[Abstract Title]. - Society for Neuroscience

Poster
249. Dyslexia, SLI, and Other Disorders of Cognition and Behavior
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 249.11/U30
Topic: C.05.d. ADHD, SLI, dyslexia and other specific disorders of neurobehavior
Support: NIH Grant R03HD050372
NIH Grant R01HD42527
Title: Changed motor cortical excitability in children with Developmental Coordination Disorder
Authors: *F. A. KAGERER 1,2,3 , J. WHITALL 2 ;
1 Dept Kinesiol, Grad Prog Neurosci, Univ. Maryland, College Park, MD; 2 Dept. of Physical
Therapy & Rehabil. Sci., Univ. of Maryland, Baltimore, MD; 3 NACS Program, Univ. of
Maryland, College Park, MD
Abstract: Recent studies in adults and children have demonstrated that cortical inhibition is
altered in attention-deficit/hyperactivity disorder (ADHD). Little is known whether and how
other developmental dysfunctions such as Developmental Coordination Disorder (DCD) show
altered characteristics of cortical excitability and inhibition, even though certain motor
behavioral patterns - increased movement times, or increased occurrence of mirror movements -
would support this notion. Using transcranial magnetic stimulation (TMS), the present study
investigated whether cortical excitability parameters in children with DCD are different from
those in typically developing children.
Three typically developing children (between 8.5 and 11.6 years old) and two children with DCD
(9.9 and 10.9 years old) were assessed with single- and paired-pulse TMS, using a Magstim 200
magnetic stimulator (Magstim, UK), and a figure 8-shaped coil (45 mm inner diameter).
Electromyogram (EMG) signals were recorded from the abductor pollicis brevis (APB) muscle
in both hands with a sampling rate of 2kHz, amplified, and filtered at 30 Hz and 1 kHz. During
stimulation, the APB was activated with 25% of the maximum voluntary contraction. Using the
single pulse paradigm, active motor thresholds for both hands were determined. Using the shortinterval
cortical inhibition (SICI) paradigm, intracortical inhibition and facilitation were
determined, using interstimulus intervals of 2ms and 16ms, and conditioning and test stimuli at
20% below and 20% above the active motor threshold, respectively.
The preliminary findings indicate that children with DCD show substantially higher active motor
thresholds than the typically developing children in both hemispheres. Assessment of SICI in the
typically developing children showed that a 2ms interstimulus interval between conditioning and
test stimulus produced a suppression of the motor evoked potential (MEP) amplitude, compared
to MEP amplitudes resulting from single pulse stimulation at the same stimulation intensity. In
the children with DCD, suppression was found only for the dominant hand, whereas stimulation
of the non-dominant hand (or hemisphere) did not show this clear pattern.