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Abstract

The reciprocal interactions between the motor and cognitive systems are critical during development. The thesis investigates this relationship by exploring Executive Functions (EFs) in children with typical and atypical motor coordination, and the effect of this association on academic and language outcomes.

Study 1: EFs are higher-order cognitive processes needed for goal-directed behaviour. They involve flexibility of thinking, inhibition of unhelpful responses, strategy development and manipulation of diverse information simultaneously. Children with poor motor skills or Developmental Coordination Disorder (DCD) have demonstrated problems with EFs. However, no studies have explored the development of EFs in DCD longitudinally. Study 1 investigated changes in EFs in children with poor motor skills over two years. Children aged 7-11 years were assessed twice, two years apart, on verbal and nonverbal measures of EFs: executive-loaded working memory; fluency; response inhibition; planning; and cognitive flexibility. Typically developing children (TD: n=17) were compared to those with a clinical diagnosis of DCD (n=17) and those with identified motor difficulties (MD: n=17), but no formal diagnosis.

Developmental gains in EFs were similar between groups, although a gap between children with poor motor skills and TD children on nonverbal EFs persisted. Specifically, children with DCD performed significantly more poorly than TD children on all nonverbal EF tasks and verbal fluency tasks at both time points; and children with MD but no diagnosis showed persistent EF difficulties in nonverbal tasks of working memory and fluency. Both groups demonstrated EF difficulties over two years, which may impact on activities of daily living and academic achievement, in addition to their motor deficit.

Study 2: Academic underachievement has been identified in children with DCD. However, it is unclear whether it extends to all academic domains and whether it is explained by EF abilities, which play an important role in educational attainment and are poorer in DCD. Study 2 examined academic achievement performance in children with and without motor coordination impairments, taking into account the contribution of EF skills. Children with DCD (n=17) and children with MD (n=32) were compared to TD children (n=41) in measures of reading, spelling and mathematics. Two composite scores of verbal and nonverbal EF respectively were included in the analyses.

There was no evidence of academic difficulties in children with MD. Children with DCD demonstrated poorer mathematical ability compared to their TD peers, but performed as accurately on all other academic tasks. These differences in mathematics in the DCD group were still evident after EF was controlled for in the analyses. Nonverbal EF did not predict performance in any of the academic achievement tasks, whereas verbal EF was a significant predictor of mathematical ability.

Study 3: Motor coordination is fundamentally interrelated with both EF and language, which in turn are related to each other. Recent investigations on the relationship between EF and language have failed to understand the direction and nature of this association, suggesting a third factor may be involved. Study 3 explored the role of motor coordination in the relationship between EF and language. Measures of verbal EF, nonverbal EF, expressive and receptive language were administered to children with DCD (n=23), MD (n=57) and TD (n=71). A moderation model was tested using Group as the moderating variable, and, next, using motor coordination as a continuous moderating variable (i.e., across groups). Both directions of the association between EF and language were investigated.

The relationship between EF and language was not different between groups in any domains, hence Group was not a significant moderator. When using continuous motor skills data, motor coordination was a significant moderator when EF was the predictor of language outcomes, but not when language was the predictor of EF outcomes. Specifically, the interaction between motor coordination and EF had significant effects on language, as the association between EF and language was positive and significant at low and moderate levels of motor skills, but not at high levels of motor skills.

In conclusion, in this thesis interactions between EF and motor coordination produced complex effects on academic and language outcomes.

Publication Type:	Thesis (Doctoral)
Subjects:	R Medicine > R Medicine (General)
Departments:	Doctoral Theses School of Health & Psychological Sciences > School of Health & Psychological Sciences Doctoral Theses School of Health & Psychological Sciences > Language & Communication Science

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