Evidence for interhemispheric motor-level transfer in a simple reaction time task: an EEG study

 Simple visuomanual reaction time tasks require interhemispheric communication when stimuli are presented in the hemifield opposite the responding hand. Although confirmed in many studies, it is still a matter of debate when, at what functional level and at what site this interhemispheric transfer takes place. To address these questions, we recorded event-related potentials (ERPs) in 12 healthy subjects performing such a task and analyzed the data using techniques based on topographic ERP map characteristics. A method which has proved useful for associating ERP map configurations of different time periods with functional states of the brain was supplemented by a source localization procedure. The results suggest that transfer occurs late in time, on a functional motor level and at frontal sites, at least for left-to-right interhemispheric direction of transfer.