Probing the neural geometry of conscious object perception in time

Conscious object recognition is a critical brain function, key to making sense of the plethora of visual inputs and guiding adaptive behavior. Yet, the sequence of neural processing underlying conscious object recognition remains unclear. Existing proposals alternatively suggest that conscious object recognition proceeds in a "coarse-to-fine" sequence or a "fine-to-coarse" sequence. Here, we recorded high-density EEG while participants of both sexes performed a threshold-level object recognition task under different viewing conditions. Both superordinate and basic-level category information emerged early in neural activity, followed by a late superordinate category representation in an abstract format that is disentangled from low-level object features. Strikingly, in the early period, while basic-level category information positively correlated with perceptual awareness, superordinate category information negatively predicted perceptual awareness. By contrast, both superordinate and basic-level category information positively correlated with objective categorization accuracy in the early period. In the late period, both levels of category information positively correlated with awareness. These results suggest that neural processing underlying conscious object perception proceeds from the basic to the superordinate category level.Significance statement Despite significant interests, the sequence of neural processing underlying conscious perception remains unclear. Here, we investigated the unfolding of neural events in time that support perceptual awareness of visual objects. Using a threshold-level object perception task involving three image conditions (normal, low-pass filtered, masked) and high-density EEG, we reveal that basic and superordinate category information both emerge early in the neural activity (at ∼100 ms), but only the basic-level category representation positively contributes to awareness. By contrast, the early superordinate category representation negatively correlates with perceptual awareness. At ∼300 ms, an abstract superordinate category representation emerges, which also positively correlates with perceptual awareness. Therefore, category-level neural processing underlying conscious object perception proceeds from the basic to the superordinate level.