Visual field topography in the frog's nucleus isthmi.

Responses to visual stimulation were extracellularly recorded with micropipettes from 125 neurons of the left nucleus isthmi in frogs, Rana nigromaculata, and 101 electrode tip positions were marked with cobalt staining. The present study indicates that: (1) the entire contralateral hemifield and the nasal 40 degree of the ipsilateral hemifield project on the nucleus isthmi topographically, and (2) there exist binocular units in this nucleus.