Rhythmic abilities are impaired in developmental coordination disorder (DCD) but learning deficit of procedural skills implying temporal sequence is still unclear. Current contradictory results suggest that procedural learning deficits in DCD highly depend on learning conditions. The present study proposes to test the role of sensory modality of stimulations (visual or auditory) on synchronization, learning, and retention of temporal verbal sequences in children with and without DCD. We postulated a deficit in learning particularly with auditory stimulations, in association with atypical cortical thickness of three regions of interesting: sensorimotor, frontal and parietal regions. Thirty children with and without DCD (a) performed a synchronization task to a regular temporal sequence and (b) practiced and recalled a novel non-regular temporal sequences with auditory and visual modalities. They also had a magnetic resonance imaging to measure their cortical thickness. Results suggested that children with DCD presented a general deficit in synchronization of a regular temporal verbal sequence irrespective of the sensory modality, but a specific deficit in learning and retention of auditory non-regular verbal temporal sequence. Stability of audio-verbal synchronization during practice correlated with cortical thickness of the sensorimotor cortex. For the first time, our results suggest that synchronization deficits in DCD are not limited to manual tasks. This deficit persists despite repeated exposition and practice of an auditory temporal sequence, which suggests a possible alteration in audio-verbal coupling in DCD. On the contrary, control of temporal parameters with visual stimuli seems to be less affected, which opens perspectives for clinical practice. K E Y W O R D S audio-verbal coupling, motor skills disorder, procedural memory, sensorimotor synchronization, verbal responses 2 of 14 | LÊ et aL. 1 | INTRODUC TI ON Most motor activities, such as playing music, writing, dancing, etc., rely on rhythmic and timing abilities. Indeed, to acquire motor procedural skills, it is necessary to perceive sensory inputs, memorize them into a structured temporal sequence through repetitive practice, retain the sequence for a certain period, and then retrieve

Several studies have shown the influence of rhythm skills in the processing of written language, especially at the beginning of literacy development. The first objective of this study was to determine the persistence of this link at an advanced grade level. The second objective was to better understand the factors underlying this relationship and, more specifically, to examine the hypothesis of mediation by phonological and/or motor skills. In total, 278 third graders performed literacy tasks (word/pseudoword decoding and spelling), a rhythm production task, two phonological tasks (phonological awareness and rapid automatized naming), and motor tasks. Significant correlations were observed between literacy and each of rhythm skills, phonological skills, and motor skills.However, structural equation models showed that the influence of rhythm skills on literacy was mediated neither by phonological skills nor by motor abilities. These results suggest that rhythm skills continue to play a role in the acquisition of written language in third graders and that this contribution seems to be independent of phonological and motor skills.

Several nonlanguage factors influence literacy development, and motor skills are among those most studied. Despite the publication of several studies that have supported the existence of this relationship, the type of influence and underlying mechanisms have been little explored. Herein, we propose modeling the relationship between motor skills and literacy through structural equation modeling, testing the contribution of executive functions and handwriting skills as the possible mediators of this relationship. In a study of 278 third-grade children, we used a wide range of measures related to written language (reading, spelling, reading comprehension, and written production), fine motor skills (dominant hand, nondominant hand, and bimanual dexterity), executive functions (verbal and visuospatial working memory, inhibition, and shifting), and handwriting. Structural equation modeling of the relationship between these different variables indicated that in the third grade, the influence of fine motor skills on literacy is fully mediated by both executive functions and handwriting skills. These motor skills effects are observed for both low levels of processing (reading, spelling) and high levels of processing (reading comprehension, written production). The results are discussed in terms of the potential mechanisms underlying different literacy skills and their implications for pedagogical programs.