. This result fits with the finding that number representation is linked to laterally oriented actions, with small- and large-magnitude numbers generally linked to movement towards the left or the right side of space, respectively. To test whether this number–space association is specific to human motor behaviours or extends to any type of laterally oriented movements, we assessed whether the presentation of biological or nonbiological leftward or rightward movement affected a subsequent random number generation task. Biological and nonbiological movements were obtained by varying the kinematic parameters of the movements. Biological kinematics represented the tangential velocity actually observed in a human pointing movement; nonbiological kinematics represented equivalent movements but with an inverse tangential velocity along the path. The results show that only the observation of biological movements induces a space–number bias whereas observing nonbiological movements does not. This finding is the first evidence of a link between a biological marker and the semantic representation of a concept as abstract as number.

Sentence plausibility influences the link between action words and the perception of biological human movements

The present study aimed to assess the role of sentence plausibility in the functional link between action words and visual judgments of point-light human actions. Following the oral presentation of action verbs included in a plausible or implausible sentence, participants were asked to detect the presence of congruent or incongruent biological movements. Sentence plausibility was manipulated by inverting the positions of the subject and the complement (e.g., the neighbor is running in the garden vs the garden is running in the neighbor). The results showed that for both plausible and implausible sentences, the detection of human movements is greater following presentation of congruent action verbs. These results suggest that the presentation of action verbs affects the subsequent perception of point-light human movements, regardless of the associated semantic context. However, the link between action verbs and judgment of biological movements is strengthened when plausible sentences are presented, as illustrated by the increase in visual detection capacity in plausible congruent conditions. Concerning the analysis of the detection speed, the performance is only affected in plausible sentences with slower response times associated with the presentation of an incongruent action verb. These findings are discussed in light of an embodied mechanism and the domain of biological movement perception.

Are judgments for action verbs and point-light human actions equivalent?

The aim of the present study was to examine whether the ability to judge action words and the ability to judge human actions share common mechanisms. With this purpose in mind, we proposed both a lexical and an action decision task to twenty-four healthy participants. For both tasks, the participants had to judge whether the stimulus that was presented (a letter string or a point-light sequence) was valid or not (i.e. a word vs. a pseudo-word, an action vs. a pseudo-action). The data analysis showed that the action decision task has common characteristics with the lexical decision task. As for verbal material, judgements of pseudo-actions were slower than judgements for actions. Moreover, we demonstrated that the ability to judge an action verb was positively correlated with the ability to judge a point-light human action, whereas no significant correlation appeared between nouns and point-light judgements abilities. This dissociation supports the argument that the judgement of action words and the judgement of human actions share a common but specific basis through the involvement of motor representations.