RESEARCH ARTICLE Catherine J. Stoodley Æ Angela J. Fawcett Roderick I. Nicolson Æ John F. Stein Impaired balancing ability in dyslexic children Received: 25 January 2005 / Accepted: 20 April 2005 / Published online: 26 July 2005 Ó Springer-Verlag 2005 Abstract Children with developmental dyslexia struggle to learn to read and spell despite adequate intelligence and educational opportunity. Several lines of research are attempting to establish the neurobiological basis of dyslexia, and low-level sensory and motor deficits have been found in dyslexic populations; furthermore, behavioural and imaging data point to cerebellar dysfunction in dyslexia. To investigate this, normal readers (n=19) and children with developmental dys- lexia (n=16) were asked to perform various cognitive, literacy, and balancing tasks. Children balanced on the left or right foot, with eyes open or closed, for a period of 10 s during which their movements were recorded with a motion-tracking system. Dyslexic children were less stable than the control children in both eyes-open conditions (left foot P=0.02, right foot P=0.012). While there were no group differences during the eyes-closed conditions, the dyslexic children dropped a foot to correct balance significantly more often than control children (P<0.05). Incidence ana- lysis showed that 50% of the dyslexic group fell into the ‘impaired’ category on the eyes-open balancing tasks; when the mean balancing scores and the foot drops were considered, only three of our dyslexic children showed no evidence of balancing difficulties. There were strong correlations between reading and spelling scores and the mean eyes-open balancing score (r=0.52 and 0.44, respectively). Thus, while not all children with developmental dyslexia show im- paired balancing skills, low-level motor dysfunction may be associated with impaired literacy development. This could be due to several factors, including the involvement of the cerebellum, the magnocellular sys- tem, or more general developmental immaturity. Keywords Developmental dyslexia Æ Balance Æ Cerebellum Æ Magnocellular Introduction Developmental dyslexia affects between 3 and 10% of children (Rutter and Yule 1975). It is currently defined as deficient literacy acquisition despite adequate intel- lectual ability and sufficient educational provision. This definition is contentious however, and a major goal of current research is to find out what neuro- logical abnormalities underlie these educational prob- lems. Difficulty with literacy acquisition is only one of the symptoms of this complex disorder; others may exist in visual, auditory and motor domains (see Stein et al. 2001; Talcott and Witton 2002; Talcott et al. 2000; Nicolson et al. 2001). Dyslexics can suffer from clumsiness and delayed motor milestones, temporal sequencing problems (telling time, remembering the months of the year), and poor spatial sequencing (map reading, differentiating left and right—Stein and Walsh 1997). Dyslexia can be co-morbid with other neurodevelopmental disorders, such as dyspraxia and attention deficit disorder (see Pennington et al. 1991). The significant heterogeneity among dyslexics has made the determination of its cause extremely difficult. Some dyslexics also experience motor coordination and balance problems (see Fawcett and Nicolson 1999); such motor difficulties are characteristic of subjects with cerebellar damage (Holmes 1939). Furthermore, recent research suggests that the processing power and exten- sive cortical and sub-cortical connections of the cere- bellum may be used not only for motor but also for cognitive tasks (for examples see Schmahmann and C. J. Stoodley (&) Æ J. F. Stein University Laboratory of Physiology, University of Oxford, Oxford, OX1 3PT, UK E-mail: cjs@physiol.ox.ac.uk Tel.: +44-1865-272540 Fax: +44-1865-272469 A. J. Fawcett Æ R. I. Nicolson Department of Psychology, Sheffield University, Sheffield, UK Exp Brain Res (2005) 167: 370–380 DOI 10.1007/s00221-005-0042-x