Disentangling feedforward versus feedback processing in numerosity representation

Numerosity is a fundamental aspect of the external environment, needed to guide our behavior in an effective manner. Previous studies show that numerosity processing involves at least two temporal stages (~100 and ~150 msec after stimulus onset) early visual cortex. One possibility reflect initial feedforward followed by feedback signals from higher-order cortical areas underlie segmentation inputs into perceptual units define numerosity. Alternatively, multiple might progressively refine input leading segmented representation. Here, we distinguish these hypotheses exploiting connectedness illusion (i.e., systematic underestimation pairwise-connected dots), backward masking (to suppress signals), serial dependence bias making appear be more similar its preceding one). Our results connected dot array biases representation subsequent based on illusory perception, irrespective whether it visible or suppressed masking. These findings demonstrate not strictly necessary for gives rise perceived numerosity, instead suggest different activity presumably carrying low high spatial frequency information are sufficient create areas.