Hemispheric specialization for imitating hand-head positions and finger configurations - A study with hemispherectomy...

Imitation deficits after brain damage are commonly assessed with meaningless hand positions (HP) and finger configurations (FP). Previous studies on unilateral brain damage and callosotomy individuals revealed left-hemispheric specializations for HP and bilateral representation for FP, with a right-hemispheric dominance. This study examined hemispheric specialization for HP and FP imitation, as well as FP subtypes, in five hemispherectomy individuals (n = 3 with a remaining left (rLH); n = 2 with a remaining right hemisphere (rRH)). Imitation performance was analysed with the NEUROGES®-ELAN system, considering error types and reaction times. Bayesian analyses revealed no group differences in performance scores, error types and reaction times for HP or FP imitation. The qualitative analysis of error types revealed group differences, particularly for FP imitation, with rRH individuals showing predominantly self-corrections, whereas rLH individuals showed diverse error patterns (e.g., position errors). However, considerable interindividual variability was foremost observed across imitation tasks and subtypes. Overall, the findings do not support a strict hemispheric specialization for HP and FP imitation following hemispherectomy. Rather, they highlight the importance of individual variability.