Dissociating the hierarchical processing of perceptual and food category information under different task demands.

To clarify whether food category selectivity in the ventral visual pathway arises from genuine category-specific processing or low-level perceptual differences-a core premise of the diagnostic feature encoding hypothesis-and how it is modulated by task demands, this study assigned participants to perform either a perceptual (color-matching) or categorical (food/nonfood) one-back task. Using multivariate pattern analysis (MVPA) and cross-task representational similarity analysis (RSA) of EEG data, we found that perceptual features dominated early processing (100-200 ms), whereas food category information emerged around 120 ms and gradually became dominant after 200 ms, with the categorical task selectively enhancing the strength of category information during late time windows. Searchlight analysis revealed a spatiotemporal dissociation between perceptual and categorical processing, consistent with hierarchical visual processing theories. For ERP correlates, high perceptual similarity amplified P3 amplitude and low perceptual similarity enhanced N2 amplitude in the perceptual task, with a parallel neural pattern observed under the categorical task. Cross-task comparisons further demonstrated a task-specific modulation pattern: The N2 conflict effect for perceptual similarity was exclusive to the perceptual task, while P3 amplitude was selectively boosted for task-relevant stimulus dimensions. These findings confirm that food category representations are independent and not merely secondary byproducts of low-level perceptual features, thus challenging a core premise of the diagnostic feature encoding hypothesis. This work further underscores the critical regulatory roles of visual attention and task goals in sculpting object representations within the ventral visual pathway.