(Amphithéâtre)

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  Lausberg, Hedda (Dept. of Neurology, Free University of Berlin)
  Kita, Sotaro (Dept. of Experimental Psychology, University of Bristol)

Speech-gesture discoordination in split brain patients’ left-hand gestures : Evidence for right-hemispheric generation of co-speech gestures

This study concerns hemispheric specialization for production of cospeech gestures. We examined Lavergne and Kimura’s (1987) hypothesis that the linguistically dominant (left) hemisphere is obligatorily involved in production of gestures. More specifi cally, we investigated gestures in three patients with complete callosotomy (two with left-hemisphere language, and one with bilaterally represented language) and nine healthy control participants. We examined which hands were used to produce gestures and how well gestures were synchronized with speech for each hand. The latter question was addressed by assessing proportion of gesture strokes produced during silence : when gesture and speech are synchronized well, this proportion should be low. It was found that all three patients gestured with both hands. Furthermore, unlike healthy controls and the patient with bilaterally represented language, the two patients with left-hemisphere language synchronized their gestures with speech better with their right hand than with their left hand. This indicates that the two patients’ left hand gestures were generated in the linguistically non-dominant right hemisphere, leading to relatively poor coordination with speech. It is concluded that linguistically non-dominant hemisphere alone can generate co-speech gestures, just as the linguistically dominant hemisphere can.