Inbar Avni¹, Marlene Behrmann^1,2; ¹University of Pittsburgh, ²Carnegie Mellon University

While studies have examined each hemisphere's role in various cognitive tasks, much remains to be learned about the neural dynamics governing inter- vs. intra-hemispheric information processing. We investigated these processes using concurrent EEG and behavioral data from 18 participants performing two tasks: an Identity task (perceptual matching) and an Ordinal task (numerosity comparison). Each trial involved the presentation of two target stimuli in opposite visual fields and a probe stimulus appearing randomly in either field. This arrangement required either interhemispheric (across visual fields) or intrahemispheric (within visual field) processing and response hand was counterbalanced between and within participants. EEG data were recorded using a customized high-density 128-channel cap, and analyzed to decode neural representations of stimulus-specific information and interhemispheric signal transfer. Behavioral accuracy and reaction time patterns revealed significant task-specific differences: interhemispheric trials reduced accuracy in the more complex Ordinal task, whereas intrahemispheric trials were more efficient for the simpler Identity task. EEG decoding demonstrated that contralateral neural representations were stronger and emerged earlier than ipsilateral representations, particularly in the right hemisphere. Furthermore, decoding accuracy differentiated between intra- and interhemispheric processing in the left hemisphere, and between task types in both hemispheres, highlighting the distinct neural signatures associated with each condition. Overall, decoding accuracy was higher in the left hemisphere. These findings indicate that interhemispheric communication is dynamically modulated to support the computational demands of specific tasks. The results advance our understanding of lateralized neural processing and the mechanisms underlying hemispheric cooperation during complex cognitive tasks.

Acknowledgements: MB acknowledges support from P30 CORE award EY08098 and from EY027018 from the NEI, unrestricted supporting funds from The Research to Prevent Blindness Inc, NY, and from the Eye & Ear Foundation of Pittsburgh.