Alain Kaelin

P2. Theta burst stimulation over left posterior parietal cortex interferes with imitation of gestures

Introduction Clinico-anatomical studies have shown that, after brain damage, the ability to imitate meaningless and meaningful gestures may be selectively affected suggesting that different posterior parietal structures may be involved (dual route model). The aim of the present study was therefore to investigate the effect of imaging-guided neuro-navigated continuous theta burst stimulation (cTBS) on the imitation domain over inferior (IPL) and superior parietal cortex (SPL). We hypothesized that SPL stimulation mainly affects meaningless and IPL stimulation predominantly meaningful gestures. Subjects and methods Twelve healthy subjects participated in this study. All subjects underwent structural MRI acquisition to be used for imaging guided neuro-navigation cTBS. Participants were targeted with one train of cTBS in three experimental sessions: sham stimulation over vertex and real cTBS over left SPL and IPL, respectively. The imitation task was performed ‘offline’ including 24 meaningless and 24 meaningful (communicative and tool-related). Results cTBS over left posterior parietal cortex, irrespective of whether IPL or SPL was stimulated, significantly affected gestural imitation. By contrast, differential effects on gesture subtypes (meaningless versus meaningful) could not be detected. Discussion The present study shows that a single train of cTBS over left posterior parietal regions significantly interferes with gestural imitation confirming the domain-specific role this region has. However, the findings do not support the predictions based on the dual route model.