Foveal Word Reading Requires Interhemispheric Communication

Abstract

The left cerebral hemisphere is dominant for language processing in most individuals. It has been suggested that this asymmetric language representation can influence behavioral performance in foveal word-naming tasks. We carried out two experiments in which we obtained laterality indices by means of functional imaging during a mental word-generation task, using functional transcranial Doppler sonography and functional magnetic resonance imaging, respectively. Subsequently, we administered a behavioral word-naming task, where participants had to name foveally presented words of different lengths shown in different fixation locations shifted horizontally across the screen. The optimal viewing position for left language dominant individuals is located between the beginning and the center of a word. It is shifted toward the end of a word for right language dominant individuals and, to a lesser extent, for individuals with bilateral language representation. These results demonstrate that interhemispheric communication is required for foveal word recognition. Consequently, asymmetric representations of language and processes of interhemispheric transfer should be taken into account in theoretical models of visual word recognition to ensure neurological plausibility.