Central connections of the retinal ON and OFF pathways

Abstract

Slaughter and Miller have recently demonstrated that in the isolated eye cup of the mudpuppy and the rabbit, DL-2-amino-4-phosphonobutyric acid (APB) reversibly blocks the ON responses in the retina: on infusion of APB, ON bipolar, ON amacrine and ON ganglion cells become unresponsive; receptors, horizontal cells, OFF bipolars, OFF amacrines and OFF ganglion cells are unaffected¹. The centre-surround organization of OFF-centre ganglion cells appears unaltered. I have used these findings to determine how the ON-centre and OFF-centre retinal ganglion cells, whose characteristics have been extensively studied in mammals^2–7, exert their influence on the neurones of the central visual system. Recordings made in the lateral geniculate nucleus (LGN) and striate cortex of the rhesus monkey while the retinal ON responses were reversibly blocked with APB showed that in the LGN, retinal APB infusion blocked the responses of ON-centre cells and had little effect on OFF-centre cells. The centre-surround organization of OFF-centre cells was unaffected. APB infusion eliminated the light-edge responses of cortical cells, revealed a dark-edge response in some, but had no discernible effect on orientation and direction specificities. These results suggest that the ON and OFF systems do not interact significantly at the level of the LGN, but do so in the striate cortex.