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The well‐established right visual field (RVF‐lh) advantage in word recognition is commonly attributed to the typical left hemisphere dominance in language; words presented to the LVF‐rh are processed less efficiently due to the need for transcallosal transfer from the right to left hemisphere. The exact stage for this hemispheric transfer is currently unsettled. Some studies suggest that transfer occurs at very early stages between primary visual regions, whereas other studies suggest that transfer occurs between the left visual word form area and its right hemisphere homolog. This study explores these conflicting accounts and finds evidence for both. Participants conducted a lateralized lexical decision task with both unilateral and bilateral display conditions. Connectivity analyses were conducted from magnetoencephalography signals that were localized to the left middle occipital gyrus (LMOG), right middle occipital gyrus (RMOG), left visual word form area (LVWFA), and right visual word form area (RVWA). Results from unilateral trials showed asymmetrical interhemispheric connectivity from the RMOG to LMOG and symmetrical interhemispheric connectivity between the LVWFA and RVWFA. Furthermore, bilateral presentations led to reduced interhemispheric connectivity between both homologous region of interest pairs. Together, these results suggest that lateralized word recognition involves multiple stages of interhemispheric interactions and that these interactions are reduced with bilateral displays.

Language comprehension is left-lateralized but with variable contributions from the right hemisphere. When both hemispheres are stimulated simultaneously using divided visual field presentation, performance may be enhanced or hindered depending on the complexity of the task, and these effects may relate to independent processing in both hemispheres or to information transfer between hemispheres. Simultaneous stimulation of both hemispheres is thought to suppress interhemispheric interactions, but information transfer may nonetheless occur. Studies with simultaneous bilateral displays have demonstrated that semantic information from the contralateral visual field (and hemisphere) can facilitate relatedness judgments and lexical decisions. The current study extends this line of research by assessing semantic information transfer in a bilateral word identification task. Task manipulations involving directed spatial attention and asymmetric primes (e.g., ATOM → BOMB) were used to isolate automatic priming as opposed to top-down processing. The results revealed 2 main findings: (a) interhemispheric priming in the form of improved word recognition occurred specifically in conditions designed to isolate automatic transfer of semantic information, that is, in the attended visual field for the target word in asymmetric prime pairs, and (b) there is evidence for an asymmetrical transfer of semantic information, in that the subordinate left visual field−right hemisphere benefited more from such transfer. Together, these results demonstrate evidence for automatic interhemispheric transfer of semantic information, even under conditions of simultaneous bilateral display.

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