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Neural dynamics of global and local visual processing: magnetoencephalography (MEG) decoding with Navon letters

Poster Session F - Tuesday, March 10, 2026, 8:00 – 10:00 am PDT, Fairview/Kitsilano Ballroom

Advitya Hajela¹ (), Peter Kim¹, Sang-Ah Yoo², Hayoung Cho¹, Sung Jun Joo², Sang Chul Chong³, Hee Yeon Im^1,4; ¹University of British Columbia, ²Pusan National University, ³Yonsei University, ⁴BC Children’s Hospital Research Institute

Humans flexibly switch between the global and local levels of visual scenes, seeing the “forest” or the “trees”. Yet, neural dynamics supporting hierarchical visual processing remain poorly understood. Using Navon stimuli, in which a global letter is composed of smaller letters, we examined representational patterns of neural activity measured with magnetoencephalography (MEG). Participants (N=49) identified a letter “H” or “S” at the global or local level in separate, randomized blocks. Whole-brain source-localized MEG activity was classified using linear discriminant analysis, and representational similarity analysis was applied to identify neural patterns that reliably distinguished between global and local processing. Classification accuracy was robustly above chance across the time series, both before and after stimulus onset, indicating a sustained neural state specific to global and local visual processing. Time-resolved classification results were projected onto the brain surface using Haufe forward maps, which transformed classifier weights to determine when and where neural patterns distinguished between global and local processing. Haufe maps indicated that early visual regions, including cuneus/precuneus (temporal cluster: 260–360 msec), as well as posterior (60–160 and 260–360 msec) and anterior cingulate (660–860 msec) regions of the right hemisphere, carried neural patterns that more reliably distinguished local from global trials. In contrast, right inferior frontal regions (160–260 msec) contributed more to distinguishing global from local trials. These findings demonstrate that global and local processing modes instantiated before stimulus onset are maintained across time, reflecting sustained attentional states supported by coordinated activity between visual and frontal regions.

Topic Area: ATTENTION: Spatial