Fig 1. Probing surround effects in CNNs.

Top left: A neuron was taken from either Alexnet or VGG16. Top middle: The optimal spatial frequency and grating orientation were found by grid search. Top right: Then the grating summation field (GSF) was read from the grating diameter tuning curve. Bottom left: We simulated a set of in-silico physiology experiments with the stimuli that were used in neurophysiology studies. Representative stimuli are shown. The responses of CNN neurons are compared with cortical neurons. Bottom right: We visualized surround effects in CNN neurons by a two-step optimization approach. First, the most facilitative center was optimized within the grating summation field. Then, the most suppressive and facilitative surround were optimized with the fixed most facilitative center.