Figure 1. The Retina Responds Explicitly to Motion Reversal.

(A) A salamander ganglion cell’s response to a dark bar moving across the receptive field (i), a dark bar reversing at three different locations (ii), and a light bar reversing at one position (iii). The position of the bar relative to the receptive field center at time zero is shown by a pictogram (right). As shown by the key (top), arrowheads mark the time that the leading edge of the bar crossed the center of the receptive field (solid arrowhead) and the time it recrossed the same point after the reversal (gray arrowhead). Some cells, especially in the mouse, had a late response after the bar left the receptive field surround (asterisk, used for exits both to the right and left of the surround), which occurred regardless of whether there was a motion reversal or not.

(B) A ganglion cell from mouse responding to the same moving dark bars.