Matthew Heath (PhD.): Hemispheric Specialization and Movement Outcomes in Down Syndrome: A Functional Systems Approach

Matthew Heath, PhD.
Department of Kinesiology and Program in Neuroscience
Indiana University
UNITED STATES OF AMERICA

Over the last 25 years there have been a number of studies involving children and adults with Down syndrome (DS) aimed at determining if this unique karyotype impacts cerebral development and specialization. As a member of an international DS research team, my talk will outline a series of focused investigations leading to the proposal of a biological dissociation between the hemisphere responsible for speech perception and the hemisphere responsible for executive-motor functions. Specifically, behavioral (e.g., Heath et al. 2000) as well as emergent neuroimaging (e.g., Weeks et al. 2002) research has shown that persons with DS exhibit an atypical right hemisphere advantage for the perception of speech but demonstrate a typical left hemisphere advantage for executive-motor processes underlying speech production and complex limb movements (e.g., Heath and Elliott 1999). Furthermore, work has shown that verbal – as opposed to visual – movement instruction imparts greater difficulty in the DS population relative to chronological and mental age-matched participants (Heath et al. 2005). In concert with the just mentioned findings, most recent work has identified a specific between-hemisphere delay of information transfer in the DS brain. Thus, it is proposed that some of the specific information-processing difficulties found in the DS population may be partially attributed to the functional separation between the cerebral systems supporting receptive language (i.e., the right hemisphere) and movement output (i.e., the left hemisphere): systems normally subserved by the same (left) hemisphere.