摘要
Visual responses of 125 units have been extracellularly recorded with glass micropipettesfrom the left nucleus isthmi in the frog Rana nigromaculata, and 101 electrode tip positionsmarked with cobalt staining to reconstruct a visual field map in the nucleus. 80% of the unitsrecorded show ON-OFF responses to a stationary spot of light and many are directionally selec-tive in response to black or white targets moving through their receptive fields. All the cobalt-marked ssots are within the nucleus, indicating that the nucleus isthmus proper is a restrictedpart of the frog visual system. There is a visual field map in the nucleus. The entire contra-lateral hemifield and the nasal 40°of the ipsilateral hemifield project on the nucleus topog-raphically. A cell-free band inside the nucleus is a boundary line separating the contralat-eral hemifield from the ipsilateral one. Dorsal to it is the contralateral field representation.The upper visual field projects on the rostral half of the nucleus and the central and medio-ventral portion of its caudal half. The lower field is represented on the dorsal and lateralpart of the caudal half. Fifteen binocular units have been found from the nucleus, 13 ofwhich arc dominantly activated by the contralateral eye, the other two are almost equallyexcited by either eye. These binocular units are mainly situated in the medulla of the rostralhalf of the nucleus isthmus.
Visual responses of 125 units have been extracellularly recorded with glass micropipettesfrom the left nucleus isthmi in the frog Rana nigromaculata, and 101 electrode tip positionsmarked with cobalt staining to reconstruct a visual field map in the nucleus. 80% of the unitsrecorded show ON-OFF responses to a stationary spot of light and many are directionally selec-tive in response to black or white targets moving through their receptive fields. All the cobalt-marked ssots are within the nucleus, indicating that the nucleus isthmus proper is a restrictedpart of the frog visual system. There is a visual field map in the nucleus. The entire contra-lateral hemifield and the nasal 40°of the ipsilateral hemifield project on the nucleus topog-raphically. A cell-free band inside the nucleus is a boundary line separating the contralat-eral hemifield from the ipsilateral one. Dorsal to it is the contralateral field representation.The upper visual field projects on the rostral half of the nucleus and the central and medio-ventral portion of its caudal half. The lower field is represented on the dorsal and lateralpart of the caudal half. Fifteen binocular units have been found from the nucleus, 13 ofwhich arc dominantly activated by the contralateral eye, the other two are almost equallyexcited by either eye. These binocular units are mainly situated in the medulla of the rostralhalf of the nucleus isthmus.
