developmental dyslexia

Links between Action and Perception in
Developmental Dyslexia
Alice van de Walle de Ghelcke (1), Marie-Anne Schelstraete (1), Martin Gareth Edwards (1),
Patrick Quercia (2,3) & Charalambos Papaxanthis (2).
(1) Faculté de Psychologie et des Sciences de l’Éducation, Université Catholique de Louvain (U.C.L.), Louvain-la-Neuve, Belgium.
(2) Laboratoire INSERM U 1093 Cognition, Action et Plasticité sensorimotrice, Université de Bourgogne (U.B.), Dijon, France.
(3) Département d’Ophtalmologie, Centre Hospitalier Universitaire (C.H.U.), Dijon, France.
Participants and method
Introduction
Developmental dyslexia is a specific, severe and persistent disorder of reading
acquisition that appears independent of mental, neurological, visual, hearing or
educational deficits (W.H.O., 1993 as cited in Habib, 19971), is frequently observed
(Barrouillet et al., 20072) and significantly interferes with school learning and daily living
activities (W.H.O., 1993 as cited in Habib, 19971). Despite this term, there remains a poor
understanding of the relation between developmental dyslexia and other cognitive and
motor disorders which are frequently associated to it (Barrouillet et al., 20072 ;
Grammaticos & Klees, 20003 ; Bosse, 20044).
In this study, we propose to revise the understanding of developmental dyslexia using a
cognitive-motor perspective suggesting that dyslexia can be understood as a
proprioceptive dysfunction syndrome (Quercia et al., 20045). Proprioceptive system is
involved in the postural regulation but also in the motor control. During the execution of a
movement, the C.N.S. uses feedback and feedforward control (Berthoz, 19976) involving
the parietal cortex and the cerebellum, which are coincidently involved in the motor
control (Decety, 1996 ; Ehrsson et al., 2003 ; Fadiga et al., 2004 ; Jeannerod, 2001 as
cited in Skoura et al., 20097) and reading ability (Price, 1998 ; Nicolson et al., 1995 ;
Fullbright, 1999 ; Turkeltaub, 2002 as cited in Barrouillet et al., 20072 ; Quercia et al.,
20088). These brain areas are recognized as presenting constitutional and functional
abnormalities associated to developmental dyslexia (Léonard et al., 1993 ; Paulesu et al.
1996 ; Simos et al., 2000 ; Brown, 2001 ; Nicolson et al., 2001 as cited in Habib, 20029).
18 dyslexics and 18 normo-readers teenagers (mean age = 15.2 ± 1.1 years)
were selected from anamnesis, speech therapist and praxis standardized assessments.
1) General motor imagery ability ; MIQ-R (Hall & Martin, 199711)
= motor imagery scores for visual and kinesthetic modalities
2) Fitt’s target pointing task (Sirigu et al., 199612)
Figure A : Illustration of the pointing movement
Figure B : 5 target’s sizes and their corresponding I.D.
According to simulation theory, the same feedforward cognitive processes used for
planning an action are used for mentally simulating an action (Jeannerod, 200910).
We propose that developmental dyslexia may be linked to impairments in the use of
feedforward motor control processes, and therefore, participants with developmental
dyslexia should present difficulties in the use of action imager simulation.
= movement times (real, mental) and kinesthetic imagery scores
Results
1) General motor imagery ability ; MIQ-R : dyslexic group < control group for visual (U=64, p=0.002) and kinesthetic (U=66, p=0,002) imagery modalities.
2) Fitt’s target pointing task
Discussion and conclusion
By revealing significant differences between the two groups, these two tasks highlight a motor imagery deficiency in the dyslexic group. Unlike the control group, it seems that the
dyslexic group was unable to cognitively simulate the action, perhaps suggesting a deficit of feedforward action models. To our knowledge, this study is the first investigation
concerning the motor imagery ability of dyslexics participants. The results encourages additional investigations concerning the links between motor imagery, action execution and
developmental dyslexia. By using new motor imagery tasks, sensory-motor rehabilitation, several techniques of accurate measures and additional controls groups, these next studies
will allow to better understand the origin of the observed effects, their relation to reading acquisition and the contribution of this new perspective in clinical practice.
References
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