a, Horizontal recording through 0.9 mm of cortex. From top to bottom, the first three panel rows show series of OFF, ON and ON–OFF receptive fields (left) and receptive fields averaged across horizontal cortical distance (right). The bottom row shows the orientation or direction tuning (left) and the retinotopy (Retinot.) of the strongest response within each receptive field (right; ON, red; OFF, blue). The small circles in the orientation plots illustrate the preferred orientation predicted from the ON–OFF receptive field. b, c, Horizontal recordings through binocular regions of length 0.5 mm (b) and 0.7 mm (c). Notice the accurate binocular match in ON–OFF retinotopy between the two eyes and also the striking binocular similarity in orientation preference, direction preference and orientation and direction selectivity. Each receptive field box has a side of 27° (a), 23° (b) or 23.6° (c).