Color- and motion-specific units in the tectum opticum of goldfish

Extracellular recordings were performed from 69 units at different depths between 50 and [Formula: see text]m below the surface of tectum opticum in goldfish. Using large field stimuli (86[Formula: see text] visual angle) of 21 colored HKS-papers we were able to record from 54 color-sensitive units. The colored papers were presented for 5[Formula: see text]s each. They were arranged in the sequence of the color circle in humans separated by gray of medium brightness. We found 22 units with best responses between orange, red and pink. About 12 of these red-sensitive units were of the opponent "red-ON/blue-green-OFF" type as found in retinal bipolar- and ganglion cells as well. Most of them were also activated or inhibited by black and/or white. Some units responded specifically to red either with activation or inhibition. 18 units were sensitive to blue and/or green, 10 of them to both colors and most of them to black as well. They were inhibited by red, and belonged to the opponent "blue-green-ON/red-OFF" type. Other units responded more selectively either to blue, to green or to purple. Two units were selectively sensitive to yellow. A total of 15 units were sensitive to motion, stimulated by an excentrically rotating black and white random dot pattern. Activity of these units was also large when a red-green random dot pattern of high L-cone contrast was used. Activity dropped to zero when the red-green pattern did not modulate the L-cones. Neither of these motion selective units responded to any color. The results directly show color-blindness of motion vision, and confirm the hypothesis of separate and parallel processing of "color" and "motion".