Directional units in the rat optic nerve.

Single units with directional receptive fields were recorded from the rat optic nerve and thus revealed, in contrast to earlier reports, the presence of at least one class of non-concentric retinal unit in this species. In confirmation of prior work, examples of concentric, surround-dominated and centre-dominated receptive fields were also encountered. In some respects their properties resembled those of either brisk or sluggish classes in the cat retina.