The dynamics of object coding within and across the hemispheres

The human brain integrates information across the hemispheres to construct a coherent representation of the world. Characterising how visual information is coded in each hemisphere is crucial for understanding the nature of information transfer in the brain. Here, we investigated information processing within each hemisphere and its distinctiveness across hemispheres. We presented participants (N = 20) with images of faces, words and objects in rapid sequences while neural responses were measured using electroencephalography (EEG). To drive distinct responses in each hemisphere, stimuli were presented either centrally or lateralised to the left or right visual fields. Participants performed an orthogonal colour change task on dots that marked possible image positions. Multivariate pattern analyses were applied to the neural data to assess coding of object information in the brain, separately for electrode clusters over each hemisphere. Stimulus information was more robust and emerged earlier in the contralateral than the ipsilateral hemisphere. Interestingly, the temporal dynamics within the two hemispheres followed different trajectories. Representational structure was consistent across the hemispheres with delays approximating interhemispheric transmission time. These results provide insights into the dynamics of object perception and the competitive versus cooperative nature of hemispheric processing.